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Perturbation Studies for Separation Dynamics of Store During Release from Aircraft



Store separation dynamics is very crucial from the safety aspects, when the store is released from parent aircraft. The store behavior should not be abrupt in proximity of aircraft. Store separation studies at subsonic release speed are carried out for a canard with tail controlled store with the help of 6-DOF coupled CFD simulations using ANSYS software. Initially, CFD methodology is validated with Eglin Wing Store Separation test case. Then store separation study is carried out for canard-tail controlled store and results are obtained. The estimation of flight parameters (such as CG Position, body attitudes, body rates and store velocity) help to provide adequacy before actual release. However it is difficult to a flight pilot to achieve the specific release flight condition at which the separation studies are being worked out. Therefore it is essential to examine whether the release is safe for those operating conditions which have minor variations over the specified nominal flight conditions as per release envelope. This study is carried out with the help of perturbation analysis to account for variations in input flight conditions. The perturbations studies are time consuming if they are attempted with the help of 6-DOF coupled CFD simulations. However the studies can be easily done with the already available aerodynamic data of specified flight conditions and an offline 6-DOF solver. Aerodynamic data from 6-DOF coupled CFD simulations is post processed using regression analysis to fit the aerodynamic coefficients as a function of separation distance (vertical movement), angle of attack and side slip. An isolated 6-DOF model using MATLAB Simulink is developed. Random variations in release conditions such as altitude, angle of attack, side-slip, center of pressure and Mach number with respect to the nominal operating condition are considered. A Monte-Carlo trajectory simulations are carried out considering above variations and the results are presented in this paper. The band consisting of variations in trajectory parameters is obtained and can be further used to assess the separation dynamics of the store.

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