Accession Number:

ADA231259

Title:

Prediction of Unsteady Transonic Separated Flow for Missile Applications

Descriptive Note:

Final rept. 1 Jul 1987-15 Oct 1990

Corporate Author:

NIELSEN ENGINEERING AND RESEARCH INC MOUNTAIN VIEW CA

Personal Author(s):

Report Date:

1990-11-20

Pagination or Media Count:

121.0

Abstract:

A theory was developed to treat flow separation and related vortex effects in unsteady transonic flow around slender bodies. This theory involves the simultaneous solution of a modified Transonic Small Disturbance Equation, a kinematic vector potential equation, and a three-dimensional transport equation for the streamwise vorticity. In this theory, flow separation is modeled using normal vorticity jets placed along the separation line. The location and strength of the separating vorticity was determined from empirical criteria. A steady version of the theory was implemented using a considerably developed form of the TWING potential code, while the unsteady implementation was performed using an enhanced version of the computational aeroelasticity program CAP-TSD. A critical result was that a second order correction to the pressure, namely, the inclusion of the rotational streamwise velocity component, is necessary to account for the tilting of vortices away from the body axis. Time-accurate computations of subsonic, transonic, and supersonic flow show that it is possible to compute the flow around realistic angle of attack missile configurations, thus showing considerable potential for aeroelastic computations and unsteady aerodynamics. Results of two-dimensional Navier-Stokes calculations indicate that several key aspects characterizing the time-dependent behavior of boundary layer separation may be accurately predicted using indicial theory. These results demonstrate the possibility of significant phase lags and fluctuation overshoots of the normal vorticity flux at separation.

Subject Categories:

  • Guided Missile Dynamics, Configurations and Control Surfaces
  • Fluid Mechanics

Distribution Statement:

APPROVED FOR PUBLIC RELEASE