vmopt用于控制虚拟质量如何施加，可以是0,1,2
，，中的空白表示默认坐标系，这里可以自己指定坐标系
第五个11可以随意指定，只需要后面的elist中的11对应即可，无任何含义，可以是任意大于0的数
1，thru，544代表从单元号1一直到单元号544的所有单元，此处为了方便定义，一般需要对相应模型进行重新编号
关于vmopt的值0,1,2的含义可以看下面的说明：
VMOPT
Default = 0
If VMOPT=0 or 1, then the virtual mass will be included in the mass matrix at the same time as all other
mass elements. In other words, the component modes will reflect the virtual mass. By default, virtual
mass is included after the component modes are computed.
If VMOPT=2 the modes of the structure or component without the fluid are computed first (“dry”
modes). The fluid effects are added in the modal basis during the residual flexibility computation to
produce the “wet” modes for the component. Both eigenvalue tables are printed, allowing comparison
of the dry and wet modes. The wet modes are used in modal dynamic analysis. The cost savings result
from the dense Virtual Mass matrix being kept out when computing dry modes in the physical basis. Its
presence can increase memory and computation times by an order of magnitude. The VM is added only
in the smaller generalized basis used in Residual Flexibility Computations. The approximations
introduced by this approach are generally small due to the homogeneous nature of the fluid. This
approach was provided in earlier versions with the vma.v* series of SSSALTERS. It is the preferred
method when the number of wetted elements exceeds several hundred, for reasons of efficiency.
If VMOPT is not equal to 0, 1 or 2 then no virtual mass is computed.
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发表于 2012-12-20 17:23:10
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