Distributed mass-In modal analysis

If what you are looking for is the effect of the fluid movements and of the coupling of fluid with the structure (part of the oil will vibrate together with the pipe wall) you need a code capable of treating fluid coupled analyses: then by following the instructions you be able to go.
ANSYS has such capabilities, but I never used them, so can't give any details. prex
motori@xcalcsREMOVE.com
Online tools for structural design

Hi,
well quite complex question in that u havent posed ur question with many a details. i just put a thought, i have a few points to discuss i dont know how far it would help u may be it might give an insight.

1) the direction of the forcing function with respect todynamic analysis and influence of oil pressure on the forcing function is to be understood . reason being

one should know as to which direction or DOF are u going to assign the mass. in this problem probably the mass is to be represented along DOF in readial direction such that the oil inside though exerts a static pressure but it must have a damping effect from inside.

2) generaly a "consistent or distributed mass matrix in FEM is written in the form as below
M= row * Integral over entire volume( N-trans * N * dv)
where N is the interpolation
Ntrans being its transpose
for a lumped mass system the above equation results in a diagonal matrix.

3) the problem here s in either case how wil u condense outthe other mass l ess degress of freedom. the effect of condensing out massless degrees of freeedom is again goverened by exact selection of Dof along which u intend to lump or assume ur mass to be acting consistently.

ref to book by RD cook introductory FEA

hope it helps
regds
raj Raj