Fluid Coupling Research Articles

Analytical Study of Free Vibrations of Fluid Coupling and Structure in Collision of Turbulent Fluid with FGM Plate

In this paper, the free and forced vibration of a functional rectangular plate in contact with a turbulent fluid is investigated. Functional plates have been considered due to their high thermal resistance to residual stresses. The geometry of the problem is that one side of the reservoir in which the fluid is placed is covered with a plate of Functionally Graded Material (FGM). In order to approximate the displacement of the plate, assuming the third-order theory of shear deformation, trigonometric harmonic test functions are used, which determine the boundary conditions of the simple and fixed plate support. In the equations governing fluid oscillating behavior, the potential velocity of the fluid is obtained by determining the boundary conditions of the fluid in the form of February series functions. To achieve the natural frequency of the plate in contact with turbulent fluid and the shape of the vibrating mode, the Rayleigh-Ritz energy method is used based on the minimum potential energy. In order to check the accuracy of the method used, the results of analytical solution after solving the equations by coding in Wolfram Mathematica software have been compared with numerical solution of Abaqus software and then with accurate results in references, which shows the appropriate accuracy of the solution. Finally, the effect of volumetric coefficient parameters, volume ratio, length ratio, plate thickness ratio, fluid height, reservoir width and boundary conditions on the natural frequency of the plate in contact with turbulent fluid has been investigated and analyzed.

Experimental Study on the Effect of Gas Adsorption on the Effective Stress of Coal Under Triaxial Stress

The deformation of coal during the injection of sorptive gases can be classified into two types: deformation due to the pore pressure and the swelling deformation of the coal matrix induced by adsorption. These types of deformation have not been investigated separately in the previous researches. The main reason is that measuring the radial strain of the coal core directly and accurately is extremely difficult under triaxial stress. This paper demonstrates that by injecting both sorptive and non-sorptive gases into a coal sample with different pore pressures, while measuring the radial deformation of the coal sample with a high precision instrument (± 0.227 mm3), deformations due to the pore pressure and deformations induced by adsorption were separated from each other. The adsorption-induced deformations have an important influence on the effective stress. We studied the relationship between Biot coefficient and the swelling deformation due to the adsorption based on the Biot effective stress theory. The experimental results show that the Biot coefficient is the bilinear function in terms of the volumetric stress and pore pressure, shown as $$\alpha = a + b\Theta + cp + d\Theta p$$ . The data and results obtained in this experiment played a fundamental role in the applications of gas extraction, coal and gas outburst prevention and control, displacement of coalbed methane with CO2, and the establishment of the solid–fluid coupling model.

Model coupling biomechanics and fluid dynamics for the simulation of controlled flapping flight

This paper proposes a multiphysics computational framework coupling biomechanics and aerodynamics for the simulation of bird flight. It features a biomechanical model based on the anatomy of a bird, which models the bones and feathers of the wing. The aerodynamic solver relies on a vortex particle-mesh method and represents the wing through an immersed lifting line, acting as a source of vorticity in the flow. An application of the numerical tool is presented in the modeling of the flight of a northern bald ibis (Geronticus eremita). The wing kinematics are imposed based on biological observations and controllers are developed to enable stable flight in a closed loop. Their design is based on a linearized model of flapping flight dynamics. The controller solves an underdetermination in the control parameters through minimization. The tool and the controllers are used in two simulations: one where the bird has to trim itself at a given flight speed, and another where it has to accelerate from a trimmed state to another at a higher speed. The bird wake is accurately represented. It is analyzed and compared to the widespread frozen-wake assumption, highlighting phenomena that the latter cannot capture. The method also allows the computation of the aerodynamic forces experienced by the flier, either through the lifting line method or through control-volume analysis. The computed power requirements at several flight speeds exhibit an order of magnitude and dependency on velocity in agreement with the literature.

Measurement of the temperature-dependent output of lead zirconate titanate transducers

The effect of temperature and electrical drive conditions on the output of lead zirconate titanate (PZT) transducers is of particular interest in ultrasound metrology and medical ultrasound applications. In this work, the temperature-dependent output of two single-element PZT transducers was measured between 22 °C and 46 °C. Two independent measurement methods were used, namely radiation force balance measurements and laser vibrometry. When driven at constant voltage using a 50 Ω matched signal generator and amplifier using continuous wave (CW) or quasi-CW excitation, the output of the two transducers increased on average by 0.6 % per degree, largely due to an increase in transducer efficiency with temperature. The two measurement methods showed close agreement. Similar trends were observed when using single cycle excitation with the same signal chain. However, when driven using a pulser (which is not electrically matched), the two transducers exhibited different behaviour depending on their electrical impedance. Accounting for the temperature-dependent output of PZT transducers could have implications for many areas of ultrasound metrology, for example, in therapeutic ultrasound where a coupling fluid at an increased or decreased temperature is often used.

Adaptive Finite Element–Discrete Element Analysis for the Stress Shadow Effects and Fracture Interaction Behaviours in Three-Dimensional Multistage Hydrofracturing Considering Varying Perforation Cluster Spaces and Fracturing Scenarios of Horizontal Wells

Optimization of complex fracture networks improves the fracturing effects and enhances production in multistage hydrofracturing technology. To understand the controlling mechanisms of multistage hydrofracturing in unconventional tight reservoirs, some governing issues, such as hydro-mechanical coupling, stress shadow effects, propagation interaction behaviours of three-dimensional (3D) multiple fractures, and 3D multistage hydrofracturing, should be addressed. However, the characterization of perforation cluster spaces and fracturing scenarios of horizontal wells, which significantly affect the evolution of the stress field and 3D morphology of the fracture network, is a challenge. In this study, to overcome the drawbacks of the traditional finite-element method in simulating 3D fracture propagation, the adaptive finite element–discrete element method is used. This method uses a local remeshing and coarsening strategy to ensure the accuracy of solutions, reliability of the fracture propagation path, and computational efficiency. The study proposes 3D engineering-scale numerical models, considering the crucial hydro-mechanical coupling and fracturing fluid leak-off, to simulate 3D multistage hydrofracturing and fracture interaction behaviours. The numerical results show that the stress shadow effects and fracture interaction behaviours become more intense once the spaces between different propagating fractures become thinner due to superposition and reduction effects in fracturing-induced shear stress variation areas. The alternate fracturing can reduce the stress shadow effects through adjusting the sequence of perforation clusters that are activated and injected with fracturing fluid. When the perforation cluster spaces become narrow, the alternate fracturing scenario can yield more fracturing fracture areas and improve the fracturing effects as compared to sequential and simultaneous fracturing.

Hybrid multi-plate magnetorheological clutch featuring two operating modes: Fluid coupling and mechanical friction

Recently, there has been a rising demand for high-performance clutches in mechanical systems owing to the development of industrial technologies. This paper, therefore, proposes a hybrid multi-plate Magnetorheological (MR) clutch that has both fluid coupling and mechanical friction modes. To reduce impact when the plates are in contact with each other, a fluid coupler’s operating mode was used at the beginning of the clutch operation. For this, torque modeling in each mode was induced based on the Bingham model of the MRF. Using the induced torque modeling and ANSYS Maxwell’s magnetic field analysis results, the design procedure for a multi-plate clutch was implemented. Based on the design results, a hybrid multi-plate MR clutch was manufactured. Finally, the performance of the manufactured MR clutch was evaluated using a torque tester. The assessment confirmed that the proposed torque modeling and simulation results mostly matched the test results.

1D/3D Finite-Volume coupling in conjunction with beam/shell elements coupling for fast transients in pipelines with fluid–structure interaction

A 1D/3D Finite-Volume coupling is proposed for the Euler/Homogeneous Equilibrium Model equations. The present approach is based on the Finite-Volume framework making it possible to tackle general equations of state. A special attention is given to the conservation of mass, momentum and energy at the common 1D/3D interface. For fluid–structure interaction induced by fast-transient phenomena occurring in pipelines, the present 1D/3D fluid coupling is also associated with a beam/shell elements coupling to deal with the mechanical pipe behavior. A series of test-cases involving both purely fluid, purely structural and coupled fluid–structure problems with available analytical or experimental references is considered to demonstrate the performance of the present 1D/3D coupling.

Adaptive finite element–discrete element analysis for stratal movement and microseismic behaviours induced by multistage propagation of three-dimensional multiple hydraulic fractures

PurposeOptimized three-dimensional (3D) fracture networks are crucial for multistage hydrofracturing. To better understand the mechanisms controlling potential disasters as well as to predict them in 3D multistage hydrofracturing, some governing factors, such as fluid injection-induced stratal movement, compression between multiple hydraulic fractures, fracturing fluid flow, fracturing-induced microseismic damaged and contact slip events, must be properly simulated via numerical models. This study aims to analyze the stratal movement and microseismic behaviours induced by multistage propagation of 3D multiple hydraulic fractures.Design/methodology/approachAdaptive finite element–discrete element method was used to overcome the limitations of conventional finite element methods in simulating 3D fracture propagation. This new approach uses a local remeshing and coarsening strategy to ensure the accuracy of solutions, reliability of fracture propagation path and computational efficiency. Engineering-scale numerical models were proposed that account for the hydro-mechanical coupling and fracturing fluid leak-off, to simulate multistage propagation of 3D multiple hydraulic fractures, by which the evolution of the displacement, porosity and fracture fields, as well as the fracturing-induced microseismic events were computed.FindingsStratal movement and compression between 3D multiple hydraulic fractures intensify with increasing proximity to the propagating fractures. When the perforation cluster spaces are very narrow, alternate fracturing can improve fracturing effects over those achieved via sequential or simultaneous fracturing. Furthermore, the number and magnitude of microseismic events are directly proportional to the stratal movement and compression induced by multistage propagation of fracturing fracture networks.Originality/valueMicroseismic events induced by multistage propagation of 3D multiple hydraulic fractures and perforation cluster spaces and fracturing scenarios that impact the deformation and compression among fractures in porous rock matrices are well predicted and analyzed.

Modeling and solution method of gas-liquid-solid three-phase flow mixing

The mixing process of gas-liquid-solid three-phase flow is a complex multi-fluid-structure coupling dynamic problem. The relationship between the particle parameters and the physical spatial scale of the flow channel directly affects the calculation convergence. Numerical modeling and mesh processing of fluid-structure bidirectional interaction in the strong shear zone are difficult. Aiming at the above problems, a method of modeling and solving the gas-liquid-solid three-phase flow mixing is proposed. Based on the volume-of-fluid coupled with discrete-element-method model, a three-phase dynamic model considering particle motion is established. By solving the momentum equation, the bidirectional coupling of two-phase fluid and particle is realized. The user-defined function communication interface is developed independently to obtain the interaction force between fluid and particles, and a porous-interphase coupling solution is proposed to describe the trajectory of particles. Taking the mixing process of three-phase flow with strong shear for example, this method is used to study the influence of different aeration conditions on the free surface, velocity distribution and particle suspension characteristics in the physical space of the flow channel. The results show that strong shear and wall action can convert the tangential velocity of the fluid into axial and radial velocity; choosing an appropriate inflation velocity can eliminate the instability of the free surface and increasing the flow velocity of the fluid has a limited effect on the suspension of particles in some areas. The research results can provide a useful reference for studying the interaction mechanism of complex multiphase flow, and also provide technical support for the mixing production control of gas-liquid-solid three-phase particles.

Study on torque density enhancement mechanism of elliptic arc multi-disk MRF coupling

The transfer energy of a magnetorheological fluid (MRF) coupling can be dynamically regulated by changing the MRF mechanical properties of its input and output shafts. In addition, the dynamic characteristics of its drive system can automatically be in the tune with its load characteristics to effectively suppress vibration and shock responses, to achieve overload protection of the system, and to improve its mechanical performance and safety reliability. However, the weak mechanical properties of MRF materials result in so small a coupling torque density that the MRF coupling applications for high-torque transfer is restricted. Thus, to increase the coupling torque density is becoming an urgent key technological challenge in this field. A technique based on shear-pressure mixed mode was proposed here to increase the torque density by utilizing the formation mechanism of MRF arc flux linkage. Futhermore, a new high torque arc multi-disk MRF coupling structure was designed and its corresponding mechanical torque transfer model was established. A FEA electromagnetic simulation was performed to study the distribution of the magnetic field in the MRF chamber under different current excitations. Effects of the key parameters of the elliptical arc on its transfer torque were also investigated. Finally, experimental analysis of the mechanical properties of the elliptical disk MRF coupling was conducted to verify the feasibility of the proposed technique and the validity of the torque transfer model.

Modelling of Electric Arcs for Industrial Applications, a Review

Electric arcs are a necessary heat source in many industrial processes that take place in Submerged Arc Furnaces (SAFs). Arcs exhibit non-linear electrical characteristics and behave in a complex manner. Therefore, an improved understanding of their behaviour enables better control of furnace operation. Modelling of industrial arcs is a multiphysics process that involves simultaneously solving several coupled physical phenomena, such as electromagnetics, fluid dynamics and heat transfer, including a radiative heat transfer from the plasma arc. Coupling fluid dynamics and electromagnetics is known as Magnetohydrodynamics (MHD). There are also simpler approaches to arc modelling, either based on simplified physical principles or empirical behaviour. A number of MHD models for electric arcs have been presented in the literature, but most of them involve simplifications such as axial-symmetry to reduce the simulation time, pertain to currents much lower than for industrial arcs, focus on DC arcs rather than arcs carrying AC current or do not have the plasma properties of the actual gas in the furnace. In a recently started project, the ambition is to create a full-scale 3D MHD model for an industrial AC arc at the conditions to be found in Si-metal furnaces. As much can be learned from previous arc modelling, this paper will review different arc modelling approaches and develop a classification framework to categorize the modelling methods, both the more intricate MHD models as well as the simpler modelling approaches. Among the available simplified models, one will be selected and coupled with a submerged arc furnace electrical circuit model. The complete circuit model parameters such as resistances and inductances are updated using a 3D submerged arc furnace that has been developed in ANSYS Maxwell using an eddy current solver.

Fluid-structure interaction analysis of the return pipeline in the high-pressure and large-flow-rate hydraulic power system

This paper aims to investigate the dynamic characteristic of the return pipeline in the high-pressure and large-flow-rate hydraulic power system. First, the geometry model of the pipeline is established, and a one-way coupling fluid structure method is introduced. The modal analyses with empty and filled pipelines are performed and compared. Then, the pipeline resonance phenomenon is investigated, and the response frequency is achieved by the fast Fourier transformation (FFT) analysis, the results are inconsistent with the experiments. Besides, the dynamic response of the pipeline is simulated. Dynamic mesh and user define function (UDF) are adopted, and the pipeline vibration and water hammer phenomenon are observed. Finally, the dynamic characteristics of the pipeline under different fluid velocities and wall thickness are investigated. The results show that the pipeline valve-induced vibration cannot be lightened by reducing the fluid inlet velocity but can be significantly mitigated by increasing the wall thickness.

Fluid-structure interaction analysis of the return pipeline in the high-pressure and large-flow-rate hydraulic power system

This paper aims to investigate the dynamic characteristic of the return pipeline in the high-pressure and large-flow-rate hydraulic power system. First, the geometry model of the pipeline is established, and a one-way coupling fluid structure method is introduced. The modal analyses with empty and filled pipelines are performed and compared. Then, the pipeline resonance phenomenon is investigated, and the response frequency is achieved by the fast Fourier transformation (FFT) analysis, the results are inconsistent with the experiments. Besides, the dynamic response of the pipeline is simulated. Dynamic mesh and user define function (UDF) are adopted, and the pipeline vibration and water hammer phenomenon are observed. Finally, the dynamic characteristics of the pipeline under different fluid velocities and wall thickness are investigated. The results show that the pipeline valve-induced vibration cannot be lightened by reducing the fluid inlet velocity but can be significantly mitigated by increasing the wall thickness.

Coupling fluid flow to hydrogel fluidic devices with reversible "pop-it" connections.

Hydrogels are soft, water-based polymer gels that are increasingly used to fabricate free-standing fluidic devices for tissue and biological engineering applications. For many of these applications, pressurized liquid must be driven through the hydrogel device. To couple pressurized liquid to a hydrogel device, a common approach is to insert tubing into a hole in the gel; however, this usually results in leakage and expulsion of the tubing, and other options for coupling pressurized liquid to hydrogels remain limited. Here, we describe a simple coupling approach where microfluidic tubing is inserted into a plastic, 3D-printed bulb-shaped connector, which "pops" into a 3D-printed socket in the gel. By systematically varying the dimensions of the connector relative to those of the socket entrance, we find an optimal head-socket ratio that provides maximum resistance to leakage and expulsion. The resulting connection can withstand liquid pressures on the order of several kilopascals, three orders of magnitude greater than traditional, connector-free approaches. We also show that two-sided connectors can be used to link multiple hydrogels to one another to build complex, reconfigurable hydrogel systems from modular components. We demonstrate the potential usefulness of these connectors by established long-term nutrient flow through a 3D-printed hydrogel device containing bacteria. The simple coupling approach outlined here will enable a variety of applications in hydrogel fluidics.

ИССЛЕДОВАНИЕ СВОЙСТВ МАГНИТНЫХ СМАЗОЧНЫХ МАТЕРИАЛОВ НА ОСНОВЕ КРЕМНИЙОРГАНИЧЕСКОЙ ЖИДКОСТИ

The results of research on lubricants which are magnetic fluids are presented. The positive effect on the characteristics of the lubricant of pondemotor force that occurs when an external magnetic field is applied is noted. The purpose of this work is to study the properties of magnetic lubricants based on polyethylsiloxane liquids and confirm the previously stated theoretical assumptions. The main objectives of the research are to develop the composition of a lubricant based on a polyethylsiloxane magnetic fluid, to determine the characteristics of adhesion of this material to a metal base, to obtain an adequate mathematical model describing the characteristics of adhesion of the lubricant to the surface, and to determine its stability during operation. Experimental installations and methods for determining the characteristics of the coupling of magnetic fluids with the friction surface, as well as the stability of magnetic fluid itself during operation, have been developed. The prospects of introducing oleic acid into the organosilicon base of the magnetic liquid are noted. A decrease in the adhesion coefficient with an increase in the rotational speed of the samples at loads from 160 N to 320 N was revealed by an average of 1.6...2.7 times. It is proved that the magnetic lubricant adheres to the metal base more strongly than Litol-24 by an average of 6 times, which prevents the rolling elements from slipping during the operation of the samples. Different patterns of changes in adhesion to metal surfaces of Litol-24 and magnetic fluids are noted. An increase in the adhesion coefficient of magnetic fluids under the conditions of applying a constant magnetic field at loads on samples from 480 N to 800 N due to the magnetorheological effect by 20...30% is established. A mathematical model is obtained that adequately describes the change in the adhesion coefficient of the obtained magnetic lubricant. The composition of the magnetic liquid is recommended, consisting of a polyethylene siloxane carrier liquid, a surfactant-oleic acid, and a ferromagnetic phase-magnetite with a particle size of 7.5 nm. High stability of the developed magnetic fluids during longterm operation has been experimentally established. The stability coefficient of the magnetic fluid decreased by 2.51 times in 366 hours.

Numerical Simulation of Tribocorrosion of CoCr Alloy and Ti with Galvanic Coupling in Simulated Body Fluid

Numerical Simulation of Tribocorrosion of CoCr Alloy and Ti with Galvanic Coupling in Simulated Body Fluid

A microchannel shell-and-tube absorber for ammonia-water absorption

A shell-and-tube absorber with microscale geometric features that yields significant volumetric heat duties is investigated. A vertically-oriented baffled shell-and-tube heat exchanger with a tightly packed tube bundle is designed to serve as the absorber for a 10.5 kW nominal cooling capacity absorption chiller. The heat and mass transfer in this absorber is investigated experimentally at operating conditions spanning a wide range of working fluid and coupling fluid flow rates and ambient temperatures. An experimental facility is fabricated to closely simulate the operating conditions in an absorption refrigeration system. Absorption heat duties in the range of 5–15 kW are measured. In addition to operating the absorber in the baseline co-current flow configuration with premixed inlet, fluid ports are provided to enable operation in counter-current flow, where the dilute solution enters from the top and vapor enters from the bottom. The performance of these two flow configurations is compared. A preliminary heat and mass transfer model is developed to quantify the local temperatures, concentrations, and mass flow rates of the solution and vapor streams along the length of the absorber. The model predictions for total heat duty agree with the experimental results within 10% for almost all the data points, with an AAD of ~ 3.4%. The results of this study, along with the modeling framework, can guide further development of highly compact and efficient absorbers absorption systems.

Mesoscale analysis of the suction stress characteristic curve for unsaturated granular materials

There is still no theoretical framework accounting for linkage between seepage and deformation of unsaturated granular materials. Using a mesoscale liquid bridge model, we propose the first approach for deriving the suction stress characteristic curve (SSCC). Then, we verify the method by obtaining both the soil–water characteristic curve and SSCC for cubic and tetrahedral granular packing. The approach is further validated by generating the SSCCs of granular packings with different particle size distributions. On this basis, a new two-parameter model is suggested that satisfactorily predicts the SSCCs of various real granular materials. The nonlinear variation of strength versus suction is also properly described by a new formula for three kinds of soil. We believe that this SSCC model can help resolve solid–fluid coupling in seepage and deformation problems in unsaturated granular engineering.

Numerical and experimental investigation of the effect of interstitial gases on conductive heat transfer for dense particulate systems

Many industrial processes involve granular heat transfer. Within these processes are a sub-set of applications where the particles are densely packed and the surrounding gas is predominantly stagnant. For materials with low thermal conductivity much of the heat transfer will occur through the interstitial gases so capturing this effect is critical to represent these systems numerically. Resolving the gas phase explicitly using a fluid solver and coupling to a particle method is possible but computationally expensive. Higher fidelity models often make simulation of applications at the industrial scale intractable. With this in mind we seek a numerical method that captures the important heat transfer phenomena in dense granular systems with minimal additional computational effort. In this work we first characterize one common particle based approach proposed by Rong and Horio that calculates the contribution through a stagnant gas film surrounding each particle. We compare this approach to fluid simulations of a particle-wall and a particle-particle collision to evaluate the validity of the underlying assumptions of the Rong and Horio model. We then use a multi-scale approach to examine the relationship between the local packing structure and the contribution of the interstitial gas. From this we propose a new dimensionless parameter that permits the inclusion of the gas effect in a particle based simulation method with minimal additional computational effort and without explicitly having to include the gas phase. The model is then validated against a static experiment and compared with the Rong and Horio model.

Transcranial photoacoustic computed tomography based on a layered back-projection method

A major challenge of transcranial human brain photoacoustic computed tomography (PACT) is correcting for the acoustic aberration induced by the skull. Here, we present a modified universal back-projection (UBP) method, termed layered UBP (L-UBP), that can de-aberrate the transcranial PA signals by accommodating the skull heterogeneity into conventional UBP. In L-UBP, the acoustic medium is divided into multiple layers: the acoustic coupling fluid layer between the skull and detectors, the skull layer, and the brain tissue layer, which are assigned different acoustic properties. The transmission coefficients and wave conversion are considered at the fluid–skull and skull–tissue interfaces. Simulations of transcranial PACT using L-UBP were conducted to validate the method. Ex vivo experiments with a newly developed three-dimensional PACT system with 1-MHz center frequency demonstrated that L-UBP can substantially improve the image quality compared to conventional UBP.