Index of /turbdata/agard/chapter8/CMP10
1. FLOW TITLE: Case CMP10; Cantwell, B. J. And Coles, D.,
"A Flying Hot Wire Study Of The Turbulent Near Wake Of A
Circular Cylinder At A Reynolds Number Of 140000"
2. REVISION DATE: November 18, 1980
3. EVALUATOR: Cantwell, B. J., Department Of Aeronautics And
Astronautics, 371 Durand, Stanford University, Stanford, Ca. 94305.
4. EXPERIMENT LOCATION AND DATE
Graduate Aeronautical Laboratory Of California Institute Of
Technology(Galcit) 10 Foot Tunnel, October 1975.
5. ABSTRACT OF EXPERIMENT
Measurements were made in the near wake of a circular cylinder at a
reynolds number of 140000, to study the phenomenology of the processes
of vortex formation and transport. The reynolds number was high enough
to cause a fully turbulent wake but low enough to insure laminar
separation. X-array hot wire probes mounted on the ends of a pair of
whirling arms were used for the measurements. By applying a large enough
velocity to the wires, the relative flow angle was maintained within the
+/- 30 degree range of sensitivity of x-array so that, the usual velocity
rectification problem was avoided. The data acquisition system was computer
controlled. A signal synchronized with the vortex shedding process and
recorded along with hot wire data was used to sort data into populations
with the same phase. Ensemble averages conditioned in this way yield
an average picture of the instantaneous flow field in which the vortices
are frozen as in a photograph. The processed data are specified on a
grid which covers -0.5<=x/d<=8.0 and -3.0<=y/d<=3.0 with grid lines
spaced 0.1*d apart in both directions.
6. REFERENCES
(1) Cantwell, B. J., "A Flying Hot Wire Study Of The Turbulent Near
Wake Of A Circular Cylinder At A Reynolds Number Of 140000",
Ph.D. Thesis, California Institute Of Technology, 1976.
(2) Coles, D., Cantwell, B. J. And Wadcock, A. J., "The Flying Hot
Wire And Related Instrumentation", Nasa Contractor Report 3066,
1978.
7. INSTRUMENTATION
Velocity: modified DISA55a38 x-array hot wire probes
Pressure: Barocel electronic manometers
Temperature: electronic thermometer (National model no. LX5606)
Data acquisition: a 16 channel Preston analog to digital converter
with a resolution of 14 bits plus sign( maximum conversion rate
500000 words/second on 1 channel); a HP2100 minicomputer with a
disk operating system and 32k words of core; digital tape recording
of edited data.
8. GLOBAL PARAMETERS
1. Cylinder diameter, Lref(or d) =10.137 cm
3. Dynamic pressure for wake data runs, Qref = 1.955 mmhg
4. Free-stream speed, Uref = 2120 +/- 10 cm/sec
6. Free-stream temperature, Tref= 24 +/- 2 degree Celsius
7. Kinematic viscosity, nu = 0.1535 cm**2/sec
8. Reynolds number, Re = Uref*D/nu = 140000
9. Free-stream turbulence level, <=0.006
10. Drag coefficient, Cd = 1.227
11. Base pressure coefficient, Cpb = -1.21
12. Shedding period = 26.65 millisec
13. Strouhal number = 0.179
9. MEASURED VARIABLES
U/Uref, V/Uref, U2/Uref2, V2/Uref2,
U1V1/Uref2, U3/Uref3, V3/Uref3, U4/Uref4,
V4/Uref4, U2V1/Uref3, U1V2/Uref3 AND GAMMA(Intermittency)
10. MEASUREMENT UNCERTAINTY
None specified.
11. FILE ORGANIZATION
Files CMP10d01.dat to CMP10d17.dat are data at phases
1 to 17. Phase 17 is a population weighted average of other phases.
Organization of records within each of these data files is
as follows:
RECORD VARIABLES FORMAT
1 MAXIMA OF U/UREF,V/UREF,U2/UREF2,V2/UREF2 4E20.7
2 MAXIMA OF U1V1/UREF2,U3/UREF3,V3/UREF3,U4/UREF4 4E20.7
3 MAXIMA OF V4/UREF4,U2V1/UREF3,U1V2/UREF3,GAMMA 4E20.7
4 MINIMA OF U/UREF,V/UREF,U2/UREF2,V2/UREF2 4E20.7
5 MINIMA OF U1V1/UREF2,U3/UREF3,V3/UREF3,U4/UREF4 4E20.7
6 MINIMA OF V4/UREF4,U2V1/UREF3,U1V2/UREF3,GAMMA 4E20.7
7 Y indices specifying range of actual data
boundary in upper half of grid in fig.1
for X index = 1(X/D=-0.5) 2I6
8 Y indices ... For X index= 2(X/D=-0.4) 2I6
... ... ...
92 Y indices ... For X index=86(X/D= 8.0) 2I6
93 Normalized and integerized
U/UREF,V/UREF,U2/UREF2,
V2/UREF2,U1V1/UREF2,U3/UREF3,
V3/UREF3,U4/UREF4,V4/UREF4,
U2V1/UREF3,U1V2/UREF3,
GAMMA (intermittency) at grid point
with X index=1 and Y index=1 12I6
94 Norm... X index=1 and Y index=2 12I6
... ... ...
5338 Norm... X index=86 and Y index=61 12I6
variables in records 93-5338 are normalized as follows:
XNORM = (X-XMIN)/(XMAX-XMIN)
Normalized variables are made into integers by multiplying
by 10000 and rounding to the nearest integer.
IXNORM = XNORM*10000
Thus each number in records 93-5338 is an integer in the range 0 to 10000.
All null data are written as 20000.
The equation describing the relation between actual data and
the normalized data on tape is:
X=((XMAX-XMIN)*IXNORM)/10000.+XMIN
WHERE X, XMAX AND XMIN ARE REAL AND IXNORM IS INTEGER.
The data are given at each of the points of the rectangular
grid enclosing the actual data boundary shown in fig. 1.
The order of the points is determined by the y index
varying most rapidly and the x index varying least rapidly(similar
to fortran array storage convention).
File CMP10d18.dat is the pressure distribution around
360 degrees of the cylinder surface. The cylinder angle alpha is measured
in degrees. Alpha = 0 degree corresponds to the forward stagnation
point. Records within this file are organized as follows:
RECORD VARIABLE FORMAT
1 ALPHAMAX,ALPHAMIN,CPMAX,CPMIN 4E20.7
2-74 Normalized and integerized Alpha,Cp 2I6
Variables in records 2-74 are normalized and integerized as
in files 1 - 17.