Two-way Fluid-solid Coupling Research Articles

Research on Air Cushion Flow Field and Bearing Characteristics of Single Row Hole Air Cushion Belt Conveyor

In order to obtain information regarding changes in the air cushion flow field and load-bearing characteristics of a single row hole air cushion belt conveyor, a structural model of the air cushion of the belt conveyor was established, with the single row hole air cushion belt conveyor as the research object. Firstly, according to the theory of fluid lubrication, a mathematical model of the air cushion was established. Then, the effects of air cushion thickness, pore velocity, and belt velocity on the pressure and bearing characteristics of the air cushion flow field were studied using FLUENT software. In addition, the equivalent stress, displacement, and pressure curves between the air cushion flow field and the conveyor belt and the material were analyzed using the two-way fluid–solid coupling method. Finally, the experimental platform of a single row hole air cushion belt conveyor was built, and the flow field and bearing characteristics of the belt were verified through experiments. The results show that reducing the thickness of the air cushion and increasing the pore flow rate can improve the pressure and bearing characteristics of the air cushion, while speed has little effect at lower belt speeds.

DiffFR: Differentiable SPH-Based Fluid-Rigid Coupling for Rigid Body Control

Differentiable physics simulation has shown its efficacy in inverse design problems. Given the pervasiveness of the diverse interactions between fluids and solids in life, a differentiable simulator for the inverse design of the motion of rigid objects in two-way fluid-rigid coupling is also demanded. There are two main challenges to develop a differentiable two-way fluid-solid coupling simulator for rigid body control tasks: the ubiquitous, discontinuous contacts in fluid-solid interactions, and the high computational cost of gradient formulation due to the large number of degrees of freedom (DoF) of fluid dynamics. In this work, we propose a novel differentiable SPH-based two-way fluid-rigid coupling simulator to address these challenges. Our purpose is to provide a differentiable simulator for SPH which incorporates a unified representation for both fluids and solids using particles. However, naively differentiating the forward simulation of the particle system encounters gradient explosion issues. We investigate the instability in differentiating the SPH-based fluid-rigid coupling simulator and present a feasible gradient computation scheme to address its differentiability. In addition, we also propose an efficient method to compute the gradient of fluid-rigid coupling without incurring the high computational cost of differentiating the entire high-DoF fluid system. We show the efficacy, scalability, and extensibility of our method in various challenging rigid body control tasks with diverse fluid-rigid interactions and multi-rigid contacts, achieving up to an order of magnitude speedup in optimization compared to baseline methods in experiments.

Study on Vibration Attenuation Performance of Pump-Jet Propulsor Duct with an Axial Slot Structure

To reduce the structural vibration of the duct structure in pump-jet propulsors (PJPs) and lower the induced vibration noise, this study learned from the “processor box” in an aero-engine and set a certain number of axial slots in the PJP. First, using finite element analysis, both dry and wet modes of the PJP ducts with and without an axial slot structure were simulated for analysis. Next, with the two-way fluid–solid coupling calculation method, the vibration performances of the PJP ducts with and without axial slots were contrasted and studied. The differences in calculation results under different duct structures were compared from three aspects—the vibration displacement, velocity, and acceleration of the duct and mesh nodes. According to the present results, after the addition of axial slots, the vibration displacement, the vibration velocity, and the vibration acceleration can be significantly reduced, especially in the back segment of the duct. Meanwhile, it can be concluded that it is quite important to select vibration acceleration for structural analysis in evaluating the PJP vibration. This study can provide a reference for further designs of low-noise PJPs.

Study on the heat transfer enhancement characteristics by flow-induced vibration of inserting polyethylene membrane inside the channel

With the development of science and technology, the heat dissipation problem of high-density electronic products has gradually emerged in engineering practice. In this paper, the enhanced heat dissipation process of fluid induced oscillation through flexible membrane is proposed, which belongs to the multi-field synergistic bidirectional coupling effect of thermal-fluid-solid coupling. Through the comparative numerical analysis of the flow induced oscillation of the flexible membrane and the fixed rigid fin in the flow channel, the mechanism of the fluid induced oscillation of the flexible polyethylene membrane is revealed. Based on the two-way fluid-solid coupling method, a numerical model for the heat transfer process of polyethylene membrane with thickness of 0.02 mm in the fluid channel was established. The temperature field, Nu (Nusselt number) and PEC (Performance comparison index) number of the rigid fin and polyethylene membrane installed in the channel under different Reynolds numbers were calculated respectively. The ratio of the length of the membrane to the height of the channel was adjusted for multiple groups of calculations to verify the positive effect of the polyethylene membrane installed in the channel on the heat exchange effect. The results show that in the fully developed area of heat transfer, the channel with polyethylene membrane is better than that with rigid fins in terms of turbulence and vortex shedding; at Re = 4400, the comprehensive enhanced heat transfer factor of heat exchange is the largest, up to 1.27; as the ratio of the height of the new flexible membrane to the height of the channel is 1, the heat transfer enhancement effect is best. In the next step, the correlation theory between oscillation characterization parameters and heat transfer enhancement effect under pulsating fluid excitation will be investigated.

Case study: Analysis and research on pipeline vibration of liquid oxygen kerosene of rocket engine and vibration reduction measures Measures

Abnormal vibration often occurs in the liquid oxygen kerosene transmission pipe- line of rocket engines, seriously threatening the safety of rocket engines. Improper handling will result in rocket launch failure and enormous economic losses. Therefore, the vibration of the transmission pipeline must be studied. In this paper, a three-dimensional high-pressure transmission pipeline model comprising a corrugated pipe, a multi-section bending pipe, and other auxiliary structures is established. Using the two-way fluid–solid coupling method, vibration analysis is performed on the pipeline under external pressure pulse excitation. The accuracy of the computation results is verified by a thermal test. Two vibration reduction strategies are presented and validated by simulation in accordance with the findings of the vibration study. The main conclusions are as follows: (1) At the same frequency, the amplitude distribution of vibration acceleration significantly correlates with the flow field pressure, indicating that fluid pressure fluctuation is the root cause of the abnormal vibration of the pipeline, and the vibration of the pipeline increases with the average pressure. (2) The time-average value and fluctuation amplitude of the larger stress and strain are mainly concentrated in the two supports, namely, the inside of the elbow and the bellows, which is different from the distribution of vibration acceleration. Such places are prone to structural failure and should be given attention. (3) The guide plate and the support enhancement method can reduce the vibration, but the support enhancement method has a better effect, reducing the vibration velocity and acceleration by 86.4% and 93%, respectively.

Fluid-solid Coupling Analysis of Riser based on CFD

The riser is the only channel connecting the submarine pipeline oil gas and offshore platform structures, offshore oil and gas development and utilization of lifelines, offshore pipeline system is the weakest vulnerable link. Due to its long and thin structure, the marine riser is easy to failure and failure in the complex working conditions. Marine vibration pipe safety or not directly affects the marine engineering and the surrounding environment and marine biology, in the event of damage, can cause the economic loss and environmental pollution, will result in a casualties, and even cause serious secondary disasters. Therefore, the safety and reliability of marine riser has been the focus of marine oil and gas industry research. In order to ensure the safety and reliability of the marine riser, it is usually necessary to evaluate the safety and reliability of the marine riser. The two-way fluid-solid coupling analysis of the riser system with a water depth of 500m is carried out by Ansys workbench software. The results show that the maximum flow rate of the flow field at the interface between the fluid and the riser occurs in the middle of the riser near the two ends. As time increases, the maximum flow rate will gradually shift from both ends to the middle of the riser, and the maximum value is 0.85m/s; the maximum stress of the riser will appear at the upper and lower end points, the maximum is 81.43Mpa; the lateral displacement of the upper end of the riser reaches the maximum, about 0.69m; indicating that these positions are the vortex induced lateral vibration of the riser dangerous area; therefore, this part can be improved by structural design or protection to increase the working life of the riser.

Investigation on aortic hemodynamics based on physics-informed neural network.

Pressure in arteries is difficult to measure non-invasively. Although computational fluid dynamics (CFD) provides high-precision numerical solutions according to the basic physical equations of fluid mechanics, it relies on precise boundary conditions and complex preprocessing, which limits its real-time application. Machine learning algorithms have wide applications in hemodynamic research due to their powerful learning ability and fast calculation speed. Therefore, we proposed a novel method for pressure estimation based on physics-informed neural network (PINN). An ideal aortic arch model was established according to the geometric parameters from human aorta, and we performed CFD simulation with two-way fluid-solid coupling. The simulation results, including the space-time coordinates, the velocity and pressure field, were obtained as the dataset for the training and validation of PINN. Nondimensional Navier-Stokes equations and continuity equation were employed for the loss function of PINN, to calculate the velocity and relative pressure field. Post-processing was proposed to fit the absolute pressure of the aorta according to the linear relationship between relative pressure, elastic modulus and displacement of the vessel wall. Additionally, we explored the sensitivity of the PINN to the vascular elasticity, blood viscosity and blood velocity. The velocity and pressure field predicted by PINN yielded good consistency with the simulated values. In the interested region of the aorta, the relative errors of maximum and average absolute pressure were 7.33% and 5.71%, respectively. The relative pressure field was found most sensitive to blood velocity, followed by blood viscosity and vascular elasticity. This study has proposed a method for intra-vascular pressure estimation, which has potential significance in the diagnosis of cardiovascular diseases.

Influence of Turbulence Intensity on the Aerodynamic Performance of Wind Turbines Based on the Fluid-Structure Coupling Method

The deformation and vibration of wind turbine blades in turbulent environment cannot be ignored; therefore, in order to better ensure the safety of wind turbine blades, the study of air-elastic response of wind turbine blades under turbulent wind is indispensable. In this paper, the NREL 5MW wind turbine blades are modeled with accurate 3D lay-up design, firstly, based on the joint simulation of commercial software STAR CCM+ and ABAQUS, the two-way fluid-solid coupling technology, the wind turbine under uniform wind condition is simulated, and the results from thrust, torque, structural deformation and force perspective and FAST are compared with good accuracy and consistency below the rated wind speed. Secondly, the aerodynamic performance, flow field distribution and structural response of turbulent winds with different turbulence strengths at 10 m/s were studied. The results show that the turbulence intensity has a greater impact on the amplitude of the wind turbine blade, and the stress distribution of the blade is more concentrated, which in turns affects the stability and safety of the wind turbine blade and is not conducive to the normal operation of the wind turbine.

A Lagrangian vortex method for smoke simulation with two-way fluid–solid coupling

We propose a pure Lagrangian vortex particle dynamics framework to simulate the various phenomena of turbulent smoke and two-way coupling between fluid and solid. In the framework, we model the fluid using vorticity and velocity fields that are discretized on the vortex particles. We extend a segment-based vortex stretching strategy with the subdivision of long segments to capture the fine details of smoke while maintaining good numerical stability. In addition, a vorticity field correction mechanism based on the merging and splitting of particles is proposed to avoid excessive particle counts and reduce the associated unnecessary computational overhead. We also present a fast and approximate two-way coupling method for simulating the interaction between solid and fluid. Our method can be used to solve various fluid phenomena, including Kármán vortex streets, jets, and some examples of two-way fluid–solid coupling.

Analysis of Runner Dynamics of Reversible Hydraulic Turbine by Alternating Fluid–Solid Action

In order to study the effect of alternating fluid–solid action on the dynamic characteristics of the runner of a reversible hydraulic turbine, a reversible hydraulic turbine model is used as the research object, and the two-way fluid–solid coupling method is used to iteratively calculate and analyze the fluid and structural equations to obtain the effect of the reversible hydraulic turbine on the runner under the two-way fluid–solid coupling action of the runner of the reversible hydraulic turbine under typical operating conditions. The results showed that under the influence of a high-speed water ring area under a certain working condition, the incoming flow direction forms a certain impulse angle with the blade, and under the joint action of the runner rotating at high speed, the vortex structure is generated in the blade area, and the speed change in the inlet area has a large random fluctuation, which is not conducive to the stability of the runner area and causes a strong pressure pulsation at the inlet. Under different working conditions, the runner stress area phenomenon is obvious, concentrated in the runner blade inlet side and the upper crown, lower ring connection. The maximum deformation region appears in the lower region of the middle of the blade inlet. The comparison of the modal analysis shows that the dynamic stress frequency caused by the dynamic interference is very unlikely to trigger the resonance of the runner.

Numerical simulation and experimental verification of the front air intake system of heavy trucks based on fluid-solid coupling and discrete phase models

The research object in this study was the front air intake (FAI) system of heavy trucks. Dust with various particle sizes was used to emulate the actual working conditions of a heavy-truck forward gas flow system and improve on research that considered only the internal flow field. On this basis, various changes in the flow field caused by the feedback effect of the pipe wall on the flow field were considered. Two-way fluid–solid coupling and discrete phase models were constructed. The models included the FAI pressure field, velocity field, other flow field characteristics, and filtration efficiency. The pressure drop, dust particle velocity and deposition, and the output of its filtration efficiency were also determined. A numerical simulation was conducted for experimental verification, including the overall pressure drop of the front intake system of the heavy truck and the filtration efficiency for three different particle sizes. The filtration statuses of various sizes of dust particles were found, and the rationality of the FAI system structure was examined and evaluated. The established simulation model can provide a tool for studying the flow characteristics and working performance of an FAI design and provide a verification platform for design optimization.

Numerical simulation of hydraulic fracturing process with consideration of fluid–solid interaction in shale rock

As a critical technology for the efficient exploitation of shale gas, hydraulic fracturing is a two-way fluid-solid coupling interaction process of water-rock. The accurate water pressure calculation in single shale rock fracture during hydraulic fracturing is critical to the fluid-solid coupling analysis. This paper selected the fractured shale rock from the shale reservoir for analysis based on the Saint-Venant principle. Moreover, the water pressure in a single shale rock fracture was calculated by solving the Navier-Stokes equations. Meanwhile, a fluid-solid coupling model of fractured shale rock during hydraulic fracturing was established and evaluated the changing process of hydraulic fracturing. Our results show that in the hydraulic fracturing process, the changing process of water pressure in a single shale fracture with or without fluid-solid coupling is similar, and both have a water hammer effect. Single shale rock fracture opened instantly in an elliptical shape. The maximum instantaneous water pressure at the fracture tip considering fluid-solid coupling was 3.01 times the initial water pressure. The Mises stress at the fracture tip caused by the maximum instantaneous water pressure was 2.97 times the Mises stress at the fracture tip caused by the water pressure in the fracture after stable water pressure change. Mode Ⅰ fracture occurred in the fractured shale rock when high-pressure water rapidly invaded 2/3 of the length of the fracture. The findings in this study may help to understand the hydraulic fracturing mechanism in shale rock.

Fast and versatile fluid-solid coupling for turbulent flow simulation

The intricate motions and complex vortical structures generated by the interaction between fluids and solids are visually fascinating. However, reproducing such a two-way coupling between thin objects and turbulent fluids numerically is notoriously challenging and computationally costly: existing approaches such as cut-cell or immersed-boundary methods have difficulty achieving physical accuracy, or even visual plausibility, of simulations involving fast-evolving flows with immersed objects of arbitrary shapes. In this paper, we propose an efficient and versatile approach for simulating two-way fluid-solid coupling within the kinetic (lattice-Boltzmann) fluid simulation framework, valid for both laminar and highly turbulent flows, and for both thick and thin objects. We introduce a novel hybrid approach to fluid-solid coupling which systematically involves a mesoscopic double-sided bounce-back scheme followed by a cut-cell velocity correction for a more robust and plausible treatment of turbulent flows near moving (thin) solids, preventing flow penetration and reducing boundary artifacts significantly. Coupled with an efficient approximation to simplify geometric computations, the whole boundary treatment method preserves the inherent massively parallel computational nature of the kinetic method. Moreover, we propose simple GPU optimizations of the core LBM algorithm which achieve an even higher computational efficiency than the state-of-the-art kinetic fluid solvers in graphics. We demonstrate the accuracy and efficacy of our two-way coupling through various challenging simulations involving a variety of rigid body solids and fluids at both high and low Reynolds numbers. Finally, comparisons to existing methods on benchmark data and real experiments further highlight the superiority of our method.

Study on flexible deformation of waste plastic film by fictitious particle method

Waste plastic sorting and recycling is an efficient and energy-saving way of domestic waste treatment. The deformation of waste plastic film affects the accuracy of plastic sorting. In this paper, a new method for calculating the deformation of waste plastic film, fictitious particle method, is proposed. The calculation model of film deformation is established and the formula of line element is deduced. The deformation law of plastic film is studied and the calculation results of fictitious particle method are obtained. The experimental platform was set up to obtain the film deformation data. The two-way fluid–solid coupling method was used for simulation experiment. Compared with the experimental results and simulation results, it is verified that the algorithm is in good agreement. The average error rate of the fictitious particle method is 4.26%, and the calculation time is 3.5 s. The algorithm has small amount of calculation and fast calculation speed. It laid the foundation for effectively improving the accuracy of wind separation and the optimization of plastic film wind separation machinery. • A new numerical calculation method called fictitious particle method is proposed. • The deformation law of the film in the separation process of waste plastic film was explored. • The fictitious particle method reduces the calculation amount and the calculation speed is fast. • The superiority of fictitious particle method in studying the deformation of waste plastic film was verified. • Improve the accuracy of wind sorting waste plastic film.

Analysis of Characteristics of Damping Valve Based on High-Order Discrete Scheme

In this paper, based on the high-order discrete scheme, a two-way fluid-solid coupling numerical simulation is for the damping valve plate. According to the discrete method, the governing equations of fluid structure coupling of damping valve plate are studied, including the basic conservation laws; Meanwhile, it analyzes the discretization of the control equation, including the discretization method and the high-order discretization format when the finite volume method is adopted. And based on this discrete format, a numerical simulation was performed on the damping valve, the oil flow condition is analyzed, and the velocity of the throttling hole at different time points and the throttling pressure are analyzed.

Numerical Research on Vibration-Enhanced Heat Transfer of Elastic Scroll Tube Bundle

Based on a new type of elastic scroll tube bundle (ESTB) heat exchanger, the influence of shell-side fluid inlet velocity and tube bundle constraint condition on the enhanced heat transfer performances are researched by a two-way fluid–solid coupling calculation method. Numerical results show that the average heat transfer coefficient (HTC) increases with the shell-side fluid inlet velocity increases when the single group of scroll copper tubes is unconstrained. Within the range of calculated parameters in this paper, the maximum increase of average HTC is 140% under vibration conditions, and the maximum increase of average HTC is 216% under nonvibration conditions. The average HTC decreases as the number of constraints increases under vibration conditions, and the maximum decrease is 42.69%. The average performance evaluation criteria values are greater than 1.00, so the overall heat transfer performance of the ESTB heat exchanger is better.

Investigation of Fluid-Induced Vibration and Heat Transfer of Helical Elastic Coiled Tube

The study of fluid-induced vibration of helical elastic coiled tubes to enhance heat transfer is very important for engineering practice and energy saving. Fluid-induced vibration and enhanced heat transfer of a helical elastic coiled tube heat exchanger were analyzed based on its finite element model, by using a two-way fluid–solid coupling method. Vibration response of the helical elastic coiled tubes, heat transfer coefficient per unit volume, and Nusselt number in vibration and nonvibration were studied at different entrance velocities and winding numbers. The results illustrate that there are a lot of vortexes in the heat exchanger and around the helical elastic coiled tubes. In the range of the entrance velocity , the vibration frequency is constant, whereas the vibration amplitude increases, and the tube vibration enhances the heat transfer of the helical elastic coiled tubes by 0.38%, 0.89%, 1.93%, and 13.65%, respectively. As the winding number increases from 5 to 9, it has a greater effect on the vibration amplitude, and the tube vibration enhances the heat transfer of the helical elastic coiled tubes by 1.93%, 3.39%, and 3.59%, respectively.

Numerical Study on Aerodynamic Performance of Different Forms of Adaptive Blades for Vertical Axis Wind Turbines

The wind energy exploitation technique has been developed very quickly in recent years. The vertical axis wind turbine is a hot research domain due to several advantages: low noise, flexible for installation, ease of maintenance, great safety and credibility, etc. The aerodynamic performances of different forms of airfoils including an active deformation airfoil and a fluid-solid coupling passive airfoil with two-dimensional (2D) and three-dimensional (3D) cases have been investigated numerically in this paper. Firstly, the aerodynamic performances of the airfoils with the maximum deformation amplitudes of their cambers which are 3%, 5% and 7% of the chord length have been discussed, respectively, with the angles of attack in the range of 0° and 20°. Secondly, for the angle of attack set at 18°, the two-way fluid-solid coupling simulations with the Young’s Modulus of 1 Mpa and 2 Mpa have also been investigated. Results show that: (1) for the pseudo 3D and real 3D single active deformation airfoil cases, the lift coefficients increase as the maximum deformation amplitudes augment from 3% to 7% of the chord length at the same angle of attack. With the same maximum deformation amplitude, when the angles of attack increase from 0° to 20°, the lift coefficients which increase firstly and then decrease are bigger than that of the original NACA0012 airfoil. When the maximum deformation amplitude of the pseudo 3D airfoil reaches 5% of the chord length, a relatively good aerodynamic performance with better inhibition effect of vortex generation can be obtained. The 3D vortex distribution demonstrates that the deformable airfoil has a better vortex generation controlling effect at the middle cross-section along the spanwise direction than the non-deformable airfoil. (2) From the aspect of fluid-solid coupling, the lift increases and the drag decreases so that the lift to drag ratio has a big improvement when the Young’s Modulus is equal to 1 Mpa and 2 Mpa. The deformable airfoil can inhibit the generation and the shedding of the surface vortex when the fluid-solid coupling effect is considered.

Experimental and Numerical Study on Fracture Characteristics of Interface between In Situ Engineered Cementitious Composites and Steel Deck

In this study, engineered cementitious composite (ECC) is used as the pavement of orthotropic steel deck bridge and an epoxy adhesive is used to achieve wet‐bonding between the steel deck and cast‐in‐place ECC. To investigate the fracture properties of bimaterial interface, the double cantilever beam (DCB) and 4‐point end notched flexure (4ENF) specimens were used to obtain the fracture toughness, and virtual crack closure technology (VCCT) was used to calculate the energy release rates. A mixed fracture criterion was also established based on the blister test in this study. In addition, for the phenomena of water accumulation in the interface cracks, the hydrodynamic pressure under load was evaluated with a two‐way fluid‐solid coupling model and the propagation mechanism of cracks at the water‐bearing interface was explored. The results showed that the energy release rates at the crack front showed obvious nonuniform distribution characteristics. The blister test indicated that a mixed fracture was in good agreement with the linear fracture criterion. The fracture effect produced by the hydrodynamic pressure of the interfacial water‐bearing crack was far less than the fracture toughness of the interface, which indicated that the hydrodynamic pressure could hardly destroy the interface at one time but might cause the erosion fatigue damage of the interface.

Analysis of aerodynamic characteristics of flexible flapping flap with bidirectional fluid–structure interaction

Birds in nature adjust the shape of their wings in time according to the change in wind resistance to achieve the purpose of increasing lift and reducing drag, thereby achieving higher flight efficiency. Aiming at the aerodynamic change caused by the flexible deformation of the flapping wing, an analysis model of the flexible wing is established. The two-way fluid–solid coupling method is used to construct the control equations in an arbitrary Lagrange–Euler coordinate system and analyze the overall aerodynamic changes in the flapping process of the flexible flapping wing and the deformation of the wing surface and skeleton. The simulation results show the following: The larger lift force and forward thrust can be obtained from the flapping of the flexible wing, but the larger flexible deformation will lead to the increase in resistance, which leads to the decline of the overall aerodynamic efficiency. Therefore, the flexible wing structure should be designed to ensure that the wing has a certain degree of flexibility and improve the stiffness of the wing.