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Geometric Perturbations and Asymmetric Vortex Shedding about Slender Pointed Bodies
The flow about slender, pointed bodies can be characterized by different states with angle of attack. At moderate-to-high angles of attack (alpha approx. = 40 deg.), a steady, asymmetric vortex pattern develops along the body, leading to a net lateral force. At higher angles of attack (alpha approx. = 60 deg.), the aft-end of the body develops an unsteady von Karman shedding. As the angle of attack approaches 90 deg., the entire body length exhibits a time-dependent vortex shedding pattern. The current work uses three-dimensional, thin-layer Navier-Stokes simulations to investigate the physical mechanisms of asymmetric vortex shedding at alpha = 40 deg. and alpha = 60 deg. The development of an asymmetric vortex pattern via a convective instability mechanism is investigated using tip bumps, surface roughness, and tip curvature. It's found that surface roughness simulations can incite an asymmetric vortex state at alpha = 60 deg. which is consistent with the application of a tip bump, and the experimentally observed flowfield. The unsteady von Karman vortex shedding on the aft. portion of the body is also well resolved. The use of surface roughness did not incite a flow asymmetry at alpha = 40 deg., and it was necessary to simulate tip curvature at this angle of attack in order to generate an asymmetric vortex state.
Geometric Perturbations and Asymmetric vortex shedding About Slender Pointed Bodies
The flow about slender, pointed bodies can be characterized by different states with angle of attack. At moderate-to-high angles of attack (alpha approximately equals 40deg), a steady, asymmetric vortex pattern develops along the body, leading to a net lateral force. At higher angles of attack (alpha approximately equals 60deg), the aft-end of the body develops an unsteady von Karman shedding. As the angle of attack approaches 90deg, the entire body length exhibits a time-dependent vortex shedding pattern. The current work uses three-dimensional, thin-layer Navier-Stokes simulations to investigate the physical mechanisms of asymmetric vortex shedding at alpha = 40deg and alpha = 60deg. The development of an asymmetric vortex pattern via a convective instability mechanism is investigated using tip bumps, surface roughness, and tip curvature. It's found that surface roughness simulations can incite an asymmetric vortex state at alpha = 60deg which is consistent with the application of a tip bumps, and the experimentally observed flowfield. The unsteady von Karman vortex shedding on the aft portion of the body is also well resolved. The use of surface roughness did not incite a flow asymmetry at alpha = 40deg, and it was necessary to simulate tip curvature at this angle of attack in order to generate an asymmetric vortex state.
Theoretical investigation of the effects upon lift of a gap between wing and body of a slender wing-body combination
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Effect of Body Perturbations on Hypersonic Flow Over Slender Power Law Bodies
Hypersonic-slender-body theory, in the limit as the free-stream Mach number becomes infinite, is used to find the effect of slightly perturbing the surface of slender two-dimensional and axisymmetric power law bodies, The body perturbations are assumed to have a power law variation (with streamwise distance downstream of the nose of the body). Numerical results are presented for (1) the effect of boundary-layer development on two dimensional and axisymmetric bodies, (2) the effect of very small angles of attack (on tow[dimensional bodies), and (3) the effect of blunting the nose of very slender wedges and cones.
On the dynamic characteristics of a variable- mass slender elastic body under high accelerations.
Dynamic characteristics of variable mass slender elastic body, solving vector differential equations
On the dynamic characteristics of a variable- mass slender elastic body under high accelerations.
Dynamic characteristics of variable mass slender elastic body, solving vector differential equations
Comparison of the Experimental and Theoretical Distribution of Lift on a Slender Inclined Body of Revolution at M = 2
Pressure distributions and force characteristics have been determined for a body of revolution consisting of a fineness ratio 5.75, circular-arc, ogival nose tangent to a cylindrical afterbody for an angle-of-attack range of 0 degrees to 35.5 degrees. The free-stream Mach number was 1.98 and the free-stream Reynolds number was approximately 0.5 x 10 sup 6, based on body diameter. Comparison of the theoretical and experimental pressure distributions shows that for zero lift, either slender-body theory or higher-order theories yield results which are in good agreement with experiment. For the lifting case, good agreement with theory is found only for low angles of attack and for the region in which the body cross-sectional area is increasing in the downstream direction. Because of the effects of cross-flow separation and the effects of compressibility due to the high cross-flow Mach numbers at large angles of attack, the experimental pressure distributions differ from those predicted by potential theory. Although the flow about the inclined body was, in general, similar to that assumed as the basis for Allen's method of estimating the forces resulting from viscous effects (NACA RM A91I26), the distribution of the forces was significantly different from that assumed. Nevertheless, the lift and pitching-moment characteristics were in fair agreement with the estimated value.
Application of local linearization and the transonic equivalence rule to the flow about slender analytic bodies at Mach numbers near 1.0
The local linearization method for axisymmetric flow is combined with the transonic equivalence rule to calculate pressure distribution on slender bodies at free-stream Mach numbers from .8 to 1.2. This is an approximate solution to the transonic flow problem which yields results applicable during the preliminary design stages of a configuration development. The method can be used to determine the aerodynamic loads on parabolic arc bodies having either circular or elliptical cross sections. It is particularly useful in predicting pressure distributions and normal force distributions along the body at small angles of attack. The equations discussed may be extended to include wing-body combinations.
A Study of Effects of Viscosity on Flow over Slender Inclined Bodies of Revolution
The observed flow field about slender inclined bodies of revolution is compared with the calculated characteristics based upon potential theory. The comparison is instructive in indicating the manner in which the effects of viscosity are manifest. Based on this and other studies, a method is developed to allow for viscous effects on the force and moment characteristics of bodies. The calculated force and moment characteristics of two bodies of high fineness ratio are shown to be in good agreement, for most engineering purposes, with experiment. (author)
On the dynamic characteristics of a variable- mass slender elastic body under high accelerations
Differential equations of motion for determining dynamic characteristics of variable mass slender elastic body moving under high accelerations
Nonconical theory of flow past slender wing bodies with leading-edge separation
Nonconical theory of flow past slender wing bodies with leading edge separation
Nonlinear lift and pressure distribution of slender conical bodies with strakes at low speeds
Nonlinear lift and pressure distribution of slender conical bodies with strakes at low speed
FORTRAN 4 program NONCON - Nonconical flow past slender wing bodies with leading-edge separation
FORTRAN 4 program for nonconical flow past slender wing bodies with leading edge separation
Calculation of supersonic flows at large distances from slender lifting bodies
Solving exact gas dynamic equations for supersonic flows far from axis of slender lifting bodies
Hypersonic weak-interaction solutions for flow past a very slender axisymmetric body.
Navier-Stokes hypersonic weak interaction theory for viscous heat conducting compressible fluid flow past slender axisymmetric body
Experimental Investigation of Some Aerodynamic Effects of a Gap Between Wing and Body of a Moderately Slender Wing-body Combination at a Mach Number of 1.4
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Recent advances in the nonlinear aerodynamics of tactical missiles
It is suggested that nonlinear extensions of the slender-body theory may be of use in obtaining simple nonlinear models for missile aerodynamics. It is pointed out that the transonic equivalence rule and the slender-body theory are nearly identical; the difference is that the flow around the equivalent body is governed by the nonlinear small-disturbance equation rather than by the linear Prandtl-Glauert equation. Five examples of nonlinear extensions of the slender-body theory are presented.