Development and validation of a multi-strand solver for complex aerodynamic flows. (2nd April 2017) - Lakshminarayan, Vinod K.
Highlights: Strand grid approach offers several advantages, most importantly the ability to generate meshes in a nearly automatic manner. A fully parallel, highly efficient, robust multi-strand solver (mStrand) is introduced. A simple and elegant approach of robustly handling multiple strands emanating from a surface node is presented. Second-order accuracy the solver is verified using Method of Manufactured solution. Several test cases are presented to demonstrate the accuracy and stability of the flow solver. Strand solver provided the best turnaround time when compared to established structured and unstructured grid solvers for a rotor simulation on large processor counts. Abstract: The strand grid approach is a flow solution method where a prismatic-like grid using "strands" is grown to a short distance from the body surface to capture the viscous boundary layer and the rest of the domain is covered using an adaptive Cartesian grid. The approach offers several advantages in terms of nearly automatic grid generation and adaptation, ability to implement fast and efficient flow solvers that use structured data in both the strand and Cartesian grids, and the development of efficient and highly scalable domain connectivity algorithm. An improvement to this approach is the multi-strand strategy, where multiple strands are allowed from each surface vertex to enhance grid resolution near sharp corners. This paper introduces a fully parallel and highly efficient flow solver called mStrand that is developed from ground-up to operate on multi-strand meshes. The strand solver is integrated to HPCMP CREATE TM -AV Helios framework to simulate complex aerodynamic flows. Detailed validation of the solver is shown on problems with varying degrees of complexity and comparison with experimental data. A performance study shows that the strand solver is nearly as efficient as a structured grid solver.