Multi‐resolution implicit large eddy simulations using a high‐order overset‐grid approach

Abstract

SUMMARYA parallel, high-order, overset-grid method is validated for use in large eddy simulation (LES) through its application to fundamental turbulent flow problems. The current method employs a high-order, compact finite-difference approach to evaluate spatial derivatives, with up to tenth-order low-pass filters used to remove high-frequency spurious wave content. These filters have also been found to be effective in modelling the dissipation that occurs at the unresolved scales in the flow for LES simulations. Temporal integration is based on an implicit, approximately factored and diagonalized, second-order algorithm, which reduces the time-step constraints present in explicit time-marching methods for wall-bounded viscous flows. Parallelization, geometric complexity, and local grid refinement are all addressed through the use of an overset-grid approach, with grid communication provided by high-order Lagrangian interpolation. The problems investigated in this work include fully turbulent channel flow at Re = 590 and 1017, and the transitional wake generated by flow over a single circular cylinder at Re D = 3900. The results obtained with the current approach are validated against well-resolved benchmark calculations or experiments and the impact of the order-of-accuracy of the interpolation method is investigated. The benefits obtained by using the general overset-grid technique to reduce grid point requirements compared to single-grid simulations are also examined. It is shown that for the problems considered in this work, substantial grid-point savings may be obtained with an overset-grid approach compared to a single-grid approach, and that the use of high-order interpolation at overset boundaries is important in maintaining overall solution accuracy.

Simulation of Various Turret Configurations at Subsonic and Transonic Flight Conditions Using OVERFLOW

“…This case has been studied computationally using a wide variety of solvers. [11][12][13][14][15] Research conducted on this problem in the past showed that the difficulty arose due to the transitional nature of the flow at such low Reynolds number and the flow features emerging were a three-dimensional To investigate the spatial schemes present in the OVERFLOW solver, the following three schemes were selected: the third-order HLLC inviscid flux scheme, fifth-order WENO scheme, and fifth-order WENOM scheme. The spatial schemes were used in conjunction with an implicit unfactored Successive Symmetric Over Relaxation (SSOR) algorithm.…”

A high-order compact finite-difference scheme for large-eddy simulation of active flow control

“…Simulations for subsonic transitional flow past a circular cylinder [38,8,41] again illustrated the benefit of local grid refinement, and properly captured the correct experimentally measured behavior, which was not possible when SGS models were employed. Computations for a spatially evolving supersonic flat-plate boundary layer [44] also compared well with experimental data, and performed better than simulations that utilized SGS models.…”

“…Among these are the simulation of decaying compressible isotropic turbulence [18,38,41], for which it was shown that better results were realized with use of the compact differencing/filtering scheme than could be obtained with either a constant coefficient [42] or dynamic Smagorinsky [43] SGS model [18]. For turbulent channel flows [18,38,8,41], the use of local grid refinement indicated that high accuracy was achieved with a minimal number of grid points, if the mesh system was distributed properly. It was also found [41] that the numerical approach attained DNS level resolution for high-Reynolds channels.…”

“…Due to the spectral-like dissipation properties of the filter, it also serves the same function as that of an SGS model without additional computational expense. In order to accommodate geometrically complex configurations, an overset grid technique is adopted, with high-order interpolation [7,8] to maintain spatial accuracy at overlapping mesh interfaces. Details of these features are described in sections that follow.…”

1303 Unmanned Ccombat Air Vehicle Flowfield Simulations and Comparison with Experimental Data

“…These simulations are compared with experimental data recently acquired from the freesurface water channel at Lehigh University. The high-order oversetgrid solver has been applied to canonical problems with elementary geometries [25,26] as well as component-level studies involving more complex overset-grid topologies [27,28]. One of the goals of this study was to develop and validate computational tools to simulate a more realistic, but still relatively clean, complete aircraft using the high-order overset-grid algorithm.…”