Fluid Coupling Research Articles

Thermal and Fluid Coupling Field Analysis of MR Damper for Gun Recoil

Thermal and Fluid Coupling Field Analysis of MR Damper for Gun Recoil

Influence of different underexcited operations on thermal field in the turbogenerator end region with magnetic shield structure

The losses and temperatures of end parts will increase obviously in the turbogenerator end region under underexcited operation. In order to study the influence of different underexcited operations on temperature of end parts in the turbogenerator end region with magnetic shield structure, a turbogenerator is considered as an example in this paper. Three-dimensional transient electromagnetic field of turbogenerator end region is given. The magnetic density distribution of clamping plate and magnetic shield is researched. The losses of end parts and stator end cores from three-dimensional transient electromagnetic field calculation are applied to end region as heat sources under different underexcited operations. Pressure value of fan outlet and velocity values of different inlets from flow network calculations are applied to end region as boundary conditions in the 3-D fluid and thermal coupling analysis model. Further, fluid field and thermal field are calculated under different underexcited operations. The distribution laws of fluid velocity and fluid temperature in the turbogenerator end region are determined. The temperature distribution laws of the stator-end copper windings, press finger, clamping plate, screen plate, magnetic shield, and stator end cores are studied under different underexcited operations. The accuracy of numerical calculation is validated by measured values.

The dynamics of an insulating plate over a thermally convecting fluid and its implication for continent movement over convective mantle

Continents exert a thermal blanket effect to the mantle underneath by locally accumulating heat and modifying the flow structures, which in turn affects continent motion. This dynamic feedback is studied numerically with a simplified model of an insulating plate over a thermally convecting fluid with infinite Prandtl number at Rayleigh numbers of the order of $10^{6}$. Several plate–fluid coupling modes are revealed as the plate size varies. In particular, small plates show long durations of stagnancy over cold downwellings. Between long stagnancies, bursts of velocity are observed when the plate rides on a single convection cell. As plate size increases, the coupled system transitions to another type of short-lived stagnancy, in which case hot plumes develop underneath. For an even larger plate, a unidirectional moving mode emerges as the plate modifies impeding flow structures it encounters while maintaining a single convection cell underneath. These identified modes are reminiscent of some real cases of continent–mantle coupling. Results show that the capability of a plate to overcome impeding flow structures increases with plate size, Rayleigh number and intensity of internal heating. Compared to cases with a fixed plate, cases with a freely drifting plate are associated with higher Nusselt number and more convection cells within the flow domain.

Incorporating Full Attenuation Mechanisms of Poroelastic Media for Realistic Subsurface Sensing

Porous materials are ubiquitous in the subsurface formations of the earth where acoustic and seismic waves are used for remote sensing. However, it is not well understood how the dissipation and the dispersion of poroelastic waves are caused by the viscoelastic and viscous properties of the constituents such as solid grains and pore fluid and by the viscoelastic dissipation of the solid frame, as well as the viscodynamic coupling of the pore fluid to the solid frame due to its global and local flows relative to the solid grains. Such attenuation mechanisms have seldom been incorporated in subsurface sensing simulations, although they can be very important to applications. In this paper, we propose a complete attenuation model, including both full stiffness and viscodynamic dissipation, for poroelastic media in seismic wave simulations. Completely based on a generalized Zener model, the effects associated with physical dissipation and frequency-dependent dispersion are accurately simulated by a finite-difference time-domain algorithm. Verifications with analytical solutions show the accuracy, efficiency, and flexibility of our method. Numerical results demonstrate that the attenuation of Biot’s model in the sediment of the seafloor has significant effects on acoustic wave scattering from complex geologic structures.

Using Cohesive Zone Model to Simulate the Hydraulic Fracture Interaction with Natural Fracture in Poro-Viscoelastic Formation

Hydraulic fracturing is a widely used production stimulation technology for conventional and unconventional reservoirs. The cohesive element is used to explain the tip fracture process. In this paper, the cohesive zone model was used to simulate hydraulic fracture initiation and propagation at the same time rock deformation and fluid exchange. A numerical model for fracture propagation in poro-viscoelastic formation is considered. In this numerical model, we incorporate the pore-pressure effect by coupling fluid diffusion with shale matrix viscoelasticity. The numerical procedure for hydraulically driven fracture propagation uses a poro-viscoelasticity theory to describe the fluid diffusion and matrix creep in the solid skeleton, in conjunction with pore-pressure cohesive zone model and ABAQUS was used as a platform for the numerical simulation. The simulation results are compared with the available solutions in the literature. The higher the approaching angle, the higher the differential stress, tensile stress difference, injection rate, and injection fluid viscosity, and it will be easier for hydraulic fracture crossing natural fracture. These results could provide theoretical guidance for predicting the generation of fracture network and gain a better understanding of deformational behavior of shale when fracturing.

Waste-heat driven ammonia-water absorption chiller for severe ambient operation

A packaged ammonia-water absorption chiller using a waste-heat stream and operating at severe ambient conditions is developed and experimentally evaluated. The chiller is designed to provide 2.6 kW of cooling at an ambient temperature of 51.7 °C. The system is directly coupled to exhaust gas from a diesel generator to drive the absorption cycle. The absorber and condenser reject heat directly to ambient air. Direct coupling to the heat source and the ambient heat sink leads to reduced system size and minimization of parasitic electrical power required for coupling fluid pumps. The dimensions of the unit are: 0.66 m × 0.61 m × 0.48 m (L × W × H). An autonomous control system is also developed and demonstrated experimentally. System performance is measured at ambient temperatures of 40–52 °C, delivering cooling duties of 2.5–1.8 kW, with overall coefficients of performance (COPs) of 0.38–0.3. Performance limitations and areas for future development are discussed.

A Thermoelectric Device for Coupling Fluid Temperature Regulation During Continuous Skin Sonoporation or Sonophoresis.

During skin sonoporation and sonophoresis, time-consuming duty cycles or fluid replacement is often required to mitigate coupling fluid temperature increases. This study demonstrates an alternative method for temperature regulation: a circulating, thermoelectric system. Porcine skin samples were sonoporated continuously for 10min at one of three intensities (23.8, 34.2, 39.4W/m2). A caffeine solution was then applied to the skin and left to diffuse for 20h. During sonoporation, the system was able to maintain the temperature between 10 and 16°C regardless of the intensity. No increase in transdermal transport was achieved with an intensity of 23.8W/m2. Intensities of 34.2 and 39.4W/m2 resulted in 3.5-fold (p< 0.05) and 3.7-fold (p< 0.05) increases in mean transport, relative to a control case with no ultrasound. From these results, it is concluded that a significant transport increase can be achieved with a system that circulates and cools the coupling fluid during ultrasound application. Relative to the previous methods of temperature control (duty cycles and fluid replacement), use of this circulation system will lead to significant time savings in future experimental studies.

Understanding the Mechanism of Interwell Fracturing Interference With Reservoir/Geomechanics/Fracturing Modeling in Eagle Ford Shale

Summary Tightly spaced horizontal wells are widely used in the development of unconventional resources. The effectiveness of this strategy is largely affected by interwell fracturing interference, indicated by interwell fracture geometry and fracture hits, because interwell interference affects both the parent- and infill-well production. This work proposes a reservoir/geomechanics/fracturing modeling work flow for understanding the interference mechanism and quantifying effects of parent-well fracture geometry, differential stress, and the design of infill-well completion on interwell fracturing interference. Reservoir models are constructed for the analysis of Eagle Ford scenarios. The numerical work flow involves a finite-element model that fully couples reservoir flow and geomechanics, and a complex multifracture propagation model coupling rock mechanics and fluid flow in wellbore and fractures. The work flow characterizes the temporal-spatial evolution of pressure and stress caused by legacy-parent-well production. The fracture model is used to simulate the complex fracture geometry created by infill-well completion, on the basis of an updated heterogeneous reservoir stress state. The resulting fracture geometry quality is quantified by the occurrence of fracture hits and the relative growth of fractures in longitudinal and transverse directions. Nonuniform fracture geometries lead to more-complex stress changes, induced by depletion, rather than by uniform fracture geometries along parent wells. A smaller in-situ differential stress results in stronger stress reorientation that is caused by parent-well depletion, which induces longitudinal fractures along infill wells, and greatly reduces stimulated reservoir volume (SRV) and initial well performance of infill wells. A larger in-situ differential stress induces less stress reorientation and is more likely to lead the fractures to propagate toward pre-existing fractures, generate fracture hits, and affect the production of parent wells. The quantification study in the sensitivity analysis indicates that differential stress and the infill-well completion design have the most significant influences on interwell interference. This study suggests optimal infill-well completion designs for Eagle Ford scenarios. The study also provides insights for an infill-well completion design in unconventional reservoirs developed by tightly spaced horizontal wells, in terms of how to adjust field operational schedules to avoid fracture hits, and change the complexity of the interwell fracture networks.

Semi‐analytical solution of MHD flow through boundary integrals on the pipe wall

A mathematical model is given for the magnetohydrodynamic (MHD) pipe flow as an inner Dirichlet problem in a 2D circular cross section of the pipe, coupled with an outer Dirichlet or Neumann magnetic problem. Inner Dirichlet problem is given as the coupled convection‐diffusion equations for the velocity and the induced current of the fluid coupling also to the outer problem, which is defined with the Laplace equation for the induced magnetic field of the exterior region with either Dirichlet or Neumann boundary condition. Unique solution of inner Dirichlet problem is obtained theoretically reducing it into two boundary integral equations defined on the boundary by using the corresponding fundamental solutions. Exterior solution is also given theoretically on the pipe wall with Poisson integral, and it is unique with Dirichlet boundary condition but exists with an additive constant obtained through coupled boundary and solvability conditions in Neumann wall condition. The collocation method is used to discretize these boundary integrals on the pipe wall. Thus, the proposed procedure is an improved theoretical analysis for combining the solution methods for the interior and exterior regions, which are consolidated numerically showing the flow behavior. The solution is simulated for several values of problem parameters, and the well‐known MHD characteristics are observed inside the pipe for increasing values of Hartmann number maintaining the continuity of induced currents on the pipe wall.

The effect of completion strategy on fracture propagation from multiple cluster perforations in fossil hydrogen energy development

The hydraulic fracturing is extensively used to stimulate the production of fossil hydrogen energy. Perforation parameters have a great influence on the performance of hydraulically fractured horizontal wells in fossil hydrogen energy development. In this work, a practical model to study the effect of a completion scheme on simultaneous fracture propagation is proposed, in which the coupling fluid flow and stress interaction is considered, and a fracture propagation uniform index model is used to optimize the completion strategy. Moreover, this model is well validated by Wu's model and Zhang's model. The numerical study results indicate that a uniform completion scheme causes a non-uniform fracture development; an optimal completion method is proposed by reducing the cluster number, non-uniform spacing, and practical limited entry technique in a fracturing stage. Furthermore, the combined use of unequal cluster spacing and a limited entry strategy can significantly reduce the suppression effects between multiple clusters, improve the fluid flow into each cluster, and enhance the uniform propagation to achieve the maximum production. Our present work illustrates a better understanding of the effect of the completion strategy on the multiple fracture propagation, and paves a path for a more optimal completion design for fossil hydrogen energy development.

Sound transmission loss behavior of sandwich panel with different truss cores under external mean airflow

This paper presents an analytical study on the sound transmission loss characteristics of sandwich plate with different truss cores under external mean airflow. Three types of truss cores are considered, which include pyramidal core, tetrahedral core and 3D-kagome core. The sandwich plate is immersed in a mean airflow of velocity tangential to the acoustically deformed boundary and it is impinged by a plane sound wave in the incident acoustic field. By applying velocity continuity condition at fluid–structure interfaces, the coupling of fluid–structure interaction is described analytically. The validity and feasibility of the proposed theoretical model are verified by comparisons with numerical simulation results calculated by commercial finite element software (LMS Virtual.Lab). Based on the developed theoretical model, the influences of the truss core radius and height, different truss core types, external mean flow and material combination types on sound transmission loss are subsequently presented.

Splitting schemes and unfitted-mesh methods for the coupling of an incompressible fluid with a thin-walled structure

Abstract Two unfitted-mesh methods for a linear incompressible fluid/thin-walled structure interaction problem are introduced and analyzed. The spatial discretization is based on different variants of Nitsche’s method with cut elements. The degree of fluid–solid splitting (semi-implicit or explicit) is given by the order in which the space and time discretizations are performed. The a priori stability and error analysis shows that strong coupling is avoided without compromising stability and accuracy. Numerical experiments with a benchmark illustrate the accuracy of the different methods proposed.

A Model of [Formula: see text] Dynamics in an Accurate Reconstruction of Parotid Acinar Cells.

We have constructed a spatiotemporal model of [Formula: see text] dynamics in parotid acinar cells, based on new data about the distribution of inositol trisphophate receptors (IPR). The model is solved numerically on a mesh reconstructed from images of a cluster of parotid acinar cells. In contrast to our earlier model (Sneyd et al. in J Theor Biol 419:383-393. https://doi.org/10.1016/j.jtbi.2016.04.030 , 2017b), which cannot generate realistic [Formula: see text] oscillations with the new data on IPR distribution, our new model reproduces the [Formula: see text] dynamics observed in parotid acinar cells. This model is then coupled with a fluid secretion model described in detail in a companion paper: A mathematical model of fluid transport in an accurate reconstruction of a parotid acinar cell (Vera-Sigüenza etal. in Bull Math Biol. https://doi.org/10.1007/s11538-018-0534-z , 2018b). Based on the new measurements of IPR distribution, we show that Class I models (where [Formula: see text] oscillations can occur at constant [[Formula: see text]]) can produce [Formula: see text] oscillations in parotid acinar cells, whereas Class II models (where [[Formula: see text]] needs to oscillate in order to produce [Formula: see text] oscillations) are unlikely to do so. In addition, we demonstrate that coupling fluid flow secretion with the [Formula: see text] signalling model changes the dynamics of the [Formula: see text] oscillations significantly, which indicates that [Formula: see text] dynamics and fluid flow cannot be accurately modelled independently. Further, we determine that an active propagation mechanism based on calcium-induced calcium release channels is needed to propagate the [Formula: see text] wave from the apical region to the basal region of the acinar cell.

A novel device for measuring the ultrasonic wave velocity and the thickness of hyperelastic materials under quasi-static deformations

An innovative low-cost testing machine for measuring simultaneously the ultrasonic longitudinal wave velocity and the thickness of hyperelastic material specimens, while applying a quasi-static deformation, is described. In a pulse-echo ultrasonic immersion test, both of these parameters can be obtained by measuring several times of flight, once the speed of sound in the coupling fluid at the testing temperature is known. The variation in ultrasonic longitudinal wave velocity through the sample when the deformation changes is called the acoustoelastic effect. Knowledge of this effect allows the material characterization. The results obtained on SBR-1502 reinforced with carbon black (20%) are in accordance to the values presented in literature and thus confirm the validity of the proposed experimental device.

Analysis of landslides employing a space–time single-phase level-set method

Landslide dynamics are characterized by a phase transition from a solid like behavior to a fluid one. Since the material is moving through space special discretization techniques are required. Four-dimensional space–time finite elements for fluid–structure interactions are applied together with the single-phase level-set method to investigate the dynamics of 3D landslides interacting with flexible walls. The wall is modeled as a geometric nonlinear solid with elastic–viscoplastic material behavior, whereas the liquefied soil is described with the Navier–Stokes equations for incompressible Bingham fluids. Between fluid and solid advanced coupling conditions are taken into account incorporating friction. In order to solve the governing equations of the multi-field problem, the weighted-residuals method is applied, which is discretized by time-discontinuous space–time elements. Within the monolithic solution procedure for the coupled problem, the kinematics of both solid and fluid are described using velocities as primary variables. A pseudo-structure adapts the coordinates of the fluid mesh to the deformations of adjacent structures. The single-phase level-set method describes the motion of the free surface of the sliding material. To accurately transport the free surface a pde-based extrapolation is used for the velocities. Various effects in 3D landslide dynamics are investigated.

Structural and functional analysis of the centrifugal pump development as a technical system

Pumping equipment is one of the main systems of water supply and sewerage, where centrifugal pumps are mostly used due to the simple design and the optimal interval of the parameters of flow and pressure. The paper considers the development of a centrifugal pump from the point of view of system analysis, since this approach considers any technical object as a complex of interacting elements having the properties that are not reduced to the properties of individual elements designed to perform certain useful functions. The aim of the paper is to find patterns of development of the centrifugal pump as a technical system to predict its further evolution. Domestic and foreign patent fund of Class F 04 D in the amount of 724 units was used as the main source. In the paper, the device of the centrifugal pump as a technical system is divided into the following main structural subsystems: impeller blades, impeller disks; housing; pressure pipe and suction pipe. Each of these elements has its main useful function and a number of auxiliaries, which are discussed in detail. It is established that an increase in the degree of control of the centrifugal pump can be achieved by dynamization of transmission, specifically, the regulation of the revolutions transmitted from the engine to the impeller mechanically, with the help of fluid coupling and frequency converters.

Modal Analysis of a Super-large FRP Combined Tank System with Floating Roof Considering the Coupled Effect of Tank Fluid

The modal analysis of the super-large FRP combined tank structure system with floating roof is carried out. Firstly, the finite element model of the super-large FRP combined tank structure system with floating roof is established. Then, the modal analysis of the super-large FRP combined tank structure system with floating roof is carried out. The results show that when the storage height is less than or equal to 50% of the total storage height, the first-order frequency of the FRP combined tank fluid coupling vibration is very small. When the storage height is large, the vibration frequency of the FRP combined storage tank liquid coupling is larger than that when the water storage state is less than or equal to 50%. The vibration frequency of the tank fluid coupling also decreases with the increase of the tank radius. The larger the tank radius is, the more significant the tank fluid coupling effect is.

Sloshing hydrodynamic performance in cryogenic liquid oxygen tanks under different amplitudes

To deeply understand fluid sloshing behavior in non-isothermal fuel storage tanks, a numerical model is built by coupling fluid flow and heat exchange. The external heat leaks and the interfacial phase change are considered. Both the thermal boundary and external sinusoidal excitation are realized by user-defined functions. To capture the movement of liquid-vapor interface during sloshing, the mesh motion treatment is specially adopted with the volume of fluid method coupled. Validated against the experimental results, the standard k-ε model is selected to predict fluid sloshing. Based on the numerical model, the influence of sloshing amplitude on hydrodynamic performance is studied. Variations of the vapor and liquid pressure, the sloshing force suffered by the tank and the sloshing moment are investigated. Moreover, to study the dynamic response of the liquid-vapor interface, different monitors are set to measure variations of the interfacial liquid elevation. The results show that the external sloshing excitation has caused great influences on the sloshing hydrodynamic characteristics in liquid oxygen tank. With some valuable conclusions being achieved, the present study is significant to in-depth investigation on the non-isothermal sloshing dynamic process and may supply technique guidance for anti-slosh design on aerospace storage tanks.

Fluid-structural coupling in metamaterial plates for vibration and noise mitigation in acoustic cavities

Locally resonant metamaterials exhibit sub-wavelength tunable bandgaps that can be exploited for vibroacoustic mitigation. The present work investigates the use of metamaterial plates for the simultaneous control of structural vibration and acoustic sound radiation in an adjacent acoustic cavity. We adopt a coupled fluid-structure finite element model based on a variational mathematical framework in terms of structural displacement and fluid pressure to capture the vibroacoustic characteristics of the coupled system and shed light onto the spatial average pressure levels inside the cavity. The model is used to predict and distinguish between structural and fluid modes within frequency ranges of interest. Furthermore, differences between the metamaterial’s structural response in the presence and lack of fluid coupling are explained. The pressure changes inside the cavity are discussed in relation to the frequency bandgap range predicted theoretically via a dispersion analysis for a couple of different metamaterial designs. Results obtained from the numerical analysis can be used to set design guidelines to optimally tune locally resonant metamaterials to achieve prescribed acoustic properties in the fluid component of such coupled systems.

Modulation of the turbulence regeneration cycle by inertial particles in planar Couette flow

Two-way coupled direct numerical simulations are used to investigate the effects of inertial particles on self-sustained, turbulent coherent structures (i.e. the so-called regeneration cycle) in plane Couette flow at low Reynolds number just above the onset of transition. Tests show two limiting behaviours with increasing particle inertia, similar to the results from previous linear stability analyses: low-inertia particles trigger the laminar-to-turbulent instability whereas high-inertia particles tend to stabilize turbulence due to the extra dissipation induced by particle–fluid coupling. Furthermore, it is found that the streamwise coupling between phases is the dominant factor in damping of the turbulence and is highly related to the spatial distribution of the particles. The presence of particles in different turbulent coherent structures (large-scale vortices or large-scale streaks) determines the turbulent kinetic energy of particulate phase, which is related to the particle response time scaled by the turnover time of large-scale vortices. By quantitatively investigating the periodic character of the whole regeneration cycle and the phase difference between linked sub-steps, we show that the presence of inertial particles does not alter the periodic nature of the cycle or the relative length of each of the sub-steps. Instead, high-inertia particles greatly weaken the large-scale vortices as well as the streamwise vorticity stretching and lift-up effects, thereby suppressing the fluctuating amplitude of the large-scale streaks. The primary influence of low-inertia particles, however, is to strengthen the large-scale vortices, which fosters the cycle and ultimately reduces the critical Reynolds number.