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

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TVD - Total Variation Diminishing operator flag

Structured Grids

TVD [OFF | FACTOR factor | MINMOD [factor] | KOREN [factor] | ALBADA] \ [zone_selector]

Unstructured Grids

Structured Grids

For structured grids, this keyword controls the TVD flux limiter in the explicit operator, which is helpful in preventing overshoots in flowfield properties in regions of high gradients. TVD may be used with the Coakley, Roe, Van Leer, HLLC, HLLE, and Rusanov explicit schemes. TVD is enabled by default for these schemes, using the standard minmod TVD limiter with the default compression parameter, and disabled for all others.

OFF Disables TVD for the specified zone(s)

FACTOR Use the standard minmod TVD limiter. The value of factor specifies the "compression" parameter for the TVD algorithm, which controls the amount of limiting applied.

MINMOD

Use the standard minmod TVD limiter. This is the same as FACTOR, except that the factor may be defaulted. The value of factor specifies the "compression" parameter for the TVD algorithm, which controls the amount of limiting applied. The default compression parameter is the maximum value which assures TVD properties for the explicit operator being used (as specified by the RHS keyword). The default values are shown in the following table for the various versions of the explicit differencing scheme.

	Explicit Operator		factor
	First-order, upwind		0 (i.e., not applicable)
	First-order, upwind, modified for stretched grids		2
	Second-order fully upwind		2
	Second-order central		2
	Second-order upwind-biased		3
	Second-order upwind-biased, modified for stretched grids		3
	Third-order upwind-biased		4
	Third-order fully upwind		Not available
	Fourth- and fifth-order		Not available

KOREN Use the Koren TVD limiter. With this limiter, the default value of factor is 1.0, and does not depend on the explicit operator being used.

ALBADA Use the van Albada TVD limiter. With this limiter, no factor value is input.

If TVD flux limiting is turned on for an invalid explicit scheme, but without specifying a compression parameter, TVD flux limiting will automatically be disabled and the run will continue. Otherwise, an error message is generated and the run will abort.

See Also: BOUNDARY TVD, RHS

Unstructured Grids

For unstructured grids, the Barth-Jespersen slope limiting method is the default. Various other options are available.

OFF Disables slope limiting for the specified zone(s)

FACTOR Use the standard slope limiting procedure. The value of factor specifies the slope limiting parameter, and must be specified.

MINMOD Use the standard slope limiting procedure. This is the same as FACTOR, except that the factor may be defaulted. The default slope limiting parameter is 0.0 for first-order spatial differencing, and 3.0 for second-order differencing.

SUPERBEE Use "super-bee" slope limiting. The slope limiting parameter factor must be specified.

BARTH-JESPERSEN

Use Barth-Jespersen slope limiting.

[Barth, T. and Jespersen, D., "The Design and Application of Upwind Schemes on Unstructured Meshes," AIAA Paper 1989-366, Jan. 1989.]

	`factor`		Used to set the slope limiting parameter. A value of 0.0 corresponds to first-order, and a value of 3.0 corresponds to second-order. Intermediate values result in linear interpolation between the first-order and second-order face states. The default (and maximum allowed) value for factor is 3.0.
	`CELL \| FACE`		Optional keyword that specifies the neighborhood of adjacent cells to include in the limiting. `CELL` utilizes all node-neighbors of cell to prevent introducing local extrema in the reconstruction at the face center. `FACE` utilizes only the face neighbors and can allow creation of local extrema but will not result in limiting of linear variations in certain mesh situations. The default setting is `CELL`.
	`SCALAR \| DIRECTIONAL`		Optional keyword that controls how the limiter is applied. `SCALAR` applies a scalar factor to the cell gradient to ensure monotonicity. `DIRECTIONAL` provides a successive correction on each face. On most grids, `DIRECTIONAL` will tend to be excessively dissipative. The default setting is `SCALAR`.

VENKAT

Use Venkatakrishnan slope limiting.

[Venkatakrishnan, V., "Convergence to Steady State Solutions of the Euler Equations on Unstructured Grids with Limiters," Journal of Computational Physics, Vol. 118, 1995, pp. 120-130.]

	`factor`		Used to set the slope limiting parameter. A value of 0.0 corresponds to first-order, and a value of 3.0 corresponds to second-order. Intermediate values result in linear interpolation between the first-order and second-order face states. The default (and maximum allowed) value for factor is 3.0.
	`KVENKAT` K_Venk		Optional keyword used to specify a coefficient that determines the value of a "knob" that controls the allowable amount of oscillation. The value is set to (K_VenkD_cell), where D_cell* is the diameter of a sphere with the same volume as the current cell. The default for K_Venk is 20.

See Also: CONVERGE LOAD, RHS, DEBUG 64

Last updated 1 Apr 2016