CVA Version 1.0

Authors: Shishir A. Pandya, James Jensen

Date: March, 2025.

The cva program (stands for Control Volume Analysis) allows users to setup control volumes or Treftz planes and integrate them. Process steps are as follows:

• 1. Take arbitrary planar cuts through an overset grid.
• 2. Create a single triangulation for each cut by retracting the overlap regions and subsequently stitching the gap between grids.
• 3. Portions of these planes can then be extracted.
• 4. These planar portions can then be combined with mesh surfaces to create complex control volumes.
• 5. Integrate the resultant control volume surfaces.

The planar cuts can be specified in four different ways:

• 1. Specify a Cartesian plane (constant x, y, or z)
• 2. Specify the analytical coefficients of the plane formula (ax+by+cz+d=0).
Note that this is the same as defining a normal and a distance from the origin.
• 3. Specify 3 points that define the plane
• 4. Specify a point and a normal.

Input files are assumed to be in the plot3d format.

An input mesh filename must be specified. (It will automatically default to grid.in or x.save in command-line mode).

An input Q file name can be specified as well. If it is not specified, it is assumed that no Q information will be processed (can not integrate flow quantities).

Output is a triangulation in the CART3D triq format, which includes the triangulation plus solution variables. This output triq file contains the overflow variables in the Q file.

If a Q file is not specified, a tri file is generated instead of a triq file. At the moment, only the plane cutting is available.

Execution:

The Input File Mode:

This is the interactive mode where questions are asked and the user must drive the execution by answering the questions. A novice will find this useful.

Once familiar with the inputs, the user can make an input file with the same information that can be redirected with a less than sign on the command-line.

For example, cva

The Commandline Mode:

cva [-ig gridFileName] [-iq qFileName] [-o output_rootName] [-grids comma_sepearated_list_of_grids_to_cut] [-plane specificaton] where specification examples are given below.

To specify a constant plane:

c,x,0.9

To specify the plane analytically:

a,1,0,0,0.9

To specify the plane wih 3 points:

p,0.9,1,0,0.9,1,1,0.9,0,1

To specify the plane with a point and a normal: n,0.9,0,0,1,0,0

Last modified: Mon Nov 17 12:28:00 PDT 2025