Coupled Fluid Structure Simulations Research Articles

Fluid structure coupling simulation analysis of vibration assisted 3D bioprinting extruder

Aiming at the problem of high wall shear stress at the nozzle of micro extrusion biological 3D printing technology, this paper proposes a method of reducing the viscosity of biological ink through vibration, so as to reduce the shear stress and improve printing efficiency and cell vitality. The 3D bioprinting extrusion device is taken as the research object, and the influence of vibration parameters on the printing process is studied on by fluid structure coupling simulation of the extrusion device.

Experimental study and numerical analysis of fluid-structure coupling vibration characteristics for the reciprocating compressor pipeline

The fluid-structure coupling has been one of the hot issues of academic research in recent years, the achievements in various fields of study also emerge in an endless stream, but on the current research status, The study of fluid structure interaction in the field of dynamic equipment, especially compressor, is not very common. With the development of industrial compressors in the direction of large-scale and high-parameters, the analysis of coupling characteristics represented by fluid-solid coupling can evaluate the safe and stable operation of the system, and the evaluations are ofen more close to the actual situation. Therefore, it has gradually been valued. Through the comparison and analysis of the vibration test system of the reciprocating compressor before and after the pipeline inflation, the vibration response caused by the coupling factor is obtained, for the correctness verification of the fluid-structure coupling simulation. the numerical model of the experimental system is established based on ANSYS WORKBENCH, and the boundary conditions of the model are simulated by the experimental data, verified the feasibility of simulation program. Finally, the effects of medium density, pressure, flow rate, elastic modulus of pipe and Poisson’s ratio on fluid solid coupling vibration are discussed by using the verified simulation model. The results show that the medium density, dynamic fluid flow rate and pipe Poisson’s ratio have relatively little influence on the fluid-solid coupling vibration of the pipeline, while the medium pressure and the elastic modulus of the pipe have a great influence.

Cracking analysis of an aero-engine combustor

Failure analysis on an aero-engine combustor is carried out for the cranking failure of combustor liner during its service period. Crack macroscopic observation and microscopic observation are performed. Fluid-structure coupling simulation of aero-engine combustor under typical working conditions is carried out to obtain the temperature distribution of combustor using a CFD commercial code, ANSYS FLUENT. Based on the results of fluid–structure coupling simulation, nonlinear statics analysis of the aero-engine combustor liner is carried out using a commercial code, MSC/NASTRAN. The visual inspection results show that obvious fatigue characteristics are found at fractures, and fatigue is responsible for observed cracks. The simulation results show that the maximum plastic strain of the combustor is located at the edge of the mixing holes near the two cracks. The maximum plastic strain is 0.4476%, 0.4154% respectively. During aero-engine’s service period, the start and stop of engine would cause cyclic loading of plastic strain, which give rise to fatigue damage and fatigue damage leads to cracking of combustor.

Sheet cathode design and experimental study on the electrochemical machining of deep narrow slots in TB6 titanium alloy

TB6 titanium alloy is extensively applied in lightweight vehicles, biomedicine, and other domains because of its high specific strength, excellent fracture toughness, and excellent corrosion resistance. Electrochemical machining is a non-contact processing technology that has significant advantages in processing materials that are difficult to cut, such as cemented carbide, high-temperature alloys, and titanium alloys. To improve the consistency of deep narrow slots fabricated in TB6 titanium alloy via electrochemical machining, a sheet cathode design and experimental studies were carried out in this work. Based on a unidirectional fluid–structure coupling simulation, the influence of the stiffener arrangement on the cathode rigidity and flow-velocity distribution was studied. Furthermore, by modifying the geometry of the stiffener, the cathode deformation was significantly reduced, and flow-velocity uniformity at the cathode outlet was improved. The influence of a superimposed low-frequency oscillation on the gap distribution and the profile error of a deep narrow slot was investigated experimentally. The results revealed that when an applied voltage of 24 V, an oscillation frequency of 50 Hz, and an amplitude of 0.05 mm were adopted, a highly homogeneous deep narrow slot with an entrance gap of 0.24 mm and a side gap of 0.33 mm was machined into the TB6 titanium alloy.

Modal equivalent method of full-area membrane and grid membrane

Pre-tension rectangular membrane is a promising structure in space engineering due to lightweight, high area-to-weight ratio and excellent folding capability. However, its dynamic characteristic of ground experiment can be largely affected by air, meaning the vibration behavior in air is quite different from the behavior in orbit vacuum. Therefore, a grid membrane is explored as the alternative structure, which can be less affected by air. Based on the small deformation theory, a modal equivalent method is established to make the natural frequencies and vibration modes of the original full-area membrane and the alternative grid membrane identical. A finite element code is utilized to verify this method, and the modals of the two structures are basically same. Meanwhile, a fluid–structure coupling simulation is conducted. The result indicates that the air effect on the alternative grid membrane is quite small compared with the original full-area membrane. Consequently, this grid membrane can be used as the alternative structure of the full-area membrane, as a mean to reduce the air effects in a ground structure experiment.

Coupled fluid-structure simulation of a vibration-assisted rotary percussion drilling tool

ABSTRACTPercussion drilling is considered to be an efficient method to promote the rate of penetration among the numerous tools. Therefore, a vibration assisted rotary percussion drilling tool is presented in this paper, which is driven through the motion of drill string. Three simplified models of designed structures are compared in this paper to define which one is to the most appropriate. Results indicated the structure of model 3 presented the best performance, and that the static and amplitude of the load is dependent on the flow rate and outlet size, the amplitude of dynamic load increased by increasing of the frequency and the displacement.

A two way fully coupled fluid structure simulation of human ureter peristalsis

Numerical simulations of ureter peristalsis have been carried out in the past to understand both the flow field and ureter wall mechanics. The main objective of the current investigations is to have a better understanding of the urine transport due to the peristalsis in the ureter, thus making the information helpful for a better treatment and diagnosis of ureteral complications like urine reflux. In the current study, a numerical simulation is performed using a finite-element-based solver with a two-way fully coupled fluid structure interaction approach between the ureter wall and urine. For the first time, the ureter wall is modeled as an anisotropic hyper-elastic material based on experiments performed in previous literature on the human ureter. Peristalsis in the ureter is modeled as a series of isolated boluses. By observing the flow field it is clear that the peristalsis mechanism has a natural tendency to create a backflow as the isolated bolus moves forward. As a result, the urine can flow back from the bladder to the ureter at the ureterovesical (ureter-bladder) junctions, if the one-way valve starts to malfunction.

Passive control of vortex-induced vibration by spanwise grooves

The objective of this numerical study is to investigate the effect of spanwise grooves on the suppression of vortex-induced vibration (VIV) and the reduction of drag force. For this purpose, we consider a standard configuration of the elastically mounted circular cylinder, which is free to vibrate in both streamwise and transverse directions with identical natural frequency. We introduce a novel staggered groove configuration whose geometry is especially designed by offsetting the cross-sectional portion of the cylinder continuously along the spanwise direction. We assess the characteristic VIV responses of the proposed staggered groove configuration against the helical surface grooves for the identical dimensions and physical conditions. The staggered and helical groove configurations differ only in their arrangement of cross-section geometry along the spanwise direction. Three-dimensional coupled fluid–structure simulations are conducted at low mass and damping values with moderate Reynolds number of Re=4800. The effective width and the depth of surface grooves are determined to characterize the size effects for the assessment of staggered and helical groove configurations. Results show that the staggered groove configuration is effective in suppressing VIV, wherein the net reductions of 37% in the peak transverse amplitude and about 25% in the mean drag coefficient are observed in comparison to the plain cylinder counterpart. Staggered groove configuration produces three dominant effects by introducing a continuous jump in the cross-sectional geometry along the spanwise direction: (i) reduction of the spanwise correlation, (ii) enhancement of the three-dimensional effects in the near-wake flow, and (iii) broadening of the frequency spectra of fluid forces. As a result of these physical effects, the transfer of energy from the surrounding fluid flow to the vibrating grooved-cylinder system is reduced as compared to its plain cylinder counterpart. Owing to the simplicity of mechanical design and the ease of installation, the proposed passive control concept has a potential application to deepwater marine risers and tall structures in a wind environment.

Numerical analysis of fluid-added parameters for the torsional vibration of a Kaplan turbine model runner

The impact of fluid on the runner of a hydraulic turbine is a recurrent problem. Fully coupled fluid–structure simulations are extremely time-consuming. Thus, an alternative method is required to e...

Experimental and numerical studies of a microfluidic device with compliant chambers for flow stabilization

This paper reports experimental and numerical studies of a passive microfluidic device that stabilizes a pulsating incoming flow and delivers a steady flow at the outlet. The device employs a series of chambers along the flow direction with a thin polymeric membrane (of thickness 75–250 µm) serving as the compliant boundary. The deformation of the membrane allows accumulation of fluid during an overflow and discharge of fluid during an underflow for flow stabilization. Coupled fluid-structure simulations are performed using Mooney–Rivlin formulations to account for a thin hyperelastic membrane material undergoing large deformations to accurately predict the device performance. The device was fabricated with PDMS as the substrate material and thin PDMS membrane as the compliant boundary. The performance of the device is defined in terms of a parameter called ‘Attenuation Factor (AF)’. The effect of various design parameters including membrane thickness, elastic modulus, chamber size and number of chambers in series as well as operating conditions including the outlet pressure, mean input flow rate, fluctuation amplitude and frequency on the device performance were studied using experiments and simulations. The simulation results successfully confront the experimental data (within 10%) which validates the numerical simulations. The device was used at the exit of a PZT actuated valveless micropump to take pulsating flow at the upstream and deliver steady flow downstream. The amplitude of the pulsating flow delivered by the micropump was significantly reduced (AF = 0.05 for a device with three 4 mm chambers) but at the expense of a reduction in the pressure capability (<20%). The proposed device could potentially be used for reducing flow pulsations in practical microfluidic circuits.

Coupled fluid–structure simulations for evaluating a performance of full-scale deepwater composite riser

A global–local analysis methodology based on fluid–structure coupling is used to investigate the mechanical responses of both composite and steel risers. Since the design of the riser system can be a daunting task, involving hundreds of load cases for global analysis, semi-empirical fluid load models are considered for the reduced order computations of full-scale riser models. The structural performance of composite risers under real sea current conditions is investigated systematically and discussed with regard to the practical concerns in full-scale settings. The failure envelops of internal liners are found to be within that of the composite layers, which reveals that the liner is the weakest link for composite riser design. Results show that the composite risers can be more prone to vortex-induced vibration (VIV) due to their lower structural frequencies. In the present study, the composite riser yields 25.5% higher RMS strains than the steel riser. Placement of buoyancy modules along the riser may be critical for the design against VIV, and our results show that the modules are not recommended at the top region of the riser, especially if a top-sheared current is expected. Instead, it is preferable to implement them at the bottom-half portion of the riser and as a continuously buoyed region rather than short discrete buoys separated with gap spaces. Composite risers with different metallic liners are studied, and the titanium liner riser is found to be favourable over the steel and aluminum liner risers.

Dynamic Characteristics Study on Hydraulic Impact of Cartridge Valve in High Pressure and Large Flow Depressurization Process

Dynamic analysis software ANSYS/LS-DYNA is applied to fluid-structure coupling simulation analysis of cartridge valve. Transient mechanical properties of cartridge valve and impact characteristics of interaction between hydraulic oil and valve spool in depressurization process were got. The result of study showed that the stability of depressurization process is related to the contacting time between valve spool and valve sleeve. The squeezing time of hydraulic oil is best not more than 0.01s. The peak impact time of hydraulic oil to valve spool in steady depressurization process is 140kN. And the maximum VonMises between valve spool and valve sleeve is 456MPa.

An integrated coupling framework for highly nonlinear fluid-structure problems

An integrated coupling framework is provided for the transient simulations of large scale highly nonlinear fluid-structure problems with extreme large domain changes. The ALE finite element method is employed for viscous fluid flow, both geometrical and material nonlinearity is considered for dynamic structure analysis. The strong coupling behavior between fluid and solid that causes the high linearity of the coupled system is treated by the strong coupling methods. Advanced morphing and automatic remeshing technology are used for dealing with the extreme fluid domain changes. Time and spatial stabilization, auto-time step and bisection schemes are employed in this research to improve the stability and efficiency of the coupling simulation. Hybrid parallel technologies are adopted for large scale simulation. The fully coupled fluid-structure simulation of a Hydraulic Engine Mounts (HEM) has been carried over by this framework. The mechanical characteristics of the HEM are clarified, and the comparisons of the numerical results with experimental results are demonstrated to show the reliability of this platform. The advanced morphing and automatic partial domain remeshing schemes are employed for the fluid-structure coupling simulation of a flapping wing structure in a water channel. These features have been fully implemented in a general purposed multi-physics simulation and design optimization software named INTESIM.

Transient fluid–structure interaction with non-matching spatial and temporal discretizations

This paper presents a review of spatial and temporal discretization schemes for unsteady flow interacting with structure. Two types of spatial coupling schemes are analyzed: (i) point-to-element projection and (ii) common-refinement based projection. It is shown that the point-to-element projection schemes may yield inaccurate load transfer from the source fluid mesh to the target solid mesh, leading to a weak instability in the form of spurious oscillations and overshoots in the interface solution. The common-refinement scheme resolves this problem by providing an accurate transfer of discrete interface conditions across non-matching meshes. With respect to the temporal discretization, three coupling techniques are assessed: (i) conventional sequential staggered (CSS); (ii) generalized serial staggered (GSS) and (iii) combined interface boundary condition (CIBC). Traditionally, continuity of velocity and traction along interfaces are satisfied through algebraic interface conditions applied in a sequential fashion, which is often referred to as staggered computation. In existing partitioned staggered procedures, the interface conditions may undermine stability and accuracy of coupled fluid–structure simulations. By utilizing the CIBC technique on the velocity and traction boundary conditions, a staggered coupling procedure can be constructed with similar order of accuracy and stability as standalone computations. The effectiveness of spatial and temporal coupling schemes is investigated with the aid of simple 1D examples and new 2D subsonic flow-shell aeroelastic simulations.

Fluid–structure coupling for an oscillating hydrofoil

Fluid-structure investigations in hydraulic machines using coupled simulations are particularly time-consuming. In this study, an alternative method is presented that linearizes the hydrodynamic load of a rigid, oscillating hydrofoil. The hydrofoil, which is surrounded by incompressible, turbulent flow, is modeled with forced and free pitching motions, where the mean incidence angle is 0° with a maximum angle amplitude of 2°. Unsteady simulations of the flow, performed with ANSYS CFX, are presented and validated with experiments which were carried out in the EPFL High-Speed Cavitation Tunnel. First, forced motion is investigated for reduced frequencies ranging from 0.02 to 100. The hydrodynamic load is modeled as a simple combination of inertia, damping and stiffness effects. As expected, the potential flow analysis showed the added moment of inertia is constant, while the fluid damping and the fluid stiffness coefficients depend on the reduced frequency of the oscillation motion. Behavioral patterns were observed and two cases were identified depending on if vortices did or did not develop in the hydrofoil wake. Using the coefficients identified in the forced motion case, the time history of the profile incidence is then predicted analytically for the free motion case and excellent agreement is found for the results from coupled fluid–structure simulations. The model is validated and may be extended to more complex cases, such as blade grids in hydraulic machinery.

Combined interface boundary condition method for unsteady fluid–structure interaction

Traditionally, continuity of velocity and traction along interfaces are satisfied through algebraic interface conditions applied in a sequential or staggered fashion. In existing staggered procedures, the numerical treatment of the interface conditions can undermine the stability and accuracy of coupled fluid–structure simulations. This paper presents a new loosely-coupled partitioned procedure for modeling fluid–structure interaction called combined interface boundary condition (CIBC). The procedure relies on a higher-order treatment for improved accuracy and stability of fluid–structure coupling. By utilizing the CIBC technique on the velocity and momentum flux boundary conditions, a staggered coupling procedure can be constructed with similar order of accuracy and stability of standalone computations for either the fluids or structures. The new formulation involves a coupling parameter that adjusts the amount of interfacial traction in the form of acceleration correction, which plays a key role in the stability and accuracy of the coupled simulations. Introduced correction terms for velocity and traction transfer are explicitly added to the standard staggered time-stepping stencils based on the discretized coupling effects. The coupling scheme is demonstrated in the classical 1D closed- and open-domain elastic piston problems, but further work is needed to consider the analytical stability of these schemes, 3D problems and comparison to monolithic integration.

Numerical Analysis of Stress on Pump Blade by One-Way Coupled Fluid-Structure Simulation

Numerical Analysis of Stress on Pump Blade by One-Way Coupled Fluid-Structure Simulation

Virtual Temperature Cycle Testing of Automotive Heat Exchangers by Coupled Fluid Structure Simulation

Virtual Temperature Cycle Testing of Automotive Heat Exchangers by Coupled Fluid Structure Simulation

A computationally efficient approach to swimming monofin optimization

Monofins provide swimmers with an efficient alternative to the standard pair of fins. For example, all short and long distance human swimming records have been established using monofins. Current monofin design is mostly empirical, so the objectives of this work are to analyze monofin propulsion through coupled fluid–structure simulation and to optimize its flexural stiffness distribution. The optimization process maximizes the propulsive power provided by the monofin with a constraint on the total expended power. To be able to carry out the optimization of the coupled fluid–structure system, which is numerically costly to evaluate, the following simplifications are proposed: (1) a 2-D unsteady, inviscid, and incompressible fluid flow is considered; (2) the swimmer is composed of linear articulated segments, whose kinematics is imposed and identified from experimental data; and (3) the monofin is represented by rigid bars linked by torsional springs. For various allowable swimmer powers, optimal 2-D stiffness distributions are obtained using the Globalized and Bounded Nelder–Mead algorithm. Finally, an identification procedure is described to translate the optimal 2-D stiffness distributions into 3-D thickness profiles for a given monofin planform shape.

Pathophysiology of ureteral obstruction.

Pathophysiology of ureteral obstruction.