Adaptive large eddy simulation for complex unsteady flows

Authors
Rane, Jitesh, Dilipkumar
ORCID
Loading...
Thumbnail Image
Other Contributors
Gandhi, Farhan
Shephard, Mark
Letchford, Christopher
Sahni, Onkar
Issue Date
2023-05
Keywords
Aeronautical engineering
Degree
PhD
Terms of Use
This electronic version is a licensed copy owned by Rensselaer Polytechnic Institute (RPI), Troy, NY. Copyright of original work retained by author.
Full Citation
Abstract
Large eddy simulation (LES) is an attractive turbulence modeling approach due to thebalance it provides between computational cost and turbulence/scale-resolving capabilities. LES is shown to be robust and provides accurate predictions for complex flow problems including unsteady aerodynamic flows with spatiotemporal inhomogeneity. In this work, the specific problem of interest involves flow over surging airfoils, which arises in many aerodynamic applications. For example, for a rotorcraft in a forward flight, or for wind turbines in non-uniform flows (e.g., shear). Mesh resolution requirements for such complex and unsteady flow problems are notknown a priori. In this work, we develop an adaptive approach for LES where the mesh resolution is changed (refined or adapted) based on an a posteriori error estimator leading to error-driven/controlled adaptive LES. In addition, a flow feature-based adaptation criterion that can use the error estimator is developed. Both the LES methodology and the error estimator used here are based on the variational multiscale (VMS) framework. A range of Reynolds numbers and advance ratios is considered in adaptive LES forsurging airfoils. Three different adaptive strategies based on VMS error estimator are ex- plored: (i) zonal-based refinement/adaptation, (ii) nodal size field-based adaptation, and (iii) feature-based refinement/adaptation. The zonal-based strategy is found to be most effective. This strategy is applied for adaptive LES of flow over surging airfoils to construct a series of adapted meshes and to demonstrate mesh convergence. In particular, for quantities of interest including pressure coefficient and leading edge vortex (LEV) evolution. In addition, very high advance ratios are considered, where a massive trailing edge separation also occurs due to flow reversal. In these cases, LES includes active flow control in the form of active reflex camber that is applied to dynamically morph the airfoil shape during flow reversal (i.e., only for a part of the surging cycle). Active reflex camber results in a significant reduction in drag force and its fluctuations.
Description
May2023
School of Engineering
Department
Dept. of Mechanical, Aerospace, and Nuclear Engineering
Publisher
Rensselaer Polytechnic Institute, Troy, NY
Relationships
Rensselaer Theses and Dissertations Online Collection
Access
Restricted to current Rensselaer faculty, staff and students in accordance with the Rensselaer Standard license. Access inquiries may be directed to the Rensselaer Libraries.
Collections