Aerodynamic Characteristics of Bodies of Revolution at Near-Sonic Speeds

Abstract

pressure distributions, drag, and flow characteristics around a family of sting- mounted truncated parabolic bodies of revolution at near-sonic and low-supersonic speeds by comparisons with an extensive existing wind-tunnel database. The analyses included both inviscid and viscous coupled boundary layer analyses. The investigations also included assessments of wind-tunnel wall interference effects as influenced by the various body geometries and test conditions. Extensive test versus theory comparisons of surface pressure distributions, flowfield pressures, anddrag forces are presented for subsonic through low-supersonic Mach numbers for the family of test configurations. An additional objective of these studies was to demonstrate the value of using existing and even rather historic experimental data. The experimental data used in the current studies were obtained from NACA wind-tunnel tests reported in 1958. ECENT near-sonic and low-sonic boom transport aircraft development studies have sparked a renewed interest in the natureoftheaerodynamicsaboutconfigurationsdesignedtocruiseat near-sonic or low-supersonic speeds. The validity of both the wind- tunnel test facilities and the computational methods are challenged by the characteristics of the flow at near-sonic speeds. The flow disturbances induced by a configuration at near-sonic and low- supersonic speeds extend to very large lateral distances. This presents a significant challenge to obtain interference-free wind- tunnel test data and also greatly increases the required lateral extent of the typical computational domain. Consequently, a number of fundamental aerodynamic studies were conducted to assess the ability of the TRANAIR full potential code to predict pressure distributions, drag, and flow characteristics around a family of sting-mounted truncated parabolic bodies of revolution at near-sonic and low-supersonic speeds by comparisons with an extensive existing wind-tunnel data base (1,2). The analyses includedbothinviscidandviscouscoupledboundarylayeranalyses. The investigations also included assessments of the effects of wind- tunnelwallinterferenceasinfluencedbythevariousbodygeometries and test conditions. The physics of the actual flow characteristics separating behind a truncated body and flowing onto a support sting are not correctly modeled by inviscid computational fluid dynamics (CFD) methods which typically include a constant area wake equal to the base area that trails behind the body. Using an analogy between the separated flowfromtheaftbodytothestingandthatofseparated flowbehinda backward facing step, a simple representation of the wake shape was developed and implemented in the TRANAIR analyses. The total drag for each configuration included the pressure drag obtainedbyintegrationofthepressuredistributions,plustheviscous drag. For the inviscid analyses, the viscous drag was estimated by using flatplateskinfrictiontheory.Theviscousdragestimatesforthe coupled boundary layer viscous analyses were obtained by integration of the calculated local skin friction distribution over the surface area of each body. This report presents the results of the subsonic, near-sonic, and supersonic investigations. An additional objective of these studies was to demonstrate the value of using existing and even rather historic experimental data. The experimental data usedin the current studies were obtained from NACA wind-tunnel tests reported in 1958. The study reported in this paper illustrates a process of using the essential tools of the aerodynamist shown in Fig. 1. These tools include computational fluid dynamics (CFD), experimental fluid dynamics (EFD), simplified fluid dynamics (SFD), visual fluid dynamics (VFD), and the most important tool of all, understanding fluid dynamics (UFD).