{"id":312710,"date":"2023-10-22T07:29:44","date_gmt":"2023-10-22T07:29:44","guid":{"rendered":"\/forum\/forums\/topic\/implement-of-constraints-between-two-objects-in-frequency-domain-calculations\/"},"modified":"2023-10-22T07:29:44","modified_gmt":"2023-10-22T07:29:44","slug":"implement-of-constraints-between-two-objects-in-frequency-domain-calculations","status":"closed","type":"topic","link":"https:\/\/innovationspace.ansys.com\/forum\/forums\/topic\/implement-of-constraints-between-two-objects-in-frequency-domain-calculations\/","title":{"rendered":"Implement of constraints between two objects in frequency-domain calculations"},"content":{"rendered":"

Deal all<\/p>\n

For a coaxial double-buoy device, e.g., RM3, the two bodies are only allowed to move relative to each other in the heave direction. In the linear frequency-domain calculations, the wave-excitation loads are obtained by fixing the two objects without any motion. On the other hand, the wave-radiation loads are obtained by forcing one of the objects to move with unit ampitude in one direction.<\/p>\n

<\/p>\n

For example, added mass coefficient matrix of the two objects has a size of 12*12. Added mass A(3,3) is obtained by forcing object 1 to move with unit ampitude in the heave direction, and A(3,9) is the added mass imposed on object 2 by the forced motion of object 1 in the heave direction. However, due to the rigid constraint between the two bodies, I don’t think the added mass and radiation damping can be implemented in the surge direction.<\/p>\n

Specifically, the added mass A(1,1) is obtained by forcing object 1 to move with unit ampitude in the surge direction, and A(1,7) is the added mass imposed on object 2 by the forced motion of object 1 in the surge direction. Likewise, A(7,7) is obtained by forcing object 2 to move in the surge direction, and A(7,1) is the added mass imposed on object 1 by the forced motion of object 2 in the surge direction.<\/p>\n

Considering the existence of rigid constraints between the two bodies, should the radiation coefficients be calculated in the surge, sway, roll, pitch and yaw directions? For the outer bodies with a moonpool, the forced motions of one of the two objects in the five directions would cause large-amplitude radiation waves, especially if the gap between the two objects is small.<\/p>\n

For the RM3 device with a structural height of 38 m, radiation waves generated by the forced motion of inner body in the pitch direction are monitored to be as high as a few hundred meters, and the radiation waves generated by that in the surge direction are tens of meters. This is obviously not normal. I think it has something to do with the forced motion of a single object. Can AQWA implement constraints between two objects in frequency-domain calculations, and could you please give me some suggestions on this issue? <\/p>\n

Best regards, Tianyuan<\/p>\n","protected":false},"template":"","class_list":["post-312710","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\n\t\t\n\t\t\n\t\t