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Predicting High-Lift Aerodynamics on NASA Common Research Model - Part III: Wall Modeled Large Eddy Simulations

AMS Seminar Series

Speaker: Aditya Ghate, Science and Technology Corporation/NASA Ames Research Center

Presentation

Seminar Slide Deck (PDF-25MB)

Abstract

A new immersed boundary Wall-Modelled Large Eddy Simulation (WMLES) formulation is developed to study high-lift aerodynamics on the NASA High-Lift Common Research Model (HL-CRM). A sequence of Cartesian Octree grids with sizes ranging from 100 Million through 2.02 Billion grid points is utilized to systematically assess grid-sensitivity and convergence for the in-tunnel (QinetiQ) configuration of the model. Based on the findings of the grid refinement study a new coarser “best-practice” grid utilizing targeted refinement is constructed and remarkable agreement between the immersed boundary and the curvilinear body-aligned WMLES formulations is reported on grids with comparable resolutions. In the free-air configuration of the model, consistent predictions between the Curvilinear Overset and the Cartesian Octree formulations are reported for angles of attack up to CLmax at alpha=19.57o. However, some differences in the onset of stall are seen between the two methods for alpha>20o while the curvilinear WMLES experiences wing-root separation with increasing angle of attack (Topology A), the Cartesian Octree formulation shows a different flow topology characterized by boundary layer weakness on the main element, emanating from the pylon-wing attachment (Topology B). To obtain further insight into the two-distinct topologies, carefully designed numerical experiments to isolate effects of the model standoff and the tunnel wall-boundary layers are conducted using the immersed boundary WMLES formulation. The increased incidence angle-of-attack on the inboard portion of the wing due to the standoff is shown to be sufficient for triggering a switch from Topology B to Topology A in Cartesian WMLES. The role of the floor boundary layer is further examined in detail by identification of additional corner-flow vorticity generated by the viscous juncture flow interactions between the floor boundary layer and the standoff leading to formation of a strong coherent and persistent vortex on the belly-side of the fuselage. The intensity of this vortex is shown to increase with the thickness of the floor boundary layer. A further increase in the incidence angle of attack near the leading-edge strake caused by the presence of this belly-side vortex is quantified for two-distinct floor boundary layers. Both of the floor boundary layers considered result in the onset of large-scale wing-root separation at alpha=21.47o in non-confined (free-air) configurations.

Funded by the Transformational Tools and Technologies (T3) project under the NASA Aeronautics Research Mission Directorate's Transformative Aeronautics Concepts Program (TACP).

Biography

Photo of Aditya Ghate
Aditya Ghate joined the Computational Aerosciences Branch of the NASA Advanced Supercomputing (NAS) Division at NASA Ames Research Center in 2018. His research within the Launch, Ascent, and Vehicle Aerodynamics (LAVA) group involves development Large Eddy Simulations (LES) tools for prediction of complex flow physics seen in a large array of engineering applications, involving smooth-body, corner flow and geometry induced flow separation, as well as shock-boundary layer interactions including buffet. Aditya obtained his PhD in Aeronautics & Astronautics from Stanford University in 2018 where his thesis work focused on theory and modeling on subfilter-scale turbulence in LES.