1、NASA CGNTRACTOR REPORT NASA Ck-61365 RESULTS OF A STUDY OF MACH NUMBER AND REYNOLDS NUMBER EFECTS ON THE CROSSFLOW DRAG CHARACTER ISTICS OF OG IVE-CY LINDERS AND OG IVE-CY LINDER-FRUSTUM-CY LINDERS AT ANGLES OF ATTACK TO 30 DEGREES By J. E. Foiey Chrysler Corporation Space Division Huntsville, Alaba
2、ma October 22, 1941 - u#)Zr fb N72-13976 (NASA-CB-61365) RESULTS OF A STUDY OF HACB BUlBEB AND REYNOLDS HUlBBB BPFZCTS ON THE CROSSPLOW DRAG CHABACTERISTICS OF OGIVE Unclas CYLINDBBS AND J.E. Poley (Chrysler Corp. ) It229 22 oct. 1971 68 p CSCL 20D G3/01 3 - Prepared for NASA-GEORGE C. MARSHALL SPAC
3、E FLIGHT CENTER Marshall Space Flight Center, Alabama 358 12 Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-TECHNICAL REPORT STANDARD TITLE PAGE 4. TITLE AND SUBTlrLE RESULTS OF A STUDY OF MACH NUMBER AND REYNOLDS NUMBER EFFECTS ON THE CROSSFLObI DR
4、AG CHARACTERISTICS OF OGJXl$-CYLINDERS AND OGIVE: -CYLINDER-FRUSTUM-CYLINDERS AT ANGLES OFe ATTACK TO 30 DEGREES 7. Author(s) by J, E. Foley 9. PERFORMING ORGANIZATION NAME AND ADDRESS Washington, D. C. 3. RECIPIENTS CATALOG NO; 1. REPORT NO. NASA CR-61365 5. REPORT DATE October 22, 1971 6. PERFORMI
5、NG ORGANIZATION CODE 8. PERFORMING ORGANIZATION REPORT R TN-AP-71-527 10. WORK UNIT NO. Chrysler Corporation Space Division Huntsville, Alabama 12. SPONSORING AGENCY NAME AND ADDRESS NASA 14. SPONSORING AGENCY CODE 2. GOVERNMENT ACCESSION NO. 1 I. CONTRACT OR GRANT NO. NAS 8-21152 . - - .- -. 13. TY
6、PE OF REPORT a vsln a! V Free-stream velocity X Model axial station, meaaureg from nose vertex Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-SYMBOLS AND NOMENCLATURE (continued) Axial location of initial cross-flow separation Angle- of attack Merid
7、ian angle, measured from windward plane of symmetry Kinematic viscosity Model roll angle Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-INTRODUCTION The non-linear variations of the force characteristics of slender bodies of revolution with angle of
8、 attack have long lieen recognized to be primarily due to the effects of boundary layer separation induced by the crossflow. unk(1) (1924) first pointed out a useful analogy between the development of the crossflow along a body of revolution at angle of attack and the development of the crossflow ab
9、out a two-dimensional circu- lar cylinder impulsively started from rest. This analogy is based on a simplified one-dimensional approach to the flow wer a body of revolution at angle of attack, as illustrated in figure 1. A plane lamina of air, perpendicular to the axis of the body, is considered to
10、be moving with constant velocity in the stream direction. This lamina sees the body as a segment of a circular cylinder, suddenly introduced as the lamina po -sea the nose of the body, and moving in the plane of the lamina at a velocity Vsin a!. Neglecting the effect of the changing cylinder radius
11、at the nose, this situation is identical to the classical flow about a two-dimensional circular cylinder impulsively started from rest to a velocity Vsin a! , with the crossflow distance X/D. tana! for the body of revolution being equivalent to the distance S/D = Vsin A t/ traveled by the impulsivel
12、y started cylinder. The experimentally detefmined flow about the impulsively started cylinder is described by oldsteint?) : for a range of Reynolds numbers as being characterized by the symmetrical development of a pair of vortdces on the lee side of the cylinder, fed by vortex sheets emanating from
13、 the point of bocndary layer separation on the cylinder. This flow is illustrated in figure 1, at various stages of development, as applied to, the case of the body of revolution at angle of attack. The above description of the crossflow phenomenon has been exploited theoretically and empirically by
14、 many investigators (e.g. references 3 through 7) in the development of methods to predict the resulting forces on bodiesof revolution at angle of attack. The empirical methods generally consist of adding to the predicted local potential normal force distribution, which accounts for the forces gener
15、ated by the nose, a local crossflow drag coefficient determined from impulsively-started andlor s teady-state ex- perimental drag data for two-dimensional _circular cyl.inders. Theoretical methods utilize a “lumped“ vorticity approximation for the vortices in a “slender body“ potential flow field. T
16、he methods have met with various degrees of success but none are capable of accurate predictions over 9 practical range of Mach numbers, Reynolds numbers and body shapes. A basic shortcoming of previous studies has been a lack of syst is tics - The date: presented in figures 4 and 5 show some very s
17、ignificant in- fluences of Reynolds number and Mach number on the characteristics of these confLgurations. The greatest effect of Reynolds number is observed for the O/C configuration at M = 0.4, even excluding the high Reynolds number LTV data. The normal force coefficients versus Reynolds number a
18、t the higher angles of attack exhibit all the features of the classical variation:-of drag coefficient with Reynolds number of two-dimensional circular cylinders in incompressible transverse flow (e.g. reference 2). There is a sub- critical maximum associated with laminar boundary layer separation a
19、nd a minimum value at a critical Reynolds number associated with transition of the boundary layer to burbulent flow. The subcritical maximum nopal force coefficients are approximately twice the minimum values at the higher angles of attack. The center of pressure for the O/C at M = 0.4 also shows la
20、rge variations with Reynolds number. Largest CP/D variations occur at an angle of attack of 20 where the CP/D at subcritical Reynolds numbers is located at 5.5 calibers from the base, and moves forward to 6.9 calibers at the critical Reynolds number. Data for the O/C at higher Mach numbers exhibit a
21、 decreasing effect of Reynolds number with increasing Mach number. At M = 2.0, significant Reynolds number effects are confined to angles of attack of 10 and 15O where the crossflow Mach number ( = M sinar) is .35 and .52 respectivel*. This is also consistent with circu “F ar cylinder data (referenc
22、es 11, 12) which show little ef feet of Reynolds number abduQ MC = 0.4 to 0.5. Data for the ogive/cylinder/f rustum/cy linder shown in figure 5 indicate very small effects of Reynolds number as compared with the ogive/cylinder configuration. This is due to the combination of (1) a small forward cyli
23、nder planform area which reduces the contribution of its crossflow drag to the total normal force, (2) the large, 25O, slope of the frustum which delays crossflow separation effects on the frustum to angles of attack above 250, and (3) the relatively short aft cylinder length, with flow at the forwa
24、rd end controlled to a large extent by axial flow pressure distribution and a large potential carryover normal force from the frustum. These factors are illustrated later using the integrated pressure data from the WFC pressure tests. Correlation of O/C ormal Force Characteristics Correlations of th
25、e O/C normal force data were made for the purpose of gaining some insight into the effects of Mach number and Reynolds number, and to develop correlation parameters for use in the analysis of the local normal force and pressure data. As indicated above, the M = 0.4 data hows the greatest sensitivity
26、 to Reynolds number. At thia Mach number no com- pressibility effects should be present, and these data were thus used to isolate the effects of Reynolds number. The data was reduced to crogsflow drag coefficients according to the equation. Provided by IHSNot for ResaleNo reproduction or networking
27、permitted without license from IHS-,-,-The inviscid normal force slope, $ , was taken tq be the slender body a! theory value of 2.0 radl and was in close agreement with the experimental data. According to Allens theory (reference 3), the crossf low drag coefficient at incompressible speeds should be
28、 a function of the crossflow Reynolds number Res I A correlation of the M = 0.4, O/C crossflow drag data with crossflow Reynolds number,.CDC (ReC) is shown in figure 6 for various values of free stream Reynolds numbers based on diameter, R%, and for angles of attack of 10, 15, 20, 25 and 300. This c
29、orrelation was developed using the normal force data represented by the faired (solid) curves of figure 4 (a), for ReD between 105 and 4 x lo5. The lack of any correlation of crossflow drag with crossflow Reynolds number in figure 6 is obvious. u It was pointed out by Schindel (reference 6) that bod
30、y lengths parallel to the free stream (i.e. streamwise lengths) are approximations of particle paths, as indicated ir the sketch below, and shoudd represent appropriate lengths for determination of boundary layer transition. A Reynolds number based on a characteristic body length parallel to the fre
31、estream should therefore provide an approximate correlation of boundary layer transition and its effect on the crossflow drag characteristics. This hypothesis was tested by correlating the O/C crossflow drag data at M = 0.4 as a function of a “streamwise“ Reynolds number, Res = VD . This Reynolds nu
32、mber v sin a! is based on the streamwise length of the cylindrical portion of body, Dlsina. The correlation is shown in figure 7 and it is seen that the streamwise Reynolds number does in fact correlate the crossflow drag data quite well. Provided by IHSNot for ResaleNo reproduction or networking pe
33、rmitted without license from IHS-,-,-The effect of compressibility on crossflow drag coefficient was investi- gated by plotting the data vs crossflow Mach number at two free stream Reynolds numbers, RD = 2 x lo5 and 5 x 106, representative of the minimum and maximum values of the test range. The res
34、ults, shown in figure 8, were developed from CN(ar) data for each fsee stream.Mach number and Reynolds number, at iingles of attack from 10 to 30. The high Reynolds number (LTV) data at M = 0.4 was excluded for the previously stated reasons. Crossflow-Mach number correlates the compressibility effec
35、ts on cross- flow drag coefficients very well for the high Reynolds number data (ReD = 5 x lo6) at J$.= 0.8 and above. These data are in the supercritical Reynolds number range and should be relatively insensitive to Reynolds number. The low Reynolds number data (Reg = 2 x 105) is not correlated by
36、crossflow Mach number at M = 0.4 and 0.8. This data is in the sybcritical Reynolds number range where the large effects of Reynolds number were found to be correlated by the ttstreamwisett Reynoldo number, Res, and an improved correiation of compressibility effects could be expected for subcritical
37、Reynolds numbers if it were developed for constant values of the streamwise Reynolds number. The streamwise Reynolds number cannot be considered to be a universal correlation parameter, of course, even at incompressible speeds, as it does not consider the effects of nose shape, is not appropriate at
38、 low angles of attack where Res * cr, ., and does not consider the effects of finite cylinder length which are known to be quite significant an angles of attack approach- ing 900. The above correlations do, however, show the superiority of the streamwise Reynolds number over the crossflow Reynolds n
39、umber as a correlation parameter and should lead to an improved understanding of the effects of Reynolds number on the crossflow separation phenomena. Although direct measurements of the actual state of the boundary layer were not availhble for the conditions of these tests, the crossflow drag corre
40、lations infer that for the angle of attack range 2.Osor s30, the MSFC test conditions corresponded to a fully laminar boundary layer at the lowest Reynolds numbers and that transition occurred on the body at the highest Reynolds ntlmbers. Also, a preliminary evaluation of the rerun LTV data infers a
41、 fulljj turbulent boundary layer at the higher Reynolds number conditions. Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-PRESSKW DATA !Be pressure data, on which the local crossflow drag analysis is based, was obzained on models with high orifice d
42、ensity in order to obtain the large amount of data required in a practical amount 09 wind tunnel occupancy time. The models were basically instrumenteq with 7 longitudinal rows of orifices at 15 azimuthal increments in one quadrant and 2 longitudinal rows of orl- fices at intermediate azimuth angles
43、 in an adjacent quadrant as described on page 3. This arrangement was selected based on the assumption of symmetrical flaw and no orifice effects on the resulting pressure data such that the data zit model roll positions of 0 and 90 could be transposed snd combined to give a detailed pressure distri
44、bution on one side of the model. The pressure data and the local and total force and moment characteristics resulting from integrating the pressure distributions over the surface of the models are reported in their entirety in reference 9. Inspection of these data revealed large asymmetries in the p
45、ressure data andpoor correlation of inte- grated pressure data with the results of the force test for the O/C configura- tion (figure 4) at the lower Mach numbers and higher angles of attack. Limited surface flow visualization tests at M = 0.4 utilizing the actual one in. dia. agive/cylinder pressur
46、e model confirmed the existence of severe flow a symmet- ries at sub-critical Reynolds number, apparently induced by the pressure ori- fices. ffect of Pressure Orifices on Total Normal Force A comparison of the force and integrated pressure data as a function of Reynolds number is illustrated in fig
47、ure 9 for the ogivelcylinder configuration. In general, the pressure models indicate lower normal force at sub-critical Reynolds numbers and higher normal forces at super critical Reynolds numbers as compared with the force model data. This type of result is very similar to the effect of roughness o
48、n the drag characteristics of circular cylinders in transverse flow (reference 2) and indicates that the orifices on the pressure model acted as surface roughness elements. Agreement of force data with inte- grated pressure data for the O/C/F/C configuration was gaod at all conditions indicating lit
49、tle effect of orifices for this configuration. This is consis- tant with the low sensitivity to Reynolds number for this configuration and is due to the geometry of the configuration as discussed on page 6. Effect of Pressure Orifices on Surface Flow and Pressure Distributions The effect of the orifices on the surface flow patterns at the conditions where pressure asymetries were the grea
