Fluid-solid Coupling Model Research Articles

Nonlinear seismic response analysis of layered seabed considering seawater-seabed coupling effects

Earthquake in the sea area is an important factor affecting the safety of marine engineering construction, seabed site seismic response analysis is an important preliminary work for marine engineering construction. Based on a fluid-solid weak coupling model which could simulate seawater-seabed interaction, four typical borehole sections along the proposed tunnel at Qiongzhou strait are selected to establish layered seabed models for studying the seabed site seismic responses affected by the seawater, seabed soft sediments and bedrock earthquake motion under bidirectional seismic excitation, in which the dynamic nonlinearity of the seabed soft soil is simulated by a generalized non-Masing constitutive model (DCZ model). The result shows: the suppression effect of seawater on seabed seismic motion exists only in the shallow range of seabed (< 50 m), and the suppression effect on the vertical seismic response is higher than that along the horizontal direction; the suppression effect of seawater on the seabed surface seismic motion and the frequency response phenomenon of “high frequency suppression, low frequency amplification” of seabed seismic response is positively correlated with seawater depth; The mean lines of the horizontal and vertical spectrum β obtained by numerical calculation are higher than the design spectrum in the land code within several period ranges, and the possibility of adverse effects induced by seawater and seabed soft sedimentation on the seismic resistance of marine engineering should be considered.

Propagation characteristics analysis of high-frequency vibration in pumped storage power station based on a 1D fluid-solid coupling model

High-frequency pressure fluctuation is a common hydraulic phenomenon in pumped storage power station (PSPS), which is caused by the rotor-stator interaction in the pumped turbine. The propagation of the high-frequency vibration (HFV) could transmit the vibration energy to the upstream headrace tunnel, inducing severe environmental vibration and noise pollution. This study aims to establish an applicable numerical model to investigate the propagation characteristics of HFV, and evaluate the vibration magnitude of both solid and fluid in the headrace tunnel of the PSPS. In this study, a one-dimensional (1D) numerical model is established for the fluid solid interaction (FSI) behavior of the pipe, where the equations of solid and fluid are solved intuitively in the time domain by the Finite Difference Method (FDM) and Method of Characteristics (MOC), respectively. Detailed discretization schemes and solution procedures are deduced and presented in this study. Four validation cases are carried out to examine the established model. The results demonstrate that the established mode is applicable for predicting the vibration in the fluid-filled pipe (FFP). The non-reflect boundary conditions are proposed to eliminate the influence of the reflected wave from the boundary. The propagation characteristics of the high-frequency vibration (HFV) in FFP are comprehensively analyzed and summarized based on a real PSPS. And magnitude distributions of the pressure fluctuation, axial and radial vibration along the pipeline axis are presented and discussed.

Coupled CFD-DEM simulation of submarine landslide movement behavior

Submarine landslide is a common disaster geological phenomenon in the ocean, which can be destructive to underwater infrastructure. Therefore, it is necessary to simulate the evolutionary behavior of submarine viscous landslides. In this paper, computational fluid dynamics (CFD) and discrete element method (DEM) are used to establish the fluid-solid coupling model of water-particle interaction. Firstly, the inter-particle cohesion model is introduced to train the coupled CFD-DEM analysis of the kinematic evolution process, and at the same time, two typical cases are carried out to verify the analysis. In the experimental simulation, the kinematic and morphological characteristics of the submarine landslide were simulated considering the viscous effect and initial velocity of the landslide, and the influence mechanism of the landslide motion and evolution process was investigated in depth. The results show that the coupled method can better simulate the motion of submarine landslide, and the viscous effect of the landslide has a significant influence on its kinematic and morphological characteristics, and the initial velocity also significantly affects the evolution and distribution characteristics of the particle flow field of each part of the landslide in the process of motion. This study is important for the simulation and effective prediction of the kinematic evolution process of real submarine landslides.

Research on identification of the hydraulic and structural vibration sources in a tubular pumping station

The hydraulic and structural vibration sources of pumping station are investigated in current research. Based on a vertical shaft tubular pumping station project in an eastern province of China, a three-dimensional fluid-solid coupling model of the pumping station is established, including the fluid in the flow channel, concrete structure, and hydraulic machinery. Two-way fluid-structure interaction (FSI) method is used to calculate the coupled vibration responses of the pumping station. Based on the FSI simulation results, the hydraulic and structural vibration sources of the pumping station are explored from the frequency perspective based on the Fourier transform theory and the vibration energy transmission perspective based on the time-delayed transfer entropy method. Research results show that the fluid pulsation generated by the rotation of the impeller is the main hydraulic vibration source, and the rotating impeller is the main structural vibration source that causes the vibration of the unit and the concrete structure. This research could provide a scientific basis for structural vibration control, vibration reduction, and isolation design of the pumping station.

Numerical Simulation and Experimental Research on the Quenching Process of 1045 Steel Based on Thermo–Fluid–Solid Coupling Model

In the numerical simulation research on quenching, the heat transfer coefficient is an important input parameter. However, owing to its complexity and various influencing factors, the measured results are not universal and will significantly increase the simulation complexity and error. This article proposes a new numerical simulation method for quenching processes by extending the simulation domain and introducing the coupled heat exchange between the liquid quenching medium and workpiece, replacing the role of the heat transfer coefficient in the numerical simulation. The method is validated through experimental studies on 1045 steel rod quenched in water, with the maximum relative errors of the simulation results compared to the experimental results being 3.6%, 9%, and 5.1% for hardness, cooling curve, and residual stress, respectively. Furthermore, the article investigates the effect of different flow parameters of quenching media on the quenching effect. Under the studied conditions, the 1045 steel rod has the lowest risk of cracking and the highest hardness value when quenched in water at 50 °C. The proposed method improves the universality and convenience of numerical simulation for the quenching process and can be used to guide the formulation of quenching process parameters when the heat transfer coefficient is unknown.

Evolution mechanism of tunnel water and sand inrush considering water-rich sandy dolomite hazard-causing structures

Water-rich sandy dolomite stratum is prone to water and sand inrush disasters during tunnel construction. It is of great significance to explore its hazard-causing structure and water inrush mechanism for disaster control. The physical and mechanical properties of dolomite samples are tested to reveal the difference between unsanded dolomite and sandy dolomite. Based on the advanced geological prediction and geological sketching, three types of water and sand inrush hazard-causing structures are identified. Furthermore, three types of water and sand inrush mechanisms under different hazard-causing structures are explored by using fluid–solid coupling model test. One is the progressive failure type of water and sand inrush caused by crack coalescence for the broken unsanded dolomite outburst prevention structure, another is the failure type in which the seepage failure of sandy dolomite strips promotes the crack coalescence of unsanded dolomite, and the other is seepage failure type for the overall sandy dolomite outburst prevention structure. Finally, fluid–solid coupling simulation is used to discuss the failure characteristics of outburst prevention structure with different factors. The results show that the critical sandy dolomite area ratio of the three types is 25 % and 75 %. The factors affecting the inrush disaster are ranked as follows: sandy dolomite area ratio > unsanded dolomite fragmentation degree > buried depth > water storage structure pore pressure > water storage structure size. The findings provide valuable reference for disaster control in water-rich sandy dolomite area.

Thermo-hydro-mechanical coupling simulation for fracture propagation in CO2 fracturing based on phase-field model

CO2 fracturing is extensive used in unconventional oil and gas reservoir, geothermal resources, metal uranium mining, and CO2 geological storage. At present, the fluid-solid coupling model for fracture propagation with CO2 does not consider the influence of heat exchange between CO2 fracturing fluid and the formation, which leads to the deviation between the simulation results and field. Based on the phase-field models, considering the thermal stress and CO2 physical properties change induce by thermal effect, a Thermo-hydro-mechanical coupling model is established for CO2 fracturing. This paper studies the influence of formation horizontal stress difference, approaching angle and fracturing fluid injection temperature. The results indicate that, compared with hydraulic fracturing, CO2 fracturing can significantly reduce the fracture initiation pressure and time, and obtain a more complex fracture morphology with the same stress difference. For natural fractures, the approaching angle is linearly related to the initiation pressure and initiation time of opening new fractures. With the growth of approaching angle, the initiation pressure and initiation time increase respectively. The fracture shows increase in fracture morphology complexity induced by a stronger thermal stress with the growth of temperature differences. CO2 fracturing simulation thermal stress should be considered for a precision of fracture morphology.

Research on the impact of irregular structure group construction on rail transit bridge piers and its response to wind load

The possibility of deformation and collision in existing railway bridge foundation structures due to the construction of a group of large irregular structures in close proximity and their potential for overturning under strong wind loads is posed as a potential threat. The impact of the construction of large irregular sculptures on bridge piers and their response under strong wind loads is primarily investigated in this study. A modeling method based on real 3D spatial information of the bridge structure, geological structure, and sculpture structure is proposed to accurately reflect their spatial relationships. Finite difference method is employed to analyze the impact of sculpture structure construction on pier deformations and ground settlement. The bridge structure exhibits small overall deformation, with maximum horizontal and vertical displacements of the piers located at the edge of the bent cap on the side of the critical neighboring bridge pier J24 adjacent to the sculpture. A fluid–solid coupling model of the interaction between the sculpture structure and wind loads with two different direction is established using computational fluid dynamics, and theoretical analysis and numerical calculations are conducted on the sculpture's anti-overturning performance. The internal force indicators such as displacement, stress, and moment of the sculpture structure in the flow field under two working conditions are studied, and comparative analysis of typical structures is conducted. It is shown that sculpture A and B have different unfavorable wind directions and specific internal force distributions and response patterns due to the influence of size effects. Under both working conditions, the sculpture structure remains safe and stable.

Numerical investigation of variable-mass seepage mechanism of broken rock mass in faults

The continuous migration and loss of small particles in fractured rock mass with water flow is the main cause of water inrush in fault zones. In this study, a fluid–solid coupling model for fault zone was established to study the complex coupling between the groundwater seepage and migration of broken rock mass, and reveal the mechanism of erosion-induced water inrush. The rock skeleton and broken rock mass in the fault zone were modelled by large skeleton particles and small filling particles, respectively, in 3D particle flow software while the fluid flow through the fault was modelled by the built-in computational fluid dynamics module. The numerical results show that: (1) with the increase of water pressure, the loss of filling particles increases continuously, and the whole seepage process can be divided into three stages: slow seepage, abrupt seepage and steady seepage, (2) the mass loss, porosity and permeability first increase slowly, then increase rapidly, and finally tend to be stable, (3) higher fine particle content are more likely to cause structural instability due to mass loss, thus increases the risk of water inrush and mud outburst.

Fluid-solid coupling model and biological features of large vestibular aqueduct syndrome.

Objective: Computed tomography (CT) images of the temporal bone of large vestibular aqueduct syndrome (LVAS) patients were used to establish 3D numerical models based on the structure of the inner ear, which are, in turn, used to construct inner ear fluid-solid coupling models. The physiological features and pathophysiology of LVAS were analyzed from a biomechanical perspective using finite element analysis. Methods: CT images of the temporal bone were collected from five children attending the Second Hospital of Dalian Medical University in 2022. The CT images were used to build 3D models of the inner ear containing the vestibular aqueduct (VA) by Mimics and Geomagic software, and round window membrane models and fluid-solid coupling models were built by ANSYS software to perform fluid-solid coupling analysis. Results: By applying different pressure loads, the deformation of the round window membranes occurred, and their trend was basically the same as that of the load. The deformation and stress of the round window membranes increased with the increase in load. Under the same load, the deformation and stress of the round window membranes increased with the expansion of the midpoint width of the VA. Conclusion: CT images of the temporal bone used clinically could establish a complete 3D numerical model of the inner ear containing VA. Fluctuations in cerebrospinal fluid pressure could affect inner ear pressure, and VA had a limiting effect on the pressure from cerebrospinal fluid. The larger the VA, the smaller the limiting effect on the pressure.

Numerical investigation on hydraulic fracture propagation and multi-perforation fracturing for horizontal well in Longmaxi shale reservoir

Hydraulic fracturing is one of the key technologies of shale gas extraction. Deeply comprehending the distribution characteristics of hydraulic fracture networks in shale reservoirs is significant for the shale gas fracturing design and production estimation. The efficient description of fluid–solid coupling is essential for modeling the hydraulic fracturing process. In this paper, based on the mechanical parameters from the laboratory test results, the fluid–solid coupling model in PFC2D is improved and employed to establish a DEM model for the hydraulic fracturing of shale reservoirs. The key factors affecting the hydraulic fracture propagation characteristic are investigated, furthermore, based on the geological parameters of Changning shale gas production areas, a multi-perforation fracturing numerical model of the shale reservoir horizontal well is established, and the distribution characteristics of the hydraulic fracture network in staged fracturing are analyzed and revealed. The results indicate that the main factor affecting the formation of a fracture network in the vertical section of the shale reservoirs is the coalescence of interbedding fractures. A large number of secondary interbedding fractures generated by the primary through-bedding fracture can form a complex fracture network, which is exactly the fracture morphology required for hydraulic fracturing in shale gas exploitation. According to the results of hydraulic fracture distribution characteristics under different perforation spacings, the optimal perforation spacing requires that the fractures extend to the maximum range under the premise of hydraulic fracture coalescence can form an effective network and guarantee low economic cost and construction technical difficulties.

Structure improvement and parameter optimization of micro flow control valve

Aiming at the sticking phenomenon between the valve core and the valve sleeve when the valve core moves, and to solve the problem that the torque required to drive the valve core to rotate is large, the fluid–solid coupling simulation analysis of the valve core is carried out in this study, and then the valve core structure of the valve core is improved and its parameters are optimized based on the bird colony algorithm. The combination structure of the valve sleeve and valve core is studied, and the fluid–solid coupling model is established by Ansys WorkBench, and the static structure simulation analysis of valve sleeve and valve core before and after structural improvement and parameter optimization is performed. The mathematical models of triangular buffer tank, U-shaped buffer tank and combined buffer tank are established, and the structural parameters of the combined buffer tank are optimized by bird swarm optimization. The results demonstrate the triangular buffer tank has good depressurization effect but great impact, the pressure of the U-shaped buffer tank is stable and gentle but the depressurization effect is not ideal, while the combined buffer tank has obvious depressurization effect and good stability. At the same time, the optimal structural parameters of the combined buffer tank are cut-in angle of 72, plane angle of 60 and depth of 1.65 mm. The excellent structure and parameters of the combined buffer groove are obtained, so that the pressure buffer of the regulating valve at the key position of the valve port achieves the best effect, and an effective solution is provided for solving the sticking problem of the valve core of the regulating valve when working.

Research on hydrate-bearing reservoir deformation and wellbore wall stability during natural gas hydrate exploitation

Marine natural gas hydrate currently attracts increasing research attention as a potential resource of alternative clean energy. However, exploitation disturbance threatens the stability of the wellbore wall as the physical parameters and mechanical properties of hydrate-bearing reservoirs change due to hydrate decomposition, which causes the futility of conventional analysis. This study determines the influence of production disturbance on wellbore wall stability by solving the fluid–solid coupling model during the hydrate decomposition based on a self-developed solver. Through this model, the conditions of depressurized hydrate production are simulated to obtain the horizontal deformation and settlement laws of hydrate-bearing reservoirs and overburden layers. These deformations and settlements cause uneven horizontal in-situ stress on hydrate-bearing reservoirs, which will cause wellbore wall instability during hydrate production. Results show that the middle of the hydrate-bearing reservoir is the best depressurization position for production. In addition, production time, production pressure, and reservoir permeability are the key factors that affect the hydrate decomposition and cause inhomogeneous in-situ stress. The borehole wall first destabilizes at the minimum effective horizontal stress direction. Results can provide a reference for the safe and efficient exploitation of marine NGH.

Lubrication analysis of stern bearing during ship severe turning maneuver

Stern shaft deformation caused by ship maneuvering will lead to stern bearing lubrication failure and wear. Based on the displacement superposition method, the deflection equation of the stern shaft under the action of the interface force and the propeller load was established. The fluid-solid coupling model of the stern bearing was established by using the averaged Reynolds equation, the Greenwood-Tripp model, and the influence coefficient method. The model was experimentally validated. The influence of the shaft bending deformation caused by the propeller load change on the lubrication characteristics is discussed. The results show that the shaft bending deformation leads to the changes in lubrication characteristics along the axial and circumferential directions. Compared with the vertical load alone, the existence of horizontal propeller load will significantly reduce the minimum nominal oil film thickness and friction coefficient. Under hydrodynamic lubrication, the direction of horizontal load has little effect on friction coefficient.

Intelligent Feedback Analysis of Fluid–Solid Coupling of Surrounding Rock of Tunnel in Water-Rich Areas

To realize parameter feedback optimization of tunnel construction in water-rich areas, a feedback analysis method for tunnel parameters under fluid–solid coupling conditions was established based on an intelligent optimization algorithm. Firstly, the numerical calculation model was established and solved using the fluid–solid coupling model. In orthogonal design analysis, the displacement of surrounding rock and pore water pressure distribution in different rock mass parameter combinations were obtained, and the learning samples needed for machine learning were established. The input group was surrounding rock displacement and pore water pressure, and the output was rock mass parameters. Then, the Gaussian process algorithm was used to obtain the nonlinear mapping relationship contained in the learning samples. A differential evolution algorithm was used to optimize the critical parameters involved in this process. Furthermore, according to the established regression model and the measured displacement and pore water pressure in the research area, differential evolution was used again to optimize the rock mass parameters and obtain the parameter feedback analysis results. Finally, the inversion values were compared with the actual measured values, and the reliability of the surrounding rock parameters obtained from the feedback analysis was verified, providing an effective method for obtaining surrounding rock parameters for similar projects.

Research on prevention and control methods of land subsidence induced by groundwater overexploitation based on three-dimensional fluid solid coupling model—a case study of Guangrao County

Land subsidence is an environmental geological phenomenon with slowly decreasing ground elevation, The North China Plain is one of the areas with the most serious land subsidence in China, and Guangrao County is one of the subsidence centers. This paper is based on the hydrogeological and engineering geological data of Guangrao County, the groundwater monitoring data for many years and the land subsidence monitoring data, systematically analyzes the dynamic characteristics of groundwater, the distribution and evolution of land subsidence, and the correlation between groundwater exploitation and land subsidence development in different layers of this area. Based on Biot porous medium consolidation theory, establishes a three-dimensional fluid solid coupling numerical model of land subsidence in Guangrao County, restores the development process of land subsidence, predicts and analyzes the subsidence evolution law under different groundwater exploitation schemes, and proposes targeted prevention and control measures. The research results show that: the shallow groundwater forms a cone of depression with Guangbei Salt Field as the center, and the deep groundwater forms an elliptical regional cone of depression with the urban area as the center. The ground is gradually formed two small settlement areas with the urban area of Guangrao County and Guangbei Salt Field as the settlement center, and there is a trend of interrelated expansion. The three-dimensional fluid solid coupling model of land subsidence accurately restored the development process of land subsidence in the study area, predicted that under the current groundwater exploitation conditions, by 2040, the settlement of Guangrao urban settlement center will increase to 1,350 mm, forming a large regional funnel centered around the urban area, and gradually developing and expanding around. Prohibition of groundwater exploitation in the main funnel area is a more reasonable and effective exploitation plan to prevent the development of land subsidence.

Modeling and experiment study of hydraulically damped rubber mount under larger amplitude excitation at low frequency

To improve the ride comfort of the cab of construction machinery and reduce the harm of vibration to the driver, a nonlinear lumped parameter model of passive hydraulic damping rubber mount (PHDRM) is first proposed. The nonlinearity of multi-inertial tracks is fully considered. Then, the global FE (finite element) fluid-solid coupling model of the isolator is developed in ABAQUS. The multi-field coupling solution and a joint simulation mode are employed in this paper. Meanwhile, the rubber element and inertial track parameters are identified respectively. Finally, multiple sets of dynamic performance experiments are performed on the different PHDRM samples. The experiment results indicate that the simulation results for two modeling methods of the vibration isolation system are consistent with the experimental datum. The modeling approaches have both reliability and accuracy under larger amplitude excitation at low frequency. Furthermore, the effects of different rubber elements and inertial track of PHDRM on low-frequency dynamic characteristics under larger amplitude are investigated and discussed, respectively. The experimental outcomes also provide a practical reference value for nonlinear modeling method research and dynamic performance analysis of PHDRM with complex structures further.

Numerical simulation of the thermal inertia of an adiabatic reaction calorimeter in reaction thermal safety process

Obtaining accurate thermal risk assessment parameters of chemical processes and substance properties is essential for improving the safety of chemical production and substance use and storage, and the adiabatic reaction calorimeter (ARC) has been employed by many researchers for this purpose. However, with the improvement and upgrading of the instrument, an examination of the factors that affect its detection accuracy is warranted. A simplified reaction model of the adiabatic thermal decomposition of tert-butyl peroxyacetate was constructed using computational fluid dynamics in which the adiabatic thermal decomposition kinetic model and fluid-solid coupling model were combined to simulate heat transfer. To verify the reliability of the parameters of the numerical calculation model, the effects of the sample cell's material, wall thickness, and mass were investigated in relation to the thermal inertia of the ARC. The results indicated that the thermal inertia of the system was lowest when the sample cell was composed of titanium. When the sample pool's composition is determined, the thermal inertia of the system can be reduced to a certain extent through an approximate increase in the sample mass. Finally, an analysis of the heat flow cloud diagram of the wall of sample pools made from different materials revealed that the thermal conductivity of titanium was high; this information can assist in controlling the adiabatic process.

Optimization of Wing Structure Based on Fluid-solid Coupling and Vibration Model

With the development of ages, human beings have made more efforts to develop the sky, and aircraft is widely used as the main tool for human beings to set foot in the sky. Therefore, optimizing wing structure is positive for saving resources and improving efficiency. In this paper, by establishing the conventional wing structure model and the wing model after changing its rib density, we compared results based on fluid-solid coupling and vibration mode analysis. It is found that: The wing structure optimization should appropriately increase or decrease the wing-rib aperture (i.e., increase/decrease by 10%) based on ensuring the flight performance of the wing, and it can effectively reduce the overall deformation of the wing and ensure the flight performance of the wing, which provides a valuable reference for the design of the wing structure.

Numerical Simulation of the Microscopic Plugging Mechanism and Particle Flow Process of the Microsphere System.

The microsphere system has small initial particle size, excellent swelling performance, simple manufacturing process, and strong plugging ability. It has great application potential in the field of plugging and profile control of deep reservoirs. Microspheres can effectively plug the pores of fractured cores, inhibit the rapid breakthrough process, and improve the sweep efficiency of the injected fluids. However, the microscopic plugging mechanism of microspheres on fractured cores is still unclear. In this study, the distribution of microspheres after plugging was observed through specially prepared core models. Furthermore, the microscopic plugging mechanism of microspheres in fractured reservoir cores was clarified, including direct microsphere plugging, cluster bridging plugging, adhesion plugging, extrusion-deformation plugging, and extrusion-crushing plugging. Then, particle flow simulation software was used to establish the fluid-solid coupling model of microsphere plugging, and then, the numerical simulation of the plugging process was realized by Python module programming. Through this study, the plugging effect of microspheres under different fracture opening conditions was clarified. Moreover, the effects of injection pressure difference, fracture width, and particle size ratio on the fluid-solid structures of microsphere plugging were analyzed. The results show that the smaller the particle size ratio, the greater the injection pressure difference, the fracture width, and the reduction magnitudes in fracture porosity and core permeability and the higher the plugging rate. The numerical simulation results well support the microsphere plugging mechanism obtained by experiments. The results of this study can provide theoretical and technical support for the development of deep profile control and flooding and enhanced oil recovery technology of the polymer microsphere dispersion system in fractured low-permeability reservoirs.