Comparisons of Different Spatial Schemes and Limiters for Helicopter Flows

Kurzfassung

The requirements for a computational fluid dynamics solver to simulate the vortex-dominated helicopter rotor flows correctly are high. In recent years, many higher order methods and strategies have evolved to meet these requirements. This paper investigates a 3rd and 4th order accurate upwind scheme and compares this with a hybrid approach, where a 2nd order solution is generated near the rotor blades and a 4th order solution is computed in the wake. The investigated test cases are an inviscid vortex, an inviscid NACA0012 computation at zero-lift, two model rotors in hover and one model rotor in descent flight. From the exploration of different combinations of numerical schemes for the inviscid flux computation, it is seen that higher order methods are necessary to capture the trends of helicopter flows correctly. A modification to the upwind scheme is proposed to further decrease numerical dissipation and increase tip-vortex preservation. The outcome is that the 4th order accurate upwind scheme with the added modification prevails over the existing strategy.