Advanced overset methods for vortex dominated flows

A newly implemented computational method of high-order accuracy is presented for the accurate calculation of unsteady vortical structures that may produce aeroacoustic sources, or affect downstream structural responses. The method involves prediction of the mean flow field by solving the Navier-Stokes equations (NSE) using a computational fluid dynamics (CFD) solver that employs high-order discretization on overlapping (overset) grid systems. The method dramatically reduces the artificial dissipation and dispersion of vortical flow features that would ordinarily be lost or degraded with the use of current methods. Complex domains are discretized using an overset grid strategy that allows for the use of multiple high quality structured meshes. The high-order method is developed and incorporated into a generalized overset grid assembly scheme, which allows high-order spatial accuracy of the NSE solutions to be maintained across overset grid boundaries. Comparisons are made to calculations that do not preserve high-order accuracy at overset boundaries, and insight is obtained into the effects and sensitivities of different treatments of overlapping boundaries.;A nested block adaptive mesh refinement (AMR) method has also been developed, within the context of the overset paradigm. The method is shown to significantly improve accuracy for a given computational cell count by tracking dynamic vortical features using appropriate dynamic refinement and coarsening, and its implementation in the context of the high-order overset method is presented.;The computational procedures presented herein are tested against analytic and canonical cases (slightly compressible, M ≤ 0.5, and incompressible mean flows) in order to characterize the accuracy of flow field calculations using high-order discretization and overset schemes across overlapping grid boundaries. The methods are also extended to far more complex systems including the transport of rotorcraft hub vorticity to distances relevant to interactions with vehicle fuselage and tail empennages. These calculations, using high-order overset techniques on grid systems in relative motion, and their comparisons to experimental data are the first of their kind.