FoT25: Studier av inre vapenutrymme - sammanfattningsrapport

This report summarizes the efforts and conclusions made in the FoT25-project "Studies of Embedded weapons bays". Employing internally embedded weapons bays improves stealth properties and may increase manoeuvre ability and range for future air vehicles. The main purpose of the project has been to gain knowledge about the impact of unsteady flow around weapons bays on flight performance, on the cavity walls and on store separation trajectories. Numerical simulations of flow around the FS2020 military aircraft model with internally embedded weapons bays are carried out. The spatial resolution in the modelling is focused inside and around the weapons bay. Emphasis has been on unsteady simulations using the DES and a hybrid RANS-LES modelling approach. Initial investigations of spatial resolution and various flow physics models were carried out. The effect of a wedge along the upstream edge of the weapons bay damped the pressure fluctuations substantially. In order be able to predict trajectories, quasi-steady aerodynamics is coupled to flight mechanics. An integrated system for store separation computations with the flow solver Edge has been developed. The relative movement between the aircraft and the store is mapped by a sequence of deformed and locally remeshed grids. The flight mechanics model consists of the equations for rigid body motion solved by a fifth order Runge-Kutta scheme. In order to validate the implementation, an AGARD-test case for external store separation was computed. A finned missile is separated from a generic wing-sting-pylon configuration with use of an ERU (Eject Release Unit). The computed trajectories and attitudes agree well with experiment.