Research on the topic of shock wave/turbulent boundary layer interaction was carried out. Skin friction and surface pressure measurements in fin-induced, swept interactions were conducted, and heat transfer measurements in the same flows are planned. The skin friction data for a strong interaction case (Mach 4, fin-angles equal 16 and 20 degrees) were obtained, and their comparison with computational results was published. Surface pressure data for weak-to-strong fin interactions were also obtained

Lee, Y.

Settles, G. S.

English

NASA Technical Reports Server

Department of Mechanical Engineering
Penn State University, University Park, PA 16802
Report PSU-ME-R-89/90-0011
SWEPT SHOCK/BOUNDARY LAYER INTERACTION
EXPERIMENTS IN SUPPORT OF CFD CODE
VALIDATION
by G.S. Settles and Y. Lee
INTERIM TECHNICAL REPORT FOR
THE PERIOD JANUARY 15, 1989 - JANUARY 14, 1990
Funds for the support of this study have been allocated
by the NASA-Ames Research Center, Moffett Field, CA
under NASA Grant No. NAG 2-592
submitted to:
Dr. C.C. Horstman, Technical Officer
NASA-Ames Research Center
Experimental Fluid Dynamics Branch, MS 229-1
Moffett Field, CA 94035
MARCH 1990
PENNSTATE
__iEEE
GAS DYNAMICS LABORATORY
(NASA-CR-I66397) SWEPT SHOCi_/eQUNDARY LAYER
INTERACTIgN EXP[RIMENTS IN SUPPORT rlF CFD
CODE VALIDATIC?N Intorim T_chni¢_l Roport, I5
Jan. 19_9 - I4 J_n. i990 (_nsylvania
State Univ.) 7 p CSCL 200
N90-19535
uncl as
G3/34 0270346
https://ntrs.nasa.gov/search.jsp?R=19900010219 2020-03-19T23:02:12+00:00Z

SWEPT SHOCK BOUNDARY/LAYER INTERACTION
EXPERIMENTS IN SUPPORT OF CFD CODE
VALIDATION
BY: Y. Lee and G .S. Settles
Interim Technical Report for the Period
January 15, 1989 -January 14, 1990
Funds for the support of this study have been allocated
by the NASA-Ames Research Center, Moffett Field, CA
under NASA Grant No. NAG 2-592
SUMMARY
Research on the topic of shock wave/turbulent boundary-layer interaction has been
carried out under the subject Grant during the past one-year period at the Penn State Gas
Dynamics Laboratory. Skin friction and surface pressure measurements in fin-induced,
swept interactions have been conducted, and heat transfer measurement in the same flows
are planned. The skin friction data for a strong interaction case (Mach 4, fin angles = 16
and 20 deg.) were obtained, and their comparison with computational results was published
(Ref. 1). Surface pressure data for weak-to-strong fin interactions were also obtained and
remain unpublished. The heat transfer measurements for the same interactions are planned
for early 1990.
INTRODUCTION
The study of shock wave/turbulent boundary-layer interaction is very important for
the solution of internal and external aerodynamic problems in the design of high-speed
vehicles and associated numerical simulations. However, only a little knowledge in this field
has been available in the past, and more extensive experimental work is still needed for a
sufficient understanding of the fluid dynamics of such flows. When an oblique shock wave
impinges on a solid surface, a large separation bubble of reverse flow can form, generating
a complicated 3-dimensional flow structure. It was found that the peak pressure, peak skin
friction and peak heat transfer occur near the region of reattachment of this separated flow.
These peak ratios are of great practical importance in predicting high aerodynamic and
aerothermal loading due to interacting flows on high-speed flight vehicles.
Therefore, the present experimental program is being conducted to provide
"benchmark" data that can be used both to obtain a clear understanding of the physical
behavior of swept shock wave/turbulent boundary-layer interactions, and as a fundamental
database for CFD code validation.

Since our resultsof skin friction measurementshave already been reported in the
literature, only a brief description of the surfacepressuremeasurementsand the designof
the heat transfer experimentsis given in this report. A copy of the most recent published
paper on the skin friction measurementsis attached asan Appendix.
SURFACE PRESSURE MEASUREMENT
As in our previous experiments, a flat plate was used to produce a supersonic
equilibrium turbulent boundary layer. This bound_ layer interacts with the planar oblique
shock generated by a sharp, unswept-leading-edge fin.
Surface pressures were measured at 96 pressure taps which were radially distributed
on the flat plate with respect to fin leading edge. This was found to produce sufficiently-
detailed data in the interaction region. This radial pressure-tap distribution was based on
the theory of quasiconical symmetry of the interaction flowfield, which has been supported
by many previous investigators.
A two-channel Scanivalve system was used for scanning the 96 pressure taps during
the tunnel running time. The signal from the Scanivalve pressure transducer passed through
a low-pass filter, the cutoff frequency of which was 30 Hz, and thence was routed to the data
acquisition system (Metrabyte Dash-16 analog-to-digital converter board). The A/D
conversion rate of the pressure was 2 kHz, and 15 data points were averaged for each
surface pressure. Besides the surface pressure, stagnation pressure, reference static pressure,
and stagnation temperature were also measured for the calculation of Reynolds number and
Mach number.
The total data-acquisition time for the whole process required about 22.4 seconds.
During each scanlvalve "step," a dwell-time of about 0.3 seconds was allowed to elapse
before data were taken. This dwell-time was checked and proved to be sufficiently long to
allow the pressure in the pressure tubes to equilibrate.
Weak-to-strong swept interaction cases were tested over a broad range (from Mach
2.5, fin angle = 6 deg. to Mach 4, fin angle = 22 deg.).
Since the wind tunnel stagnation pressure is slightly decreasing during the data
acquisition process, each measured surface pressure was normalized by the stagnation
pressure measured at the same instant. A weak streamwise pressure gradient which existed
on the flat plate with no fin in place (presumed due to weak reflecting waves in test section)
has been removed from the data, and the final surface pressure distributions for four cases
tested are tabulated in Table 1.
The validity of the current pressure measurement-Was roughly checked by comparing
the local peak pressure ratio calculated from the four measurements with the correlation
equation suggested by J. R. Hayes AFFDL TR 77-10). It was found that a good agreement
occurred between our measured peak pressures and the Hayes correlation. Also an
extensive error estimate was carried out, taking into account electric noise, repeatability, and
calibration uncertainty. The detailed analysis of these surface pressure data is under way
and will be available soon.
2

HEAT TRANSFER MEASUREMENT
Basis for the Measurements
The thermal investigation of complicated shock wave/turbulent boundary-layer
interactions involves many difficult problems. One of these is the fact that many
conventional heat transfer measurement techniques cannot be directly applied to tests in
near-adiabatic wind tunnel facilities. Also, to measure high spatial resolution steady-state
heat transfer coefficient distributions and high-frequency fluctuating temperature variations
in fin interactions (which is current purpose of this study), the development of a new
measurement technique was needed.
Recent heat transfer measurement using advanced multi-layered thin-film gauges
were carried out at MIT and in Japan. However, these multi-layered heat transfer gauges
were found to be very difficult and time-consuming to fabricate, and needed to be handled
with extreme care.
An entirely new type of technique which can provide qualitative local heat transfer
coefficient distributions has been developed and reported in the literature (Refs. 2-5). This
method uses a thin foil heater to generate a uniform heat flux over the surface of interest
and a liquid-crystal-coated sheet to sense the local surface temperatures. The heat
convection equation is then used to calculate the local heat transfer coefficient from the
measured surface temperatures and the known heat flux from the heater. However, this
method has been used only for relatively low-speed flow cases, and cannot produce
quantitative heat transfer data.
Here we combine these new heat transfer measurement technologies to obtain a
high-resolution, high-frequency techniques which works even though the flow is naturally in
a near-adiabatic condition. The heated-film concept is used in conjunction with an array
of thin-film plated gauges which are fabricated by way of microlithography.
The initial step of this study is to check the validity of the heat transfer technique by
comparing the experimental results for the case of the flat plate with no fin in place with
the computational calculations. After this, the interaction itself will be primarily studied.
The Design of System Components
The current heat transfer measurement system consists of four parts: the surface
temperature sensors, heater element, insulation board, and additional temperature sensors
to measure the temperature gradient across the insulation board (see Fig. 1). The heat
transfer coefficient can be calculated by dividing the difference between the surface
temperature and the adiabatic wall temperature by the heat dissipated through the sensor
from the thin foil heater. The exact heat flux through the sensor is obtained by considering
both the total heat generation from the heater and the heat loss through the insulation
board. The basic equations of the system are also illustrated in Figure 1.
3

1) SurfaceTemperature Sensors
A radial distribution of 38 temperature sensors (radius = 3.50 inches from the fin
leading edge) on the flat plate was chosenfrom the symmetry of the fin interaction to
maximizethe data resolution. Commercially-availabletemperature sensorscannot be used
becausethey do not have a suitable size and the high frequency responsewe need, and
further have difficulties being installed on our heater without disruption of the flowfield.
Therefore, in this study, thin film resistance-temperature-detector(RTD) sensors
deposited on a plastic substrate by vacuum-depositionare being used. Such thin-film
temperature sensors,which are being currently manufactured by the NASA-Langley
ResearchCenter, have sufficiently-high frequency responseand are easyto install on our
fiat plate.
2) Heater Element
The heat flux from a foil heater canbe calculatedfrom the relationship betweenthe
electrical resistanceof the heater and the current suppliedto it. To calculateaccurateheat
transfer coefficient distributions, it is very important that the heat flux generated by the
heating element over the surfaceis uniform. Several typesof heatingelements havebeen
checked,and it is believed that the thin foil resistor-typeheater is suitable for our purpose.
Commercially-manufacturedInconel unetched-foilheater materialhasbeenchosen,because
the uniformity of heat flux from the heater surface can be quantitatively checked. This
calibration method wasdescribedby Simomichand Moffat (Ref. 3), wherethe voltage-drop
distribution was measuredat specific intervals acrossthe heater surface for a set voltage
applied acrossthe two copperbus barsand a given current.
3) Insulation
We need as much heat flux from the heater as possiblefor a good signal-to-noise
ratio. But, since the heat flux from the thin foil heater is limited becauseof the small
resistanceof the heatingelement (Inconel), and sincemost of the heat flux is dissipatedby
convectionto the high-speedflow in thetest section,low-conductivity insulation is important.
This insulation shouldalsobe ruggedagainstthe temperaturevariation andhigh shearstress
on the surface during the test. "Rexolite" polymer plastic (thickness -- 3/16 inches) has
been chosenfor this purpose.
4) Measurementof dT/dy AcrossInsulation Board
Fast-responsethermocouplesare installed on both sidesof the insulation board to
measurethe temperature gradient acrossthe board. The responseof thesethermocouples
is much slower than that of the surfacetemperaturesensors,however. Therefore, the heat
loss through insulation board cannot be calculated at the same rate as the surface
temperature variation, and the heat convectionequation,which is used for the calculation
4

of heat transfer coefficient, cannot be applied at the same high-frequency rate. For this
reason, the possibility of high-frequency-fluctuating heat transfer measurements using this
technique remains undecided. But the steady-state heat transfer measurement, which is one
key purpose of this study, is possible. The surface temperature variation at high frequency
is also measurable.
5) Data Acquisition
For high-speed data acquisition, a LeCroy system is used having an 8-channel, 12-bit
waveform recorder with a digitizing and sampling rate of up to 5 Megasamples/sec. Further
consideration of signal conditioning (filtering and amplification) is under way.
Plans and Schedule
All components of the heat transfer plate have been fabricated or obtained save the
sensors themselves. A first try at fabricating these by NASA-Langley personnel had some
minor problems which are now being corrected. It is expected that fabrication will be
complete by the end of April, 1990. Calibrations and initial testing will then take place.
Initial data from this set of experiments is expected during the Summer of 1990.
5

REFERENCES AND BIBLIOGRAPHY
1) Kim, K-S., Lee, Y., Alvi, F. S., Settles, G. S., and Horstman, C. C., "Laser Skin
Friction Measurementsand CFD Comparisonof Weak-to-Strong SweptShock/Boundary
Layer Interactions," AIAA Paper 90-0378, presented at the AIAA 28th Aerospace Sciences
Meeting, Reno, NV, January 1990.
2) Simonich, J. C., and Moffat, R. J., "New Technique for Mapping Heat-Transfer
Coefficient Contours," Rev. Sci. Instrum. 53, 5, 1982, pp. 678-683.
3) Hippensteele, S. A., Russell, L. M., and Stepka F. S., "Evaluation of a Method for
Heat Transfer Measurements and Thermal Visualization Using a Composite of a Heater
Element and Liquid Crystals." J. of Heat Transfer 105, 1983, pp.184-189.
4) Abuaf, N., S. P. Urbaetis, and O. F. Palmer, "Convection Thermography" Technical
Report No. 85CRD168, General Electrics, September 1985.
5) Eibeck, P. A. and J. K. Eaton, "An Experimental Investigation of the Heat Transfer
Effects of a Longitudinal Vortex Embedded in a Turbulent Boundary Layer," Report MD-
48, Thermosciences Division, Department of Mechanical Engineering, Stanford University,
November 1985.
6

Table 1. Static Pressure (P/Pinf) Data along the Arc, R-- 4.0 in.
M -- 3.0 M -- 3.0 M = 4.0 M -- 4.0
beta alpha=lO alpha=16 alpha=16 alpha=20
14 1.931
16 1.905
18 1.844 2.991 4.058
20 1.708 2.932 4.165
22 1.608 3.057 3.324 5.050
24 1.517 2.933 2.177 5.534
26 1.476 2.382 1.568 4.804
28 1.456 1.830 1.493 2.520
30 1.463 1.630 1.631 1.579
32 1.405 1.580 1.820 1.508
34 1.310 1.658 1.835 1.742
36 1.190 1.763 1.773 1.862
40 1.006 1.707 1.584 2.005
44 1.005 1.577 1.022 1.878
47.5 0.999 1.183 0.996 1.701
50 1.005 1.009 1.000 1.376
52.5 0.996 1.002 1.000 1.005
56 1.000 1.001 1.000 1.004
58 1.000 0.999 1.000 0.999

Figure 1. The Structure of Heat Transfer Mesurement System
and Heat Convection Equation
points to measure
temperature
fin
flow
protecting-layer_.__
-
lead _NN__ -'j_
substrate
temperature
sensor
thin foll heater
insulatlon board l I
(Rexolite) I [
-//./////) :__ _\
" _
where
and
II
]% --" qcon u
(Zwall - radiabatic)
II II I! II
qconv -- qheater -- qconduction-loss -- qradiation-loss
IIqheatcr = V x i = i × R 2
II II
qconduction-loss ,,,a 0.05 X qheater
II II
qradiation-loss "" O.OOl × qheater



Swept shock/boundary layer interaction experiments in support of CFD code validation

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