DSWT

DSMC Wind Tunnel Program

• The data is entered through interactive menus and comprises the approximate number of megabytes to be used, the size of the working section, the definition of the surface(s), and the specification of the stream.
• The program sets the computational cells, the surface sampling segments, and the time steps. It also determines whether an ideal or real (with vibration and chemical reactions) gas is required, and sets the initial uniform flow.
• The time steps are variable and are adaptively set to a set fraction of the local mean collision time in order to meet one of the two criteria for a good DSMC calculation. The sub cells are also set adaptively and the program checks whether the number of simulated molecules is sufficient to meet the other criterion for a valid calculation. There are no numerical intabilities associated with DSMC calculations.
• The calculation starts from zero time. The overall forces on the surfaces are displayed and the user has many options for the display of flow and surface properties.
• Flow samples are automatically reset during the unsteady phase and time averaging is employed when (and if) the flow becomes steady at large times. A progressive plot of the total number of molecules provides an indication of the status of the flow.
• The units employed in the display may be switched between metric and imperial. Alternatively a non-dimensional display may be chosen.
• A left click of the mouse on a point in the flow contour display generates a list of flow properties at the point. A right click genates a flow streamline through the point.
• Text and bitmap files may be generated as required to document and report on the flow.

The DSWT program consists of a new general program DS2A with a special front-end and GUI for the wind tunnel geometry. Similar extensions to the DS2A program could be made for other geometries and classes of flow.