Development of an Unstructured Solution Adaptive Method for the Quasi-Three-Dimensional Euler and Navier-Stokes Equations

Development of an Unstructured Solution Adaptive Method for the Quasi-Three-Dimensional Euler and Navier-Stokes Equations
Author: National Aeronautics and Space Administration (NASA)
Publisher: Createspace Independent Publishing Platform
Total Pages: 286
Release: 2018-07-24
Genre:
ISBN: 9781723558153

A general solution adaptive scheme based on a remeshing technique is developed for solving the two-dimensional and quasi-three-dimensional Euler and Favre-averaged Navier-Stokes equations. The numerical scheme is formulated on an unstructured triangular mesh utilizing an edge-based pointer system which defines the edge connectivity of the mesh structure. Jameson's four-stage hybrid Runge-Kutta scheme is used to march the solution in time. The convergence rate is enhanced through the use of local time stepping and implicit residual averaging. As the solution evolves, the mesh is regenerated adaptively using flow field information. Mesh adaptation parameters are evaluated such that an estimated local numerical error is equally distributed over the whole domain. For inviscid flows, the present approach generates a complete unstructured triangular mesh using the advancing front method. For turbulent flows, the approach combines a local highly stretched structured triangular mesh in the boundary layer region with an unstructured mesh in the remaining regions to efficiently resolve the important flow features. One-equation and two-equation turbulence models are incorporated into the present unstructured approach. Results are presented for a wide range of flow problems including two-dimensional multi-element airfoils, two-dimensional cascades, and quasi-three-dimensional cascades. This approach is shown to gain flow resolution in the refined regions while achieving a great reduction in the computational effort and storage requirements since solution points are not wasted in regions where they are not required. Jiang, Yi-Tsann and Usab, William J., Jr. Unspecified Center NASA-CR-193241, NAS 1.26:193241 NAG3-1127...

Solution-adaptive Calculation of Unsteady Blade Row Interactions in Transonic Turbomachinery

Solution-adaptive Calculation of Unsteady Blade Row Interactions in Transonic Turbomachinery
Author: Scott M. Richardson
Publisher:
Total Pages: 236
Release: 1996
Genre: Aerodynamics, Transonic
ISBN:

This report describes the development of an implicit, viscous method for the solution of the quasi-three-dimensional flow equations for rotor-stator interaction in transonic turbomachinery. The flow algorithm is described, followed by the implicit time-marching scheme, and the one-equation turbulence model. The algorithm is implemented on an unstructured grid arrangement of locally structured micro-blocks called 'patches.' Solution-dependent adaptation is used to refine the grid in regions containing flow features which require enhanced resolution. An overlapped sliding grid interface is used to transfer flow equation information between the respective blade grids. The resulting computational algorithm has been used to perform a number of validation exercises and has been demonstrated on a modern transonic turbine stage. Where possible, these results are compared with experimental data and show the ability of the method to accurately capture the unsteady flow physics in a robust and computationally efficient manner.