VIV drawing

When using the time domain VIV models, you can control how various aspects of VIV are drawn on the 3D view through the VIV drawing data on the line data form.

Arc length intervals

You can control which nodes have VIV detail drawn, by specifying one or more arc length intervals. An arc length interval specifies a contiguous length of line from one arc length to another. The VIV details (see below) are drawn for all nodes whose arc lengths fall in the specified intervals. For convenience, ~ in the from column denotes end A of the line, and ~ in the to column end B.

For example, to view the detail for one node only, give one arc length interval with from and to values equal to the arc length of that node. Or to view the detail for the whole line again give just one arc length interval, this time with from and to values both '~'.

What is drawn

The following VIV details are drawn for all nodes in the specified arc length intervals.

For all the time domain VIV models, the vortex force is drawn as a line radiating from the disc centre in the direction of the vortex force. The line length is scaled so that a vortex force equal to the standard Morison drag force with $\CD{=}1$ in a relative velocity of 1m/s, is represented by a line 1 disc radius long (i.e. just reaching the edge of the disc).

For the vortex tracking models only, and only if the maximum number of vortices logged is greater than zero, then the following extra details are drawn.

• The node is drawn as a disc (even if you have not selected nodes drawn as discs) and the stagnation and separation points are drawn on the edge of the disc.
• The positive and negative vortices are drawn as circles whose areas are proportional to the vortex strengths. The constant of proportionality can be controlled by setting area per unit strength.
• The centrelines of the positive and negative vortex sheets, and the wake line, are drawn.

For all these items you can control the pen used for drawing. With the vortex tracking models, for example, this allows you to suppress (by setting the pen style to clear) or downplay (by choosing a suitable colour) individual aspects of the detail.