----------------- FILE NUMBER 103----------------- 1. FLOW TITLE: CASE 0211; BRADSHAW, P, HANCOCK, P. E., "EFFECT OF FREE STREAM TURBULENCE". 2. REVISION DATE: NOVEMBER 18, 1980 3. EVALUATOR: BRADSHAW, P., IMPERIAL COLLEGE OF TECHNOLOGY, LONDON, SW7 2BY, ENGLAND. 4. EXPERIMENT LOCATION AND DATE: IMPERIAL COLLEGE OF TECHNOLOGY, LONDON, ENGLAND 1975 - 1978 5. ABSTRACT: TEST CASE CONSISTS OF THE CORRELATION OF THE FRACTIONAL CHANGE IN THE SKIN FRICTION COEFFICIENT, CF, WITH A VARIABLE (UP/UE)*(L/DELTA995+2). UP IS THE RMS STREAMWISE COMPONENT INTENSITY (UP = SQRT(U1U1)), MEASURED AT A NORMAL DISTANCE, Y, GREATER THAN 2*L, WHERE L IS A CHARACTERISTIC LENGTH SCALE. MEASUREMENTS WERE MADE FOR A GIVEN VALUE OF REYNOLDS NUMBER BASED ON THETA (RTHETA). REYNOLDS NUMBER EFFECTS SEEM TO BE SMALL FOR RTHETA ABOVE 2000. IN THE HANCOCK EXPERIMENT FLUCTUATING SIGNALS WERE DIGITIZED FOR OFF-LINE ANALYSIS. SQUARE BAR BIPLANAR TURBULENCE GENERATING GRIDS WITH MESH LENGTHS FROM 0.076 M TO 0.152 M AND VARIOUS OPEN AREA RATIOS WERE USED. ALL THE DATA POINTS ARE FOR CONSTANT PRESSURE BOUNDARY LAYERS BELOW GRID TURBULENCE. PREVIOUSLY, IN MANY CASES ONLY UP WAS MEASURED AND, AFTER ESTIMATING THE DISSIPATION (EPSILON) FROM THE DECAY RATE, THE LENGTH SCALE, L, WAS DEFINED FROM -UP**3 / L = -2*EPSILON / 3 = UE* DU1U1/DX IN OBTAINING THIS RELATION IT HAS BEEN ASSUMED THAT MEAN-SQUARE INTENSITIES IN THE FREE STREAM ARE RELATED BY V1V1 = W1W1 = 0.8 * U1U1. THUS BOUNDARY CONDITIONS FOR CALCULATIONS MUST SIMULATE DECAY OF UP. IF NOT CALCULATED TAKE UP TO VARY AS X**(-.6), L AS X**(0.4) RANGE, UP .LE. 0.05*UE AND 0.5 < L/DELTA995 < 4.0 DATA EVALUATION ASSUMES ACCURACY OF THE LOGARITHMIC LAW. THUS THE CF CORRELATION IMPLIES A CORRELATION FOR THE WAKE PARAMETER PI (BEST DEFINED AS THE WAKE STRENGTH AT Y = DELTA995, SINCE COLES' COSINE WAKE IS A POOR FIT AT HIGH FREE-STREAM TURBULENCE). START CALCULATIONS WITH STANDARD CONSTANT PRESSURE PROFILES, FOR SIMPLICITY, AND HIGH FREE STREAM UP. RUN THEN DESCRIBES A TRAJECTORY IN THE UP, L/DELTA995 PLANE AND CF PREDICTIONS CAN BE PLOTTED ON THE (UP/UE)*(L/DELTA995+2) VERSUS (CF-CFO)/CFO CORRELATION PLANE, IGNORING THE EARLY PART OF THE RUN WHERE THE PROFILES ARE MISMATCHED. CFO IS THE ZERO FREE-STREAM TURBULENCE VALUE OF CF. CHOOSE INITIAL RTHETA AS AT LEAST 2000. 6. REFERENCES: 1. HANCOCK, P. E. "THE EFFECT OF FREE-STREAM TURBULENCE ON TURBULENT BOUNDARY LAYERS" PH.D. THESIS, IMPERIAL COLLEGE OF SCIENCE AND TECHNOLOGY, LONDON UNIVERSITY, 1980, AVAILABLE ON MICROFICHE FROM EVALUATOR. 7. INSTRUMENTATION: MEAN VELOCITY: (HANCOCK EXPERIMENT) PITOT TUBE. SKIN FRICTION: PRESTON TUBE. TURBULENCE: DISA 55D01 CONSTANT TEMPERATURE BRIDGES OPERATING DISA 55P51 CROSS WIRE PROBES WITH PLATINUM WIRES (5E-6 M IN DIAMETER, 1E-3 M IN LENGTH). 8. EXPERIMENTAL PARAMETERS: WIND TUNNEL DIMENSIONS: ...................... 0.91 M X 0.91 M REFERENCE FREE STREAM VELOCITY (UREF): ....... 15 M/S FREE-STREAM TURBULENCE LEVEL(WITHOUT GRIDS): <0.0003 FLAT PLATE CHORD: ............................ 2.5 M FLAT PLATE SPAN: ............................. 0.91 M 9. MEASURED VARIABLES: EXTENSIVE TURBULENCE DATA, INCLUDING VELOCITY EXTERNAL TO THE BOUNDARY LAYER (UE) STREAMWISE COMPONENT RMS INTENSITY (UP) WALL SHEAR STRESS (TW) THE DATA ARE REPORTED AS A TABLE OF VALUES OF (CF - CFO)/CFO CORRESPONDING TO VALUES OF THE VARIABLE (UP/UE)*(L/DELTA995 + 2) 10. UNCERTAINTY: U/UE : ..................... <0.01 IN DATA SHEAR STRESS: /RHO*UE**2.... 0.02 (ABSOLUTE), 0.01 (RELATIVE) 11. TAPE ORGANIZATION: THE TAPE IS A 2400 FOOT, 9 TRACK, PHASE ENCO DED, ODD PARITY, UNLABELLED TAPE WRITTEN AT A DENSITY OF 1600 BITS PER INCH ACCORDING TO EBCDIC CODE. THE RECORD FORMAT IS FIXED AND BLOCKED; RECORD LENGTH = 80 BYTES; BLOCKSIZE = 8000 BYTES NORMALIZED DATA ARE CREATED FROM MEASURED DATA AS FOLLOWS: XNORM = (X - XMIN)/(XMAX - XMIN) NORMALIZED VALUES ARE INTEGERIZED BY MULTIPLYING BY 10000 AND ROUNDING UP OR DOWN TO THE NEAREST INTEGER. IXNORM = XNORM * 10000. THUS EACH NORMALIZED DATUM IS WRITTEN ONTO TAPE AS AN INTEGER VALUE BETWEEN 0 AND 10000. ALL NULL DATA ARE WRITTEN AS 20000 THE EQUATION DESCRIBING THE RELATION BETWEEN ACTUAL DATA AND THE NORMALIZED DATA ON TAPE IS X = XMIN + (((XMAX - XMIN) * IXNORM)/10000.) WHERE X, XMAX AND XMIN ARE REAL AND IXNORM IS INTEGER. FILE# NREC CONTAINS FORMAT COMMENTS 1 - TEXT FILE - CONTAINS ITEMS 1 TO 11 OF THIS WRITE-UP 2 19 (UP/UE)*(L/DELTA995 + 2), 2E13.6 RECORD 1- MAXIMUM (CF-CFO)/CFO VALUES (UP/UE)*(L/DELTA995 + 2), 2E13.6 RECORD 2- MINIMUM (CF-CFO)/CFO VALUES (UP/UE)*(L/DELTA995 + 2), 2I6 RECORDS 3-19 (CF-CFO)/CFO NORMALIZED VALUES A SAMPLE PROGRAM FOR READING FILE 7 AND PRINTING IT IS SHOWN BELOW. THE JCL SHOWN IS FOR THE STANFORD CIT FACILITY. CHECK WITH YOUR OWN COMPUTER INSTALLATION FOR THE EXACT JCL NEEDED //TAPE JOB BZC$NJ /*SETUP TAPE=1,INPUT=(LIBRARY NUMBER ASSIGNED TO TAPE) // EXEC FORTCG //FORT.SYSIN DD * C TO READ FILE 2 OFF TAPE C PRINT MAXIMAS AND MINIMAS OF ALL THE VARIABLES C PRINT NORMALIZED INTEGERIZED VALUES OF ALL THE VARIABLES. INTEGER VELRAT(17),CFRAT(17) READ (23,30) VELRMX,CFRAMX READ (23,30) VELRMN,CFRAMN DO 10 I = 1, 17 10 READ (23,40) VELRAT(I),CFRAT(I) WRITE (6,50) VELRMX,CFRAMX WRITE (6,50) VELRMN,CFRAMN DO 20 I = 1, 17 20 WRITE (6,60) VELRAT(I),CFRAT(I) 30 FORMAT(2E13.6) 40 FORMAT(2I6) 50 FORMAT(1X,2E13.6) 60 FORMAT(1X,2I6) STOP END //GO.FT23F001 DD UNIT=T1600,VOL=SER=(TAPE LIBRARY NUMBER), // DISP=(OLD,KEEP),DCB=(RECFM=FB,LRECL=80,BLKSIZE=8000,DEN=3), // LABEL=(2,NL) // -------------- END OF FILE NUMBER 103------------- ----------------- FILE NUMBER 104----------------- 0.220000E-01 0.242000E 00 0.000000E 00 0.000000E 00 0 0 455 41 909 165 1364 372 1818 744 2273 1240 2727 2149 3182 3017 3636 3760 4091 4463 4545 5041 5455 6322 6364 7314 7273 8140 8182 8843 9091 9504 10000 10000 -------------- END OF FILE NUMBER 104------------- 2 6364 7314 7273 8140 8182 8843 9091 9504 10000 10000 -------------- END OF FILE NUMBER 104--------