The Earthquake Engineering Online Archive

Hydrodynamic pressure and added mass for axisymmetric bodies

Nilrat, Fukij

UCB/EERC-80/12, Earthquake Engineering Research Center, University of California, Berkeley, 1980-05, 171 pages (555.1/N555/1980)

An effective finite element method for determining the hydrodynamic pressure distribution on rigid axisymmetric bodies oscillating in a fluid is presented. The bodies considered are symmetric about a vertical axis, and they can be either totally or partially submerged. To reduce computational effort, a transmitting boundary is used to truncate the horizontal unbounded fluid domain. The formulation of added masses in the equations of motion of rigid bodies in fluid is presented. A computer program is developed which calculates pressure distributions and added masses for axisymmetric bodies oscillating at a specified frequency in the horizontal, vertical, and rotational directions. The results of the finite element analysis are compared with experimental results showing good comparisons in most cases. The effects of compressibility of fluid and surface waves generated by oscillating bodies are also studied. Surface waves are found to have an effect on the added mass and hydrodynamic damping at low frequency while compressibility of the fluid has a significant effect at high frequency for cases involving large fluid depths.

Available online: http://nisee.berkeley.edu/documents/EERC/EERC-80-12.pdf (4 MB)