21st Congress of International Council of the Aeronautical Sciences, Melbourne, Australia, 13-18 September, 1998
Paper ICAS-98-2.4.4

UNSTEADY TRANSONIC HYBRID INTEGRAL-EQUATION / FINITE-VOLUME SCHEME FOR TRAJECTORY SIMULATION OF STORES WITH TIME-STEP ADAPTATION

Bhattacharya A. K., Kanagarajan V.*, Mohan S. R.
Aeronautical Development Agency, India; * National Aerospace Lab., India

Keywords: unsteady transonic, trajectory simulation, stores, simulation

Development of a simulation program AMAR to predict the state-histories of stores released from fighter aircraft is described in this paper. AMAR computes configuration aerodynamics using a coupled integral-equation finite-volume scheme to solve the unsteady full-potential equation. This scheme discretizes the problem using surface panels embedded in a configuration-independent rectangular field grid -an approach that 'naturally' facilitates solution of flow over configurations with components in relative motion, as typical of the separating store problem. Computed aerodynamics is accuracy-accretized by accounting for real-flow effects, through synthesis with a-priori test data on stores in freestream using concurrently developed concepts. Aerodynamic prediction techniques are synergized with store and aircraft flight dynamics in the AMAR code to simulate trajectories of arbitrary stores released from aircraft. Fuzzy logic control to optimize time step size ~t for maximum simulation accuracy in minimum computation time is implemented. Trajectories obtained using steady-flow computations are compared against NAL 1.2m trisonic wind tunnel CTS simulations on fuel tanks released from fighter aircraft models at subsonic and transonic speeds. Finally the concept of 'artificial hysteresis' is introduced to isolate and measure unsteady effects on bodies executing non-oscillatory motion as typical of separating stores.

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