Uniform Velocity Field Research Articles

Optimizing flow uniformity and velocity fields in aquaculture tanks by modifying water inlets and nozzles arrangement: A computational fluid dynamics study

Ensuring optimal conditions for fish, especially in terms of uniform velocity fields, is crucial for aquaculture systems to attain self-cleaning efficiency in rearing tanks and better fish behavior, which ultimately impacts their survival and growth. The current study presented a full-scale computational fluid dynamics (CFD) model of three types of circular, square and square arc angle tanks used in aquaculture farms to choose the most optimal tank based on the flow uniformity and velocity field. At the next step, the optimal arrangement of the inlet number, inlet location, inlet angle, as well as the number of nozzles on each inlet was reconfigured to create the most optimal tank. The simulations were done using the CFD software FLUENT distributed by the ANSYS Corporation. The software calculates velocities in the tanks by solving the Reynolds-averaged Navier-Stokes equations of continuity and momentum that govern the mean turbulent flow of water. The results illustrated circular and square arc angle tanks had significantly more uniform fluid velocity compared to the square tanks, which the square arc angle tank due to better flow velocity near the wall and space utilization was selected for further rearrangements. Additionally, the implementation of two entrance pipes near the corner of the two parallel walls with an entry angle of 0° in a square arc angle tank resulted in a more consistent water velocity. As the number of inlet nozzles increased to six, the water streamlines became more uniform, suggesting a more consistent water velocity throughout the tank. However, when the number of input nozzles increased to nine, the tension on the nozzle apertures were increased probably due to the decrease of distance between them. Findings of the present study concluded that two inlets in the corner with an entry angle of 0° and six nozzles on each inlet pipe could provide the optimum water velocity in the square arc angle tanks.

A bound- and positivity-preserving discontinuous Galerkin method for solving the γ-based model

In this work, a bound- and positivity-preserving quasi-conservative discontinuous Galerkin (DG) method is proposed for the γ-based model of compressible two-medium flows. The contribution of this paper mainly includes three parts. On one hand, the DG method with the extended Harten-Lax-van Leer contact flux is proposed to solve the γ-based model, and satisfies the equilibrium-preserving property which preserves uniform velocity and pressure fields at an isolated material interface. On the other hand, an affine-invariant weighted essentially non-oscillatory (Ai-WENO) limiter is adopted to suppress oscillations near the discontinuities. The limiter with the Ai-WENO reconstruction method to the conservative variables not only is able to maintain the equilibrium property, but also generates sharper results around the locations of shock waves in contrast to that applying to the primitive variables. Last but not least, a flux-based bound- and positivity-preserving limiting strategy is introduced and analyzed, which preserves the physical bounds for auxiliary variables in the non-conservative governing equations, and the positivity for density and internal energy. Extensive numerical experiments in both one and two space dimensions show that the proposed method performs well in simulating compressible two-medium flows with high-order accuracy, equilibrium-preserving and bound-preserving properties.

Friction through molecular adsorption at the sliding interface of hydrogels: theory and experiments.

We report on the frictional properties of thin (≈μm) poly(dimethylacrylamide) hydrogel films within contacts with spherical silica probes. In order to focus on the contribution to friction of interfacial dissipation, a dedicated rotational setup is designed which allows to suppress poroelastic flows while ensuring a uniform velocity field at the sliding interface. The physical-chemistry of the interface is varied from the grafting of various silanes on the silica probes. Remarkably, we identify a velocity range in which the average frictional stress systematically varies with the logarithm of the sliding velocity. This dependency is found to be sensitive to the physical-chemistry of the silica surfaces. Experimental observations are discussed in the light of a molecular model where friction arises from thermally activated adsorption of polymer chains at the sliding interface, their elastic stretching and subsequent desorption. From this theoretical description, our experimental data provide us with adhesion energies and characteristic times for molecular adsorption that are found consistent with the physico-chemistry of the chemically-modified silica surfaces.

Quantifying heat losses from experimental setup and their effect on annular channel heat flux using CFD

An advanced experimental setup in the form of a double-pipe heat exchanger has been developed to investigate various flow and heat transfer regimes in an annular channel. The experimental setup is designed for heat transfer measurements and flow visualization in a transparent annular channel with temperature-controlled heating of the inner tube. It allows measurements in both, single-phase and two-phase (boiling) flow regimes. The transparent annular channel is connected at the front and rear end by specially designed inlet and outlet headers, which ensure a uniform velocity field of the coolant (primary fluid) in the annular channel. The heating water (secondary fluid) heats the inner tube made of copper, which contains unique turbulators positioned equidistantly. These are designed to enhance the heat transfer on the inner side of the copper tube and to accommodate the thermocouples measuring the surface temperature of the tube.The main purpose of this study is to assess as accurately as possible the influence of heat losses in the experimental setup on the heat fluxes in the transparent annular channel. Therefore, it is necessary to accurately estimate the heat losses at the inlet and outlet header, upstream and downstream of the annular section. To this end, a detailed three-dimensional conjugate heat transfer CFD model has been developed and validated with a series of single-phase measurements, including the measured temperatures in both headers and the temperature profile along the heated inner copper tube. The simulated velocity and temperature fields have been used to quantify the heat flux distribution in the experimental setup. This study clearly demonstrates that properly validated numerical simulations can provide missing experimental information and significantly improve the interpretation of complex experimental results.

Numerical and experimental investigation of additively manufactured shell-lattice copper heat exchanger

Triply periodic minimal surface (TPMS) shell lattices have superior heat transfer properties due to their staggered channels. Based on these structures, a series of TPMS heat exchangers (HEs) are fabricated and investigated. However, the existing research is mainly limited to the performance investigation of HEs based on low-thermal-conductivity materials or the simulation study of the representative parts. In this study, we successfully fabricated a pure copper TPMS HE and performed a comprehensive numerical analysis. Three HEs, including Copper TPMS, SS316L TPMS, and SS316L plate were studied and compared to reveal the mechanism of their performance differences. Numerical analysis showed that TPMS HEs owned more uniform temperature and velocity fields than plate HE. The calculated heat-exchange effectiveness of the copper TPMS HE is about 58%–96% higher than that of SS316L plate HE, while the measured value of that of SS316L TPMS HE is about 38%–48% more than that of SS316L plate HE, respectively. The convective heat-transfer coefficient of copper TPMS HE is approximately 2.16–2.69 times that of SS316L plate HE and 1.17–1.33 times that of SS316L TPMS HE. The volume goodness factors of copper TPMS and SS316L TPMS HEs are about 1.49–1.87 and 1.2–1.41 times that of SS316L plate HE, respectively. The volumetric heat-transfer coefficient of copper TPMS HE is much better than that of metal plate HE and approximately 18–25 times that of the polymer TPMS HEs. This study indicates that the pure copper TPMS HE is a good candidate for next-generation HEs.

FEATURES OF THE BOUNDARY LAYER ORGANIZATION IN TESLA DISC TURBINES

To ensure maximum efficiency of bladeless Tesla turbines, it is important to maintain a laminar flow regime within the boundary layer that forms on the disc surfaces. Depending on the flow regime, the state of the disc surfaces, and the geometry of the interdisk gaps, the nature of the boundary layer varies. It is crucial for the flow regime to remain laminar, and the distance between the discs should not exceed twice the thickness of the boundary layer. Experimental investigations of the characteristics of the boundary layer during the flow around turbine blades were proposed to determine the parameters necessary for achieving maximum efficiency. These experiments were conducted in an aerodynamic test rig that provided a uniform velocity field with minimal turbulence (0.7 %) within a speed range up to 0.33 Mach. The primary focus of these studies was to determine the location of the transition zone within the boundary layer, which allows for the examination of conditions for stable maintenance and characteristics of laminar flow. The transition zone was determined based on changes in the tangential friction stress in the experiments. The obtained results facilitated the establishment of the necessary dimensions for the inter-disk gaps and the optimum values of the similarity criterion Re from the perspective of flow regime. For a smooth surface, laminar flow within the boundary layer is maintained up to a relative coordinate of 0.17 x= from the start of the surface, across a wide range of Reynolds numbers. For a rough surface, the extent of the zone with a laminar boundary layer is approximately the same as that for a smooth surface at Re=3.6∙105. However, at Re=7.4∙105 the laminar flow terminates slightly earlier, at 0.13 x= , with a very short transitional zone between laminar and turbulent flow characteristics. The thickness of the laminar boundary layer on a smooth surface is 0.5…0.7 mm, while for a rough surface, it is slightly greater at 0.7…0.8 mm. Therefore, to ensure high efficiency of Tesla disc turbines, the distance between the discs should be maintained at 1…1.5 mm, considering the requirements for laminar flow.

POROUS DRAINAGES FOR CONTACT CLARIFIERS

Filtering facilities are essential for the technological schemes for natural water treatment. They provide the required water quality as well as the valuable capacity of water treatment facilities. Contact clarifiers are widely used to purify water with low turbidity and high color values. Single-stage filtration based on the principle of contact coagulation uses it. Possible complications in the operation of contact clarifiers are usually related to running the drainage distribution system. The authors formulated several basic drainage requirements, particularly the uniform distribution of wash water over a space and the absence of filter load removal. The article analyzes the existing drainage structures (drainage with supporting layers of gravel and a gravelless pipe distribution system), which shows that they do not meet the requirements. They lead to irregular washing of the filter load, a decrease in its dirt capacity, an increase in residual contaminants, a reduction in the filter cycle, and an increase in the maintenance cost. To improve reliability and durability, a drainage design is proposed that consists of perforated reinforced concrete slabs, with porous polymer concrete in their holes, made of crushed granite or gravel and a polymer binder, i.e., epoxy resin. This construction will ensure a uniform velocity field during washing and filtering, reduce water consumption for its own needs, increase the filter cycle, and prevent possible removal of the filter load. It is found that the colmatation of the pore space with a suspended matter is one of the main issues when considering the porous drainage in the structure of contact clarifiers. The article presents experimental studies of the dynamics and degree of the colmatation in porous polymer concrete with polluted water. They showed that no irreversible colmatation happens, and the data obtained will allow us to use them during the hydraulic calculations. The task of further research is to conduct full-scale tests on existing facilities.

Heat transfer intensification of turbulent forced convection by inserting discontinuous twisted tapes in a wavy tube; hydrothermal and thermodynamics analysis

The current study presents a numerical investigation on turbulent hydrothermal characteristics in a wavy passage equipped with discontinuous twisted tapes. The working fluid is water and passage walls are kept under constant wall temperature. The effect of Reynolds number (Re = 2500, 4500, 6500, 8500 and 10500), twist angle (TA = 90∘ and 180∘) and inclination angle (IA = 15∘ and 30∘) on velocity fields and streamlines, temperature contours, Nusselt number, friction factor, turbulent kinetic energy (TKE), thermal performance factor (TPF), energy efficiency factor (EEF) and entropy generation rate are evaluated. More uniform temperature and velocity fields can be found as both wavy passage and twisted tape are simultaneously applied. Both heat transfer rate and pumping power rise with increasing Reynolds number, twist and inclination angles. Results reveal that the twisted tape play more remarkable role on Nusselt number and friction factor at lower inclination angle. The best value of EEF is detected 24.6% occurring for passage with IA = 15∘ and TA = 180∘ at Re = 2500. Among all considered cases, those of empty wavy passage with IA = 30∘ at Re = 8500 and 10500 provides negative values of EEF, referring to inefficient cases from energy viewpoint. The contribution of wavy passage and twisted tape on heat transfer enhancement is individually assessed and it is found that the best value of twisted tape involvement on enhanced heat transfer is 79.6% taking place for configuration with IA = 15∘ and TA = 180∘ at Re = 4500. Finally, based on CFD results, passages are examined from thermodynamics viewpoint and it is shown that the second law efficiency growths with increasing twist and inclination angles.

A Bound-Preserving and Positivity-Preserving Path-Conservative Discontinuous Galerkin Method for Solving Five-Equation Model of Compressible Two-Medium Flows

We develop a high-order path-conservative discontinuous Galerkin method to simulate compressible two-medium flows by solving the five-equation transport model. The proposed path-conservative discontinuous Galerkin discretization is able to satisfy the equilibrium condition, which states that uniform pressure and velocity fields are preserved around an isolated material interface. In order to improve the robustness of the proposed method in simulating complex two-medium flows with large density and pressure ratios, a bound-preserving and positivity-preserving limiting strategy is developed for maintaining the bound of volume fraction and the positivity of partial densities and internal energy. A series of typical one- and two-dimensional cases are tested, which demonstrate that the proposed high-order path-conservative discontinuous Galerkin method is very capable of simulating compressible gas-gas and gas-water two-medium flows with large density and pressure ratios.

Instability of a salt jet emitted from a point source in an external electric field

The objective in the present work is to consider a simple example of instability of a conducting self-similar micro jet in the external electric field, which represents a prototype of some microfluidic instabilities. Salt from a point source is emitted into its own aquatic solution, which is subject to an external uniform velocity field together with an electrostatic field, and is convected downstream and diffused. The flow is considered in microscales so that, in contrast to the classical jets, the Reynolds numbers are practically zero, but the Péclet numbers are large. The parameters are found at which such a microjet is unstable. Along with the linear stability analysis, we have fulfilled the numerical simulations of the full nonlinear system of equations. The numerical simulation qualitatively confirmed the results of the linear stability and showed that this instability visually reminds classical instabilities of free jets and wakes.

Boundary element method solution of stationary advective–diffusive problems: A comparison between the direct interpolation and dual reciprocity technique

New industrial applications have been stimulating a continuance in developing new approaches and improvements in available Boundary Elements Method (BEM) formulations for the solution of advective–diffusive problems. Currently, one of the main demands imposed to new BEM formulations based on radial functions is dealing more effectively with advective–diffusive models when relevant convection effects are present. Thus, this paper presents the recently developed direct interpolation technique (DIBEM) compared to the widespread dual reciprocity technique (DRBEM), both applied in two-dimensional stationary problems with uniform velocity field and moderate advective effects. Performance analyses presented here consider problems with well-known analytical solutions as reference to evaluate the accuracy of the results obtained. The main contributions of this paper are the application of the DIBEM technique in advective–diffusive models, which is unprecedented, and a detailed performance analysis of DRBEM in uniform velocity field cases with moderate Peclet number, matter not suitably addressed in current literature.

New Design and Optimization of a Jet Pump to Boost Heavy Oil Production

In the Oil and Gas industry, installing pipe loops is a well-known hydraulic practice to increase oil pipeline capacities. Nevertheless, pipe loops could promote an unfavorable phenomenon known as fouling. That means that in a heavy oil-water mixture gathering system with low flow velocities, an oil-water stratified flow pattern will appear. In consequence, due to high viscosity, the oil stick on the pipe, causing a reduction of the effective diameter, reducing handled fluids production, and increasing energy consumption. As jet pumps increase total handled flow, increase the fluid velocities, and promote the homogenous mixture of oil and water, this type of pump could result attractive compared to other multiphase pump systems in reactivating heavy crude oil transport lines. Jet pumps are highly reliable, robust equipment with modest maintenance, ideal for many applications, mainly in the oil and gas industry. Nevertheless, their design method and performance analysis are rarely known in the literature and keep a high experimental component similar to most pumping equipment. This paper proposes a numerical study and the optimization of a booster multiphase jet pump system installed in a heavy oil conventional loop of a gathering system. First, the optimization of a traditionally designed jet pump, combining CFD simulation and optimization algorithms using commercials software (ANSYS CFX® and PIPEIT® tool), has been carried out. This method allowed evaluating the effect of multiple geometrical and operational variables that influence the global performance of the pump to run more than 400 geometries automatically in a reduced time frame. The optimized pump offers a substantial improvement over the original concerning total flow capacity (+17%), energy, and flow distribution. Then, the effect of the three jet pump plugin configurations in a heavy oil conventional trunkline loop was analyzed. Simulations were carried out for different driving fluid pressures and compared against a traditional pipeline loop’s performance. Optimum plugin connection increases fluid production by 30%. Finally, a new eccentric jet pump geometry has been proposed to improve exit velocities and pressure fields. This eccentric jet pump with the best connection was analyzed over the same conditions as the concentric optimized one. An improvement of 2% on handled fluid was achieved consistently with the observed uniform velocity field at the exit of the pump. A better total fluid distribution between the main and the loop line is obtained, handling around half of the complete fluid each.

An inductively coupled plasma metal organic chemical vapor deposition based on showerhead structure for low temperature growth

An inductively coupled plasma metal organic chemical vapor deposition (ICP-MOCVD) based on showerhead structure is proposed for the low temperature growth of thin solid films including GaN. The flow field of precursors in the chamber of ICP-MOCVD was analyzed and the structure of showerhead was optimized by changing the showerhead diameter to obtain uniform velocity field above the substrate. The thickness non-uniformity of GaN films grown at 600 °C was improved from 5.14% to 1.86% after the optimization of showerhead. On that basis, the influence of triethylgallium (TEG) and trimethylgallium (TMG) on low-temperature GaN growth were investigated and TEG was proved to be the more appropriate Ga source in this case. Finally, GaN film with high c-axis and in-plane orientations was obtained on sputtered AlN/sapphire template and the full width half maximums of (002) and (102) x-ray rocking curves are 0.45° and 0.57° respectively. Our results provide a practicable method for the optimization of low-temperature MOCVD, which has potential to obtain large-scale crystalline films at low temperature.

Point‐spread function convolution to simulate prestack depth migrated images: A validation study

ABSTRACTSeismic migration commonly yields an incomplete reconstruction of the Earth model due to restricted survey aperture, band‐limited frequency content and propagation effects. This affects both illumination and resolution of the structures of interest. Through the application of spatial convolution operators commonly referred to as point‐spread functions, simulated prestack depth‐migrated images incorporating these effects may be obtained. Such simulated images are tailored for analysing distortion effects and enhance our understanding of seismic imaging and subsequent interpretation. Target‐oriented point‐spread functions may be obtained through a variety of waveform and ray‐based approaches. Waveform approaches are generally more robust, but the computational cost involved may be prohibitive. Ray‐based approaches, on the other hand, allow for efficient and flexible sensitivity studies at a low computational cost, but inherent limitations may lead to less accuracy. To yield more insight into the similarities and differences between point‐spread functions obtained via these two approaches, we first derive analytical expressions of both wave‐ and ray‐based point‐spread functions in homogeneous media. By considering single‐point scatterers embedded in a uniform velocity field, we demonstrate the conditions under which the derived equations diverge. The accuracy of wave‐based and ray‐based point‐spread functions is further assessed and validated at selected targets in a subsection of the complex BP Statics Benchmark model. We also compare our simulated prestack depth migrated images with the output obtained from an actual prestack depth migration (reverse time migration). Our results reveal that both the wave‐ and ray‐based approaches accurately model illumination, resolution and amplitude effects observed in the reverse time‐migrated image. Furthermore, although some minor deviations between the wave‐based and ray‐based approaches are observed, the overall results indicate that both approaches can be used also for complex models.

Effects of pin morphology on the interface defects of the FSWed lap joints of 2A12 aluminum alloy

The current work aims to study the effects of stirring pin morphology on the FSWed lap joints defects and mechanical properties. The 2A12 aluminum alloy friction stir welding lap joints were obtained using two shapes and three thread lengths of stirring pins by experiments. Besides the interface defects forming mechanism were studied by joints plastic metal flow numerical simulation. The results show that the conical pin can lead to uniform and continuous plastic metal velocity field which forms a Hook defect with sharp end, smaller deflection angle (minimum 8°) and larger size (maximum 0.18mm). It also will lead to a larger failure load (maximum is 9.5kN), and the fracture position easily occurs at the Advancing side (AS) of lower plate. The three section pin has a periodic shearing effect causing velocity difference between the arc edge and cutting section of the pin which forms a Hook defect with thicker end, larger deflection angle (maximum 42°) and smaller size (minimum 0.06mm). It also causes discontinuous wavy debris forms in the AS. The three section pin leads to a lower failure load (maximum is just 7.6kN), and the fracture position turns to occur at the lap interface. The increase of the thread length can promote the exchange of plastic metal in the thickness direction and interface materials flow velocity. So the angle (from 20°to 150°) and size (from 0.1mm to 0.6mm) of Hook increases but the height of Cold Lap reduces (increasing the effective sheet thickness of retreating side from 0.69mm to 0.95mm). In addition, the increase of the thread length can make the periodic shear effect of three section pin gradually weak. It is also found that the fracture position is closely related to the shape and the thread length of pins. When using conical pin, the fracture occurs at AS of lower plate or Retreating Side of Nugget Zone (NZ-RS) of upper plate; When using three section pin, the fracture occurs at the bonding interface. And with the increase of the thread length, the fracture position changes from the bonding interface to the NZ-RS of upper plate, and finally to the AS of lower plate.

Effect of staggered array structure on the flow field of micro gas chromatographic column

A new design of staggered array semi-packed micro gas chromatographic column was presented based on the micro electromechanical system (MEMS) technology. It was a sensor for gas sample analysis. The internal velocity fields of ten types of semi-packed micro gas chromatographic column were studied. The effects of array spacing and dislocation spacing on the flow field distribution were investigated. The results show that on the basis of ensuring the formation of virtual wall, with the increase of array spacing, the maximum velocity difference between the flow channels in the vertical direction decreases gradually, but the velocity difference in the flow channels a and b increases. When the inlet velocity was set to be 0.18 m/s, the maximum velocity difference in the channel of the staggered semi-packed micro gas chromatography column 3 (CSAC3) was 0.05610 m/s. The maximum velocity difference in the channel a was 0.09160 m/s. The maximum velocity difference in the channel b was 0.02401 m/s. CSAC3 had a more uniform velocity field distribution, which can effectively suppress the laminar flow effect during chromatographic separation, and had a smaller pressure distribution, which puts forward lower requirements for carrier gas system. The staggered array semi-packed micro gas chromatography column proposed in this paper can effectively improve the velocity field distribution and pressure distribution in the channel, and provide a theoretical basis for the design of the new micro gas chromatography column structure.

Mass-balance and locality versus accuracy with the new boundary and interface-conjugate approaches in advection-diffusion lattice Boltzmann method

We introduce two new approaches, called A-LSOB and N-MR, for boundary and interface-conjugate conditions on flat or curved surface shapes in the advection-diffusion lattice Boltzmann method (LBM). The Local Second-Order, single-node A-LSOB enhances the existing Dirichlet and Neumann normal boundary treatments with respect to locality, accuracy, and Péclet parametrization. The normal-multi-reflection (N-MR) improves the directional flux schemes via a local release of their nonphysical tangential constraints. The A-LSOB and N-MR restore all first- and second-order derivatives from the nodal non-equilibrium solution, and they are conditioned to be exact on a piece-wise parabolic profile in a uniform arbitrary-oriented tangential velocity field. Additionally, the most compact and accurate single-node parabolic schemes for diffusion and flow in grid-inclined pipes are introduced. In simulations, the global mass-conservation solvability condition of the steady-state, two-relaxation-time (S-TRT) formulation is adjusted with either (i) a uniform mass-source or (ii) a corrective surface-flux. We conclude that (i) the surface-flux counterbalance is more accurate than the bulk one, (ii) the A-LSOB Dirichlet schemes are more accurate than the directional ones in the high Péclet regime, (iii) the directional Neumann advective-diffusive flux scheme shows the best conservation properties and then the best performance both in the tangential no-slip and interface-perpendicular flow, and (iv) the directional non-equilibrium diffusive flux extrapolation is the least conserving and accurate. The error Péclet dependency, Neumann invariance over an additive constant, and truncation isotropy guide this analysis. Our methodology extends from the d2q9 isotropic S-TRT to 3D anisotropic matrix collisions, Robin boundary condition, and the transient LBM.

On the rational form of rotary control diaphragms for steam turbines with industrial and cogeneration steam extraction

The Russian park of power steam turbines contains a large number of turbines with adjustable steam extraction from the flow path where rotary control diaphragms are used as flow controllers, which structurally easily fit into the flow path of these turbines. This method of regulating the steam flow rate is accompanied by a decrease in the efficiency of the subsequent stages of the turbine and causes the appearance, at reduced loads, of additional disturbing forces acting on the rotor blades. In the presented materials, a variant of a post-sampling stage with a radial rotary control diaphragm is considered. The performed mathematical modeling of the working fluid flows in such a stage showed that in this case, at all turbine loads, a relatively uniform velocity field is provided when steam enters the nozzle apparatus, which naturally entails the elimination of the noted drawbacks.

Recent Crustal Deformation Based on Interpolation of GNSS Velocity in Continental China

We used the interpolation method of two-dimensional vector velocity field data based on Green’s function to conduct coupled interpolation with a Poisson’s ratio of 0.5 for 1966 horizontal velocity field data from 1999 to 2017 and obtained the uniform velocity field and strain rate field with a grid of 1°. The main results are as follows: the eastern Himalayan structure as the center, the eastern Lhasa block, the eastern Qiangtang block, the Sichuan-Yunnan block, and the Burma block form a strong deformation rate zone of continuous deformation in the fan-shaped region, which has been a strong deformation rate zone for earthquakes of magnitude 7 or higher in continental China since 1963. Besides, the eastward movement of crustal material in the Tibetan Plateau is blocked by the stable South China block. Therefore, the direction of crustal material movement is deflected, which gradually forms a clockwise rotation motion system centered on the eastern Himalayan structure. Finally, our research shows that the influencing factors of strong earthquakes include velocity change, non-uniform strain distribution, accumulation of larger strain, and the difference of the second strain rate invariant. Strong earthquakes are closely related to the difference in energy accumulation in space.

A Quasi-Conservative Discontinuous Galerkin Method for Solving Five Equation Model of Compressible Two-Medium Flows

In this work, we develop a quasi-conservative discontinuous Galerkin method for the simulation of compressible gas-gas and gas-water two-medium flows by solving the five-equation transport model. This spatial discretization is a direct extension of the quasi-conservative finite volume discretization to the discontinuous Galerkin framework, thus, preserves uniform velocity and pressure fields at an isolated material interface. Furthermore, for discontinuities with a large pressure ratio, low density, and a dramatic change of material property where nonphysical values may occur, a strategy for imposing the bound-preserving limiting for volume fraction and a positivity-preserving limiting for density of each fluid and internal energy is developed and analyzed based on the quasi-conservative DG( $$p_1$$ ) discretization. Typical test cases for both one- and two-dimensional problems are provided to demonstrate the performance of the proposed method.