Name: experimental investigation of the flow structure over a delta wing via flow visualization methods
Uploaded: 2018-04-23T15:00:00
Description: Watch this Scientific Journal Video about Experimental Investigation of the Flow Structure over a Delta Wing Via Flow Visualization Methods at JoVE.com

The authors would like to thank Hong Kong Research Grants Council (no. GRF526913), Hong Kong Innovation and Technology Commission (no. ITS/334/15FP), and the US Office of Naval Research Global (no. N00014-16-1-2161) for financial support.

1. Wind Tunnel Setup
<ol>
	<li>Delta wing model
	<ol>
		<li>Construct a delta wing model from aluminum, with a sweep angle &#966; of 75&#176;, a chord length c of 280 mm, a root span b of 150 mm, and a thickness of 5 mm. Have both leading edges beveled at 35&#176; to fix the separation point17 (see Figure 1a).</li>
	</ol>
	</li>
	<li>Wind tunnel facility
	<ol>
		<li>Conduct experiments in a closed-loop low...

<ol>
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V. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Development+of+a+three-dimensional+free+shear+layer.">Development of a three-dimensional free shear layer.</a> J Fluid Mech. 369, 49-89 (1998).</li><li>Menke, M., Gursul, I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Unsteady+nature+of+leading+edge+vortices.">Unsteady nature of leading edge vortices.</a> Phys Fluids. 9 (10), 2960 (1997).</li><li>Yayla, S., Canpolat, C., Sahin, B., Akilli, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Yaw+angle+effect+on+flow+structure+over+the+nonslender+diamond+wing.">Yaw angle effect on flow structure over the nonslender diamond wing.</a> AIAA J. 48 (10), 2457-2461 (2010).</li><li>Menke, M., Gursul, I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Nonlinear+response+of+vortex+breakdown+over+a+pitching+delta+Wing.">Nonlinear response of vortex breakdown over a pitching delta Wing.</a> J Aircraft. 36 (3), 496-500 (1999).</li><li>Sahin, B., Yayla, S., Canpolat, C., Akilli, 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+structure+over+the+yawed+nonslender+diamond+wing.">Flow structure over the yawed nonslender diamond wing.</a> Aerosp Sci Technol. 23 (1), 108-119 (2012).</li><li>Kohlman, D. L., Wentz, J. W. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Vortex+breakdown+on+slender+sharp-edged+wings.">Vortex breakdown on slender sharp-edged wings.</a> J Aircraft. 8 (3), 156-161 (1971).</li><li>Lu, L., Sick, V. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=High-speed+Particle+Image+Velocimetry+Near+Surfaces.">High-speed Particle Image Velocimetry Near Surfaces.</a> J Vis Exp. (76), e50559 (2013).</li><li>Mitchell, A. M., Barberis, D., Molton, P., D&#233;lery, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Oscillation+of+Vortex+Breakdown+Location+and+Blowing+Control+of+Time-Averaged+Location.">Oscillation of Vortex Breakdown Location and Blowing Control of Time-Averaged Location.</a> AIAA J. 38 (5), 793-803 (2000).</li><li>Shen, L., Wen, C. -. y., Chen, 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=Asymmetric+Flow+Control+on+a+Delta+Wing+with+Dielectric+Barrier+Discharge+Actuators.">Asymmetric Flow Control on a Delta Wing with Dielectric Barrier Discharge Actuators.</a> AIAA J. 54 (2), 652-658 (2016).</li><li>Leibovich, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+Structure+of+Vortex+Breakdown.">The Structure of Vortex Breakdown.</a> Annu Rev Fluid Mech. 10 (1), 221-246 (1978).</li><li>Mitchell, A. M., Molton, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Vortical+Substructures+in+the+Shear+Layers+Forming+Leading-Edge+Vortices.">Vortical Substructures in the Shear Layers Forming Leading-Edge Vortices.</a> AIAA J. 40 (8), 1689-1692 (2002).</li><li>Gad-El-Hak, M., Blackwelder, R. F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+discrete+vortices+from+a+delta+wing.">The discrete vortices from a delta wing.</a> AIAA J. 23 (6), 961-962 (1985).</li><li>Zhou, J., Adrian, R. J., Balachandar, S., Kendall, T. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mechanisms+for+generating+coherent+packets+of+hairpin+vortices+in+channel+flow.">Mechanisms for generating coherent packets of hairpin vortices in channel flow.</a> J. Fluid Mech. 387, 353-396 (1999).</li><li>Adrian, R. J., Christensen, K. T., Liu, Z. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Analysis+and+interpretation+of+instantaneous+turbulent+velocity+fields.">Analysis and interpretation of instantaneous turbulent velocity fields.</a> Exp Fluids. 29 (3), 275-290 (2000).</li><li>Yoda, M., Hesselink, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+three-dimensional+visualization+technique+applied+to+flow+around+a+delta+wing.">A three-dimensional visualization technique applied to flow around a delta wing.</a> Exp. Fluids. 10 (2-3), (1990).</li><li>Greenwell, D. I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> RTO AVT Symposium. , (2001).</li><li>Furman, A., Breitsamter, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Turbulent+and+unsteady+flow+characteristics+of+delta+wing+vortex+systems.">Turbulent and unsteady flow characteristics of delta wing vortex systems.</a> Aerosp Sci Technol. 24 (1), 32-44 (2013).</li><li>Wang, C., Gao, Q., Wei, R., Li, T., Wang, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=3D+flow+visualization+and+tomographic+particle+image+velocimetry+for+vortex+breakdown+over+a+non-slender+delta+wing.">3D flow visualization and tomographic particle image velocimetry for vortex breakdown over a non-slender delta wing.</a> Exp Fluids. 57 (6), (2016).</li></ol>

This article presents the two flow visualization methods, improved smoke flow visualization and PIV measurement, to investigate flow structure over the delta wing qualitatively and quantitatively. The general procedures of the experiment are described step by step. The setups of these two methods are almost the same, while the devices involved are different. The basic principle of these two flow visualization methods is to illuminate the particles in the flow via the laser sheet. The improved smoke flow visualization can...

Flow field measurement via visualization techniques is a basic methodology in fluid engineering. Among the different visualization techniques, smoke wire flow visualization in wind tunnel experiments and dye visualization in water tunnel experiments are the most widely used to illustrate flow structures qualitatively. PIV and laser Doppler anemometry (LDA) are two typical quantitative techniques1.
In smoke wire flow visualization, smoke streaklines are generated from oil droplets on a heating wire or injected from the outer smoke generator/container during the experiments. High-power lights or laser sheets are used to illuminate the smoke streaklines. Images are then recorded for further analysis. This is a simple but very useful flow visualization method2. However, the effectiveness of this method may be limited by various factors, such as the short duration of smoke wires, the complex three-dimensional flow field, the relatively high velocity of the flow, and the efficiency of smoke generation3.
In PIV measurements, a cross-section of a flow field with entrained particles is illuminated by a laser sheet, and instant positions of the particles in this cross-section are captured by a high-speed camera. Within an extremely small time interval, a pair of images is recorded. By dividing the images into a grid of interrogation areas and calculating the average motion of particles in interrogation areas through cross-correlation functions, the instantaneous velocity vector map in this observed cross-section can be obtained. However, it is also known that compromises must be reached for factors including the size of the observation window, the resolution of the velocity map, the velocity magnitude in the plane, the time interval between the pair of images, the orthogonal velocity magnitude, and the particle density4. Therefore, many exploratory experiments may be needed to optimize the experimental settings. It would be expensive and time-consuming to investigate an unknown and complex flow field with PIV measurement alone5,6. Considering the above concerns, a strategy to combine smoke flow visualization and PIV measurement is proposed and demonstrated here to study the complex flow over a slender delta wing.
Numerous studies of LEV flows over delta wings have been conducted7,8, with flow visualization techniques used as the primary tools. Many interesting flow phenomena have been observed: spiral type and bubble type vortex breakdowns9,10, an unsteady shear layer substructure11,12, oscillations of LEV breakdown locations13, and effects of pitching and yaw angles14,15,16 on the flow structures. However, the underlying mechanisms of some unsteady phenomena in the delta wing flows remain unclear7. In this work, the smoke flow visualization is improved using the same seeding particles used in PIV measurement, instead of a smoke wire. This improvement greatly simplifies the operation of the visualization and increases the quality of the images. Based on the results from the improved smoke flow visualization, PIV measurement focuses on those flow fields of interest to acquire the quantitative information.
Here, a detailed description is provided to explain how to conduct a flow visualization experiment in a wind tunnel and to investigate unsteady flow phenomena over a delta wing. Two visualization methods, the improved smoke flow visualization and PIV measurement, are used together in this experiment. The procedure includes step-by-step guidance for device setup and parameter adjustment. Typical results are demonstrated to show the advantage of combining these two methods for measuring the complex flow field spatially and temporally.

<table>
	<tbody>
		<tr>
			<td>532 nm Nd:YAG laser</td>
			<td>Quantel Laser</td>
			<td>Evergreen 600mJ</td>
			<td></td>
		</tr>
		<tr>
			<td>High speed camera</td>
			<td>Dantec Dynamic</td>
			<td>HiSense 4M</td>
			<td></td>
		</tr>
		<tr>
			<td>camera lens</td>
			<td>Tamron</td>
			<td>SP AF180mm F/3.5 Di</td>
			<td></td>
		</tr>
		<tr>
			<td>PIV recording and processing software</td>
			<td>Dantec Dynamic</td>
			<td>DynamicStudio</td>
			<td></td>
		</tr>
		<tr>
			<td>cylindrical lens</td>
			<td>Newport</td>
			<td></td>
			<td>&#934;=12 mm</td>
		</tr>
		<tr>
			<td>convex lens</td>
			<td>Newport</td>
			<td></td>
			<td>f=700 mm</td>
		</tr>
		<tr>
			<td>neutral density filter</td>
			<td>Newport</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Calibration target</td>
			<td></td>
			<td></td>
			<td>custom made</td>
		</tr>
		<tr>
			<td>aerosol generator</td>
			<td>TSI</td>
			<td>TSI 9307-6</td>
			<td></td>
		</tr>
		<tr>
			<td>PULSE GENERATOR</td>
			<td>Berkeley Nucleonics Corp</td>
			<td>BNC 575</td>
			<td></td>
		</tr>
		<tr>
			<td>continuous laser</td>
			<td></td>
			<td>APGL-FN-532-1W</td>
			<td></td>
		</tr>
		<tr>
			<td>Digital camera</td>
			<td>Nikon</td>
			<td>Nikon D5200</td>
			<td></td>
		</tr>
		<tr>
			<td>Image processing</td>
			<td>Matlab</td>
			<td></td>
			<td>custom code</td>
		</tr>
		<tr>
			<td>wind tunnel support</td>
			<td></td>
			<td></td>
			<td>custom made</td>
		</tr>
		<tr>
			<td>laser level</td>
			<td>BOSCH</td>
			<td>GLL3-15X</td>
			<td></td>
		</tr>
		<tr>
			<td>angle meter</td>
			<td>BOSCH</td>
			<td>GAM220</td>
			<td></td>
		</tr>
	</tbody>
</table>

experimental investigation of the flow structure over a delta wing via flow visualization methods

It is well known that the flow field over a delta wing is dominated by a pair of counter rotating leading edge vortices (LEV). However, their mechanism is not well understood. The flow visualization technique is a promising non-intrusive method to illustrate the complex flow field spatially and temporally. A basic flow visualization setup consists of a high-powered laser and optic lenses to generate the laser sheet, a camera, a tracer particle generator, and a data processor. The wind tunnel setup, the specifications of devices involved, and the corresponding parameter settings are dependent on the flow features to be obtained.
Normal smoke wire flow visualization uses a smoke wire to demonstrate the flow streaklines. However, the performance of this method is limited by poor spatial resolution when it is conducted in a complex flow field. Therefore, an improved smoke flow visualization technique has been developed. This technique illustrates the large-scale global LEV flow field and the small-scale shear layer flow structure at the same time, providing a valuable reference for later detailed particle image velocimetry (PIV) measurement.
In this paper, the application of the improved smoke flow visualization and PIV measurement to study the unsteady flow phenomena over a delta wing is demonstrated. The procedure and cautions for conducting the experiment are listed, including wind tunnel setup, data acquisition, and data processing. The representative results show that these two flow visualization methods are effective techniques for investigating the three-dimensional flow field qualitatively and quantitatively.

Figure 2d shows the time histories of the LEV breakdown locations. The black curve indicates the portside LEV and the red curve indicates the starboard LEV. The time scale is nondimensionalized by the free stream velocity and chord length. The correlation coefficient between these two time histories is r = &#8722;0.53, indicating a strong anti-symmetric interaction of the LEV breakdown location oscillations. This result agrees well with the work of o...

Watch this Scientific Journal Video about Experimental Investigation of the Flow Structure over a Delta Wing Via Flow Visualization Methods at JoVE.com

Experimental Investigation of the Flow Structure over a Delta Wing Via Flow Visualization Methods

Here, we present a protocol to observe unsteady vortical flows over a delta wing using a modified smoke flow visualization technique and investigate the mechanism responsible for the oscillations of the leading-edge vortex breakdown locations.

It is well known that the flow field over a delta wing is dominated by a pair of counter rotating leading edge vortices (LEV). However, their mechanism is ...

The overall goal of this experiment is to observe unsteady vortical flows over a delta wing using visualization techniques and investigate the mechanism responsible for the oscillations of the leading edge vortex breakdown locations. This method can help answer key questions of the unsteady flow phenomenon of a cylinder delta wing, such as the oscillation of the leading edge of vertex breakdown location. The main advantage of this technique is that large scale global leading edge vortex flow field and the small scale cellular substructures can be illustrated simultaneously.Start with the model for the experiment. For this experiment, the model is an aluminum delta wing 280 millimeters long. Take the model to mount in the wind tunnel, which is closed-loop and low speed.Its test section has glass walls to allow optical access for the experiment. Here, the delta wing has been properly mounted in the wind tunnel. Two lasers can illuminate the flow structures, a dual-pulse 532 nanometer laser during particle image velocimetry or a continuous-wave 532 nanometer laser during smoke flow visualization.This schematic provides information on the optical setup with the continuous laser. A convex lens controls the laser beam size. A cylindrical lens expands the beam to a sheet.A mirror reflects the laser sheet into the wind tunnel. Wear appropriate laser goggles and begin with the continuous laser. For safety, reduce the beam transmittance with a neutral density filter.Begin with only the laser, filter, and mirror in place. Adjust the mirror to introduce the beam into the wind tunnel. Ensure the beam intersects the model at about 1/4 of the model's length behind its front.Next, install the convex lens and the cylindrical lens. Then, at the model, measure the laser line that intersects it to check the laser sheet thickness. Adjust the convex lens as necessary.Stop the adjustments when the desired thickness is obtained. Place a calibration target plate on the delta wing with its surface coincident to the laser sheet. With the laser off, move on to set up the camera.Use a commercial digital camera for smoke flow visualization and operate it manually. Place the camera to obtain the desired field of view and focus it on the calibration target plate. When the camera is ready, take several frames for calibration purposes.Then, remove the calibration target plate. Turn on the wind tunnel at a low speed, and inject oil particles to uniformly seat it. To visualize smoke flow, turn on the wind tunnel to the desired velocity.Next, turn on the continuous laser without a filter. At the camera, capture five to 10 snapshots of the flow structure. Use the images to check that the laser sheet is at the longitudinal cross-section of the leading edge vortices core.This example image shows a clear vortex core and substructures, indicating a well-positioned laser sheet. Adjust the camera settings as needed for image quality, and record images and video. When done, shut off the airflow and approach the model.There, mark the position of the laser sheet as a reference for later measurements. Finish by turning off the laser and transferring the data to the computer. This measurement requires a different laser.Replace the continuous laser with the pulsed laser. With the laser on, check its path, and if necessary, adjust the convex lens. Ensure the beam intersects the model along the line marking the position of the continuous laser.Also, replace the digital camera. In its place, substitute a high-speed CCD camera. Control the camera with the synchronizer and the dual-pulse laser.Now, go to the model and identify a region where structures can be observed. Once again, place a calibration target plate on the wing in that region. Focus on the calibration plate and take several photos.Remove the calibration plate before continuing. Start the PIV software and set the parameters. Start the wind tunnel flow at the desired velocity.Adjust the laser to its highest power level. Use the software to start data acquisition for 100 seconds. If the acquired images are acceptable, save them and continue by running other cases.This is a processed image of the longitudinal cross-section from smoke flow visualization. There is a 10 millimeter scale for reference. The image reveals the primary leading edge vortex core, the rolling-up shear layer with vortical substructures, the vortex breakdown, and the turbulent wake.This video show the oscillations of the leading edge vortex breakdown locations in the transfer's cross-sections. Analysis of the measured breakdown locations for each instant indicates a strong antisymmetric interaction. This is a time-averaged particle image velocimetry result showing the dimensionless vorticity in the longitudinal cross-section.The primary vortex core can be identified by the inflection line of the positive and negative vorticity, marked by the black dotted line. Solid lines encircle regions with the local swirling strength lower than zero, indicating shear layer vortices. Additional substructure are encircled by white dotted lines.This time-averaged particle image velocimetry vorticity result is at the span-wise cross-section. The flow separates from the leading edge, forms a shear layer, and rolls into the vortex core on either side of the wing. There are stationary vortical substructures inside the shear layers.Once mastered, this technique can be done in one hour if it performed appropriate. After watching this video, you should have a good understanding of how to observe the unsteady flow phenomenon of a cylinder delta wing using the above-mentioned flow visualization techniques. Don't forget that working with lasers can be extremely hazardous, and precautions such as wearing laser protection goggles should always be taken while performing each experiment.

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Determining 3D Flow Fields via Multi-camera Light Field Imaging

In the field of fluid mechanics, the resolution of computational schemes has outpaced experimental methods and widened the gap between predicted and observed phenomena in fluid flows. Thus, a need exists for an accessible method capable of resolving three-dimensional (3D) data sets for a range of problems. We present a novel technique for performing quantitative 3D imaging of many types of flow fields. The 3D technique enables investigation of complicated velocity fields and bubbly flows. Measurements of these types present a variety of challenges to the instrument. For instance, optically dense bubbly multiphase flows cannot be readily imaged by traditional, non-invasive flow measurement techniques due to the bubbles occluding optical access to the interior regions of the volume of interest. By using Light Field Imaging we are able to reparameterize images captured by an array of cameras to reconstruct a 3D volumetric map for every time instance, despite partial occlusions in the volume. The technique makes use of an algorithm known as synthetic aperture (SA) refocusing, whereby a 3D focal stack is generated by combining images from several cameras post-capture 1. Light Field Imaging allows for the capture of angular as well as spatial information about the light rays, and hence enables 3D scene reconstruction. Quantitative information can then be extracted from the 3D reconstructions using a variety of processing algorithms. In particular, we have developed measurement methods based on Light Field Imaging for performing 3D particle image velocimetry (PIV), extracting bubbles in a 3D field and tracking the boundary of a flickering flame. We present the fundamentals of the Light Field Imaging methodology in the context of our setup for performing 3DPIV of the airflow passing over a set of synthetic vocal folds, and show representative results from application of the technique to a bubble-entraining plunging jet.

A technique for performing quantitative three-dimensional (3D) imaging for a range of fluid flows is presented. Using concepts from the area of Light Field Imaging, we reconstruct 3D volumes from arrays of images. Our 3D results span a broad range including velocity fields and multi-phase bubble size distributions.

In the field of fluid mechanics, the resolution of computational schemes has outpaced experimental methods and widened the gap between predicted and ...

Fabrication, Operation and Flow Visualization in Surface-acoustic-wave-driven Acoustic-counterflow Microfluidics

Surface acoustic waves (SAWs) can be used to drive liquids in portable microfluidic chips via the acoustic counterflow phenomenon. In this video we present the fabrication protocol for a multilayered SAW acoustic counterflow device. The device is fabricated starting from a lithium niobate (LN) substrate onto which two interdigital transducers (IDTs) and appropriate markers are patterned. A polydimethylsiloxane (PDMS) channel cast on an SU8 master mold is finally bonded on the patterned substrate. Following the fabrication procedure, we show the techniques that allow the characterization and operation of the acoustic counterflow device in order to pump fluids through the PDMS channel grid. We finally present the procedure to visualize liquid flow in the channels. The protocol is used to show on-chip fluid pumping under different flow regimes such as laminar flow and more complicated dynamics characterized by vortices and particle accumulation domains.

In this video we first describe fabrication and operation procedures of a surface acoustic wave (SAW) acoustic counterflow device. We then demonstrate an experimental setup that allows for both qualitative flow visualization and quantitative analysis of complex flows within the SAW pumping device.

Surface acoustic waves (SAWs) can be used to drive liquids in portable microfluidic chips via the acoustic counterflow phenomenon. In this video we ...

Measuring Material Microstructure Under Flow Using 1-2 Plane Flow-Small Angle Neutron Scattering

A new small-angle neutron scattering (SANS) sample environment optimized for studying the microstructure of complex fluids under simple shear flow is presented. The SANS shear cell consists of a concentric cylinder Couette geometry that is sealed and rotating about a horizontal axis so that the vorticity direction of the flow field is aligned with the neutron beam enabling scattering from the 1-2 plane of shear (velocity-velocity gradient, respectively). This approach is an advance over previous shear cell sample environments as there is a strong coupling between the bulk rheology and microstructural features in the 1-2 plane of shear. Flow-instabilities, such as shear banding, can also be studied by spatially resolved measurements. This is accomplished in this sample environment by using a narrow aperture for the neutron beam and scanning along the velocity gradient direction. Time resolved experiments, such as flow start-ups and large amplitude oscillatory shear flow are also possible by synchronization of the shear motion and time-resolved detection of scattered neutrons. Representative results using the methods outlined here demonstrate the useful nature of spatial resolution for measuring the microstructure of a wormlike micelle solution that exhibits shear banding, a phenomenon that can only be investigated by resolving the structure along the velocity gradient direction. Finally, potential improvements to the current design are discussed along with suggestions for supplementary experiments as motivation for future experiments on a broad range of complex fluids in a variety of shear motions.

A shear cell is developed for small-angle neutron scattering measurements in the velocity-velocity gradient plane of shear and is used to characterize complex fluids. Spatially resolved measurements in the velocity gradient direction are possible for studying shear-banding materials. Applications include investigations of colloidal dispersions, polymer solutions, and self-assembled structures.

A new small-angle neutron scattering (SANS) sample environment optimized for studying the microstructure of complex fluids under simple shear flow is ...

Advanced Experimental Methods for Low-temperature Magnetotransport Measurement of Novel Materials

Novel electronic materials are often produced for the first time by synthesis processes that yield bulk crystals (in contrast to single crystal thin film synthesis) for the purpose of exploratory materials research. Certain materials pose a challenge wherein the traditional bulk Hall bar device fabrication method is insufficient to produce a measureable device for sample transport measurement, principally because the single crystal size is too small to attach wire leads to the sample in a Hall bar configuration. This can be, for example, because the first batch of a new material synthesized yields very small single crystals or because flakes of samples of one to very few monolayers are desired. In order to enable rapid characterization of materials that may be carried out in parallel with improvements to their growth methodology, a method of device fabrication for very small samples has been devised to permit the characterization of novel materials as soon as a preliminary batch has been produced. A slight variation of this methodology is applicable to producing devices using exfoliated samples of two-dimensional materials such as graphene, hexagonal boron nitride (hBN), and transition metal dichalcogenides (TMDs), as well as multilayer heterostructures of such materials. Here we present detailed protocols for the experimental device fabrication of fragments and flakes of novel materials with micron-sized dimensions onto substrate and subsequent measurement in a commercial superconducting magnet, dry helium close-cycle cryostat magnetotransport system at temperatures down to 0.300 K and magnetic fields up to 12 T.

We describe the methodology of mechanical exfoliation and deposition of flakes of novel materials with micron-sized dimensions onto substrate, fabrication of experimental device structures for transport experimentation, and the magnetotransport measurement in a dry helium close-cycle cryostat at temperatures down to 0.300 K and magnetic fields up to 12 T.

Novel electronic materials are often produced for the first time by synthesis processes that yield bulk crystals (in contrast to single crystal thin film ...

Experimental Methods for Investigation of Shape Memory Based Elastocaloric Cooling Processes and Model Validation

Shape Memory Alloys (SMA) using elastocaloric cooling processes have the potential to be an environmentally friendly alternative to the conventional vapor compression based cooling process. Nickel-Titanium (Ni-Ti) based alloy systems, especially, show large elastocaloric effects. Furthermore, exhibit large latent heats which is a necessary material property for the development of an efficient solid-state based cooling process. A scientific test rig has been designed to investigate these processes and the elastocaloric effects in SMAs. The realized test rig enables independent control of an SMA&#39;s mechanical loading and unloading cycles, as well as conductive heat transfer between SMA cooling elements and a heat source/sink. The test rig is equipped with a comprehensive monitoring system capable of synchronized measurements of mechanical and thermal parameters. In addition to determining the process-dependent mechanical work, the system also enables measurement of thermal caloric aspects of the elastocaloric cooling effect through use of a high-performance infrared camera. This combination is of particular interest, because it allows illustrations of localization and rate effects &#8212; both important for efficient heat transfer from the medium to be cooled.
The work presented describes an experimental method to identify elastocaloric material properties in different materials and sample geometries. Furthermore, the test rig is used to investigate different cooling process variations. The introduced analysis methods enable a differentiated consideration of material, process and related boundary condition influences on the process efficiency. The comparison of the experimental data with the simulation results (of a thermomechanically coupled finite element model) allows for better understanding of the underlying physics of the elastocaloric effect. In addition, the experimental results, as well as the findings based on the simulation results, are used to improve the material properties.

Experimental methods for investigation of solid state cooling processes and characterization of elastocaloric material properties of Shape Memory Alloys (SMA) are presented. A custom-built test rig has been designed for controlling and comprehensive monitoring of elastocaloric cooling processes. Furthermore, it provides a validation platform for thermomechanically coupled modeling approaches.

Shape Memory Alloys (SMA) using elastocaloric cooling processes have the potential to be an environmentally friendly alternative to the conventional vapor ...

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 ...

Design and Use of a Full Flow Sampling System (FFS) for the Quantification of Methane Emissions

The use of natural gas continues to grow with increased discovery and production of unconventional shale resources. At the same time, the natural gas industry faces continued scrutiny for methane emissions from across the supply chain, due to methane&#39;s relatively high global warming potential (25-84x that of carbon dioxide, according to the Energy Information Administration). Currently, a variety of techniques of varied uncertainties exists to measure or estimate methane emissions from components or facilities. Currently, only one commercial system is available for quantification of component level emissions and recent reports have highlighted its weaknesses.
In order to improve accuracy and increase measurement flexibility, we have designed, developed, and implemented a novel full flow sampling system (FFS) for quantification of methane emissions and greenhouse gases based on transportation emissions measurement principles. The FFS is a modular system that consists of an explosive-proof blower(s), mass airflow sensor(s) (MAF), thermocouple, sample probe, constant volume sampling pump, laser based greenhouse gas sensor, data acquisition device, and analysis software. Dependent upon the blower and hose configuration employed, the current FFS is able to achieve a flow rate ranging from 40 to 1,500 standard cubic feet per minute (SCFM). Utilization of laser-based sensors mitigates interference from higher hydrocarbons (C2+). Co-measurement of water vapor allows for humidity correction. The system is portable, with multiple configurations for a variety of applications ranging from being carried by a person to being mounted in a hand drawn cart, on-road vehicle bed, or from the bed of utility terrain vehicles (UTVs). The FFS is able to quantify methane emission rates with a relative uncertainty of &#177; 4.4%. The FFS has proven, real world operation for the quantification of methane emissions occurring in conventional and remote facilities.

Design and Use of a Full Flow Sampling System FFS for the Quantification of Methane Emissions

We have designed, developed, and implemented a novel full flow sampling system (FFS) for quantification of methane emissions and greenhouse gases from across the natural gas supply chain.

The use of natural gas continues to grow with increased discovery and production of unconventional shale resources. At the same time, the natural gas ...

Microfluidic Imaging Flow Cytometry by Asymmetric-detection Time-stretch Optical Microscopy (ATOM)

Scaling the number of measurable parameters, which allows for multidimensional data analysis and thus higher-confidence statistical results, has been the main trend in the advanced development of flow cytometry. Notably, adding high-resolution imaging capabilities allows for the complex morphological analysis of cellular/sub-cellular structures. This is not possible with standard flow cytometers. However, it is valuable for advancing our knowledge of cellular functions and can benefit life science research, clinical diagnostics, and environmental monitoring. Incorporating imaging capabilities into flow cytometry compromises the assay throughput, primarily due to the limitations on speed and sensitivity in the camera technologies. To overcome this speed or throughput challenge facing imaging flow cytometry while preserving the image quality, asymmetric-detection time-stretch optical microscopy (ATOM) has been demonstrated to enable high-contrast, single-cell imaging with sub-cellular resolution, at an imaging throughput as high as 100,000 cells/s. Based on the imaging concept of conventional time-stretch imaging, which relies on all-optical image encoding and retrieval through the use of ultrafast broadband laser pulses, ATOM further advances imaging performance by enhancing the image contrast of unlabeled/unstained cells. This is achieved by accessing the phase-gradient information of the cells, which is spectrally encoded into single-shot broadband pulses. Hence, ATOM is particularly advantageous in high-throughput measurements of single-cell morphology and texture &#8211; information indicative of cell types, states, and even functions. Ultimately, this could become a powerful imaging flow cytometry platform for the biophysical phenotyping of cells, complementing the current state-of-the-art biochemical-marker-based cellular assay. This work describes a protocol to establish the key modules of an ATOM system (from optical frontend to data processing and visualization backend), as well as the workflow of imaging flow cytometry based on ATOM, using human cells and micro-algae as the examples.

Microfluidic Imaging Flow Cytometry by Asymmetric-detection Time-stretch Optical Microscopy ATOM

This protocol describes the implementation of an asymmetric-detection time-stretch optical microscopy system for single-cell imaging in ultrafast microfluidic flow and its applications in imaging flow cytometry.

Scaling the number of measurable parameters, which allows for multidimensional data analysis and thus higher-confidence statistical results, has been the ...

Experimental Methods for Trapping Ions Using Microfabricated Surface Ion Traps

Ions trapped in a quadrupole Paul trap have been considered one of the strong physical candidates to implement quantum information processing. This is due to their long coherence time and their capability to manipulate and detect individual quantum bits (qubits). In more recent years, microfabricated surface ion traps have received more attention for large-scale integrated qubit platforms. This paper presents a microfabrication methodology for ion traps using micro-electro-mechanical system (MEMS) technology, including the fabrication method for a 14 &#181;m-thick dielectric layer and metal overhang structures atop the dielectric layer. In addition, an experimental procedure for trapping ytterbium (Yb) ions of isotope 174 (174Yb+) using 369.5 nm, 399 nm, and 935 nm diode lasers is described. These methodologies and procedures involve many scientific and engineering disciplines, and this paper first presents the detailed experimental procedures. The methods discussed in this paper can easily be extended to the trapping of Yb ions of isotope 171 (171Yb+) and to the manipulation of qubits.

This paper presents a microfabrication methodology for surface ion traps, as well as a detailed experimental procedure for trapping ytterbium ions in a room-temperature environment.

Ions trapped in a quadrupole Paul trap have been considered one of the strong physical candidates to implement quantum information processing. This is due ...

Flow-assisted Dielectrophoresis: A Low Cost Method for the Fabrication of High Performance Solution-processable Nanowire Devices

Flow-assisted dielectrophoresis (DEP) is an efficient self-assembly method for the controllable and reproducible positioning, alignment, and selection of nanowires. DEP is used for nanowire analysis, characterization, and for solution-based fabrication of semiconducting devices. The method works by applying an alternating electric field between metallic electrodes. The nanowire formulation is then dropped onto the electrodes which are on an inclined surface to create a flow of the formulation using gravity. The nanowires then align along the gradient of the electric field and in the direction of the liquid flow. The frequency of the field can be adjusted to select nanowires with superior conductivity and lower trap density. 
In this work, flow-assisted DEP is used to create nanowire field effect transistors. Flow-assisted DEP has several advantages: it allows selection of nanowire electrical properties; control of nanowire length; placement of nanowires in specific areas; control of orientation of nanowires; and control of nanowire density in the device. 
The technique can be expanded to many other applications such as gas sensors and microwave switches. The technique is efficient, quick, reproducible, and it uses a minimal amount of dilute solution making it ideal for the testing of novel nanomaterials. Wafer scale assembly of nanowire devices can also be achieved using this technique, allowing large numbers of samples for testing and large-area electronic applications.

In this paper, flow assisted dielectrophoresis is demonstrated for the self-assembly of nanowire devices. The fabrication of a silicon nanowire field effect transistor is shown as an example.

Flow-assisted dielectrophoresis (DEP) is an efficient self-assembly method for the controllable and reproducible positioning, alignment, and selection of ...