LOADS
   [PRESSURE [OFFSET] {FREESTREAM | val}]
   PRINT [PLANES] [TOTALS] [ZONES] [LIFT | DRAG] [FREQUENCY freq] \
      [MAKE_FRC file]
   [REFERENCE AREA aref]
   [REFERENCE LENGTH lref]
   [REFERENCE MOMENT CENTER xc yc zc]
   ZONE nzn
   SUBSET I range J range K range word1 [word2 [word3...]]
   SURFACE {I val | J val | K val} word1 [word2 [word3...]]
ENDLOADS

Flowfield properties may be integrated over part or all of a computational surface during the course of a WIND run to check convergence and solution quality. The values printed to the list file represent force coefficients F / A_r q_r and moment coefficients M / L_r A_r q_r in the x, y, and z coordinate directions, where F and M are the force and moment, and L_r, A_r, and q_r are the reference values of length, area, and dynamic pressure. Integrated mass and momentum fluxes may also be computed. The values are written into the list output (.lis) file.

The various elements of the LOADS input block are defined as follows:

PRESSURE [OFFSET] {FREESTREAM | val}

This keyword controls the pressure integration. By default, the code uses P - P_inf in all pressure integrations, where P_inf is the static pressure at freestream conditions. This keyword permits the user to specify the pressure offset value, such that:

	FREESTREAM	Use P - Pinf
	val	Use P - val

PRINT [PLANES] [TOTALS] [ZONES] [LIFT | DRAG] [FREQUENCY freq] \ [MAKE_FRC file]

This keyword controls the output data from the integration. Options are turned "on" by including the appropriate keyword.

	PLANES		Output the result of the integration for each subset specified.
	TOTALS		Output integration grand totals over all the zones at the end of each cycle.
	ZONES		Output integration totals for each zone.
	LIFT | DRAG		Output lift, drag, and side forces instead of (x, y, z) force components. Directions for the lift, drag, and side force components are computed from the angles of attack and yaw specified using the FREESTREAM keyword.
	FREQUENCY		Output integration results (except for grand totals) every freq iterations.
	MAKE_FRC		Write grand totals to the summary file file at the end of each cycle, in addition to the .lis file. This requires that PRINT TOTALS also be specified.

REFERENCE AREA aref REFERENCE LENGTH lref REFERENCE MOMENT CENTER xc yc zc

These keywords specify the reference area aref in square inches; the reference length lref in inches; and the coordinates (xc,yc,zc) of the reference moment center in inches. The default values are 1.0 for aref, 1.0 for lref, and (0.0, 0.0, 0.0) for (xc, yc, zc).

ZONE nzn

This keyword specifies the zone number nzn for the subsets which follow.

SUBSET I range J range K range word1 [word2 [word3...]]

The range parameters define a subset of a computational surface in zone nzn over which the integration is to be performed, and take one of the following forms:

	index1 index2		Starting and ending indices in the specified direction. LAST may be used for the last index.
	ALL		Equivalent to 1 LAST.

For three-dimensional cases, the starting and ending indices for one (and only one) of the I, J, or K parameters must be the same. For two-dimensional cases, the K parameter must be specified as either K 1 1 or K ALL; one or both of the I and J parameters may have different starting and ending indices.

The word parameters are keywords specifying what flowfield properties are to be computed, plus a couple of additional control values. The following keywords are currently available:

	FORCE		Compute pressure forces.
	MASS		Compute mass flow.
	MOMENT		Compute moments.
	MOMENTUM		Compute momentum.
	VISCOUS		Compute viscous force and moments.
	NORMAL inorm		inorm = ±1, specifying the desired normal vector direction; +1 for the increasing index direction and -1 for the decreasing index direction. inorm defaults toward the interior of the grid if the integration surface is on a boundary of the zone.
	NOSLIP		Integrate only over points where the total velocity is 0.

At least one flowfield property must be specified. For integration surfaces that are not part of a zonal boundary, the normal direction must also be specified.

SURFACE {I val | J val | K val} word1 [word2 [word3...]]

This keyword is similar to the SUBSET keyword, except that it provides a slightly simpler syntax for specifying a complete coordinate surface in zone nzn over which the integration is to be performed. The parameter val is a coordinate index specifying the surface.

The word parameters are the same as those described above for the SUBSET keyword.

Example

   LOADS
      PRESSURE OFFSET 0.0
      PRINT PLANES ZONES TOTALS LIFT FREQUENCY 2
      REFERENCE AREA 100.
      REFERENCE LENGTH 12.
      REFERENCE MOMENT CENTER 35. 36. 78.
      ZONE 4
         SUBSET I ALL J 1 1 K 15 LAST FORCE MOMENT VISCOUS NOSLIP
      ZONE 10
         SURFACE I 1 MOMENTUM MASS
   ENDLOADS