Slip Wall Module

This module was developed by ATA Engineering as an add-on to the Loci/CHEM computational fluid dynamics (CFD) solver. The module can be used to extend Loci/CHEM's viscousWall boundary condition for use in rarefied flows. The module can be used with nonequilibrium flows and supplies slip boundary conditions for velocity, translational temperature, and vibrational temperature. A Maxwellian slip model like the one shown in [1] is used.

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. A compiler with C++11 support is also required.

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 viscousWall boundary may be tagged with slip to enable the slip wall boundary condition. The enforcement of the slip condition may be delayed using the slipDelay input. This uses the traditional no-slip formulation for the first number of iterations specified to enable the flow to be established. Users can also relax the enforcement of the slip wall condition by only applying a fraction of the change to the boundary condition at each iteration. This is useful for steady problems. In the example below the BC_1 boundary is set to use a no-slip formulation for the first 1000 iterations, after which it will switch to a slip formulation where 10% of the boundary condition update will be applied at each iteration.

loadModule: slipWall

boundary_conditions: <BC_1=viscousWall(slip, Twall=298 K), ...>
slipDelay: 1000
slipRelaxation: 0.1

References

[1] Nompelis, Ioannis, et al. "Effect of Vibrational Nonequilibrium on Hypersonic Double-Cone Experiments". AIAA Journal. Vol. 41, No. 11, Nov 2003.