## General Mechanical

#### How to find the added mass and radiation damping matrix in ansys aqwa two body coupled simulation?

• aakashg57
Subscriber

Hi,

I performed a two-body simulation on Ansys Aqwa and was able to obtain radiation mass and damping values with frequency for each structure. However, I would like to get the coupled value of the added mass and radiation damping between structure 1 and structure 2. In other terms, I would like to know the way to obtain added mass and radiation damping matrix right from the aqwa interface.

How can I obtain it?

Thank you

• Mike Pettit
Ansys Employee
At the moment these coupled values are only reported in the Aqwa listing file (.LIS), which you can find in the analysis solver files directory.
The easiest way to access this from Workbench is to View -> Files from the main Workbench page, then right-click on ANALYSIS.LIS and Open Containing Folder. Open ANALYSIS.LIS with any text editor (e.g Notepad++) and search for strings 'H/I ADDED MASS' or 'H/I DAMPING'. You will find the relevant matrices reported like:
I hope this helps.
Cheers, Mike
• aakashg57
Subscriber
Hi, thank you for the response Mike. However, these are the coupled values between the degrees of freedom. I was talking more in terms of the coupling between two structures - structure 1 and structure 2. I wanted to find out how the structure 1 effects the added mass value of structure 2 and vice-versa.
• Mike Pettit
Ansys Employee

The LIS file contains both. Here is a more complete snapshot of the hydrodynamic parameters for one structure in an interacting structure group (note: I've taken some of the whitespace out):
For a pair of structures with hydrodynamic interaction we have a 12x12 matrix for the added mass/radiation damping at each analysis frequency. Considering added mass A, we can express this as
Where each of A11, A12, A21, A22 is a 6x6 sub-matrix. The information displayed in my snapshot of the LIS file is A11 (first 6x6 matrix), and A12 (third 6x6 matrix).
Cheers, Mike