Quasi-steady simulation of a complete EC-145 helicopter: fuselage + main/tail actuator discs + engines

Kurzfassung

As concluding activity for quasi-steady computations of the French-German helicopter programme CHANCE, the simulation of engine plumes using boundary conditions is presented. First, the one-dimensional theory of characteristics is used to derive boundary quantities for the Euler equations and also for their preconditioned version for low-velocities (after Choi and Merkle). A slight adaption of the scalar dissipation is also suggested for strong temperature gradients. Then, after the presentation of the EC-145 helicopter configuration, the results of a demonstration computation are presented and commented on. The engine inlet and outlet areas have reached a stable state and exhibit a relatively complex surface flow pattern. It is shown that the plumes of hot gases experience several stretch and distortion phases as they convect downstream from the engine nozzle down to aft the horizontal stabilisers. Also the influence of the downwash of both actuator discs is evidenced in showing how the separation bubble is shifted to the left and how the plume of exhaust gases deforms, thus resulting in only one hot spot on the left horizontal stabiliser instead of one on each side. The pressure distribution on the top centre-line experiences only minor modifications at engine inlet and outlet, whereas the temperature distribution increases along the tail boom. Finally, it is shown that the presence of hot gases impinging on the horizontal stabilisers may reduce the magnitude of the negative lift.