Wind-US User's Guide - Keyword Reference, COUPLING

COUPLING - Zone coupling mode specification

Structured Grids

COUPLING [MODE] {ROE [HIGH|LOW] | AVERAGE | CHARACTERISTIC}

Unstructured Grids

COUPLING [MODE] {ROE [HIGH|LOW] | AVERAGE}

This keyword controls the zone coupling algorithm used for multi-zone solutions. The possible options are defined below.

	`ROE`		The Roe coupling algorithm is more consistent with Roe's flux-difference splitting scheme, which is the default explicit operator. Instead of transferring flowfield variables between zones, this algorithm transfers flux cell "interface states," which are critical quantities in Roe's scheme. In this coupling mode, the zone boundary may be thought of as a "cell interface" in Roe's scheme. The `HIGH` option, which is the default, turns on higher-order coupling at zone boundaries. With higher-order coupling the solution derivatives are also passed between coupled zones. This results in a slight increase in memory requirements. The derivative information is used to increase the accuracy of the coupling scheme and to improve robustness at coupled boundaries.
	`AVERAGE`		This coupling algorithm sets the coupled boundary value to the average of the neighboring cell centers, which tends to greatly improve stability.

	`CHARACTERISTIC`		This coupling algorithm, available for use with structured grids only, uses one-dimensional characteristic flow theory to set boundary flowfield variables based on local flow direction and strength. These boundary variables are then transferred between zones using interpolation factors stored in the grid file (the .cgd file).

As stated above, the default setting is COUPLING MODE ROE HIGH.

The type of coupling that is allowed depends on the type of explicit differencing operator being used, set using the RHS keyword.

If RHS CENTRAL or RHS COAKLEY is specified, characteristic zone coupling is automatically used.
Unless COUPLING CHARACTERISTIC is specified, low-order Roe coupling is automatically used for first-order explicit operators.
Roe coupling (low- or high-order) requires that the Roe, Van Leer, HLLE, HLLC, or Rusanov explicit operator be used.
High-order Roe coupling may not be used with third-order fully upwind, or fourth- or fifth-order explicit operators.

Last updated 1 Apr 2016