1、NASA Technical Memorandum 87659Supersonic Axial-ForceCharacteristics of aRectangular-Box Cavity WithVarious Length-to-DepthRatios in a Flat PlateNASA-TM- 87659) OPEESCNIC AXIAL-fORCE N86-2255UCHAfiACTEBISTICS OF A EEC! ANGULAR-BOX CAVITYWITH- VARIOUS IEKG 1H-1O-DEFTH RATIOS IN AFLAT PLATE (NASA) 21
2、p HC A02/MF AOi l Dnclasv CSCL 01A G3/02 05927A. B. Blair, Jr., and Robert L. Stallings, Jr.APRIL 1986WASAProvided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-NASA Technical Memorandum 87659Supersonic Axial-ForceCharacteristics of aRectangular-Box Cavity
3、WithVarious Length-to-DepthRatios in a Flat PlateA. B. Blair, Jr., and Robert L. Stallings, Jr.Langley Research CenterHampton, VirginiaNASANational Aeronauticsand Space AdministrationScientific and TechnicalInformation Branch1986Provided by IHSNot for ResaleNo reproduction or networking permitted wi
4、thout license from IHS-,-,-INTRODUCTIONDesigners of aircraft, missiles, and reentry vehicles encounter numerous prob-lems which require knowledge of the flow characteristics in and around cavities(refs. 1 to 4). A number of studies have been conducted to investigate cavity flowphenomena (refs. 5 to
5、8). In these studies, flow visualization (schlieren and oil-flow photographs) and surface pressure measurements for various cavity configurationsare used to show that two fundamentally different types of flow fields can occur overcavities and that the two types of flow fields are strongly dependent
6、upon cavitylength-to-depth ratio i/h.Pressure coefficient distributions from reference 8 and flow-field sketches fora shallow and deep cavity that are representative of the two types of cavity flowfields are presented in figure 1. For the case of the shallow cavity (i/h = 19.0),the pressure distribu
7、tions are indications of a flow field that is often referred toas a closed, or attached, cavity flow field. For this type of flow field, the flowexpands (in a Prandtl-Meyer expansion) around the cavity front face, impinges on thecavity ceiling, and exits ahead of the rear face. The local flow turns
8、through largeangles which result in the large pressure gradients shown by the circular symbols infigure 1. Also, low pressures occur on the cavity front face as a result of the flowexpansion in the region, and large pressures occur on the rear face, which appears asa forward-facing step to the appro
9、aching cavity flow. This combination of pressureson the front and rear faces contributes to large cavity drag coefficients. The pres-sure distributions shown for the deep cavity ( t/h = 4.0) are characteristic of a flowfield that is often referred to as an open, or detached, cavity flow field. For t
10、hiscavity, the flow simply bridges the cavity and impinges on the outer edge of the rearface, resulting in relatively small turning angles for the local flow and, conse-quently, a much more uniform pressure distribution over the cavity ceiling. Also,compared with the closed cavity flow field, larger
11、 pressures are measured on thecavity front face and lower pressures are measured on the rear face, both of whichcontribute to lower cavity drag coefficients for the deep cavity with an open cavityflow field.The objective of the present investigation was to determine empty-cavity axial-force coeffici
12、ents associated with deep- and shallow-cavity configurations as part ofa continuing effort to study cavity flow-field effects with respect to cavity geome-try changes. Axial-force coefficient data were obtained for an empty, rectangular-box cavity with various cavity length-to-depth ratios. The metr
13、ic-box cavity (i.e.,box cavity attached to strain-gage balance) was mounted in a generic flat-plate wing.Variations in cavity length-to-depth ratio were investigated to establish and toverify flow conditions in the cavity for deep- and shallow-cavity configurations.The cavity flow fields generated w
14、ere of the open (detached) type or closed (at-tached) type, or both. Large changes in the cavity axial-force coefficient (based ona reference area equal to the cavity rear-face area) reflected these cavity flow-field conditions. In addition, vapor screen photographs that illustrate the complex,three
15、-dimensional nature of the box cavity flow fields were taken during theinvestigation.The tests were conducted in the Langley Unitary Plan Wind Tunnel at Mach numbersof 1.50, 2.16, and 2.86. The nominal angle-of-attack range of the flat-plate wingProvided by IHSNot for ResaleNo reproduction or networ
16、king permitted without license from IHS-,-,-was -4 to 2 at a Reynolds number of 2.0 x 10 per foot. Measurements includedaxial-force loads on the metric-box cavity at discrete cavity length-to-depth ratios.SYMBOLSThe aerodynamic coefficient data are referred to the body-axis system. Valuesare given i
17、n U.S. Customary Units. The measurements and calculations were also madein U.S. Customary Units.CA axial-force coefficient, Measured axial force/qJSC pressure coefficient, (p - ?)/to0)(0o(Us“S 000 t-t,-10)HV4(Cto O0 *-M-iCOCO “Oc -)O 8-H 55g II oO=1 IImj:cnOu =. IIinonioooOII8ns(C-PO,IinDa16Provided
18、 by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-ORIGINAL PAGE fsOF POOR QUALITYJ/hO 4.00D 6.00O 8.00A 10.00bv 12.00CM4.00Q 18.00-8(a) h = 0.50 in.Figure 6.- Effects of cavity i/h on axial-force coefficients withangle of attack.17Provided by IHSNot for Resale
19、No reproduction or networking permitted without license from IHS-,-,-l/hO 2.00D 4.00O 6.00A 8.00MO.OOFigure 6.- Concluded.18Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-1. Report No.NASA TM-876592. Government Accession No.4. Title and SubtitleSupe
20、rsonic Axial-Force Characteristics of aRectangular-Box Cavity With Various Length-to-DepthRatios in a Flat Plate7. Author(s)A. B. Blair, Jr., and Robei9. Performing Organization Name and Addressrt L. Stallings, Jr.NASA Langley Research CenterHampton, VA 23665-522512. Sponsoring Agency Name and Addre
21、ssNational Aeronautics and Space AdministrationWashington, DC 20546-00013. Recipients Catalog No.5. Report DateAoril 19866. Performing Organization Code505-43-23-028. Performing Organization Report No.L-1607510. Work Unit No.11. Contract or Grant No.13. Type of Report and Period CoveredTechnical Mem
22、orandum14. Sponsoring Agency Code15. Supplementary Notes16. AbstractA wind-tunnel investigation has been conducted at Mach numbers of 1.50, 2.16, and2.86 to obtain axial-force data on a metric rectangular-box cavity with variouslength-to-depth ratios. The model was tested at angles of attack from -4
23、 to 2.The results are summarized to show variations in cavity axial-force coefficient fordeep- and shallow-cavity configurations with detached and attached cavity flowfields, respectively. The results of the investigation indicate that for a widerange of cavity lengths and depths, good correlations
24、of the cavity axial-forcecoefficients (based on cavity rear-face area) are obtained when these coefficientsare plotted as a function of cavity length-to-depth ratio. Abrupt increases in thecavity axial-force coefficients at an angle of attack of 0 reflect the transitionfrom an open (detached) cavity
25、 flow field to a closed (attached) cavity flow field.Cavity length-to-depth ratio is the dominant factor affecting the switching of thecavity flow field from one type to the other. The type of cavity flow field (openor closed) is not dependent on the test angles of attack except near the criticalval
26、ue of length-to-depth ratio.17. Key Words (Suggested by Author(s)Supersonic aerodynamicsSupersonic cavity flowOpen cavity flowClosed cavity flowBox-shaped cavities19. Security dassif. (of this report)UnclassifiedCavity drag18. Distribution StatementUnclassified - UnlimitedSubject Category 0220. Security Classif. (of this page) 21. No. of PagesUnclassified 1922. PriceA02For sale by the National Technical Information Service, Springfield. Virginia 22161 NASA-Langley, 1986Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-
