Learning Forum

[Mike Pettit]

Hello,

For the U-tube tank: Aqwa can model this directly, using the Internal Tank capability which was introduced at Release 2019 R1. In the geometry editor, create surfaces to represent the U-tube tank, making sure that the surface normals point into the U-tube tank fluid (you may need to use the Reverse Normals operation in SpaceClaim to do this). Once you have re-imported the geometry, create an Internal Tank on the Part in the Aqwa editor. You then select the appropriate surfaces in the Internal Tank details, and define the fluid level inside the tank (either by selecting an edge from the geometry; setting a fluid level directly, with respect to the global axes; or by setting the volume of fluid in the tank, and allowing the program to estimate a fluid level from this). Finally set the fluid density as required, and re-run the hydrodynamic analyses. The effect of the U-tube tank fluid motion on the vessel response will be included automatically.

For the gyro stabilizer, Aqwa does not have a capability to simulate this directly, but if you know the dynamic effect of the gyro then it can be modelled. In the simplest case, you could model the gyro stabilizer by adding Additional Hydrostatic Stiffness to the vessel, assuming a linear relationship between the vessel roll angle and the gyro stabilizer restoring moment. For a more complex model, you would need to use the user-defined force (UDF) functionality, which allows you to calculate a nonlinear restoring moment as a function of the vessel's roll angle and/or roll velocity. There is an example of a Python UDF included in the Aqwa installation, which can be found in e.g. C:\Program Files\ANSYS Inc\v232\aqwa\utils\ExternalForceCalculation.

I hope this helps.

Mike