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ENGINEERING RESEARCH INSTITUTE UNIVERSITY OF MICHIGAN ANN ARBOR CALIBRATION REPORT ON THE UNIVERSITY OF MICHIGAN 8- BY 13-INCH SUPERSONIC WIND TUNNEL PART V. AERODYNAMIC CALIBRATION AT NOMINAL MACH NUMBER OF 2.43 By H. P. LIEPMAN J. L. AMICK T. H. REYNOLDS WTM-248 (SECOND SUPPLEMENT TO UMM-36) January, 1954

TABLE OF CONTENTS Page LIST OF FIGURES iv SUMMARY 1 INTRODUCTION 1 MACH-NUMBER DISTRIBUTION 3 FLOW INCLINATION 9 Instrumentation 9 Calibration of Instrument 9 Tests and Corrections 12 Results 13 INFLUENCE OF DEWPOINT 14 STAGNATION PRESSURE IN THE TEST SECTION 16 BLOCKING AND RUN TIME 16 REFERENCES 17 iii

LIST OF FIGURES Fig. Page 1. Nozzle Outline and Mach-Number Distribution on Centerline of Nozzle Sidewalls 3 2. Photograph of Oil Streaks on Nozzle Sidewall and Comparison with Theoretical Streamlines 4 3. Vertical Shock Pattern and Mach-Number Distribution in Test Section 5 4. Schlieren Photograph of Test Section at Mach 2.43 without Model 6 5. Mach-Number Distribution in Horizontal Plane through the Test-Section Centerline 7 6. Mach-Number Distribution in Vertical Plane through the Test-Section Centerline 7 7. Horizontal Shock Pattern in Test-Section and Sidewall-Window Junctures 8 8. Five-Cone Probe 9 9. Sensitivity of Top and Bottom Orifices to Vertical Flow Inclination 10 10. Interaction of Vertical Flow Inclination with Side Orifices 11 11. Vertical Flow Inclination 13 12. Horizontal Flow Inclination 14 13. Influence of Humidity on Static Pressure 2.5 Inches Upstream of Test-Section Centerline 15 14. Influence of Humidity on Total Pressure 2.5 Inches Upstream of Test-Section Centerline 15 iv

ENGINEERING RESEARCH INSTITUTE ~ UNIVERSITY OF MICHIGAN CALIBRATION REPORT ON THE UNIVERSITY OF MICHIGAN 8- BY 13-INCH SUPERSONIC WIND TUNNEL PART V. AERODYNAMIC CALIBRATION AT NOMINAL MACH NUMBER OF 2.43 SUMMARY The nozzle blocks used in this calibration were designed for an outlet Mach number of 2.5 by a modified Nilson method without boundary-layer correction. The average Mach number of the flow near the center of the test section was found experimentally to be 2.43. From 4 inches upstream to 4 inches downstream of the test-section center, the Mach number varies from 2.41 to 2.43 with local peaks of 2.45 due to disturbances from the window junctures. Flow conditions correspond to a Reynolds number of approximately 3.3 x 106 per foot. Most of the flow angles measured in the test-section rhombus were within + 0.2~ except for local extremes, due to window disturbances, of +0.50 to -o.60 in angle of attack and from +0.9~ to -0.9~ in angle of yaw. The stagnation pressure loss in the test section was found to be negligible. The allowable test dewpoint was estimated at -20~F. INTRODUCTION This report is the second supplement to the basic calibration report of the 8- by 13-inch supersonic wind tunnel of the Department of Aeronautical X1_.

ENGINEERING RESEARCH INSTITUTE ~ UNIVERSITY OF MICHIGAN Engineering at the University of Michigan. Reference 1 described the tunnel and the associated equipment and presented the aerodynamic calibration of the flow at M = 1.90. The first supplement2 to the basic report gave the calibration data at M = 2.84 and 1.44. In the present report the aerodynamic calibration of the flow in the test section is presented for nozzle blocks designed to give an outlet Mach number of 2.5 by a modification of the Nilson method.' without boundarylayer correction. The dimensions of the M = 2.5 nozzle blocks are listed in Table I. Frost's modification of the Nilson method consisted of the additional design requirement that the Mach-number gradient dM/dx be continuous throughout the nozzle.3 This was accomplished by assuming a sinusoidal function for the TABLE I MACH-2.5 NOZZLE ORDINATES X" Y" X" Y" X" Y" -13.445 7.500 5.651 3.049 30.183 6.381 -12.938 7.368 6.119 3.141 31.455 6.421 -12.445 7.046 6.586 3.238 32.714 6.451 -11.952 6.609 7.053 3.339 33.951 6.472 -11.459 6.129 7.519 3.444 35.159 6.486 -10.719 5.491 7.986 3.552 36.329 6.494 -10.111 5.o66 8.453 3.662 37.455 6.498 - 9.447.4.659 8.921 3.774 38.529 6.500 - 8.735 4.277 9.389 3.887 39.545 6.500 (I) 9.663 - 7.978 3.924 9.858 4.000 - 7.183 3.605 10.328 4.112 - 6.355 3.324'10.800 4.222 - 5.499 3.081 11.274 4.329 - 4.619 2.879 11.750 4.433 - 3.720 2.719 12.228 4.533 PATCHING MACH - 2.805 2.599 12.794 4.645 LINE (PML) 13.287 (PML) - 1.879 2.518 13.798 4.826 - 0.943 2.475 14.823 4.974 T 0.000 2.465 15.871 5.151 0.473 2.472 16.941 5.298 0.946 2.487 18.034 5.438 1.419 2.510 19.152 5.570 1.891 2.540 20.295 5.694 INFLECTION 2.363 2.579 21.463 5.812 POINT 2.835 2.625 22.655 5.922 THROAT (I) 3.306 2.678 253.871 6.023 (T) 3.776 2.739 25.108 6.116 4.246 2.807 26.363 6.198 4.715 2.881 27.630 6.270 5.183 2.962 28.906 6.331 2

ENGINEERING RESEARCH INSTITUTE * UNIVERSITY OF MICHIGAN area parameter h along the centerline instead of Nilson's quadratic representation. Continuity of dM/dx also assures continuity in the curvature of the nozzle contour as shown in References 3 and 5. Since most of the instrumentation and techniques used in this calibration have been adequately described in Reference 1, the experimental data will be presented without an extensive discussion of the methods, except in the case of flow-inclination measurements, which were obtained with a new probe. MACH-NUMBER DISTRIBUTION The Mach-number distribution was evaluated by means of static pressure orifices on the tunnel walls and by means of the five-prong total-head probe in the test section.l The measured static and total pressures were converted to Mach number with the assumption of isentropic flow, which is justified by the stagnation-pressure measurement presented later. Mercury manometry was used to measure the total pressures and static pressures upstream of station 40, while static pressures downstream of station 40 were measured by oil manometry. The specific gravity of the Meriam red oil used, compared with water at 390F, was found by calibration against distilled water to be 0.839 at 72F, decreasing by o.oo00367 for each F rise above 720F. The standard deviation in measurements of the ratio of static pressure to barometric pressure by oil manometry was found to be 0.00015. (T) (I) (PML)' — _____- - NOZ-ZLE OUTLINE.. 2.8 2.4 - - -_ -- 2.0 i 4 I D 7 5 7bJ 2 68 64 I 3 6 52 4 4 4 6 32 2EXPERIMENTAL Z: + WEST SIDEWALL 3:~ 1.2 - - - - - __ - - 0 EAST SIDEWALL <3[o0~~~~~~~~ -THEORY =E.8 4 80 75 72 68 64 60 56 52 48 44 40 36 32 28 24 INCHES UPSTREAM OF TEST-SECTION Fig. 1. Nozzle Outline and Mach-Number Distribution on Centerline of Nozzle Sidewalls 3

.. i. / POTENTIAL FLOW (THEORETiCAL) VISCOUS FLOW NEAR SURFAGE (EXPERIMENTAL) MAGH LINES (b) Fig. 2. Photograph of Oil Streaks on Nozzle Sidewall and Comparison with Theoretical Streamlines...... 4..;,,iiii:3~~~~~~~~~~~~~~~i~~~~ji iiiiij~~~~~~~~~~~~~iije~~~~~~~~ijiiijii............. ~~~~~~~::::r~~~~~~~~~~~~~~~~~~~.......................,~.~.~~~l~u ~.~~:~:~:~~I:~:~:~:~1* ~~:~:~:......... -------------- ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~::::.....:~r r xx xx ru w ~~: ~~~~:l::~~~~~:::1 ~ -------------------------------------------------------------— a:~:~ *:~:~~:~::~I:~~~ X I I~~~.X X X II X IIIII*L*X I*I1 V.................................................,~uUl ICUS FLD E B UFAC &XE IEF~& ~~~~-~~~~~~ PdlB~~~~~~~~~~~~~~~~~W tlfJE$~~~~~~~~~~~~................... Fig. 2. Photograph of 03_:1 Streaks on Nozzle Sidewa~~~~~~~~~~~~~~~~~~~~~~~~~~~............. and Comp~~~~~~~~~~rjson with Theoretical Stre~~~~~~~~~~~~~~~~~~~~~~.........................

ENGINEERING RESEARCH INSTITUTE ~ UNIVERSITY OF MICHIGAN Figure 1 compares the theoretical Mach-number distribution on the nozzle walls with experimental values. The agreement is good until the flow reaches a point about 20 inches downstream of the throat; beyond this point the experimental values are lower than the theoretical ones. It is believed that this deviation is due to boundary-layer thickening on the sidewalls. The vertical pressure gradients in the nozzle tend to create a boundary-layer flow from the top and bottom of the nozzle toward the sidewall centerlines. The effect is greatest above and below the intersection of the patching Mach line with the sidewall centerline, which is the upstream limit of the theoretical constant-Mach-number region. Visual evidence of this well-known phenomenon is shown in Fig. 2. Figure 2(a) shows oil streaks on the nozzle sidewalls, and Fig. 2(b) shows a comparison of these actual streamlines in the viscous layer near the wall with theoretical streamlines of the main (potential) flow. The maximum angular discrepancy between these streamlines is about 100. JUNCTURE OF NOZZLE WITH TEST SECTION e //?2,l //50 /SIDE VIEW OF TUNNEL TEST SECTION 2.50 EASTSeDEWALL A WEST SIDEWALL, 2.4-0 0 0 X 235 2.30 - 28 26 24 22 20 18 16 14 12 10 8 6 4 2 0 -2 -4 -6 -8 -10 INCHES UPSTREAM OF TEST-SECTION CENTERLINE Fig. 5. Vertical Shock Pattern and Mach-Number Distribution in Test Section The Mach-number distribution on the tunnel walls downstream of the nozzle exit and on the axial centerline in the test section is shown in Fig. 3, which is a sketch of the test section showing the location of the two principal observed shocks (see the schlieren photograph of Fig. 4) which appear to originate from the horizontal joints between the nozzle and the test section. The Mach-number distribution can be correlated with these shocks and their

ENGINEERING RESEARCH INSTITUTE. UNIVERSITY OF MICHIGAN t Mach 2.i'J }w: i thou t Model..... associ-ated expansion regions. The decreases in Mach number from station 20 to statLon.2 on the east and west sides of the tunnel, and from station 6 across3 the shocks. The increases i.n Maclh numwber from station 22 to stati-on 1.4e on the top and bottom of -the -ttmune].a from station -2 to station ~4 on the top and bott;om of thze tunne]l. and. from s~ta-ti on 1 0 to sta-t;ion 4r al<ong the section wall]s. The Mach-numnber dis tcribut:[ ons i.n -the hori.zontal anwd verti.cal p].anes of the teset sec-tion are shlown in Figs. 5j and 6 respectlve].y. The average Mach numbetograph of the f]ow ath e tesect seio t:on ion 23. att MaMh rwutaers vaclry fron 2 j wic thout Modeh k soeats grad expansion decregions.e t 2.decreases n Mach number fro36tion 20

4a 2.4 LL 245 0 2o00 n~4 0 0 0 0 I _ _ _ _ _ _ _ _ _ _ _ _ ___ ___ ___ t 2.35 2.40 Cn 2~40 i0 2 w.4 10 8 6 _16. -W.4 U_ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~~~23 045 0 0 w 0 -2 - C~~~~~~~~~g~~ ~ 2.40 (p -40 0 w 0 CI 0 2.3502. 2.45 2.45 Cr ~~~~~w 0 00 0~>~ w A-02~40 4..;J P-400J d ~2A I U F 5etM2.3aD Z I -W 2.45 402 245 OLL 2.40 01 O 2A O, in w T 2.3 T Cetrln 4 245~~~~~~~~~~~~~~~~~~~~~~~~~-1 2.4 5 U_ 0 0 0 0 0 2.40 0, 0 2.3 2. 3y 1 10 8 6 4 2 0 -2 -4 10 8 6 4 2 - CQ INCHES UPSTREAM OF TEST- SECTION INCHES UPSTREAM OF TEST- SECTIOF Fig. 5.Mach-Number Distribution Fig. 6. Mach-Number Distribto in Horizontal Plane through the in Vertical Plane througl h Test-Section Centerline Test-Section Centerline

ENGINEERING RESEARCH INSTITUTE ~ UNIVERSITY OF MICHIGAN A line drawn through the major local irregularities in the horizontal plane shows that the expansions and shock waves causing them probably originate from the window junctures. The probable path of these disturbances is indicated in Fig. 7, which also presents cross sections of the two sidewallwindow junctures. The east wall is somewhat smoother than the west wall. The east wall has one 0.008-inch drop and one 0.004-inch drop, while the west wall has a 0.005-inch drop, a 0.004-inch rise, and then a 0.013-inch drop again. It would be possible to alleviate these irregularities somewhat, but to eliminate them altogether would be very difficult. These step heights are larger than those at the juncture of the nozzle with the test section, which are probably not greater than 0.002 inch. WEST SIDE WALLI r~WINDOW FRAME GLASS WINDOW FRAME-7 DIRECTION OF FLOW ~ ~ _I POINTS OF MAJOR LOCAL IRREGULARITIES IN FLOW l' EAST SIDEWALLJ 12 10 8 6 4 2 0 -2 -4 -6 -8 - 10 INCHES UPSTREAM OF TEST-SECTION TOP VIEW OF TUNNEL WINDOW FRAME GLASS TUNNEL ~N\\\\\N \\\\\N\ WEST LOW-MELTISIDEALL POINT ALLOY.00)2. 15" 1- 7.0081" NOTE: DRAWING IS OW-ELTING POINT ALL WINDOW JUNCTURE EAST SIDEWALL WINDOW JUNGTURE Fig. 7. Horizontal Shock Pattern in Test-Section and Sidewall-Window Junctures 8

ENGINEERING RESEARCH INSTITUTE UNIVERSITY OF MICHIGAN FLOW A'LNCI NAT LON ]:n s t r ument ai,:t on........................................................................................ Y......................... Th. VO f' v coe oe probe shown 1:i i w used to measure the f'l.ow i:n.l-l.i.nrait:to-; ]:r'L:1 T, L,: cmposed of fl:ive calone,s with total cone (angl.nes oe r.60:Ih:e cente r cone, has i. equal]I]y,paced or it:i:ces; i }f the.ou.tr outier cotres: have'f:Otil' c(:ta] 11.3' -pal. eed or if:i ice::,'.I.}.ches orcti.:f':i. ces ha. re 0.0"i:':.i...l t;aet(t ial fourequ II','ji edot I hse n ( Oe hie 0 02 ineh d~iameter s and are on 0 1.9')5 i nh..i.nhci e i:i(: V i. lt.]. ( r:'hes [ enltel olf t.the out(: o~lle ar.te l,]./ mountedl on thee s-ee 0 trt u of the;:imd,tmin-lle1.. The pressu1_re at the ~~~~~~~~~~~~~~~~................. ~.............".....:X i. m i(thes f':cm't:,}e m:[d.'o(:>:i.c[ o f' tlle een b(:t"ne a~ca i;otd i~ ci~O~ Me.n';~.r'a'ls r.i~: p):co.1a. rfi ot:~tlt,(:;rJ O~1 Lh o. a;~2c... s(:.:c~c ot:,<3 [;rt~'[; o:[ [;}l(:....;................c......]?h..........,...:.....:..:...'.:;.'... or"ifice s were imeasured, on a Iifnomie~t:e. bmojrd. us.'i.ng Meri~:am red. o. ti.] F'i:g. S. Fi've-Cone Probe Ca].ibrat i.on of instrument..................... IXn ord~er -to determinw e the s>ensi-t;rivity of. the insEtrumneRt to chanzges in flow direction, it wacs mounted so that the center and side cones were very near the axis of' rotation of the strut. When the strut was revo]ved to an.... <...........

ENGINEERING RESEARCH INSTITUTE * UNIVERSITY OF MICHIGAN angle of attack, the orifices of the center and side cones remained effectively fixed. For an angle of attack of 4', the upper and lower cones moved approximately 0.1 inch from their positions at zero angle of attack. By setting the instrument at various angles of attack in the flow, the rate of change of the pressure difference between the upper and lower orifices with the angle of attack was obtained. (The center cone has two orifices on the top and two orifices on the bottom. Here the sum of the pressures of the upper orifices was subtracted from the sum of the pressures of the lower orifices.) At the same time the effect of angle of attack on the pressure difference between left and right orifices on each cone was measured. This latter effect was small and would theoretically be zero if the side orifices and the flow were perfectly symmetrical. Typical cone-sensitivity calibration plots obtained by this procedure are shown in Figs. 9 and 10. Figure 9 shows the sensitivity of the top and bottom orifices of one of the cones to flow inclination in the vertical plane, along with the theoretical sensitivity given by Reference 6. Figure 10 shows BAROMETRIC PRESSURE= 501" OIL EXPERIMENTAL THEORETICAL 3C0 25 180" ROLL 20 00 ROLL 1- 5 0 X10 5 uc. -5 0 -2 o 2 4 Fig. 9. Sensitivity of Top and Bottom Orifices to Vertical Flow Inclination 10

ENGINEERING RESEARCH INSTITUTE ~ UNIVERSITY OF MICHIGAN the interaction of vertical flow inclination with side orifices, which are intended to measure only flow angles in a horizontal plane. (The angles of attack shown in these figures are measured from an arbitrary fixed reference.) Since the circular arc strut provides only the angle-of-attack variation, it was necessary to rotate the instrument 90~ about its axis to determine the sensitivity of the side orifices to changes of flow angle in their own plane. The procedure was the same as that for the top and bottom orifices and was repeated with the instrument inverted in order to obtain a check on cone alignment with the sting. The interaction between the effects of flow angles in the vertical and horizontal planes was eliminated by solving two simultaneous equations, AP = K1c + K2 (1) and APv = K3 + K4P. (2) In these equations a and D are the flow angles in the vertical and horizontal planes, respectively; K1, K2, K3, and K4 are the calibration constants of one BAROMETRIC PRESSURE-501" OIL v I I ~ o i 1800 ROLL -5 -6 -4 -2 0 2 4 ANGLE OF ATTACK, DEGREES Fig. 10. Interaction of Vertical Flow Inclination with Side Orifices 11

ENGINEERING RESEARCH INSTITUTE * UNIVERSITY OF MICHIGAN of the cones; and ApH and Apv are the differences in pressure between two orifices in the horizontal and vertical planes, respectively. In general, K1 and K4 are small compared to K2 and K3, and would be zero if the orifices were perfectly aligned in the horizontal and vertical planes. Solving equations (1) and (2) for a and A, we get a = C lAPv - c2ApH (3) and D = C3 APv - c4 APH, (4) where K2 K4 c1 = c2 = C1 K2K3 - K4K1 c2 K2K3 - K4K1 Kl K3 3 KK4 - K1K2 K1K4 - K K2 Equations for a and P are thus obtained for each of the five cones. Tests and Corrections The flow was surveyed from 8 inches ahead of to 2-1/2 inches behind the test-section center at intervals of 1/2 inch or 1 inch. For these runs the arc-sector strut remained at a fixed angle of attack. The sting was measured before each run by a height gage to get its angle of attack and angle of yaw with respect to the tunnel floor and the west wall. The distance between the front and rear measurements was 20.3 inches for the angle-of-attack and 16.8 inches for most of the angle-of-yaw measurements. From the scatter of the measured values of sting misalignment, it is deduced that the probable maximum error in these measurements was +0.03~. The measured pressure differences between opposing orifices of each cone were converted to the indicated values of a and P by means of equations similar to (3) and (4). Corrections were then applied to a and P for cone misalignment from the sting and the sting misalignment in the tunnel. The cone-misalignment correction was obtained by averaging the flow through the test section after the sting-misalignment correctionhad been applied. Assuming that the average through the length of the surveyed region of the flow angles indicated by each cone would be zero, any deviation of this average from zero was attributed to cone misalignment. This was checked by measuring 12

ENGINEERING RESEARCH INSTITUTE * UNIVERSITY OF MICHIGAN the difference between the 00 roll calibration and the 1800 roll calibration at zero angle of attack. The two methods checked in the case of the center cone. The four outer cones could not be checked in this manner, since they change position when the probe is rotated 180~. The average cone misalignment was 0.3~. The flow-angle measurements were found to be repeatable to within +0.050. Results The flow angles obtained are shown in Figs. 11 and 12. If the flowangle deviations due to window disturbances are not considered, most of the remaining flow angles fall within the range of +0.20. The extremes due to window effects are from +0.5~ to -0.6o for the vertical plane and from +0.9~ to -0.9~ for the horizontal plane. In addition, unexplained flow deviations of about +0.5~ exist about 7 inches ahead of and 2 inches behind the testsection center. The flow angles near shock waves are not expected to be very accurate because of interference between cone and shock wave. ".4 T-.4.4 w Iii o 4 -.4 0 -8 7 6 5 4 3 2 I 0 -1 -2 -3 INCHES UPSTREAM OF TEST-SECTION. Fig. 11. Vertical Flow Inclination 15

ENGINEERING RESEARCH INSTITUTE * UNIVERSITY OF MICHIGAN w 4 0 2 -.2 o:, o LL. )- cn I 4 %.0.2 0o U. I -.2 8 7 6 5 4 3 2 I 0 -I -2 -3 INCHES UPSTREAM OF TEST- SECTION 4 Fig. 12. Horizontal Flow Inclination INFLUENCE OF DEWPOINT CDj_ T The effect of dewpoint on static pressures 2.5 inches upstream of the test-section centerline was measured by means of the single static needle described in Reference 1. The colorless fluid butyl phthalate, whose specific gravity is 1.034 at 800F, was used in the U-tube. The dewpoint effect on the total pressure at the same station was measured with the total-head rake. Figures 13 and 14 respectively show the influence of dewpoint on the static-pressure ratio Ps/Pb and the total-head probe ratio Po'/Pb, 2.5 inches upstream of the test-section center. The change in dewpoint only slightly affects the total-head measurements, because the shock from the total-head probe gets weaker as the condensation shock gets stronger. As the dewpoint decreases from +400F to -400F the static-pressure ratio decreases from 0.070 to o.o655. For dewpoints below -200F the increase in static pressure due to condensation is masked in the experimental scatter of static-pressure measurements. Consequently, the allowable test dewpoint can be considered to be -200F. 14 T.11 - - la - - - - _: - J _ - I - - I - Co n se-N % 0 - L, _ - _ - _ _ I

- J 5400 LL 0 5300 w.071 5200-.-i — / 5400 U. oO 5070 0 5300 a..~" G.. = 5200I-,,:::U) I.t W~W uJ0 CL,J 0 " 200.0 W.069 5400 D w~~~~~~~~~~~:n C Cn w 0 cn., 5300_ _ a. w H ao 5.068. 5200 [1S~~~~~EPIT O EPIT OF a: o w i. w 535c 2. Inches Upstream of Test-Section Centerline 2.5 Inches Upstream of Test-SectionBenterline __0 525C.066 - 0400 0 44~ U 4 00 -J I- 4~~~~~~~~~~~~~~~~~~~~~~L 0 05300La51 1 I l I I I 1 I _s520 C — -50 -40 -30 -20 -10 0 10 20 30 40 50 C-J -40 -30 -20 -10 0 10 20 30 40 DEWPOINT, 0F DEWPOINT, OF Fig. 15. Influence of Humidity on Static Pressure Fig. 14. Influence of Humidity on Total Pressure 2.5 Inches Upstream of Test-Section Centerline 2.5 Inches Upstream of Test-SectionCenterline

ENGINEERING RESEARCH INSTITUTE * UNIVERSITY OF MICHIGAN STAGNATION PRESSURE IN THE TEST SECTION Comparison of the static and total pressures measured 2.5 inches upstream of the test-section center at dewpoints below -200F gives values of the stagnation pressure loss through the nozzle varying between 1.0 and -0.8 percent, with an average value of 0.1 percent. Thus it can be said that there is no loss in stagnation pressure within the measuring accuracy of the equipment. The stagnation pressure loss through the turbulence screens was found to be 0.1 percent, which is small enough to be neglected. BLOCKING AND RUN TIME No tests were made of the blocking characteristics of the Mach-2.43 flow. However, blocking was tested at Mach 1.90, where model size is more critical.1 Run time was not investigated for the Mach-2.43 flow. 16

ENGINEERING RESEARCH INSTITUTE * UNIVERSITY OF MICHIGAN REFERENCES 1. Culbertson, P.E., "Calibration Report on the University of Michigan Supersonic Wind Tunnel, Parts I and II", UMM-26, Univ. of Mich., Eng. Res. Inst., November, 1949. 2. Culbertson, P.E., "Calibration Report on the University of Michigan Supersonic Wind Tunnel, Parts III and IV", WTM-213, Univ. of Mich., Eng. Res. Inst., June, 1952. 3. Frost, R.C., "Nozzle Design Considerations"', WTM-188, Univ. of Mich., Eng. Res. Inst., October, 1950. 4. Nilson, E., "Design of an Inlet for a Two-Dimensional Supersonic Nozzle", Meteor Report, UAC-13, December, 1947. 5. Frost, R.C., and Liepman, H.P., "Supersonic Nozzles with Continuous Wall Curvature", Journ. Aero. Sci., 19, No. 10, 716 (October, 1952). 6. Kopal, Zdenek, "Tables of Supersonic Flow Around Yawing Cones", Mass. Inst. of Tech., June, 1947. 17

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