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Modifications for practice

Subsections

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Under-Relaxation

Under-Relaxation reduces solution oscillations and helps to keep the computation stable. After each iteration, at each cell, a new value for variable $ \color{white} U$ in cell $ \color{white} i$ is then updated using following equation:
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where $ \color{white} \alpha$ is under-relaxation factor. The choice $ \color{white} \alpha$ $ \color{white} =$ $ \color{white} 1$ corresponds to no under-relaxation. The choice $ \color{white} \alpha$ $ \color{white} <$ $ \color{white} 1$ is under-relaxation. This may slow down speed of convergence but increases the stability of the computation, i.e. it decreases the possibility of divergence or oscillations in the solution. For more details see e.g. [3].

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Environment variables

CFD Processor reacts to several environment variables that can be used to control its operation. They are the following:
  • CFDP$ \_$VERBOSE — If set, will increase verbosity of the CFD Processor output, providing some additional (debugging) output.
  • CFDP$ \_$MKDIR$ \_$PERMISSIONS — (Linux only.) If set to a valid octal number, will be used as the permission triplet when creating new directories. By default, CFD Processor uses 770.
  • CFDP$ \_$MPIEXEC$ \_$ARGS — (Linux only.) If set, will be used as a replacement for most arguments passed to mpiexec. This variable is useful for detailed mapping / ranking / binding of processes by job schedulers.

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