The Natural Sciences and Engineering Research Council of Canada (NSERC) and L.B. Foster Rail Technologies, Corp. jointly supported this research through the NSERC Collaborative Research and Development Grant program.

1. Spinning Disk Device
<ol>
	<li>Identify desired test conditions and record test conditions in a table (e.g., ambient temperature, fluid properties, jet and surface speed, etc.).</li>
	<li>Preparation of Materials
	<ol>
		<li>Prepare glycerin-water or PEO-glycerin-water solutions for the impingement tests.
		<ol>
			<li>In the case of PEO-glycerin-water tests, gradually dissolve 4.5 g of PEO powder (viscosity-average molecular weights of one million and four million) into 1495.5 g of distilled water under gentle magnetic stirring over a 24 hr period. Avoid excessively agitating the PEO sample to prevent mechanical degradation.</li>
			<li>Gradually add 1.5 kg of USP-grade glycerin to the aqueous PEO solution over a 24 hr period to reach an aqueous solution of 0.15% PEO concentration and 50% glycerine concentration.</li>
		</ol>
		</li>
		<li>Store the test liquids separately in airtight containers under RT before and after each test to minimize evaporation, water absorption from ambient air and contamination. Characterize and spray liquids within five days of preparation.</li>
	</ol>
	</li>
	<li>Performance of Experiments
	<ol>
		<li>Make sure the spinning disk air bearing&#39;s air supply valve is open and the pressure gauge reading is in the correct working range (60-80 psig). Clear anything that might impede the disk movement and turn the disk by hand in both directions 5 rotations to check for any problems with the disk and bearings.</li>
		<li>Clean and secure the compressed gas closed accumulator for test fluid pressurization. Pour 3 kg of test liquid into the fluid port of the 1-gallon accumulator.</li>
		<li>Connect the gas port of the accumulator to the nitrogen tank via a pressure regulator. Connect the fluid port of the accumulator to the jet spray nozzle.</li>
	</ol>
	</li>
	<li>Set up control system and high-speed imaging system.
	<ol>
		<li>Start the spinning disk control software and VFD control software. Position two high-speed cine cameras 35 cm away from the impingement point and adjust the high magnification lenses to capture the impingement point from two angles.</li>
		<li>Adjust the 150 W&#160;fiber-optic light source to achieve an evenly lit background for best image quality (Figure 1). Power on the control system at this point to facilitate camera adjustment.</li>
		<li>Perform the self-check routine by clicking &#8216;Self-check&#8217; button in the control software to make sure the system is functioning as expected.</li>
	</ol>
	</li>
	<li>Perform a jet impingement test
	<ol>
		<li>Set the disk speed to the desired value with the VFD control software (500-3,000 rpm).</li>
		<li>To perform a test, launch the automated experimental sequence from the control software by clicking the &#8216;Test sequence&#8217; button. The software will determine the optimal parameters automatically and coordinate each component of the system to perform the test accordingly.</li>
		<li>Save the resultant impingement test video (see, for example, the screen shot in Figure 2). Read and record surface speed, nozzle back pressure and temperature from the control software. 
		Note: After each test, a disk cleaning sequence runs automatically to rinse and dry the disk surface. Repeat the cleaning cycle as necessary until all test fluid residue has been removed. 
		CAUTION: While water and glycerin solution test fluids may be cleaned with the cleaning sequence, other LFMs need to be cleaned with organic solvents such as acetone. In such cases, apply the cleaning material to a cloth rather than spraying the disk directly.</li>
	</ol>
	</li>
	<li>Data Analysis
	<ol>
		<li>Prepare a spreadsheet containing information on each test condition (e.g., fluid properties, ambient temperature, surface roughness, etc.).</li>
		<li>Open the recorded jet impingement images with cine viewing software, play full video recordings at normal speed and observe jet impingement behaviors.</li>
		<li>Record impingement behavior characteristics (splash/spattering/deposition; see Figure 3) in the prepared spreadsheet, logging any unusual trends that may indicate complications with the experimental set-up.</li>
		<li>Save test results and conditions in a spreadsheet. Record notable findings and unusual occurrences in test log (e.g., splash/deposition threshold point, splash/deposition transitions, etc.). Save screenshots when necessary.</li>
		<li>Conduct image analysis measurements and record data.
		<ol>
			<li>Launch the on-screen pixel measuring tool. Open impingement images, and calibrate the image scale by measuring a micro-ruler in the images with the on-screen pixel measuring tool (Figure 4).</li>
			<li>Measure dimensions of interest (e.g., lamella spread width, W, and lamella stagnation point radius, R; see Figure 5) with the pixel measuring tool at a point where the jet appears to be most stable in the video and record data in the prepared spreadsheet. Then take another group of measurements 100 frames after the first group of measurements to confirm that both the jet and the lamella are stable. Plot data points on a graph and complete the curve fitting.</li>
		</ol>
		</li>
	</ol>
	</li>
</ol>
2. Air Cannon Device
<ol>
	<li>Identify desired test conditions and prepare materials as in step 1.1 and step 1.2.</li>
	<li>Performance of Experiments
	<ol>
		<li>Power up the system-control software.</li>
		<li>Insert the projectile into the cannon barrel. Move the stop mechanism close to the barrel exit to properly capture the projectile after a test (Figure 6).</li>
		<li>Open the pressurized building air line leading to the air tank. Pressurize the tank to between 30 psi and 70 psi, depending on the desired projectile velocity. 30 psi tank pressure gives a projectile speed of around 5 m/sec, and 70 psi gives a speed of around 25 m/sec.</li>
		<li>Prepare the compressed gas closed accumulator for test fluid pressurization.
		<ol>
			<li>Pour 3 kg of test liquid into the fluid port of the accumulator. Connect tubing from the accumulator gas valve to the liquid jet spray nozzle, and set the accumulator pressure to up to 300 psig.</li>
		</ol>
		</li>
		<li>Attach the camera to the scissor jack. Secure the scissor jack to the platform positioned next to the jet spray nozzle.</li>
		<li>Secure the high-intensity light source to the platform positioned across from the camera and behind the diffusion sheet. Check lighting and camera positioning using the video camera viewing function of the software control interface, and adjust positioning as necessary (Figure 7).</li>
		<li>Put on earmuffs for protection from the air cannon sound blast.</li>
		<li>Unlock the cannon control panel, and press the warning button on the control panel multiple times to signal the start of an experiment.</li>
		<li>Hit the control panel button that opens the solenoid valve connecting the air tank with the air cannon barrel.</li>
		<li>After the device has been fired and the projectile captured, clean the device by wiping it with cleaning fluid and a sponge to remove residual test fluid. Finally, dry the impingement surface of the projectile.</li>
	</ol>
	</li>
	<li>Measure speed of the projectile in the recorded high-speed video by measuring the amount of time required for the projectile to travel a fixed (10 cm) distance. Analyze data as in step 1.5.</li>
</ol>

<ol>
	<li>Cotter, J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Top+of+Rail+Friction+Control:+Reductions+in+Fuel+and+Greenhouse+Gas+Emissions.">Top of Rail Friction Control: Reductions in Fuel and Greenhouse Gas Emissions.</a> Proc. Of the 2005 Conference of the International Heavy Haul Association (Rio de Janeiro). , 327-334 (2005).</li><li>Eadie, D. T., Bovey, E., Kalousek, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+role+of+friction+control+in+effective+management+of+the+wheel/rail+interface).">The role of friction control in effective management of the wheel/rail interface).</a> Railway Technical Conference. , (2002).</li><li>Stock, R., Eadie, D. T., Elvidge, D., Oldknow, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Influencing+rolling+contact+fatigue+through+top+of+rail+friction+modifier+application&#8211;A+full+scale+wheel&#8211;rail+test+rig+study.">Influencing rolling contact fatigue through top of rail friction modifier application&#8211;A full scale wheel&#8211;rail test rig study.</a> Wear. 271 (1), 134-142 (2011).</li><li>Eadie, D. T., Santoro, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Top-of-rail+friction+control+for+curve+noise+mitigation+and+corrugation+rate+reduction.">Top-of-rail friction control for curve noise mitigation and corrugation rate reduction.</a> Journal of Sound and Vibration. 293 (3), 747-757 (2006).</li><li>Tomeoka, M., Kabe, N., Tanimoto, M., Miyauchi, E., Nakata, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Friction+control+between+wheel+and+rail+by+means+of+on-board+lubrication.">Friction control between wheel and rail by means of on-board lubrication.</a> Wear. 253 (1), 124-129 (2002).</li><li>Chiu-Webster, S., Lister, J. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+fall+of+a+viscous+thread+onto+a+moving+surface:+a+&#8216;fluid-mechanical+sewing+machine.">The fall of a viscous thread onto a moving surface: a &#8216;fluid-mechanical sewing machine.</a> Journal of Fluid Mechanics. 569 (1), 124-129 (2006).</li><li>Hlod, A., Aarts, A. C. T., Van De Ven, A. A. F., Peletier, M. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mathematical+model+of+falling+of+a+viscous+jet+onto+a+moving+surface.">Mathematical model of falling of a viscous jet onto a moving surface.</a> European Journal of Applied Mathematics. 18 (06), 659-677 (2007).</li><li>Gradeck, M., Kouachi, A., Dani, A., Arnoult, D., Borean, J. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Experimental+and+numerical+study+of+the+hydraulic+jump+of+an+impinging+jet+on+a+moving+surface.">Experimental and numerical study of the hydraulic jump of an impinging jet on a moving surface.</a> Experimental Thermal and Fluid Science. 30 (3), 193-201 (2006).</li><li>Fujimoto, H., Suzuki, Y., Hama, T., Takuda, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Flow+Characteristics+of+Circular+Liquid+Jet+Impinging+on+a+Moving+Surface+Covered+with+a+Water+Film.">Flow Characteristics of Circular Liquid Jet Impinging on a Moving Surface Covered with a Water Film.</a> ISIJ international. 51 (9), 1497-1505 (2011).</li><li>Keshavarz, B., Green, S. I., Davy, M. H., Eadie, D. T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Newtonian+liquid+jet+impaction+on+a+high-speed+moving+surface.">Newtonian liquid jet impaction on a high-speed moving surface.</a> International Journal of Heat and Fluid Flow. 32 (6), 1216-1225 (2011).</li><li>Keshavarz, B., Green, S. I., Eadie, D. T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Elastic+liquid+jet+impaction+on+a+high+speed+moving+surface.">Elastic liquid jet impaction on a high speed moving surface.</a> AIChE Journal. 58 (11), 3568-3577 (2012).</li><li>Moulson, J. B. T., Green, S. I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Effect+of+ambient+air+on+liquid+jet+impingement+on+a+moving+substrate.">Effect of ambient air on liquid jet impingement on a moving substrate.</a> Physics of Fluids. 25 (10), 102106 (2013).</li><li>Sterling, G. E. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=An+experimental+study+on+jet+impingement+on+a+very+high+speed+moving+surface.">An experimental study on jet impingement on a very high speed moving surface.</a> UBC M.A.Sc. Thesis. , (2012).</li><li>Povarov, O. A., Nazarov, O. I., Ignat'evskaya, L. A., Nikol'skii, A. I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Interaction+of+drops+with+boundary+layer+on+rotating+surfaces.">Interaction of drops with boundary layer on rotating surfaces.</a> Journal of Engineering Physics and Thermophysics. 31 (6), 1453-1456 (1976).</li><li>Fathi, S., Dickens, P., Fouchal, F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Regimes+of+droplet+train+impact+on+a+moving+surface+in+an+additive+manufacturing+process.">Regimes of droplet train impact on a moving surface in an additive manufacturing process.</a> Journal of Materials Processing Technology. 210 (3), 550-559 (2010).</li><li>Bird, J. C., Tsai, S. S., Stone, H. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Inclined+to+splash:+triggering+and+inhibiting+a+splash+with+tangential+velocity.">Inclined to splash: triggering and inhibiting a splash with tangential velocity.</a> New Journal of Physics. 11 (6), 063017 (2009).</li><li>Range, K., Feuillebois, F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Influence+of+surface+roughness+on+liquid+drop+impact.">Influence of surface roughness on liquid drop impact.</a> Journal of Colloid and Interface science. 203 (1), 16-30 (1998).</li><li>Crooks, R., Boger, D. V. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Influence+of+fluid+elasticity+on+drops+impacting+on+dry+surfaces.">Influence of fluid elasticity on drops impacting on dry surfaces.</a> Journal of Rheology. 44 (4), 973-996 (2000).</li></ol>

The authors have nothing to disclose.

The projectile used for the air cannon set-up is composed of a lightweight, wooden base. Though the wooden material chips slightly after numerous tests, it has been found to absorb kinetic energy more effectively than projectiles composed of materials such as plastic or metal, which tend to shatter upon impacting the stop mechanism. The dimensions of the wooden projectile are designed to closely match the steel barrel interior, thus restricting air leakage. A 1/8&#8221; thick rubber sheet secured between two layers of plywood is attached to the back of the projectile to further tighten the seal around the inside of the barrel. The metal impingement surfaces mounted on top of the projectile are fastened as three separate metal plates of different roughness heights, positioned 2.5 cm apart, so that the liquid jet can impinge on all three surfaces in one test with minimal interference. The front of the projectile is shaped into an aerodynamic nose with a barb on the bottom of the nose so that the stop mechanism, which has a heavy aluminum body with a latch mechanism inside, connects securely to the projectile upon impact. Rather than being fixed in place, the stop mechanism slides backwards by roughly 60 cm upon catching the projectile. This function dissipates kinetic energy from the projectile and prevents material damage.
The high-speed cine camera attached to the air cannon device visualizes jet impaction on the projectile surface. The camera&#8217;s wide-screen CMOS sensor allows one to capture images at extremely high frame rates and resolutions. A 1 kW, high-intensity incandescent light source is used to illuminate the field of view, and a light diffusor sheet is placed between the light source and the impingement point to achieve an evenly lit background. Two cameras and light sources are installed on the spinning disk device to capture video recordings from more than one angle. One camera positioned above the impingement point records the front view of the jet impingement, while the second camera records a side view. The camera lenses are covered with a sheet of acetate film to prevent contact with test fluids and to provide a clear viewing window after each test. The side-view camera is illuminated by a high-intensity, fiber-optic light source that locally illuminates the impingement site without blocking the axle. The front-view camera is illuminated by a high-intensity, 100 W, 6,700 Lumen white LED array fitted with a collimating lens.
The two experimental set-ups are controlled electrically by two custom-built control boxes. The custom-built control software allows the user to generate and collect digital and analog signals through a USB DAQ system inside the control box. A controller then utilizes these signals to control each component of the experimental set-up (high-speed camera, light, nozzle, etc.).
The described experimental set-up is limited in that two separate machines were built to test a broad range of surface speeds. The air cannon device can only be operated at slower speeds because it is very difficult to stop non-destructively a projectile moving at velocities higher than 25 m/sec, within the limited space of a laboratory. With the spinning disk there was concern that the rotary motion of the disk would cause associated centripetal forces on the fluid, which would in turn affect the fluid mechanics. This concern proved to be unwarranted as testing with the same jet conditions and same surface speeds on the air cannon (linear surface velocity) and the spinning disk yielded almost identical impaction characteristics. The maximum allowed Reynolds number is limited by liquid jet breakup. In the experiments conducted on these set-ups, a Reynolds number of 1,500 was easily reached. Substrate speed on the high-speed set-up is limited by the capacity of the VFD motor (i.e., maximum rotational speed and maximum power output to overcome drag, inertia, etc.), provided the disk and shaft are well balanced.
The described apparatuses differ from existing techniques that examine liquid jet impingement in that they accommodate the study of high-speed liquid jet impingement over high surface speed conditions (25-100 m/sec) using small liquid jet nozzle diameters. Because liquid jet impingement processes that occur on stationary and low-speed moving surfaces differ considerably from those associated with high-speed moving surfaces with respect to liquid build-up and spread patterns, the described technique can further existing knowledge on liquid jet impingement behaviors under a broader range of conditions. The technique&#8217;s focus on splash, splatter and deposition processes associated with liquid jet impingement also addresses a knowledge gap in this field, which has previously been preoccupied with heat transfer patterns. As liquid jet impingement onto a substrate is a highly complex multiphase fluid mechanics problem that poses many possible avenues for future research, the described technique may be used for a number of technical and industrial applications such as steelmaking and ink-jet printing, cooling, heating and surface coating.

This research aims to determine strategies for applying LFM (Liquid Friction Modifier) in liquid jet form onto a moving surface while attaining high degrees of transfer efficiency and uniform deposition results. Achieving this objective involves developing a comprehensive understanding of factors that affect liquid jet impingement on moving surfaces.
The project is motivated by a need to improve the efficiency of lubrication application techniques used in the rail sector. As a means of reducing fuel consumption and locomotive maintenance costs, a thin film of friction modifying agent is now being applied to the upper rail surface of conventional railroad tracks. Recent studies have shown that applying one type of water-based LFM for top of rail (TOR) friction control reduced energy consumption levels by 6% and rail and wheel flange wear by in excess of 50%1,2. Other studies have shown that applying LFM to rail tracks reduces lateral force and noise levels as well as, more importantly, track corrugation and damage from rolling contact fatigue, which is a major cause of derailments3,4. These results were further confirmed in field tests on the Tokyo subway system5.
LFMs are currently dispensed from air blast atomizers attached to dozens of locomotives throughout Canada and the United States. In this form of application, LFM is applied to the top of railroad tracks by atomizers mounted beneath moving rail cars. This mode of LFM application is difficult to implement on many railroad locomotives because the required high-volume and high-pressure air supply levels may not be attainable. Air-blast spray nozzles are also believed to produce highly irregular rail coverage when operated in a crosswind, as crosswinds cause fine spray droplets to deviate from their original trajectory. Crosswinds are also known to be implicated in nozzle fouling, likely for the same reason. Due to problems associated with air blast atomizers, the rail sector is currently seeking alternative approaches to LFM application onto rail tracks. One viable solution involves dispensing LFM by means of a continuous (not-atomized) liquid jet, as liquid jets are less susceptible to crosswind effects due to their lower drag-to-inertia ratio. Additionally, because the high air pressure and volume levels needed for atomizing nozzles are not required in liquid jet spray technologies, the latter act as more streamlined and robust spraying mechanisms that maintain effective control over the rate of LFM application.
An area of similar physics, droplet impingement, has been studied intensively. It was found by several researchers that for droplet impingement on a moving dry smooth surface, splashing behavior is dependent on many parameters including viscosity, density, surface tension and the normal component of the impact velocity14,15. Bird et al. demonstrated that both the normal and tangential velocities were of critical importance16. Range et al. and Crooks et al. have shown that for droplet impingement on a stationary dry surface, surface roughness decreases the splash threshold significantly (i.e., it makes the droplet more prone to splash)17,18.
Despite its practical importance, jet impingement on moving surfaces has received little attention in the academic literature. Chiu-Webster and Lister performed an extensive series of experiments that examined steady and unsteady viscous jet impingement on a moving surface, and the authors developed a model for the steady flow case6. Hlod et al. modeled the flow by means of a third-order ODE on a domain of unknown length under an additional integral condition and compared predicted configurations with experimental results7. However, the Reynolds numbers examined in both of these studies are much lower than those associated with typical railroad LFM applications. Gradeck et al. numerically and experimentally investigated the flow field of water jet impingement onto a moving substrate under various jet velocity, surface velocity, and nozzle diameter conditions8. Fujimoto et al. additionally investigated flow characteristics of a circular water jet impinging onto a moving substrate covered by a thin film of water9. However, these two projects used relatively large nozzle diameters and lower surface and jet velocities compared to those employed in the present work. Furthermore, though previous experimental, numerical, and analytical studies provide a large body of data, the majority have focused on heat transfer parameters rather than on liquid flow processes such as jet splashing behavior. The experimental method provided in the present research thus contributes to liquid jet application technologies by refining such techniques under conditions involving smaller jet nozzle diameters and high-speed jet and surface velocities. The present method also refines knowledge on fundamental fluid mechanics problems associated with moving contact lines.
The studies mentioned above have generally involved the interaction of a low speed jet with a low speed moving surface. There have been comparatively few studies of laminar high speed jet impingement onto high-speed moving surfaces. During high speed liquid jet impaction the jet liquid spreads radially in the vicinity of the impingement location, forming a thin lamella. This lamella is then convected downstream by the viscous forcing imposed by the moving surface, producing a characteristic U-shaped lamella. Keshavarz et al. have reported on experiments employing Newtonian and elastic liquid jets impinging onto high-speed surfaces. They classified impingement processes into two distinct types: &#8220;deposition&#8221; and &#8220;splash&#8221;10. For impingement to be classified as deposition, the jet liquid must adhere to the surface, whereas splash is characterized by a liquid lamella that separates from the surface, and subsequently breaks up into droplets. A third impingement regime has also been described &#8212; &#8220;splatter&#8221;. In this, comparatively rare, regime the lamella remains attached to the surface, as for &#8220;deposition&#8221;, but fine droplets are ejected from near the leading edge of the lamella. In a subsequent study of non-Newtonian fluid effects, Keshavarz et al. concluded that the splash/deposition threshold is mainly determined by the Reynolds and Deborah numbers, whereas the jet impingement angle and jet velocity to surface velocity ratios only have a minor effect11. In experiments conducted under variable ambient air pressures, Moulson et al. discovered that the splash/deposition threshold Reynolds number dramatically increases with decreasing ambient air pressure (i.e., higher ambient pressures make jets more prone to splash), while decreasing ambient air pressure below a certain threshold suppresses splash completely12. This finding strongly suggests that aerodynamic forces acting on the lamella play a crucial role in causing lamella lift-off and subsequent splash. In recent work on high-speed impingement on a high-speed substrate, Sterling showed that for substrate speed and jet conditions close to the splash threshold, splash may be triggered by very small localized surface roughness and minor jet unsteadiness. He also showed that under these conditions lamella lift-off and reattachment is a stochastic process13.
The experimental protocol described here may be used to study other physical situations involving the interaction of a fluid with a moving high speed surface. For example, the same approach could be used to study helicopter blade-vortex interaction (provided that the vortex fluid was colored with tracer particles) and robotic spraying of surfaces.

<table border="0" cellpadding="0" cellspacing="0">
	<tbody>
		<tr>
			<td colspan="4">Equipment for Air Cannon Set-Up</td>
		</tr>
		<tr>
			<td>30-gallon air tank</td>
			<td>Steel Fab</td>
			<td>A10028</td>
			<td></td>
		</tr>
		<tr>
			<td>Solenoid actuated poppet valve</td>
			<td>Parker Hannifin Corp.</td>
			<td>#16F24C2164A3F4C80</td>
			<td></td>
		</tr>
		<tr>
			<td>1.5&#34;NPT rubber hose</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Rectangular steel tubing</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Stop mechanism</td>
			<td>Customized</td>
			<td>N/A</td>
			<td></td>
		</tr>
		<tr>
			<td>Stainless steel plates</td>
			<td>Customized</td>
			<td>N/A</td>
			<td></td>
		</tr>
		<tr>
			<td>Wooden projectile</td>
			<td>Customized</td>
			<td>N/A</td>
			<td></td>
		</tr>
		<tr>
			<td>1kw high-intensity incandescent light</td>
			<td>Photographic Analysis Ltd.</td>
			<td>T986851</td>
			<td></td>
		</tr>
		<tr>
			<td>Light diffuser sheet</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Optic sensor</td>
			<td>BANNER</td>
			<td>SM312LV</td>
			<td></td>
		</tr>
		<tr>
			<td colspan="4">Equipment for Spinning Disc Set-Up</td>
		</tr>
		<tr>
			<td>Motor</td>
			<td>WEG</td>
			<td>TEFC-W22</td>
			<td></td>
		</tr>
		<tr>
			<td>Bearings</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Disk</td>
			<td>Customized</td>
			<td>N/A</td>
			<td></td>
		</tr>
		<tr>
			<td>Fiber optic light source</td>
			<td>Fiberoptics Technology Incorporated</td>
			<td>MO150AC</td>
			<td></td>
		</tr>
		<tr>
			<td>High intensity LED array</td>
			<td>Torshare Ltd.</td>
			<td>TF10CA</td>
			<td></td>
		</tr>
		<tr>
			<td>Vacuum</td>
			<td>Ridge Tool Company</td>
			<td>WD09450</td>
			<td></td>
		</tr>
		<tr>
			<td>Interrupter</td>
			<td>Customized</td>
			<td>N/A</td>
			<td></td>
		</tr>
		<tr>
			<td colspan="4">Shared Equipment for Both Devices</td>
		</tr>
		<tr>
			<td>Phantom v611 high-speed cine camera</td>
			<td>Vision Research Inc.</td>
			<td>V611</td>
			<td></td>
		</tr>
		<tr>
			<td>Phantom v12 high-speed cine camera</td>
			<td>Vision Research Inc.</td>
			<td>V12</td>
			<td></td>
		</tr>
		<tr>
			<td>Zoom 7000 lens</td>
			<td>Navitar Inc.</td>
			<td>Zoom 7000</td>
			<td></td>
		</tr>
		<tr>
			<td>Zoom 6000 lens</td>
			<td>Navitar Inc.</td>
			<td>Zoom 6000</td>
			<td></td>
		</tr>
		<tr>
			<td>Compressed nitrogen tank</td>
			<td>Praxair Technology, Inc.</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Pressure regulator</td>
			<td>Praxair Technology, Inc.</td>
			<td>PRS20124351CGA</td>
			<td></td>
		</tr>
		<tr>
			<td>Hose for compressed nitrogen</td>
			<td>Swagelok Company</td>
			<td>SS-CT8SL8SL8-12</td>
			<td></td>
		</tr>
		<tr>
			<td>Hose for liquid</td>
			<td>Swagelok Company</td>
			<td>SS-7R8TA8TA8</td>
			<td></td>
		</tr>
		<tr>
			<td>Accumulator</td>
			<td>Accumulators, Inc.</td>
			<td>A131003XS</td>
			<td></td>
		</tr>
		<tr>
			<td>Solenoid Valve</td>
			<td>Solenoid Solutions Inc.</td>
			<td>2223X-A440-00</td>
			<td></td>
		</tr>
		<tr>
			<td>Pressure transducer</td>
			<td>WIKA Instruments Ltd</td>
			<td>#50398083</td>
			<td></td>
		</tr>
		<tr>
			<td>Nozzle assembly</td>
			<td>Customized</td>
			<td>N/A</td>
			<td></td>
		</tr>
		<tr>
			<td>Glycerin</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Poly(ethylene oxide)</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
	</tbody>
</table>

visualization of high speed liquid jet impaction on a moving surface

Two apparatuses for examining liquid jet impingement on a high-speed moving surface are described: an air cannon device (for examining surface speeds between 0 and 25 m/sec) and a spinning disk device (for examining surface speeds between 15 and 100 m/sec). The air cannon linear traverse is a pneumatic energy-powered system that is designed to accelerate a metal rail surface mounted on top of a wooden projectile. A pressurized cylinder fitted with a solenoid valve rapidly releases pressurized air into the barrel, forcing the projectile down the cannon barrel. The projectile travels beneath a spray nozzle, which impinges a liquid jet onto its metal upper surface, and the projectile then hits a stopping mechanism. A camera records the jet impingement, and a pressure transducer records the spray nozzle backpressure. The spinning disk set-up consists of a steel disk that reaches speeds of 500 to 3,000 rpm via a variable frequency drive (VFD) motor. A spray system similar to that of the air cannon generates a liquid jet that impinges onto the spinning disc, and cameras placed at several optical access points record the jet impingement. Video recordings of jet impingement processes are recorded and examined to determine whether the outcome of impingement is splash, splatter, or deposition. The apparatuses are the first that involve the high speed impingement of low-Reynolds-number liquid jets on high speed moving surfaces. In addition to its rail industry applications, the described technique may be used for technical and industrial purposes such as steelmaking and may be relevant to high-speed 3D printing.

As discussed in the introductory section, the three main behaviors associated with liquid jet impingement are deposition, splatter and splash. These jet impingement behaviors are observed using video data recorded by high-speed cine cameras positioned at various optical points. Examples of still images, obtained from the video recordings, which depict the three liquid jet outcomes are shown in Figure 3. Figure 3A depicts liquid jet deposition, in which the jet flows in a completely straight and steady stream towards the impingement surface. The jet adheres to the surface and remains on the surface for the remainder of the experiment. Figures 3B and 3C show less optimal results in which the liquid jet only partially adheres to the impingement surface, with the remainder of the jet either splattering (Figure 3B) or splashing (Figure 3C) upon impact.
Given the fairly straightforward nature of the given video data, ambiguous results are uncommon and repeatable results have been obtained from both experimental devices. However, in very rare cases that typically involve very smooth surface roughness conditions, the lamella of a liquid jet stream may interact with droplets or roughness on the surface in such a way that causes it to lift off from the impingement surface (Figure 8). In equally unusual circumstances, a small disturbance in the flow can produce irregularities in the jet, which upon surface impaction become amplified, causing the jet to separate from the surface for a long period of time (Figure 9). These rare phenomena typically occur only for high surface speeds and for intermediate jet fluid viscosities (Re = 100~2,500). The consistency of results is largely credited to the use of a pressure accumulator for driving the test liquid, which, unlike a pump, propels liquid at a constant rate, producing a very smooth action and thus a highly consistent, uniform and steady liquid flow.
With respect to splash/deposition characteristics, the results show that for metal surfaces of average roughness heights ranging between 0.01 &#181;m and 1 &#181;m, decreasing the surface roughness makes the impinging jet more susceptible to splash. For example, Figure 3A and Figure 3C show impingement under similar jet and surface speed conditions. In Figure 3A jet deposition occurs on the surface, which has an average roughness height of 0.51 &#181;m, but jet splash occurs when the average roughness height is 0.016 &#181;m (Figure 3C). This dependence on roughness is opposite to that observed by Keshavarz et al.10,11, who studied impingement on much rougher surfaces, where the surface roughness is significantly larger than the lamella thickness.
The threshold of splash is a complex function of the liquid jet velocity; liquid jet diameter; liquid viscosity, density and surface tension; the surface speed and roughness; and the surrounding air characteristics. Although some simple theories of splash have been proposed10-12, there is currently no comprehensive explanation of the phenomenon. Lamella liftoff, which is usually a precursor to splash12, is believed to be a function of lamella geometry. As seen in Figure 10, the lamella geometry is itself a complex function of many variables, including the jet and surface speeds and liquid physical properties.
<img alt="Figure 1" src="/files/ftp_upload/52603/52603fig1.jpg" /> 
Figure 1. Schematic of optical configuration of spinning disk device. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/52603/52603fig1large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 2" src="/files/ftp_upload/52603/52603fig2.jpg" /> 
Figure 2. Screenshot of typical video recording. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/52603/52603fig2large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 3" src="/files/ftp_upload/52603/52603fig3.jpg" /> 
Figure 3. Three typical flow regimes. (A) deposition, (B) splatter, (C) splash. In all instances the substrate moves from right to left and the jet diameter is 564 &#181;m. The relevant jet and substrate conditions are: (A) Vjet = 18.3 m/sec, Vsubstrate = 7.50 m/sec, &#181;jet = 0.0194 N&#183;sec/m2, &#961;jet = 1,180 kg/m3, &#963;jet = 0.0656 N/m, Rejet = 629, Wejet = 3,400; (B) Vjet = 9.5 m/sec, Vsubstrate = 7.63 m/sec, &#181;jet = 0.0097 N&#183;sec/m2, &#961;jet = 998 kg/m3, &#963;jet = 0.0717 N/m, Rejet = 552, Wejet = 709; (C) Vjet = 17.3 m/sec, Vsubstrate = 7.71 m/sec, &#181;jet = 0.0194 N&#183;sec/m2, &#961;jet = 1,180 kg/m3, &#963;jet = 0.0656 N/m, Rejet = 594, Wejet = 3,040. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/52603/52603fig3large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 4" src="/files/ftp_upload/52603/52603fig4.jpg" /> 
Figure 4. Measurement of jet diameter and lamella geometry with image processing software. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/52603/52603fig4large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 5" src="/files/ftp_upload/52603/52603fig5.jpg" /> 
Figure 5. Planform view schematic of jet impingement showing characteristic lamella dimensions. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/52603/52603fig5large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 6" src="/files/ftp_upload/52603/52603fig6.jpg" /> 
Figure 6. Air cannon mechanical configuration. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/52603/52603fig6large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 7" src="/files/ftp_upload/52603/52603fig7.jpg" /> 
Figure 7. Air cannon optical configuration. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/52603/52603fig7large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 8" src="/files/ftp_upload/52603/52603fig8.jpg" /> 
Figure 8. Time sequence showing the transition from jet deposition to jet splash. In this sequence the transition is caused by very fine droplets adhering to the otherwise dry substrate. The substrate is moving from right to left at a speed Vsubstrate = 7.52 m/sec. The jet conditions are: Djet = 564 &#181;m; Vjet = 17.5 m/sec, &#181;jet = 0.0194 N&#183;sec/m2, &#961;jet = 1,180 kg/m3, &#963;jet = 0.0656 N/m, Rejet = 600, Wejet = 3,110. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/52603/52603fig8large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 9" src="/files/ftp_upload/52603/52603fig9.jpg" /> 
Figure 9. Time sequence showing the transition from jet deposition to jet splash. In this sequence the transition is caused by a small air bubble in the jet that perturbs the flow. The substrate is moving from right to left at a speed Vsubstrate = 7.43 m/sec. The jet conditions are: Djet = 564 &#181;m; Vjet = 15.8 m/sec, &#181;jet = 0.0194 N&#183;sec/m2, &#961;jet = 1,180 kg/m3, &#963;jet = 0.0656 N/m, Rejet = 542, Wejet = 2,530. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/52603/52603fig9large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 10" src="/files/ftp_upload/52603/52603fig10.jpg" /> 
Figure 10. Lamella spread width to jet diameter ratio, as a function of Reynolds number of substrate. Substrate speed Vsubstrate is varied from 15 m/sec to 60 m/sec, giving a Reynolds number ReS of 75 to 300. The jet conditions are: Djet = 281 &#181;m; Vjet =14.6 m/sec, &#181;jet = 0.0701 N&#183;sec/m2, &#961;jet = 1,220 kg/m3, &#963;jet = 0.0640 N/m, Rejet = 71.4, Wejet = 1,140.

Watch this Scientific Journal Video about Visualization of High Speed Liquid Jet Impaction on a Moving Surface at JoVE.com

Visualization of High Speed Liquid Jet Impaction on a Moving Surface

Two experimental devices for examining liquid jet impingement on a high-speed moving surface are described: an air cannon device and a spinning disk device. The apparatuses are used to determine optimal approaches to the application of liquid friction modifier (LFM) onto rail tracks for top-of-rail friction control.

Two apparatuses for examining liquid jet impingement on a high-speed moving surface are described: an air cannon device (for examining surface speeds ...

visualization-of-high-speed-liquid-jet-impaction-on-a-moving-surface

Nanyang Technological University

Research

Education

JoVE Journal

JoVE Core

Engineering

Physics

Mechanical Engineering

Unit 1

Planar Kinematics of a Rigid Body

Motion in Two or Three Dimensions

SCIENTISTS IN ACTION

11.4K Views.  University of British Columbia. Two experimental devices for examining liquid jet impingement on a high-speed moving surface are described: an air cannon device and a spinning disk device. The apparatuses are used to determine optimal approaches to the application of liquid friction modifier (LFM) onto rail tracks for top-of-rail friction control.

Video: Visualization of High Speed Liquid Jet Impaction on a Moving Surface

High-resolution, High-speed, Three-dimensional Video Imaging with Digital Fringe Projection Techniques

Digital fringe projection (DFP) techniques provide dense 3D measurements of dynamically changing surfaces.&#160;Like the human eyes and brain, DFP uses triangulation between matching points in two views of the same scene at different angles to compute depth.&#160;However, unlike a stereo-based method, DFP uses a digital video projector to replace one of the cameras1. The projector rapidly projects a known sinusoidal pattern onto the subject, and the surface of the subject distorts these patterns in the camera&#8217;s field of view. Three distorted patterns (fringe images) from the camera can be used to compute the depth using triangulation.
Unlike other 3D measurement methods, DFP techniques lead to systems that tend to be faster, lower in equipment cost, more flexible, and easier to develop.&#160;DFP systems can also achieve the same measurement resolution as the camera.&#160;For this reason, DFP and other digital structured light techniques have recently been the focus of intense research (as summarized in1-5). Taking advantage of DFP, the graphics processing unit, and optimized algorithms, we have developed a system capable of 30&#160;Hz 3D video data acquisition, reconstruction, and display for over 300,000 measurement points per frame6,7.&#160;Binary defocusing DFP methods can achieve even greater speeds8.
Diverse applications can benefit from DFP techniques. Our collaborators have used our systems for facial function analysis9, facial animation10, cardiac mechanics studies11, and fluid surface measurements, but many other potential applications exist.&#160;This video will teach the fundamentals of DFP techniques and illustrate the design and operation of a binary defocusing DFP system.

This video describes the fundamentals of digital fringe projection techniques, which provide dense 3D measurements of dynamically changing surfaces.&#160;It also demonstrates the design and operation of a high-speed binary defocusing system based on these techniques.

Digital fringe projection (DFP) techniques provide dense 3D measurements of dynamically changing surfaces.&#160;Like the human eyes and brain, DFP uses ...

High-speed Particle Image Velocimetry Near Surfaces

Multi-dimensional and transient flows play a key role in many areas of science, engineering, and health sciences but are often not well understood. The complex nature of these flows may be studied using particle image velocimetry (PIV), a laser-based imaging technique for optically accessible flows. Though many forms of PIV exist that extend the technique beyond the original planar two-component velocity measurement capabilities, the basic PIV system consists of a light source (laser), a camera, tracer particles, and analysis algorithms. The imaging and recording parameters, the light source, and the algorithms are adjusted to optimize the recording for the flow of interest and obtain valid velocity data. 
Common PIV investigations measure two-component velocities in a plane at a few frames per second. However, recent developments in instrumentation have facilitated high-frame rate (&gt; 1 kHz) measurements capable of resolving transient flows with high temporal resolution. Therefore, high-frame rate measurements have enabled investigations on the evolution of the structure and dynamics of highly transient flows. These investigations play a critical role in understanding the fundamental physics of complex flows.
A detailed description for performing high-resolution, high-speed planar PIV to study a transient flow near the surface of a flat plate is presented here. Details for adjusting the parameter constraints such as image and recording properties, the laser sheet properties, and processing algorithms to adapt PIV for any flow of interest are included.

A procedure for studying transient flows near boundaries using high-resolution, high-speed particle image velocimetry (PIV) is described here. PIV is a non-intrusive measurement technique applicable to any optically accessible flow by optimizing several parameter constraints such as the image and recording properties, the laser sheet properties, and analysis algorithms.

Multi-dimensional and transient flows play a key role in many areas of science, engineering, and health sciences but are often not well understood. The ...

Selective Area Modification of Silicon Surface Wettability by Pulsed UV Laser Irradiation in Liquid Environment

The wettability of silicon (Si) is one of the important parameters in the technology of surface functionalization of this material and fabrication of biosensing devices. We report on a protocol of using KrF and ArF lasers irradiating Si (001) samples immersed in a liquid environment with low number of pulses and operating at moderately low pulse fluences to induce Si wettability modification. Wafers immersed for up to 4 hr in a 0.01% H2O2/H2O solution did not show measurable change in their initial contact angle (CA) ~75&#176;. However, the 500-pulse KrF and ArF lasers irradiation of such wafers in a microchamber filled with 0.01% H2O2/H2O solution at 250 and 65 mJ/cm2, respectively, has decreased the CA to near 15&#176;, indicating the formation of a superhydrophilic surface. The formation of OH-terminated Si (001), with no measurable change of the wafer&#8217;s surface morphology, has been confirmed by X-ray photoelectron spectroscopy and atomic force microscopy measurements. The selective area irradiated samples were then immersed in a biotin-conjugated fluorescein-stained nanospheres solution for 2 hr, resulting in a successful immobilization of the nanospheres in the non-irradiated area. This illustrates the potential of&#160;the method for selective area biofunctionalization and fabrication of advanced Si-based biosensing architectures. We also describe a similar protocol of irradiation of wafers immersed in methanol (CH3OH) using ArF laser operating at pulse fluence of 65 mJ/cm2 and in situ formation of a strongly hydrophobic surface of Si (001) with the CA of 103&#176;. The XPS results indicate ArF laser induced formation of Si&#8211;(OCH3)x compounds responsible for the observed hydrophobicity. However, no such compounds were found by XPS on the Si surface irradiated by KrF laser in methanol, demonstrating the inability of the KrF laser to photodissociate methanol and create -OCH3 radicals.

We report on a process of in situ alteration of HF treated Si (001) surface into a hydrophilic or hydrophobic state by irradiating samples in microfluidic chambers filled with&#160;H2O2/H2O solution (0.01%-0.5%) or methanol solutions using pulsed UV laser of a relative low pulse fluence.

The wettability of silicon (Si) is one of the important parameters in the technology of surface functionalization of this material and fabrication of ...

Three-dimensional Particle Tracking Velocimetry for Turbulence Applications: Case of a Jet Flow

3D-PTV is a quantitative flow measurement technique that aims to track the Lagrangian paths of a set of particles in three dimensions using stereoscopic recording of image sequences. The basic components, features, constraints and optimization tips of a 3D-PTV topology consisting of a high-speed camera with a four-view splitter are described and discussed in this article. The technique is applied to the intermediate flow field (5 &#60;x/d &#60;25) of a circular jet at Re &#8776; 7,000. Lagrangian flow features and turbulence quantities in an Eulerian frame are estimated around ten diameters downstream of the jet origin and at various radial distances from the jet core. Lagrangian properties include trajectory, velocity and acceleration of selected particles as well as curvature of the flow path, which are obtained from the Frenet-Serret equation. Estimation of the 3D velocity and turbulence fields around the jet core axis at a cross-plane located at ten diameters downstream of the jet is compared with literature, and the power spectrum of the large-scale streamwise velocity motions is obtained at various radial distances from the jet core.

A three-dimensional particle tracking velocimetry (3D-PTV) system based on a high-speed camera with a four-view splitter is described here. The technique is applied to a jet flow from a circular pipe in the vicinity of ten diameters downstream at Reynolds number Re &#8776; 7,000.

3D-PTV is a quantitative flow measurement technique that aims to track the Lagrangian paths of a set of particles in three dimensions using stereoscopic ...

High-speed Continuous-wave Stimulated Brillouin Scattering Spectrometer for Material Analysis

Recent years have witnessed a significant increase in the use of spontaneous Brillouin spectrometers for non-contact analysis of soft matter, such as aqueous solutions and biomaterials, with fast acquisition times. Here, we discuss the assembly and operation of a Brillouin spectrometer that uses stimulated Brillouin scattering (SBS) to measure stimulated Brillouin gain (SBG) spectra of water and lipid emulsion-based tissue-like samples in transmission mode with &lt;10 MHz spectral-resolution and &lt;35 MHz Brillouin-shift measurement precision at &lt;100 ms. The spectrometer consists of two nearly counter-propagating continuous-wave (CW) narrow-linewidth lasers at 780 nm whose frequency detuning is scanned through the material Brillouin shift. By using an ultra-narrowband hot rubidium-85 vapor notch filter and a phase-sensitive detector, the signal-to-noise-ratio of the SBG signal is significantly enhanced compared to that obtained with existing CW-SBS spectrometers. This improvement enables measurement of SBG spectra with up to 100-fold faster acquisition times, thereby facilitating high spectral-resolution and high-precision Brillouin analysis of soft materials at high speed.

We describe the construction of a rapid continuous-wave-stimulated-Brillouin-scattering (CW-SBS) spectrometer. The spectrometer employs single-frequency diode-lasers and an atomic vapor notch-filter to acquire transmission spectra of turbid/non-turbid samples with high spectral-resolution at speeds up to 100-fold faster than those of existing CW-SBS spectrometers. This improvement enables high-speed Brillouin material analysis.

Recent years have witnessed a significant increase in the use of spontaneous Brillouin spectrometers for non-contact analysis of soft matter, such as ...

Preparation and High-temperature Anti-adhesion Behavior of a Slippery Surface on Stainless Steel

Anti-adhesion surfaces with high-temperature resistance have a wide application potential in electrosurgical instruments, engines, and pipelines. A typical anti-wetting superhydrophobic surface easily fails when exposed to a high-temperature liquid. Recently, Nepenthes-inspired slippery surfaces demonstrated a new way to solve the adhesion problem. A lubricant layer on the slippery surface can act as a barrier between the repelled materials and the surface structure. However, the slippery surfaces in previous studies rarely showed high-temperature resistance. Here, we describe a protocol for the preparation of slippery surfaces with high-temperature resistance. A photolithography-assisted method was used to fabricate pillar structures on stainless steel. By functionalizing the surface with saline, a slippery surface was prepared by adding silicone oil. The prepared slippery surface maintained the anti-wetting property for water, even when the surface was heated to 300 &#176;C. Also, the slippery surface exhibited great anti-adhesion effects on soft tissues at high temperatures. This type of slippery surface on stainless steel has applications in medical devices, mechanical equipment, etc.

Slippery surfaces provide a new way to solve the adhesion problem. This protocol describes how to fabricate slippery surfaces at high temperatures. The results demonstrate that the slippery surfaces showed anti-wetting for liquids and a remarkable anti-adhesion effect on soft tissues at high temperatures.

Anti-adhesion surfaces with high-temperature resistance have a wide application potential in electrosurgical instruments, engines, and pipelines. A ...

Method for Recording Broadband High Resolution Emission Spectra of Laboratory Lightning Arcs

Lightning is one of the most common and destructive forces in nature and has long been studied using spectroscopic techniques, first with traditional camera film methods and then digital camera technology, from which several important characteristics have been derived. However, such work has always been limited due to the inherently random and non-repeatable nature of natural lightning events in the field. Recent developments in lightning test facilities now allow the reproducible generation of lightning arcs within controlled laboratory environments, providing a test bed for the development of new sensors and diagnostic techniques to understand lightning mechanisms better. One such technique is a spectroscopic system using digital camera technology capable of identifying the chemical elements with which the lightning arc interacts, with these data then being used to derive further characteristics. In this paper, the spectroscopic system is used to obtain the emission spectrum from a 100 kA peak, 100 &#181;s duration lightning arc generated across a pair of hemispherical tungsten electrodes separated by a small air gap. To maintain a spectral resolution of less than 1 nm, several individual spectra were recorded across discrete wavelength ranges, averaged, stitched, and corrected to produce a final composite spectrum in the 450 nm (blue light) to 890 nm (near infrared light) range. Characteristic peaks within the data were then compared to an established publicly available database to identify the chemical element interactions. This method is readily applicable to a variety of other light emitting events, such as fast electrical discharges, partial discharges, and sparking in electrical equipment, apparatus, and systems.

Emission spectroscopy techniques have traditionally been used to analyze inherently random lightning arcs occurring in nature. In this paper, a method developed to obtain the emission spectroscopy from reproducible lightning arcs generated within a laboratory environment is described.

Lightning is one of the most common and destructive forces in nature and has long been studied using spectroscopic techniques, first with traditional ...

Impacts of Free-falling Spheres on a Deep Liquid Pool with Altered Fluid and Impactor Surface Conditions

Vertical impacts of spheres on clean water have been the subject of numerous water entry investigations characterizing cavity formation, splash crown ascension and Worthington jet stability. Here, we establish experimental protocols for examining splash dynamics when smooth free-falling spheres of varying wettability, mass, and diameter impact the free surface of a deep liquid pool modified by thin penetrable fabrics and liquid surfactants. Water entry investigations provide accessible, easily assembled and executed experiments for studying complex fluid mechanics. We present herein a tunable protocol for characterizing splash height, flow separation metrics, and impactor kinematics, and representative results which might be acquired if reproducing our approach. The methods are applicable when characteristic splash dimensions remain below approximately 0.5 m. However, this protocol may be adapted for greater impactor release heights and impact velocities, which augurs well for translating results to naval and industry applications.

This protocol demonstrates the basic experimental configuration for water entry experiments with free-falling spheres. Methods for the alteration of liquid surface with penetrable fabrics, the preparation of chemically non-wetting spheres, and steps for splash visualization and data extraction are discussed.

Vertical impacts of spheres on clean water have been the subject of numerous water entry investigations characterizing cavity formation, splash crown ...

Determination of Aggregate Surface Morphology at the Interfacial Transition Zone (ITZ)

Here, we present a comprehensive method to illustrate the uneven distribution of the interfacial transition zone (ITZ) around the aggregate and the effect of aggregate surface morphology on the formation of ITZ. First, a model concrete sample is prepared with a spherical ceramic particle in roughly the central part of the cement matrix, acting as a coarse aggregate used in common concrete/mortar. After curing until the designed age, the sample is scanned by X-ray computed tomography to determine the relative location of the ceramic particle inside the cement matrix. Three locations of the ITZ are chosen: above the aggregate, on the side of the aggregate, and below the aggregate. After a series of treatments, the samples are scanned with a SEM-BSE detector. The resultant images were further processed using a digital image processing method (DIP) to obtain quantitative characteristics of the ITZ. The surface morphology is characterized at the pixel level based on the digital image. Thereafter, K-means clustering method is used to illustrate the effect of surface roughness on ITZ formation.

Determination of Aggregate Surface Morphology at the Interfacial Transition Zone ITZ

Hereby, we proposed a protocol to illustrate the effect of aggregate surface morphology on the ITZ microstructure. The SEM-BSE image were quantitatively analyzed to obtain ITZ's porosity gradient via digital image processing and a K-means clustering algorithm was further employed to establish a relationship between porosity gradient and surface roughness.

Here, we present a comprehensive method to illustrate the uneven distribution of the interfacial transition zone (ITZ) around the aggregate and the effect ...

High Throughput Analysis of Liquid Droplet Impacts

Experimental studies of liquid drop impacts on surfaces are often restricted in their scope due to the large range of possible experimental parameters such as material properties, impact conditions, and experimental configurations. Compounding this, drop impacts are often studied using data-rich high-speed photography, so that it is difficult to analyze many experiments in a detailed and timely manner. The purpose of this method is to enable efficient study of droplet impacts with high-speed photography by using a systematic approach. Equipment is aligned and calibrated to produce videos that can be accurately processed by a custom image processing code. Moreover, the file structure setup and workflow described here ensure efficiency and clear organization of data processing, which is carried out while the researcher is still in the lab. The image processing method extracts the digitized outline of the impacting droplet in each frame of the video, and processed data are stored for further analysis as required. The protocol assumes that a droplet is released vertically under gravity, and impact is recorded by a camera viewing from side-on with the drop illuminated using shadowgraphy. Many similar experiments involving image analysis of high-speed events could be addressed with minor adjustment to the protocol and equipment used.

This protocol enables efficient collection of experimental high-speed images of liquid drop impacts, and speedy analysis of those data in batches. To streamline these processes, the method describes how to calibrate and set up apparatus, generate an appropriate data structure, and deploy an image analysis script.

Experimental studies of liquid drop impacts on surfaces are often restricted in their scope due to the large range of possible experimental parameters ...