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Journal ArticleDOI

Effect of Intake Geometry on Longitudinal Aerodynamics of Airbreathing Vehicles

01 Nov 2005-Journal of Spacecraft and Rockets (American Institute of Aeronautics and Astronautics (AIAA))-Vol. 42, Iss: 6, pp 1011-1016

TL;DR: In this article, a windtunnel test program was conducted to generate a systematic aerodynamic database for airbreathing vehicles, and a prediction method was developed to estimate the normal force and pitching moment of similar body-intake configurations based on this trend.

AbstractA wind-tunnel test program was conducted to generate a systematic aerodynamic database for airbreathing vehicles. Generic models consisting of tangent ogival nose, cylindrical body with cruciform intakes or twin intakes were tested at freestream Mach numbers ranging from 0.5 to 3.0. The length and span of intakes were varied. The intakes were two-dimensional with blocked entry. Normal force and pitching moment were nondimensionalized using planform area and distance of centroid (from nose tip) of the planform of the model rather than body cross-sectional area and body diameter, which are traditionally used. When normal-force and pitching-moment coefficients nondimensionalized this way are plotted against angle of incidence, the coefficients of different configurations coalesce for zero roll. In addition, data for different roll angles are found to coalesce when an empirical function of roll angle is introduced in the nondimensionalizing. A prediction method was developed to estimate the normal force and pitching moment of similar body-intake configurations based on this trend. Nomenclature A = cross-sectional area A B = body cross-sectional area of the configuration, = πr 2 A P = planform area of configuration APB = planform area of body API = planform area of intakes alone, A P − APB A R = reference area (equal to A P unless otherwise specified) Cdn = crossflow drag coefficient of circular cylindrical section Cm = pitching-moment coefficient about nose, M p/ qA R X CmNL = nonlinear component of pitching-moment coefficient about nose C N = normal-force coefficient, = N/ qA R C N NL = nonlinear component of normal-force coefficient cn = local normal-force coefficient per unit length d = body diameter H = height of air intake l = length of model li = length of air intake M = freestream Mach number M p = pitching moment about nose N = normal force q = freestream dynamic pressure r = body radius s = total span of body-intake configuration W = width of air intake

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References
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01 Sep 1977
TL;DR: In this paper, an engineering-type method was presented for computing normal-force and pitching-moment coefficients for slender bodies of circular and noncircular cross section alone and with lifting surfaces.
Abstract: An engineering-type method is presented for computing normal-force and pitching-moment coefficients for slender bodies of circular and noncircular cross section alone and with lifting surfaces. In this method, a semi-empirical term representing viscous-separation crossflow is added to a term representing potential-theory crossflow. For many bodies of revolution, computed aerodynamic characteristics are shown to agree with measured results for investigated free-stream Mach numbers from 0.6 to 2.9. The angles of attack extend from 0 deg to 180 deg for M = 2.9 from 0 deg to 60 deg for M = 0.6 to 2.0. For several bodies of elliptic cross section, measured results are also predicted reasonably well over the investigated Mach number range from 0.6 to 2.0 and at angles of attack from 0 deg to 60 deg. As for the bodies of revolution, the predictions are best for supersonic Mach numbers. For body-wing and body-wing-tail configurations with wings of aspect ratios 3 and 4, measured normal-force coefficients and centers are predicted reasonably well at the upper test Mach number of 2.0. Vapor-screen and oil-flow pictures are shown for many body, body-wing and body-wing-tail configurations. When spearation and vortex patterns are asymmetric, undesirable side forces are measured for the models even at zero sideslip angle. Generally, the side-force coefficients decrease or vanish with the following: increase in Mach number, decrease in nose fineness ratio, change from sharp to blunt nose, and flattening of body cross section (particularly the body nose).

85 citations