Numerical simulation of Turbulence Induced Vibrations from URANS models using the Pressure Fluctuation Model

Conference paper (2017)

Authors

S. Kottapalli NRG (Nuclear Research and Consultancy Group) Petten, Student
S Sharma NRG (Nuclear Research and Consultancy Group) Petten, Student
A Shams NRG (Nuclear Research and Consultancy Group) Petten
A.H. van Zuijlen Aerodynamics - Aerospace Engineering
M.J.B.M. Pourquie Fluid Mechanics - Mechanical, Maritime and Materials Engineering
Research Group
Fluid Mechanics (Mechanical, Maritime and Materials Engineering) (TU Delft)
FSI URANS Flow Induced Vibrations Pressure fluctuation model Turbulence Induced Vibration
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Published Date

2017

Language

English

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Faculty

Mechanical, Maritime and Materials Engineering

Department

Process and Energy

Research Group

Fluid Mechanics

Abstract

Turbulence Induced Vibrations (TIV) or Turbulence Buffeting in a nuclear reactor is an undesirable side effect of achieving high coolant flow rates. The turbulent pressure field of these flows force the structure to vibrate within the setup. High amplitude vibrations of the fuel rods can lead to structural damage within the reactor and create a safety hazard. TIV is a difficult phenomenon to predict and limited experimental data is available. Therefore, the most pragmatic method of estimating behavior of structures is through computational approach. Fluid-structure interaction problems like these are tackled by partitioned coupling of CFD (Computational Fluid Dynamics) and CSM (Computational Solid Mechanics) solvers. To simulate TIV, it is necessary to capture the turbulent eddies by resolving the fluid flow field up to the smallest scales. Use of high-fidelity CFD solvers such as LES is an ideal approach. However, this modeling approach is very expensive when an FSI simulation is considered. Low-fidelity models such as URANS are able to simulate only the large fluid structures and are inadequate to model the fluctuation at the smaller scales, resulting in an inaccurate approach for TIV. This article proposes the use of Presure Fluctuation Model for FSI simulations to estimate the effects of pressure fluctuations (p0) which trigger TIV. In the proposed model, standard URANS (Unsteady Reynolds Averaged Navier-Stokes) models are complemented with this model to calculate p0. The calculated p0 is summed to the mean pressure (p) to acts as a source of external excitation for the structure in an FSI simulation. The proposed model has an advantage over high fidelity models in terms of reduced computational costs and accurate estimation of TIV. The method is validated against a DNS of a channel flow and the results have shown to be in good agreement. Afterwards, the model is applied to two coupled FSI test cases. The results conclude that the pressure fluctuation model is capable of simulating TIV without requiring an external perturbation to trigger these vibrations.