ataengineering / cellqualityremediation

A Loci/CHEM module to improve robustness on poor quality meshes

Cell Quality Remediation Module

This module was developed by ATA Engineering as an add-on to the Loci/CHEM computational fluid dynamics (CFD) solver. The module is useful for obtaining a solution on poor quality meshes.

As part of the flux calculation for each cell face in the mesh, solution values at cell faces must be reconstructed from solution values at cell centers (since Loci/CHEM is a cell centered finite volume code). To achieve second order spatial accuracy a first order reconstruction is used. However, Loci/CHEM will by default use a more robust, but less accurate, zeroth order reconstruction in regions of poor cell quality. This zeroth order reconstruction results in locally first order spatial accuracy. Loci/CHEM determines that cells with a volume ratio greater than 50, or a maximum included angle of greater than 150 degrees constitute poor quality regions. If the region of poor cell quality is small, this local change can have a negligible effect on solution accuracy, while greatly helping robustness.

This module extends the functionality in Loci/CHEM by allowing the user to decrease the volume ratio and maximum included angle thresholds from their default values. It also allows the user to include of all cells adjacent to those flagged by the volume ratio and maximum angle thresholds in the poor quality cell region.

Dependencies

This module depends on both Loci and CHEM being installed. Loci is an open source framework developed at Mississippi State University (MSU) by Dr. Ed Luke. The framework provides a rule-based programming model and can take advantage of massively parallel high performance computing systems. CHEM is a full featured open source CFD code with finite-rate chemistry built on the Loci framework. CHEM is export controlled under the International Traffic In Arms Regulations (ITAR). Both Loci and CHEM can be obtained from the SimSys Software Forum hosted by MSU.

Installation Instructions

First Loci and CHEM should be installed. The LOCI_BASE environment variable should be set to point to the Loci installation directory. The CHEM_BASE environment variable should be set to point to the CHEM installation directory. The installation process follows the standard make, make install procedure.

make
make install

Usage

First the module must be loaded at the top of the vars file. The user can then specify lower threshold values for volume ratio and maximum included angle. The user can also set cqrIncludeAdjacentCells to 1 to include all cells neighboring those flagged by the thresholds in the locally first order accurate group.

loadModule: cellQualityRemediation

cqrVolumeRatioThreshold: 50
cqrMaxAngleThreshold: 150
cqrIncludeAdjacentCells: 1