Mark P. Wernet and Adam C. Wroblewski

Glenn Research Center, Cleveland, Ohio

Randy J. Locke

Vantage Partners, LLC, Brook Park, Ohio

A Dual-Plane PIV Study of Turbulent Heat Transfer Flows

NASA/TM—2016-219074

March 2016
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Mark P. Wernet and Adam C. Wroblewski

Glenn Research Center, Cleveland, Ohio

Randy J. Locke

Vantage Partners, LLC, Brook Park, Ohio

A Dual-Plane PIV Study of Turbulent Heat Transfer Flows

NASA/TM—2016-219074

March 2016

National Aeronautics and

Space Administration

Glenn Research Center

Cleveland, Ohio 44135
Acknowledgments

The authors would like to thank Doug Thurman and Phil Poinsatte for the use of their facility and their support in operating the 

thin fi lm cooling tunnel. We would also like to thank Garrett Clayo for his assistance in setting up and installing the Dual-Plane 

PIV system in the thin fi lm cooling rig.

Available from

This work was sponsored by the Fundamental Aeronautics Program 

at the NASA Glenn Research Center.

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This report is available in electronic form at http://www.sti.nasa.gov/ and http://ntrs.nasa.gov/
NASA/TM—2016-219074 1 

A Dual-Plane PIV Study of Turbulent Heat Transfer Flows 

Mark P. Wernet and Adam C. Wroblewski 

National Aerospace Space Administration 

Glenn Research Center 

Cleveland, Ohio 44135

Randy J. Locke 

Vantage Partners, LLC 

Brook Park, Ohio 44142 

Abstract 

Thin film cooling is a widely used technique in turbomachinery and rocket propulsion applications, 

where cool injection air protects a surface from hot combustion gases. The injected air typically has a 

different velocity and temperature from the free stream combustion flow, yielding a flow field with high 

turbulence and large temperature differences. These thin film cooling flows provide a good test case for 

evaluating computational model prediction capabilities. The goal of this work is to provide a database of 

flow field measurements for validating computational flow prediction models applied to turbulent heat 

transfer flows. In this work we describe the application of a Dual-Plane Particle Image Velocimetry (PIV) 

technique in a thin film cooling wind tunnel facility where the injection air stream velocity and 

temperatures are varied in order to provide benchmark turbulent heat transfer flow field measurements. 

The Dual-Plane PIV data collected include all three components of velocity and all three components of 

vorticity, spanning the width of the tunnel at multiple axial measurement planes. 

Introduction 

Thin film cooling is an important phenomena used in many aspects of turbomachinery and in rocket 

propulsion (Refs. 1 and 2). The applications range from cooling turbine blades to cooling combustor liners. 

In all of these applications, a thin barrier of cool air is used to protect the underlying metal surfaces from the 

hot combustion gases in the freestream flow. These cooling films are typically generated by using a series of 

perforated holes in the substrate through which the cooling air is injected into the flow. The cooling air can 

be considered jets in cross flow and these jets interact with one another to make up the thin film. The 

turbulent momentum and heat transfer occurring in these flows is complex and difficult to accurately model 

using computation fluid dynamics. 

NASA is interested in acquiring benchmark data on thin film cooling flows for use by computational 

fluid dynamics code developers for assessment of their turbulence models in these complex turbulent flow 

fields involving heat transfer. Both the mean flow and turbulence statistics are required for this assessment. 

While such data exist for unheated cases and simple geometries, there is a lack of sufficient data for flows 

where thermal mixing and/or heat transfer are the key flow phenomena. This is a multi-facetted project 

where temperature and velocity fields are to be measured. Here we only discuss the flow measurement 

aspect using Particle Imaging Velocimetry (PIV). 

A small scale wind tunnel specifically designed for studying thin film cooling was used in this work 

(Refs. 3 and 4). Traditionally, probe type surveys were used to characterize the tunnel flow. However, in this 

study, to eliminate interferences caused by the insertion of the probe body, the non-intrusive PIV technique 

was used. Instead of the more traditional PIV, the Dual-Plane PIV technique is employed in order to obtain 

all three components of velocity and all three components of vorticity at different cross-stream planes with 

respect to the main flow direction (Refs. 5 and 6). Results from the processed Dual-Plane PIV data are 

presented for two different thin film cooling models at different flow conditions and different temperatures 

of the injected air stream. This document serves as an overview guide to researchers interested in using these 

flow measurements to validate Computation Fluid Dynamics (CFD) code predictions. 
NASA/TM—2016-219074 2 

Approach 

Particle Image Velocimetry is a widely used tool across a broad range of engineering disciplines. 

Here at NASA GRC, we have used PIV over the past 20 years in a wide range of applications including 

axial and centrifugal compressors, pulse detonation engines, supersonic parachute flows, jet plume/shock 

interactions, aeroacoustics, launch abort systems testing, mechanical heart valves, chicken embryo blood 

flow and microgravity flows. The CFD modelers are interested in as many properties of the flow field as 

can be measured in order to assess the fidelity of their computer model predictions and the underlying 

turbulence models. While we have previously applied Stereo PIV in thin film cooling flows (Ref. 7) 

(see acknowledgements in Ref. 7), for this application we chose to implement a more rigorous Dual-Plane 

PIV technique. In addition to all three velocity components across a plane, Dual-Plane PIV also provides 

all three components of the vorticity and all 9 elements of the Reynolds Stress Tensor, key flow quantities 

of interest to CFD modelers. As a computational fluid dynamics benchmark data set, we are not interested 

purely in thin film cooling—but actually more interested in the turbulent behavior generated by injected 

cooling flow. We modified the operating conditions of the rig to provide the maximum temperature 

differences to provide a good CFD modelling challenge. Both a single hole and three hole floor plate 

models were tested in order to provide single isolated jet flow and also to provide an interacting jet flow. 

Thin Film Cooling Rig 

As stated earlier, a small scale wind tunnel facility with a temperature controlled coolant loop was 

used to simulate the complex, highly three-dimensional flow field anticipated in thin film cooling flows 

(Ref. 3). The test section is specifically designed to be reconfigurable, accepting various floor plate and 

injection port arrangements. Two interchangeable, 30x scale air injection hole plates were used in this 

work: a three hole configuration to study interacting jets and a single hole configuration which is a more 

fundamental case since the jet is isolated in the center of the tunnel and has no interaction with adjacent 

injection plumes. The tunnel consists of an aluminum bellmouth, flow conditioning screens, and an 

acrylic test section, illustrated in Figure 1. For the PIV test, the side walls of the tunnel were fitted from 

floor to ceiling with 3 mm thick glass windows in order to provide optical access for the PIV system and 

transmission of the high pulse energy laser sheets. 

Figure 1.—Rendering of SW-6 facility showing the flow seeding mixing manifold 

below the tunnel test section and the 3-hole floor insert. 

 
NASA/TM—2016-219074 3 

Figure 2.—Side view of the injection tube floor insert geometry with a CFD 

representation of the injection plume flow. 

The two model test configurations were achieved by using a flat plate insert in the tunnel floor. A side 

view of the floor plate geometry for the test is shown in Figure 2. The air injection floor inserts were 

made out of ABS plastic using a 3D printer. The air injection holes on the 3-hole plate were inclined at 

30 relative to the x-axis and had a z-axis hole diameter of D = 19 mm and a spacing of z/D = 3. Due to 

the oblique incidence, the elongated diameter of the hole along the flow direction (x-axis) was 38 mm. 

Perspective views of the tunnel floor plates are provided in the data results plots of Figures 5 and 9. The 

single hole floor plate had a hole diameter of 19 by 38 mm which was centered in the plate. In order to 

determine the tunnel flow rate, a total pressure probe was placed upstream of the test section and static 

pressure taps were placed on the sidewalls. Freestream temperature was measured with an open-ball 

thermocouple located upstream of the holes near the total pressure probe. Coolant temperature was 

measured with open-ball thermocouples inside the coolant tubes. 

The blowing ratio (BR) is the ratio of coolant mass flow rate per unit area to freestream mass flow 

rate per unit area. The density ratio (DR) is the ratio of coolant to freestream density computed using 

absolute temperatures. Airflow in the tunnel is provided by facility altitude exhaust. Setting the vacuum 

pressure at the diffuser of the tunnel sets the tunnel operating point. Air is drawn from the room and 

passing through flow conditioning sections prior to entering the test section. The freestream velocity was 

9.1 m/s and the Reynolds number based on freestream velocity and coolant hole diameter was 11,000. 

The test section is a square cross-section measuring 20.720.7 cm and a total length of 1.2 m. 

In normal operating mode, coolant flow is provided by blowing pressurized air through a heat 

exchanger, consisting of a copper tube coiled inside an ice–water tank. The coolant is then fed through a 

manifold to three separate flow meters, and then into acrylic tubes with L/D = 20 which are connected to 

each cooling hole in the floor of the tunnel. However, for the CFD modelling effort reported here, we 

were interested in the largest T that could be obtained. So instead of cooling the injection air, it was 

heated using two 750W in-line electrical pipe heaters. With that in mind, we shall refer to the coolant 

flow as the injection air flow. The injection air was heated to approximately 62 C, providing a 

T = 41 C above the ambient air temperature in the tunnel. When operating with the single hole floor 

plate, the outside two tubes from the manifold were capped and all of the injected flow entered the tunnel 

through the center injection tube hole. The resulting density ratio was nominally 1 for unheated air and 

0.3 for the heated injection air cases. The tunnel was operated at blowing ratios of 1 and 2. 

 

x 

y 
NASA/TM—2016-219074 4 

Dual-Plane PIV Technique 

Stereo PIV is capable of providing all three components of velocity across the illuminated 

measurement plane. In order to maximize the information extracted from the turbulent heat transfer flow, 

we decided to implement the Dual-Plane PIV technique (Refs. 5 and 6). The Dual-Plane PIV technique 

consists of two stereo PIV systems that are focused on two separate, parallel light sheet planes which are 

closely spaced in the flow. Two dual-head, pulsed PIV type lasers with properly polarized beams are 

required in order to provide the requisite parallel plane illumination. 

Polarization separation is used to isolate scattered light from the two stereo PIV systems since the 

1st and 2nd exposures for both stereo PIV systems are occurring simultaneously. The light from the two 

different dual head laser systems are orthogonally polarized and then combined using a beam combiner 

module as shown in Figure 3. The Nd:YAG lasers used in this work produced vertically polarized beams 

with pulse energies of 200 mJ at a 10 Hz repetition rate. Laser system #2 used a half wave plate (/2) to 

rotate the polarization of both laser pulses into s-polarized light (horizontally polarized). The s-polarized 

light from laser #2 passes straight through the thin film polarizer (TFP) in the beam combiner. The 

p-polarized light from laser #1 reflects off of the TFP at Brewster’s angle. A slight angular misalignment 

between the s- and p-polarized beams is required in order to obtain two closely spaced, parallel light 

sheets in the tunnel test section. The laser beams pass through cylindrical and spherical lenses to yield a 

pair of 1 mm thick light sheets that are parallel and spaced 1 mm apart in the tunnel test section. The light 

sheets exit the tunnel through the window in the back wall and are directed into a beam dump in order to 

minimize flare light. 

Figure 3.—Schematic layout of laser sheet polarization, beam combining module and Dual-Plane PIV 

system. Both lasers output at 532 nm. The purple colored, dashed laser beam is used to delineate 

the vertically polarized beam paths, compared to the horizontally polarized solid green beam. 
NASA/TM—2016-219074 5 

The stereo PIV cameras image the orthogonally polarized light sheets through polarizing beam 

splitting cubes in order to achieve isolation of the two optical systems, see Figure 3. The stereo PIV 

cameras are mounted in Schiempflug type mounts and are oriented at 45 to the plane of the laser light 

sheet. The cameras view the light sheets from both sides of the sheets so that the cameras can be mounted 

on the same side of the tunnel and both cameras are in forward scatter mode. Stereo PIV system #1 

(consisting of cameras L1 and R1) is sensitive to the p-polarized light from laser #1. Stereo PIV system 

#1’s cameras view the reflected light from the polarizing beamsplitting cube and are oriented at right 

angles to the observation direction. Stereo PIV system #2 (cameras L2 and R2) is sensitive to the 

s-polarized light from laser #2’s sheet which passes straight through the beamsplitting cube. Hence, 

although the laser light sheets are nominally 1 mm apart in the tunnel test section, each PIV system can 

only detect the light from its respective pulsed laser head. Also note that the PIV systems are configured 

in a “cross-stream” configuration, meaning the main flow direction is out of the plane of the light sheet. 

The entire optical system is mounted on an optical breadboard which is in turn mounted on a dual 

parallel stage traverse system. The axis of the traverse system is aligned with the axis of the wind tunnel 

and also level with the floor of the tunnel. The traverse system enables the measurement plane of the PIV 

system to be traversed from 50 mm upstream of the floor plate injection hole axial center to 150 mm 

downstream. PIV measurement planes are initially acquired at 25.4 mm spacing until the center of the 

injection holes is reached and then the measurements are spaced in 6.35 mm increments. 

The PIV cameras were mounted in a Schiempflug configuration, where the tilt of the camera sensor 

relative the camera lens enables a tight focus on the particles across the obliquely viewed plane of the 

laser sheet. The 20482048 pixel PIV cameras were equipped with 50 mm lenses in order to achieve a 

nominal 100200 mm field of view spanning the width of the tunnel. In addition, each camera is fitted 

with an electromechanical shutter in between the camera lens and the CCD sensor. The shutter enables 

the cameras to be operated at 5 Hz, while the PIV lasers are operated at their optimal pulse repetition rate 

of 10 Hz. The electromechanical shutters also help to reduce the exposure time down to 12 ms on the 

frame-straddled PIV cameras. All 4 cameras used in the Dual-Plane setup were controlled by a single 

computer system connected to two camera control units. Both of the laser systems were triggered at the 

same time so image acquisitions from the two stereo PIV systems were synchronized. Simultaneous 

acquisition of the flow properties at the two illuminated planes in the flow is required in order to compute 

the cross-plane flow properties. Each stereo camera pair was connected to one camera control unit. The 

computer was equipped with two framegrabbers, each connected to one camera control unit in order to 

acquire the images from all 4 cameras and stream them directly to disk in real time. Image sequences of 

400 image pairs were acquired for each axial station. PIV data were acquired at a total of 25 axial 

stations, starting from –50 mm upstream to 150 mm downstream from the injection hole centers. The 

processed Dual-Plane PIV data sets were set with the origin of the coordinate system at the leading edge 

of the center hole in the floor plate. 

The two independent stereo PIV systems were calibrated using a dual sided, dual plane calibration 

target, which was mounted on the PIV system traverse base plate below the tunnel. The calibration target 

projected up inside the tunnel test section by removing all of the tunnel floor plate inserts. The target was 

aligned with the laser light sheets. The PIV system traverse was scanned to each measurement station and 

a set of calibration images were acquired. Calibrations were performed for each axial measurement 

station to account for any variations in the wind tunnel windows or the elevation of the PIV system 

cameras. In addition to performing calibrations to a 3rd order polynomial, a calibration verification 

operation was performed to ensure that the calibration plane was accurately aligned with the laser light 

sheet plane (Ref. 8). 

The PIV image data were processed using multi-pass correlations with 6464 pixel subregions on 

32 pixel centers, followed by 3232 pixel subregions on 16 pixels centers. Subregion distortion 

processing was also used to process the PIV data (Ref. 9). Subregion distortion was used to correct for 

velocity gradients across the subregion and to minimize the “peak-locking” effect, which is the tendency 

for the estimated particle displacements to preferentially concentrate at integer values. In the subregion 
NASA/TM—2016-219074 6 

distortion technique, the local velocity gradients surrounding the current correlation subregion are used to 

distort the subregion before the cross-correlation processing operation. Distorting the subregion yields 

correlation subregions with uniform particle displacements, and hence, reduces any bias caused by the 

velocity gradients. Typically two additional passes after the multi-pass processing are used with subregion 

distortion applied to refine the correlation peak estimates. The Left and Right vector maps were then 

processed using an in-house code to obtain the 3D vector maps. The final cross-stream velocity vector 

maps had 1.4 mm spatial resolution. Sequences of 400 velocity vector maps were acquired at each 

measurement station and ensemble averaged to provide first and second order statistics over the entire 

measurement plane. Chauvenet’s criteria was used to eliminate any outliers in the ensemble averaging 

process (Ref. 10). 

The ensemble averaging step was also the point at which the data from the two laser light sheets were 

used to compute the cross-plane flow vorticity, which is the unique aspect of the Dual-Plane 

configuration. Vorticity was computed on each instantaneous velocity vector map and then the 

instantaneous vorticity was ensemble averaged to yield the final vorticity estimates. Although two 

measurement planes were acquired, the data written out were only for a single plane, including the out of 

plane vorticity component estimates. 

Accuracy of the Measurements 

The error in estimating the velocity is determined by the accuracy by which the correlation peak 

location can be measured. Nominally the error in estimating the correlation peak is 0.1 pixels. The full 

scale particle displacements for this flow were nominally 6 pixels in the injected air plumes and 2.5 pixels 

in the main tunnel flow. The relative error in the injection plume displacements (which is equivalent to 

velocity), is then u = 0.1 pixels/6 pixels = 0.016. The relative error in the main tunnel velocities is u = 

0.1 pixels/2.5 pixels = 0.04. When we compute the ensemble average velocity estimates we further reduce 

the error in velocity by 1/400. Hence, the PIV velocity data reported here have an accuracy of better than 

1 percent throughout the flow field. 

Flow Seeding 

In order for the Dual Plane PIV technique to work, we are relying on polarization separation to isolate 

the optical systems. A crucial requirement in any polarization isolation system is the seed particle size. If 

the particles are too large, then the scattered light will be depolarized and both optical systems will see the 

scattered light from both lasers, thereby cross-contaminating the recorded particle images. Particles less 

than 1 m in diameter preserve the polarization state of the incoming light. Hence, we have a strict 

requirement that the seed particles used in the experiment must be less than 1 m in diameter. 

Both the main tunnel flow and the injected flow streams were independently seeded. For the main 

tunnel flow we used a six jet atomizer, which is based on the Laskin nozzle design. When filled with olive 

oil, this seeder provides particles with a mean diameter of 0.7 m. 

The concentration of seed particles generated by the 6-jet seeder have to be diluted before entering 

the tunnel in order to avoid locally high concentrations of seed particles. In order to homogenize the 

seeded air entering the tunnel, the seeder was placed inside a 0.81.01.0 m box positioned 

approximately 0.5 m upstream from the bellmouth inlet of the tunnel. The end face of the box closest to 

the tunnel inlet was covered with a metal perforated plate, with about 50 percent open area. The end of 

the box facing away from the tunnel was completely open. A small muffin style fan was also placed in the 

box, pointed away from the tunnel inlet, in order to mix/disperse the seed emanating from the 6-jet seeder 

with the ambient air. When the tunnel was operating, air was drawn through the seeder mixing chamber 

into the tunnel bellmouth providing well mixed, uniform seeding inside the tunnel. 

 
NASA/TM—2016-219074 7 

 

Figure 4.—(a) CFD prediction of the air supply and seed streams entering the manifold below the tunnel, where the 

streamlines indicate the path of the seeded air stream; (b) Histogram of the particle residence times inside the 

manifold. 

The injected air flow was seeded using a single jet Laskin type atomizer also filled with olive oil. The 

effluent from the single jet atomizer was fed into a manifold below the tunnel. This manifold provided the 

pressurized air to all three of the injection tubes. The pressure line to the single jet seeder was adjusted to 

provide the desired seeding level in the injection air streams, as confirmed by visual inspection of the 

seeding level illuminated by the laser light sheet in the tunnel. The amount of seed material required to 

seed the injected flow was less than 1 percent of the total flow rate. An initial seeding configuration was 

used where the air supply to both the seeder and the mixing manifold were both fed through a single flow 

meter. The total flow rate for the injection air stream remain unchanged whether the seeder was turned on 

or off, confirming the contribution of the seeder flow on the total flow rate was negligible. 

Prior to the initial testing of the seeder system, several CFD studies where performed to estimate the 

mixing performance of this injection port plenum. Historically, the success of a PIV measurement 

campaign is tightly coupled to the seeding quality, so predicting this performance is more insightful than 

the more traditional trial and error approach. Based on the seed particle mixing CFD predictions, seed 

injection uniformity and seed residence time in the plenum was considered acceptable. Figure 4 illustrates 

a sample case of this analysis. Figure 4(a) on the left visualizes the predicted particle trajectories to 

quantify the seed uniformity at the inlet of each individual injection port. Figure 4(b) contains a histogram 

plot of particles’ residence times in the manifold to ensure excessive recirculation zones, where oil 

droplets may agglomerate into >1 μm in diameter, are minimized. 

Results and Discussion 

The Dual Plane PIV system was used to collect data on both the 3-hole and single hole floor insert 

models. Blowing ratios of 1 and 2 were covered. Both heated and unheated injection air streams were 

tested. With the electric heaters turned on, the injected air stream was approximately 62 C. The origin for 

all of the flow measurements was centered on the tunnel floor at the leading edge of the center injection 

port. The PIV data were collected starting at x = –31 mm upstream of the injection port leading edge. The 

second plane was acquired at x = –6 mm upstream of the hole leading edge. All subsequent measurement 

stations were acquired starting at +19 mm from the hole leading edge in increments of 6.35 mm to a 

distance of 144 mm downstream from the leading edge of the holes. The data sequences collected 

contained 400 image planes per stereo PIV system. The data were processed as described in the data 

processing section and combined into a single data set containing the mean u-, v- and w-components of 

velocity and the x-, y- and z-components of vorticity. The u’v’, u’w’ and v’w’ Reynolds stresses were 

also computed. All of the data from the 25 measurement planes were combined into a single block of data 

0 0.5 1 1.5 2 2.5 3 3.5 4 0

20

40

60

80

100

120

Particle Residence Time [s]

Sample of 1000 fog particles at given conditions

Particle Residence Time Study

Number of Particles

Residence Time [s]

(b)

(a)
NASA/TM—2016-219074 8 

which is in Tecplot format. The spatial resolution of the in-plane measurements is 1.4 mm, or y/D = z/D = 

0.073. All of the measured flow field quantities and physical dimensions were made dimensionless using 

the injection port diameter D and/or free stream tunnel velocity U. 

The PIV measurements do not span all the way to the floor or to the tunnel walls. There is always 

flare light scattered from surfaces when light travels through glass that is not anti-reflection coated. The 

flare light precludes our ability to perform the cross-correlation operation near these surfaces. We also 

had to take additional preventative measures to keep the light sheet from intersecting the tunnel floor. We 

could not simultaneously collimate the light sheet and keep the two light sheets parallel through the test 

section with the optics we had available, therefore we had to block the light sheet further above the floor 

on the near side of the tunnel to keep the diverging sheet from illuminating the floor on the far side of the 

tunnel. 

The mean flow velocity magnitude is plotted in Figures 5 to 12 for each model and test configuration. 

There are two plots for each test condition: (1) a streamwise plane with velocity vectors and an isovelocity contour depicting the edge of the air injection plume and (2) a cross-stream contour plot of 

velocity magnitude at x/D planes of 2, 3, 4, and 5. For the 3-hole model configuration, the BR = 1 case is 

shown with room temperature air and then heated air, which is followed by the BR = 2 case with 

unheated and then heated air. Next, the 1-hole model results are plotted, again first for a BR = 1 and then 

for a BR = 2. The test matrix settings are summarized in Table 1. The Experimental Configuration Name 

column is how the data was designated in the PIV notebook and also how the processed PIV data are 

organized on the archival DVD. 

The 3-hole model cases show that there is some interaction of the central plume with the plumes on 

either side, as evidenced by the asymmetry in the two outside plumes in the cross-stream plots. Secondly, 

regardless of the model, the velocity in the injected plume tends to have approximately 20 percent higher 

velocity and penetrates approximately 20 percent further into the freestream flow for the heated plume 

cases when compared to the cold-flow cases. The decreased density of the heated injection air is 

responsible for this further penetration into the freestream tunnel flow. The velocities of the injected 

plume are higher due to the reduced density of the injection air. Maintaining the same mass flow for the 

heated case requires increasing the velocity of the injected air in order to compensate for the reduced air 

density. Some of the non-uniformities observed in the peripheral regions of the tunnel are partially due to 

the mismatch in some of the tunnel floor inserts and the different sub-sections of the tunnel that are bolted 

together. The 3D printed model parts exhibit a small degree of warping after being printed, causing some 

of the mismatch. Since different model configurations were tested over several days, smoothing out the 

interfaces between the tunnel inserts was not feasible. Overall, we do not expect these small disturbances 

in the flow to significantly influence the injected plume/free stream interaction. 

Figure 5.—Streamwise and cross-stream velocity for 3-hole floor model, blowing ratio of 1 and no heat. 
NASA/TM—2016-219074 9 

Figure 6.—Streamwise and cross-stream velocity for 3-hole floor model, blowing ratio of 1 and with heat. 

 

Figure 7.—Streamwise and cross-stream velocity for 3-hole floor model, blowing ratio of 2 and no heat. 
NASA/TM—2016-219074 10 

 

Figure 8.—Streamwise and cross-stream velocity for 3-hole floor model, blowing ratio of 2 and with heat. 

Figure 9.—Streamwise and cross-stream velocity for 1-hole floor model, blowing ratio of 1 and no heat. 
NASA/TM—2016-219074 11 

Figure 10.—Streamwise and cross-stream velocity for 1-hole floor model, blowing ratio of 1 and with heat. 

Figure 11.—Streamwise and cross-stream velocity for 1-hole floor model, blowing ratio of 2 and no heat. 
NASA/TM—2016-219074 12 

Figure 12.—Streamwise and cross-stream velocity for 1-hole floor model, blowing ratio of 2 and with heat. 

TABLE 1.—TEST MATRIX CONDITIONS AND CONFIGURATIONS 

Experiment configuration name Model Freestream 

velocity, 

m/s 

Injection air,

CFM 

Injection air 

temperature, 

°C 

Density 

ratio 

21Oct15a 1-hole 9.1 10.5 21 1 

21Oct15b 1-hole 9.1 5.5 21 1 

21Oct15c 1-hole 9.1 11.5 62.7 0.33 

21Oct15d 1-hole 9.1 6.1 62.7 0.33 

20Oct15a 3-hole 9.1 24 21 1 

20Oct15b 3-hole 9.1 14.8 21 1 

20Oct15c 3-hole 9.1 25.5 63.8 0.33 

20Oct15d 3-hole 9.1 16 63.3 0.33 

 
NASA/TM—2016-219074 13 

A sample cross-stream plot of velocity vectors on top of color contours of velocity magnitude is 

shown in Figure 13, which demonstrates the spatial resolution of the data. The details of the bound vortex 

pair development in the injection plume are clearly evident. Furthermore, the depth of information 

contained in the Dual-Plane PIV data set is demonstrated in Figure 14, where a series of cross-stream 

plots of all three components (x, y, z) of vorticity are shown. The vorticity is made dimensionless by 

scaling the data by the hole diameter D and the tunnel free stream velocity U. The in-plane vorticity, x

is a common flow quantity easily computed from standard single-plane stereo PIV data. In Figure 14(a), 

we see the plot of x (out of the measurement plane) which clearly shows the roll up of the flow under the 

bound vortex pair. In Figure 14(b), the plot of y illustrates the mixing along the sides and in the interior 

of the high speed injection plume with the ambient tunnel flow. Lastly, in Figure 14(c), the plot of z

shows the interaction of the top and bottom edges of the high speed jet plume with the ambient tunnel 

flow. Figure 14 demonstrates the information gained by using Dual-Plane PIV, where in addition to the 

standard out-of-plane vorticity, we are able to compute both of the in-plane vorticity components. 

Figure 13.—Plot of the velocity vector files on top of the velocity magnitude contours for the 3-hole model case with 

2:1 blowing ratio and heated injection air. 
NASA/TM—2016-219074 14 

Figure 14.—Here we show all three measured components of vorticity: (a) x, (b) y, c) z. Measuring all three 

components of vorticity across a plane is a rarely demonstrated measurement capability. 

Conclusions 

Dual-Plane PIV has been successfully applied in a low speed wind tunnel for studying turbulent heat 

transfer flow fields. The PIV data were acquired using both a 3-hole and single hole floor plate models 

installed in the wind tunnel. Two blowing ratios were measured for each model. Both ambient 

temperature and heated air were injected into the main tunnel flow. The development of the horseshoe 

vortices in the classic jet in cross-flow configuration is readily observed in the PIV data. The penetration 

of the jet plume into the tunnel freestream flow increases with temperature. In addition to the standard inplane flow quantities, the application of the Dual-Plane PIV technique enables the computation of out-ofplane flow quantities so that all three components of vorticity are measured. The data collected here are of 

high spatial resolution and high accuracy providing a benchmark set of conditions for validating CFD 

predictions on turbulent heat transfer flows. 

 
NASA/TM—2016-219074 15 

Postnote 

The polarizing beamsplitting cubes were an essential element in the Dual Plane PIV used in this test 

program. However, the polarizing beamsplitting cubes did not perform as well as desired. The large fieldof-view requirement of the PIV systems exceeded the acceptance angle of the beamsplitting cubes 

resulting in small regions of the reflected images (vertically polarized light) seeing some the horizontally 

polarized scattered light. This small deficiency did not significantly affect our ability to make the velocity 

measurements. However, any future implementations of the Dual Plane PIV technique requiring the large 

field angles required here will employ wire grid polarizers in front of the PIV cameras for polarization 

isolation. The dual stereo system cameras will be mounted side-by-side and the small difference in the 

stereo PIV system viewing angles will be inconsequential in the data processing. 

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