High-order overset methods for rotorcraft CFD

It has been shown that for overset CFD calculations that utilize high order accurate inviscid flux discretization schemes, solution accuracy can be increased by using high-order overset interpolation. This can be critically relevant in many cases, such as those where it is important to accurately track vortical structures through the domain because of fluid-structure interactions, for example. Many block structured overset CFD solutions employ variants of Lagrangian interpolation to determine overset donor weights and, of these, most use 2nd order accurate interpolation stencils. This paper demonstrates the pitfalls of using lower-order (i.e. 2nd) overset interpolation strategies in conjunction with high-order solver numerics. Familiar canonical problems are used to demonstrate that in certain types of problems, failure to use high-order interpolation can quickly lead to errors that undermine the reasons for using an advanced numerical scheme in first place, namely accuracy. Results also include prediction comparisons to rotor hub wake test data. Two computer codes are used: OVERFLOW 2.2, and a high order code developed at Penn State.