fluid-structure interaction

The partitioned approach for solving fluid-structure interaction problems is prone to numerical instabilities, often leading to a lack of convergence. Overcoming these challenges requires stabilization techniques and reduced time steps, significantly increasing computational costs. In this study, a monolithic formulation within the Arbitrary Lagrangian-Eulerian (ALE) framework is proposed for analyzing fluid-structure interaction problems, enabling efficient tracking of moving boundaries. The Navier-Stokes equations for unsteady fluid flow and the linear elasticity equations for the structure are solved in a strongly coupled manner. Comparison with the partitioned approach revealed that the average computational time per step in the partitioned method was 51 seconds, while the proposed approach required only 7 seconds, demonstrating its computational efficiency. Furthermore, the proposed method eliminates the added mass effect, enhances solution accuracy, and prevents sudden oscillations observed in the partitioned approach.Additionally, mesh dependency analysis showed that increasing the degrees of freedom from 85,452 to 1,141,027 resulted in only a 2% increase in pressure and displacement, indicating minimal sensitivity to mesh size. This highlights the robustness and efficiency of the proposed method in solving fluid-structure interaction problems.

In this study, the hydrodynamic behavior and heat transfer of fluid flow inside a channel with heated walls in the presence of flexible fins (vortex generators) have been investigated. The inlet fluid flow into the channel is defined with a sinusoidal profile, which causes the elastic fins to oscillate and generate vortices in the fluid flow. The governing equations of fluid flow and the deformation of the elastic fins have been solved using the finite element method combined with the Arbitrary Lagrangian-Eulerian (ALE) technique. The numerical analysis includes the study of the fins' behavior and their impact on drag force, Nusselt number, and pressure drop within the channel. The results show that increasing the fins' modulus of elasticity leads to an increase in drag force, Nusselt number, and a decrease in the tip displacement of the fins. Furthermore, the results indicate that by increasing the length of the elastic fins, heat transfer on the heated walls is enhanced, and the pressure drop inside the channel is increased. For example, the presence of flexible fins with a length of 3 mm resulted in an 82% increase in the Nusselt number and a 10% improvement in the thermal performance ratio compared to the baseline case (without flexible fins). 

This research focuses on topology optimization of fluid-structure interaction (FSI) problems using the level set method. To couple the fluid and structure equations, the Arbitrary Lagrangian-Eulerian (ALE) description is employed within a monolithic formulation. The use of ALE in FSI problems, while eliminating numerical instabilities caused by the convective term, enhances the speed and accuracy of finite element solutions in fluid-structure interaction. Additionally, considering the fluid in the unsteady state allows for the interpretation of optimal topology at any given moment of the analysis. The objective function of the optimal topology design problem is to minimize the structural compliance in the dry state, subject to a fixed volume of the design domain. To determine the normal velocity in the reaction-diffusion equation (RDE), adjoint sensitivity analysis based on pointwise gradients is used. The results obtained from this approach, compared to other topology optimization methods in the literature, demonstrate higher accuracy and clearer definition of structural boundaries.

The current research has studied the piezoelectric blade sensor from different views in order to control the oscillations of the circular cylinder present upstream of the piezoelectric blade and to control the fluctuating fluid flow around the blade using the force on the piezoelectric blade. The desired arrangement of a piezoelectric blade is placed downstream of a circular cylinder and with the help of a certain limit of blade oscillations, the hardness coefficient of the cylinder spring is applied from 65 (N/M) in normal condition to 100 (N/M) in the necessary condition. The controller as well as in other cases, the damping rate increases from zero to 0.02 (Nm/S) and in this way, the oscillations of the cylinder are controlled. In the same way, by controlling the oscillations of the cylinder, its effect on the oscillations of the blade, which is located downstream, has been investigated under the title of feedback effects. By controlling the feedback of the force on the piezoelectric blade in a closed loop, it is possible to monitor the displacement of the tip of the blade and the force on the piezoelectric blade. In these studies, it has been determined that in the case where the specific limit of the controller is 0.7 mm of the oscillations of the piezoelectric blade tip, due to the earlier application of the controller compared to the specific limit of 1 and 2 mm of the oscillations of the blade tip, the oscillations of the cylinder are Also, by comparing the state where the controller is included in the circuit compared to the state without the controller, it is clear that the oscillations of the blade and cylinder have been controlled to some extent.

In this paper, the performance of a diaphragm dosing pump of the injection odorizers is simulated with the fluid-structure interaction analysis. The simulation results are validated with experimental data and the largest relative error is 16% for the average flow rate. Performance simulation of the diaphragm pump for the diaphragm oscillation period of 1 second and three different diaphragm displacement amplitudes of 0.8, 0.5, and 0.2 mm, shows that as the amplitude increases, the fluid velocity and consequently the flow rate of the pump increases. The average flow rate of the pump in the mentioned amplitudes is equal to 0.002, 0.0013, and 0.0005 kg/s, respectively. As the amplitude increases from 0.2 to 0.8 mm, the maximum stress applied to the diaphragm increases from 32.2 to 99.2 MPa (equivalent to 208%). Also, the effect of diaphragm oscillation frequency on pump performance is investigated. The results show that the pump's flow rate directly and linearly relates to the diaphragm oscillation frequency. In contrast, the applied stress on the diaphragm is not frequency-dependent and in the same ratios of the period, the applied stress is almost constant. According to the results, if the pump amplitude is set to 0.5 mm and the frequency is 1.6 Hz, instead of operating at a diaphragm amplitude of 0.8 mm and a frequency of 1 Hz, the pump's flow rate will be the same. While the maximum amount of stress in the diaphragm will be reduced by about 30% and the probability of damage will be reduced.