Numerical investigation of fluid structure interaction between unsteady flow and vibrating liner in a combustion chamber

Numerical investigations of fluid structure interaction between unsteady flow\ud and vibrating liner in a combustion chamber are undertaken. The computational study consist of two approaches. Firstly, a partioned procedure consists of coupling the LES code AVBP for combustion modelling with the FEM code CaluliX for structural dynamic analysis. The CFD code CFX together with the FEM Ansys package are then used.\ud Results of unsteady fluid structure interaction applied to combustion system are presented and compare well with experimental results

Optimization of a piezoelectric fan using fluid-structure interaction simulation

In this paper, the heat transfer from a single heat fin to the air flow in the wake of a piezoelectric fan (piezofan) is optimised. Both the heat fin and the piezofan are positioned in a channel, which has a significant influence on the flow field. The design variable is the frequency of the voltage applied to the piezofan. The heat transfer for different excitation frequencies is calculated using unsteady fluid-structure interaction simulations. To obtain a modular simulation environment, the flow equations and the structural equations are solved separately. However, the equilibrium on the fluid-structure interface is not satisfied automatically in this partitioned approach. Therefore, the interface quasi-Newton technique with an approximation for the inverse of the Jacobian from a least-squares model (IQN-ILS) is used to perform coupling iterations between the flow solver and the structural solver in each time step. With the unsteady fluid-structure interaction model, a surrogate model is constructed. The optimization of the surrogate model yields a frequency close to the first eigenfrequency of the structure

Fluid-structure interaction on the combustion instability

The multi-domain problem, the limit cycle behaviour of unstable oscillations in the LIMOUSINE model combustor has been investigated by numerical and experimental studies. A strong interaction between the aerodynamics-combustion-acoustic oscillations has been observed during the operation. In this regime, the unsteady heat release by the flame is the acoustic source inducing pressure waves and subsequently the acoustic field acts as a pressure load on the structure. The vibration of the liner walls generates a displacement of the flue gas near the wall inside the combustor which generates an acoustic field proportional to the liner wall acceleration. The two-way interaction between the oscillating pressure load in the fluid and the motion of the structure under the limit cycle oscillation can bring up elevated vibration levels, which accelerates the degradation of liner material at high temperatures. Therefore, fatigue and/or creep lead the failure mechanism. In this paper the time dependent pressures on the liner and corresponding structural velocity amplitudes are calculated by using ANSYS workbench V13.1 software, in which pressure and displacement values have been exchanged between CFD and structural domains transiently creating two-way fluid-structure coupling. The flow of information is sustained between the fluid dynamics and structural dynamics. A validation check has been performed between the numerical pressure and liner velocity results and experimental results. The excitation frequency of the structure in the combustor has been assessed by numerical, analytical and experimental modal analysis in order to distinct the acoustic and structural contribution

Coupling techniques for partitioned fluid-structure interaction simulations with black-box solvers

In partitioned simulations of fluid‐structure interaction, the flow and the displacement of the structure are calculated separately and coupling iterations between the flow solver and the structural solver are required to calculate the solution of the coupled problem if the interaction is strong. This work is a comparison of three coupling algorithms which use the flow solver and structural solver as a “black box”. Consequently, these algorithms are suitable for implementation in future versions of MpCCI. It is demonstrated that the algorithm of the interface quasi‐Newton technique with an approximation for the inverse of the Jacobian from a least‐squares model is straightforward and that this technique needs a relatively low number of coupling iterations in the simulation of an oscillating flexible beam and the propagation of a pressure wave in a flexible tube

Fluid structure interaction of a two-dimensional membrane in a flow with a pressure gradient with application to convertible car roofs

Original article can be found at : http://www.sciencedirect.com/ Copyright ElsevierThe flow-induced deformation of a membrane in a flow with a pressure gradient is studied. The investigation focuses on the deformation of aerodynamically loaded convertible car roofs. A computational methodology is developed with a line-element structural model that incorporates initial slackness of the flexible roof material. The computed flow–structure interaction yields stable solutions, the flexible roof settling into static equilibrium. The interaction converges to a static deformation within 1% difference in the displacement variable after three iterations between fluid and structural codes. Reasonably accurate predictions, to within 7%, are possible using only a single iteration between the fluid and the structural codes for the model problem studied herein. However, the deformation results are shown to be highly dependent on the physical parameters that are used in the calculation. Accurate representation of initial geometry, material properties and slackness should be found before the predictive benefits of the fluid–structure computations are sought. The iterative methodology overcomplicates the computation of deformation for the relatively small displacements encountered for the model problem studied herein. Such an approach would be better suited to applications with large amplitude displacements such as those encountered in sail design or deployment of a parachute.Peer reviewedFinal Accepted Versio