Tips & Tricks

DLF>1 when damping computed "from NCT"

This can be due to a bad conditioning of the transfer matrix used by foam module to calculate the NCT impedance to submit to the panel.

Getting Cosmic run error

I get a Cosmic run error - what may be the cause? First look at the log file, to see if there is any errors or warnings.

FE area junctions : Why is my FE area junctions discontinuous?

Its most likely due to the nature of the meshes. A fundamental assumption for FE->FE Acoustic junctions is that the FE mesh must be finer than the acoustic mesh

What is the difference in TL from the VTL and Effective TL?

The difference is that with Effective TL you select a single area junction and with VTL you select a set of panels. The only practical difference is in the area of the connection between the cavities

Why is TL dependent on the size of the panel? Shouldn't TL be independent of the shape and size of the panel?

There are some small area/perimeter dependencies in CLFs through a panel but these should usually only cause small differences. Basically, when calculating non-resonant TL AutoSEA2 needs an expression for the impedance of the fluid on either side of the panel

Can I extract results when running VA One on Linux?

Can I extract results when running VA One on Linux?, Yes, here is few options: 1. One way to do this is to execute a QuickScript on Windows, while leaving the va1 file on Linux. Eg. solve on the Linux box, and run a QS script on Windows to extract the results, while working on a Linux file system (no need to shuffle the file over). This requires no extra license, but one needs to write the script. Eg: solver file.va1 vaone -script export_script.ebs

How does VA One calculate damping from NCT?

The equation can be found in reference [1] as Eq. (21), in which • T+U ~ 2T = 0.5*m*|v|^2, where m is the mass per unit area of the SEA panel. • Pdiss = 0.5*Re{z}*|v|^2, where z is the impedance of the base of the trim. In the ratio, the wave magnitude |v| disappears and one is left with eta = Re{z}/(omega*m).

Defined absorption in VA One FEM/BEM

Can I add user defined absorption in VA One FEM/BEM?, Yes, this application of User Defined Impedances to Surfaces of BEM Fluids and FE Acoustic Cavities is implemented in VA One 2007.5

What is the size of stack space available for a compiled and uncompiled Quick Script?

In VA One 2010 the stack size for uncompiled is 8192 bytes, for compiled is 2048 bytes. In VA One 2010.5 the stack size will be 8192 bytes for both compiled and uncompiled scripts.

How do I apply a discrete velocity/acceleration constraint to an FE subsystem?

An acceleration or velocity constraint can be applied to the node of an FE subsystem using the "large mass method".