{"id":37111,"date":"2019-08-13T07:58:00","date_gmt":"2019-08-13T07:58:00","guid":{"rendered":"\/forum\/forums\/topic\/ansys-aqwa-modelling-hydrostatic-stiffness\/"},"modified":"2019-08-13T07:58:00","modified_gmt":"2019-08-13T07:58:00","slug":"ansys-aqwa-modelling-hydrostatic-stiffness","status":"closed","type":"topic","link":"https:\/\/innovationspace.ansys.com\/forum\/forums\/topic\/ansys-aqwa-modelling-hydrostatic-stiffness\/","title":{"rendered":"ANSYS Aqwa – Modelling Hydrostatic Stiffness"},"content":{"rendered":"

Good afternoon,<\/span><\/p>\n

<\/p>\n

I am currently modelling a floating structure with ANSYS Aqwa module and I believe there is an incoherence in this when considering the hydrostatic stiffness of the structure. I’ve run a test in a cylinder where the only restoring surge and sway forces are given by an added stiffness of 10000 and 2500 N\/m, respectively and all other degrees of freedom are blocked. Now, I have inserted an initial displacement in the sway direction of 20 [m] and the forces are correct (20 x 2500 = 50000 [N]). But when I add an initial condition RZ=30º things don’t seem to work. As I was trying to understand if the stiffness matrix rotates with the platform I believe two different things can happen:<\/span><\/p>\n

<\/p>\n

1 – If the matrix is defined in the global axis<\/span><\/strong><\/p>\n

<\/p>\n

In this case, the results should be the same as in the situation with RZ=0º<\/span><\/p>\n

<\/p>\n

2 – If the matrix is defined in the local axis<\/span><\/strong><\/p>\n

<\/p>\n

In this case, the forces should be computed with the respective displacement in the local axis and corresponding stiffness.<\/span><\/p>\n

<\/p>\n

However neither seems to happen. <\/span><\/p>\n","protected":false},"template":"","class_list":["post-37111","topic","type-topic","status-closed","hentry"],"aioseo_notices":[],"aioseo_head":"\n\t\t\n\t\n\t\n\t\n\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t