FSI Analysis in Nuclear Power Plant Assessments
The use of finite element codes and CFD codes for the separate analyses of structural and fluid power plant
components is of course well established. However, it can be of great importance to perform also FSI analyses,
in which the fully coupled interaction between structural and fluid components is taken into account. A decoupled
analysis can lead to conservative but also to significant
We present here briefly some results obtained in the FSI analysis of a Forsmark nuclear power plant. These results have been furnished to us by Forsmarks Kraftgrupp AB, Sweden.
We consider the vessel shown in the figures. The movie above shows the inside of the finite element model.
An important question to be addressed by the analyst is whether the fluid should be modeled as a full Navier-Stokes fluid, whether a nonlinear inviscid fluid assumption is sufficient, or whether the fluid can be assumed to be an acoustic fluid (inviscid and small deformations). To answer these questions, ADINA can be used directly with these various assumptions for the fluid, and hence the effect of the assumptions on the predicted response can be assessed.
For the analysis case considered here, it has been found that assuming the fluid to be an acoustic fluid is adequate, but the fully coupled fluid structure interactions must be modeled. The figure below shows a comparison of typical results obtained in another analysis with the corresponding experimental data.
The FSI analysis of the vessel when subjected to a pipe break was performed using
The movie below gives the dynamic displacement magnitude and predicted dynamic mean stress intensity in the core shroud as a function of time.
The effectiveness of ADINA is evident. Firstly, various complex to simplifying assumptions for the structure
and for the fluid can be made, and the effect of these assumptions can be studied. Secondly, each of the required
analyses can be performed in an efficient manner.
For the dynamic analysis pursued here, the final fully coupled FSI model could be solved on a PC within only 3 hours computing time. With such low computing time, the model can be used to efficiently make parametric studies, considering, for example, various loading conditions and boundary conditions.