# Ansys AQWA Multibody RAO calculation

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March 5, 2020, 06:56
Ansys AQWA Multibody RAO calculation
#1
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Niels van Duijn
Join Date: Mar 2020
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I am trying to calculate the RAO's of a multibody system(2 bodies) using the hydrodynamic coefficients from Ansys AQWA. In the .LIS file the hydrodynamic coefficients of the body and the coupling interaction coefficients between (Added mass and Radiation damping) between two objects are given. I assume that the interaction coefficients are given by what AQWA lists as the: 'H/I ADDED MASS/DAMPING FOR FORCE ON STR# 1/2'

The problem is I do not know how to interpret the interaction coefficients. What I am currently doing is placing the interaction matrices at the non-diagonal location of the 12x12 matrice. (See attached image)

However, when I calculate the RAO's of both the bodies I get a result which is different compared to the RAO's AQWA gives.
Attached Images
 RAO CALC.jpg (32.4 KB, 28 views)

June 9, 2021, 08:19
#2
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Benjamin M
Join Date: Jun 2021
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Quote:
 Originally Posted by nielssievd I am trying to calculate the RAO's of a multibody system(2 bodies) using the hydrodynamic coefficients from Ansys AQWA. In the .LIS file the hydrodynamic coefficients of the body and the coupling interaction coefficients between (Added mass and Radiation damping) between two objects are given. I assume that the interaction coefficients are given by what AQWA lists as the: 'H/I ADDED MASS/DAMPING FOR FORCE ON STR# 1/2' The problem is I do not know how to interpret the interaction coefficients. What I am currently doing is placing the interaction matrices at the non-diagonal location of the 12x12 matrice. (See attached image) However, when I calculate the RAO's of both the bodies I get a result which is different compared to the RAO's AQWA gives.
HI,I have the same problem. Have you solved your problem?
many thanks for the help!

 June 9, 2021, 08:23 #3 New Member   Benjamin M Join Date: Jun 2021 Posts: 2 Rep Power: 0 Maybe the 'H/I ADDED MASS/DAMPING FOR FORCE ON STR# 1/2' is not real non-diagonal coefficients. It needs to be divided by a coefficient

 Tags ansys, aqwa, hydrodynamic coefficient, hydrodynamic interaction, rao