# Solver Damping

This Panel Consists of Various Damping Settings that are used for Flow Simulator solver runs.

Parameter | Description |
---|---|

Solver Damping Method (WHITNEY) | Flag that activates the Flow Simulator
Whitney Damping feature, which seeks the optimal values of static
pressure (DAMPS) and total pressure (DAMPT) damping based on the
iterative progression of chamber errors. 0: Constant Damping - The input values of DAMPS and DAMPT are used for all iterations. 1: Whitney Adaptive Damping - The input values of
DAMPS and DAMPT are used until iteration number ISTRTW.
Subsequently, Whitney damping is activated and begins to
automatically adjust the damping factors DAMPS and DAMPT at each
iteration step. 2: Robust Whitney Damping - The input values of DAMPS and DAMPT are used until iteration number ISTRTW. Subsequently, a modified version of Whitney damping is activated. This modified version of Whitney damping may improve stability at the expense of speed. (Default value = 1.) |

Iteration Where Whitney Damping Becomes Active (ISTRTW) | Flow Simulator solver iteration when
Whitney damping starts, provided Whitney damping is active (WHITNEY
value of 1 or 2). (Default value = 7.) |

Static Pressure Damping Parameter (DAMPS) |
Damping factor for the iteration-by-iteration adjustment of the
calculated change in static pressure at each internal
chamber. Inversion of the Flow Simulator solution matrix at each iteration step yields the Newton-Raphson step sizes for each chamber static pressure. DAMPS is used as a scale factor, which is often less than one, and thus provides a more conservative step towards the solution than standard Newton-Raphson method. This improves robustness and convergence properties in the face of the non-linear and discontinuous behavior of the flow equations. The optimum values for DAMPS and DAMPT are model dependent. Values between 0.3 and 1.0 are commonly used. Values greater than one are used when the maximum errors become progressively smaller on successive iteration steps. (Default value = 0.4) |

Total Pressure Damping Parameter (DAMPT) |
Damping factor for the iteration-by-iteration adjustment of the
calculated change in total pressure at each internal
chamber. Inversion of the Flow Simulator solution matrix at each iteration step yields the Newton-Raphson step sizes for each chamber total pressure. DAMPT is used as a scale factor, which is often less than one, and thus provides a more conservative step towards the solution than standard Newton-Raphson method. This improves robustness and convergence properties in the face of the non-linear and discontinuous behavior of the flow equations. The optimum values for DAMPS and DAMPT are model dependent. Values between 0.3 and 1.0 are commonly used. Values greater than one are used when the maximum errors become progressively smaller on successive iteration steps. (Default value = 0.4) |

Upper Limit for Adaptive Static Pressure Damping (DAMPMX) | Upper bound for the damping factors DAMPS and DAMPT. (Default value = 2.0) |

Lower Limit for Adaptive Static Pressure Damping (DAMPMN) | Lower bound for the damping factors DAMPS and DAMPT. (Default value = 0.2) |

Feedback Control Parameter for Whitney Damping (RMOD) | Controls how strongly the Whitney feedback is applied in modifying
DAMPS and DAMPT from iteration to iteration. Any non-negative number is allowable; however, setting it greater than the default risks unstable numerical behavior. Setting RMOD equal to a (non-negative) value much less than the default effectively disables Whitney damping. (Default value = 0.05) |

Temperature change for properties call, 0 (least calls) – 1 (most calls) (TLIM_FACT) | Controls how frequently properties are called for various elements
and chambers. This improves run-time performance. 1.0: then properties are called every time. 0.0: calls properties as sparingly as possible according to an adaptive scheme. The properties are updated according to how much total temperature has changed from the last properties call. 0.5: has behavior that is between 0.0 and 1.0. (Default value = 0.0) |

Pressure change for properties call, 0 (least calls) – 1 (most calls) (PLIM_FACT) | Controls how frequently properties are called for various elements
and chambers. This improves run-time performance. 1.0: then properties are called every time. 0.0: calls properties as sparingly as possible according to an adaptive scheme. The properties are updated according to how much static pressure has changed from the last properties call. 0.5: has behavior that is between 0.0 and 1.0. (Default value = 0.0) |

Thermal Network Solution Parameter Damping (DAMP_THERMAL) | Damping factor for Thermal Network Solver (Default: 1.0) The solver automatically adjusts this damping to lower the values, if needed, using a scheme similar to the Whitney damping for the flow solver. |

Relaxation Factor on Thermal Fluid Coupling (DAMP_TFCOUP) | Relaxation Factor for Integrated Flow & Thermal Network Models
(Default 1.0). The solver automatically adjusts this based on the iteration number. |

Stagnant Tube Convergence Helper (ROBUST_TUBE) | -1: On → Solve as Incompressible Tube for any un-converged
Compressible Tube due to low Mach number (Cut off Mach Number is
0.00012) 0: Off 0-1: Cut off Mach Number → Solve as Incompressible Tube for any Compressible tube with Mach less than cutoff |

Chamber fluid temperature damping (TFLUID_DAMP) | Chamber fluid temperature damping factor. 1: No Damping (Default) 0.01 – 1: Enter Number from (0.01 - 1) 99: Automatic Damping |