Quasi-structured anisotropic quad-dominant mesh adaptation using metric-orthogonal approach

International audienceWe present a strategy for the generation of mixed-element quasi-structured meshes. This strategy is based on the tools of metric-based mesh adaptation. Using metricorthogonal point placement, we can generate a pattern of points following the underlying structure of the metric-field, from which we generate a quasi structured triangular or mixed-element mesh. This paper presents some enhancement of the adaptation loop towards the generation of quad-dominant meshes. Especially, since this method highly depends on the prescribed metric-field, we present a tailored gradation process that favors the formation of structured elements. We also explore two processes to recover the quadrilaterals: an indirect method based on combining right triangles from a preliminary orthogonal triangular mesh, and a quadrilateral detection at the point-placement step

Verification of Unstructured Grid Adaptation Components

Adaptive unstructured grid techniques have made limited impact on production analysis workflows where the control of discretization error is critical to obtaining reliable simulation results. Recent progress has matured a number of independent implementations of flow solvers, error estimation methods, and anisotropic grid adaptation mechanics. Known differences and previously unknown differences in grid adaptation components and their integrated processes are identified here for study. Unstructured grid adaptation tools are verified using analytic functions and the Code Comparison Principle. Three analytic functions with different smoothness properties are adapted to show the impact of smoothness on implementation differences. A scalar advection-diffusion problem with an analytic solution that models a boundary layer is adapted to test individual grid adaptation components. Laminar flow over a delta wing and turbulent flow over an ONERA M6 wing are verified with multiple, independent grid adaptation procedures to show consistent convergence to fine-grid forces and a moment. The scalar problems illustrate known differences in a grid adaptation component implementation and a previously unknown interaction between components. The wing adaptation cases in the current study document a clear improvement to existing grid adaptation procedures. The stage is set for the infusion of verified grid adaptation into production fluid flow simulations

Verification of Unstructured Grid Adaptation Components

Adaptive unstructured grid techniques have made limited impact on production analysis workflows where the control of discretization error is critical to obtaining reliable simulation results. Recent progress has matured a number of independent implementations of flow solvers, error estimation methods, and anisotropic grid adaptation mechanics. Known differences and previously unknown differences in grid adaptation components and their integrated processes are identified here for study. Unstructured grid adaptation tools are verified using analytic functions and the Code Comparison Principle. Three analytic functions with different smoothness properties are adapted to show the impact of smoothness on implementation differences. A scalar advection-diffusion problem with an analytic solution that models a boundary layer is adapted to test individual grid adaptation components. The scalar problems illustrate known differences in a grid adaptation component implementation and a previously unknown interaction between components. Laminar flow over a delta wing is verified with multiple, independent grid adaptation procedures to show consistent convergence to fine-grid forces and pitching moment

On a robust boundary layer mesh generation process

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Some progress on CFD high lift prediction using metric-based anisotropic mesh adaptation

International audienceThis papers points out some weaknesses of the solution-adapted process. They have been solved by improving the Newton's method of the flow solver enabling convergence to machine zero at each run of the solution adaptive process. This work also presents the benefits of using metric-based anisotropic mesh adaptation for the numerical simulation of high lift configurations. For instance, we reconsider the CRM-HL geometry of the 3rd AIAA CFD High Lift Prediction Workshop and we obtain a prediction of the lift value similar to that of the x-fine mesh generated with the best practices (206 million vertices) with an adapted mesh composed only of 2.7 million vertices. This represents a reduction in the mesh size by a factor of 75

Assessment of mesh adaptation algorithms for LES and DES simulation of detached flows

International audienceThe proposed communication, discusses the adaptation of a transient fixed point adaptation algorithm to the computation of detached flows with LES of VMS type [3, 4] and DDES (Delayed Detached Eddy Simulation) models