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ROTATE - Perform calculation in a rotating frame of reference

ROTATE xcntr ycntr zcntr Ωx Ωy Ωz [zone_selector]

The ROTATE keyword allows the user to compute the flow in a rotating reference frame. The center of rotation and rotation rates are specified via the arguments:

    xcntr, ycntr, zcntr   Center of rotation, in grid units.
Ωx, Ωy, Ωz Rotation rates about the three Cartesian coordinate axes, in degrees/sec. (Note: prior to Wind-US 2.184 these were in radians per second. Input data files using this keyword with earlier versions of Wind-US will need to be changed if used with Wind-US 2.184 or later.)

If the zone_selector is used (e.g., to specify that only selected zones are rotating), the REL-ROT-ZONE keyword block must be used to specify the location of the interface between the zones, and how flow conditions are to be transferred between zones. In addition, the axis of rotation must align with one of the Cartesian coordinate axes. Thus, although all three of the rotation rates Ωx, Ωy, and Ωz must be specified, two of them must be zero. The use of zone_selector with the ROTATE keyword is only available for structured grids.

Note that a similar capability is given by the ROLL keyword, in which the grid is rotated about an axis. However, ROLL does the calculation in inertial space, and uses the grid velocity to impart a rotating component. Unfortunately, unless ROLL is run in a true time-accurate mode which moves the grid each time step (not currently available), as well as giving it velocity, the ROLL capability neglects the rotational potential energy, and so is not correct for high rotation rates.

This keyword cannot be used with the Van Leer differencing scheme (RHS VANLEER).


Last updated 12 Mar 2008