Flow Scheme Research Articles

Quasi all-speed schemes for magnetohydrodynamic flows in a wide range of Mach numbers

We present novel numerical schemes for ideal magnetohydrodynamic (MHD) simulations aimed at enhancing stability against numerical shock instability and improving the accuracy of low-speed flows in multidimensions. Stringent benchmark tests confirm that our scheme is more robust against numerical shock instability and is more accurate for low-speed, nearly incompressible flows than conventional shock-capturing schemes. Our scheme is a promising tool for tackling MHD systems, including both high and low Mach number flows.

Extension of finite particle method simulating thermal-viscoelastic flow and fluid–rigid body interactional process in weakly compressible smoothed particle hydrodynamics scheme

In computational non-Newtonian fluid dynamics, heat transfer has obvious effects on motions of viscoelastic fluids, mechanical mechanism of elasticity, and flow regimes. This study suggests an extended numerical scheme of smoothed particle hydrodynamics and finite particle method within density smoothing (SPH_DSFPM), which involves the discretization of smoothed particle hydrodynamics (SPH) and finite particle method (FPM) within density smoothing (DS) in the weakly compressible flow scheme. A corrected particle shifting technique is incorporated to eliminate tensile instability and inhomogeneity near solid boundaries. A corrected dynamic solid coupled boundary is introduced to deal with casting molding within high-pressure operations, which has a good compatibility between virtual particle method and repulsive force model. Numerical results show that the present scheme has the nearly lower relative error (0.5%) than conventional SPH (2.6%) in the case of evolutionary thermal-viscoelastic Poiseuille flow and heat effects have active influences on velocity, pressure variations for viscoelastic fluid flow around periodic circular cylinders. Three different printing modes of moving printers significantly generate into differentiated forming regimes through high-pressure extrusion. Adaptive particle distributions possess robust flow evolutions, by which the shocked jets can be tracked well and the sinking velocities of wedge entering into solutions can be numerically probed well considering different cuspidal biting angles. In the case of macroscopic fluid–rigid body interactions, the statistical degree of deviation on probed forces with experiments is relatively 4.35% and that is 12.5% for SPH. The proposed numerical scheme has a good performance on improved accuracy, convergence, and stability for simulating transient thermal-viscoelastic flows.

Жоғары вольтты электр желілерінің аспалы оқшаулағышының конструкциясы

The article substantiates the relevance of theoretical studies of partial discharge currents. Electromagnetic processes occurring on the surface of a suspended insulator are considered. The design of a poppet suspension insulator is given. The physical process of the pulse current occurrence is described. A replacement scheme of partial discharge current flow on the surface of a suspended insulator has been developed

DETERMINATION OF GRAVITY COAL SHOOT GEOMETRICS FOR A COAL MINE

This article presents the results of scientific research carried out by the authors in the field of transportation technology in industrial transport. The application of a gravity coal intake device designed to lower coal from the upper horizon to the averaging warehouse of the lower horizon of a coal mine is considered. The velocities of the uniform movement of the load along the gravitational angle are determined depending on the angle of inclination. The numerical integration algorithm is implemented in the software environment of the Scilab application program. The results of calculating the speed of movement from the current value of the descent depth, for the required descent depth of 40 meters and for placement options in various sections of the section at the angles of inclination of the acceleration sections of 30, 40 and 45 degrees are presented. The main geometric parameters of the gravitational coal intake device for a coal mine are determined from the condition of limiting the speeds of coal movement. The design of the gravitational coal intake must be performed based on the condition at the beginning of accelerated movement, then movement at a steady speed and then slow motion to the required speed of coal exit from the coal intake at the required speed of 2 m/sec. The presented research results allowed us to determine the main parameters of the gravitational device (coal intake) proposed for use in the cyclic flow scheme of the «Molodezhny» coal mine of «Kazakhmys Corporation» LLP. Keywords: coal mine, cyclic flow technology, coal transportation, gravity device, coal intake.

Investigation of thermal radiations impacts with double diffusive convection for Prandtl nanofluid with slip in an asymmetric ciliated channel

Thermal radiations are extensively utilized in the medical sciences, and the investigation of thermal radiation combined with double diffusive phenomena is the burning research area because of its enormous applications in treatment of various diseases. Cilia play significant part in many physiological processes of animal and humans. A novel mathematical prodigy for Prandtl nanofluid with thermal radiations and double diffusion convection by implementing slip at boundaries is presented for cilia induce flow in an asymmetric microchannel. Mathematical scheme for the physiological flow is developed and then pertinent equations are designed exploiting low Reynolds number and long wavelength simplifications. Solution for the physiological nanofluid is gathered by emphasizing on the novel BVP4C technique in MATLAB and resulting outcomes are elaborated with aid of graphical illustrations. Pros and cons of various physical flow parameters like thermal slip parameters, Prandtl fluid parameters, Grashof parameter, Prandtl parameter , Brownian motion parameter, thermal radiation parameter, Brinkmann number, Soret parameter are examined on the velocity, magnetic force function, temperature profile, concentration and nanoparticles volume fraction. It is reported that slip parameter really effects the nanofluid transport within the ciliated microchannel, it reduces the fluid flow, diffusion phenomena of the nanoparticles in the ciliated microchannel surges when radiation parameter is strengthened. The reported investigation will be instrumental in heat radiation effect for regulation of blood circulation to cure the cancer tissues in multiple drug delivery systems and will pave the way for the designs of certain diagnostic and pharmacological devices.

A high-order limiter-free arbitrary Lagrangian–Eulerian discontinuous Galerkin scheme for compressible multi-material flows

In this paper, a high-order limiter-free arbitrary Lagrangian–Eulerian discontinuous Galerkin (ALE-DG) scheme is proposed for simulating one-dimensional compressible multi-material flows. The system is discretized by the DG method, and a kind of Taylor’s expansion basis functions in the general cell is used to construct the interpolation polynomials of the variables. The mesh velocity at the node recognized as the material interface is set to approximate fluid velocity, which makes our scheme can capture the material interface accurately and clearly. For controlling the oscillations and reducing the numerical dissipation, a reconstruction based on the boundary variation diminishing (BVD) algorithm and Tangent of Hyperbola for INterface Capturing (THINC) function is employed to minimize the jump between the values at the left and right sides of cell boundaries. Due to the essentially monotone and bounded properties of THINC function, the difficulties caused by solving discontinuous solutions and complexities of designing limiters can be avoided. Finally, several examples are presented to demonstrate the accuracy and good performance of our scheme such as the essentially non-oscillatory property and so on for simulating the compressible multi-material flows.

Ensuring the Security of Information Flows at University Departments

The relevance of the study is caused by possible threats to the information security of information flows at the university department revealed during the latest information security audit. The purpose of our research is to detect information flows of the department and a detailed analysis of methods for their protection. The object of the study is the process of ensuring security of information flows at the university department. The subject of the research is the creation of information flow schemes of the department and developing network interaction schemes of the university department based on the user access policy. Particular attention is paid to the description of the identified potential risks arising from unauthorized access, external or internal attacks. It is important to note that the suggested ideas to improve the security of information flows of the university department are an application of existing methods of protecting information necessary for practical use in the educational process. The possibility of implementing the security of applied software and network support of the department is shown.

A centered limited finite volume approximation of the momentum convection operator for low‐order nonconforming face‐centered discretizations

AbstractWe propose in this article a discretization of the momentum convection operator for fluid flow simulations on quadrangular or generalized hexahedral meshes. The space discretization is performed by the low‐order nonconforming Rannacher–Turek finite element: the scalar unknowns are associated with the cells of the mesh while the velocities unknowns are associated with the edges or faces. The momentum convection operator is of finite volume type, and its expression is derived, as in MUSCL schemes, by a two‐step technique: computation of a tentative flux, here, with a centered approximation of the velocity, and limitation of this flux using monotonicity arguments. The limitation procedure is of algebraic type, in the sense that its does not invoke any slope reconstruction, and is independent from the geometry of the cells. The derived discrete convection operator applies both to constant or variable density flows and may thus be implemented in a scheme for incompressible or compressible flows. To achieve this goal, we derive a discrete analogue of the computation (with the velocity, one of its component, the density, and assuming that the mass balance holds) and discuss two applications of this result: first, we obtain stability results for a semi‐implicit in time scheme for incompressible and barotropic compressible flows; second, we build a consistent, semi‐implicit in time scheme that is based on the discretization of the internal energy balance rather than the total energy. The performance of the proposed discrete convection operator is assessed by numerical tests on the incompressible Navier–Stokes equations, the barotropic and the full compressible Navier–Stokes equations and the compressible Euler equations.

Technical analysis of a novel economically mixed CO2-Water enhanced geothermal system

Geothermal energy has undoubtedly been considered a promising low-carbon resource in future energy supply responding to the rising energy demand and severe climate concerns. CO2 has been demonstrated as a comparable alternative for water in developing an Enhanced geothermal system (EGS), which simultaneously unlocks the potential to sequester CO2 against climate concerns. However, an earlier thermal breakthrough is always observed owing to higher mobility in geothermal reservoirs for CO2-EGS, and an expensive cost of CO2 consumption makes CO2-EGS challenging to achieve economic profitability. In this study, a novel CO2-water-EGS is proposed to investigate the feasibility of solving the obstacles in conventional EGSs. An integrated analysis for multiple EGS scenarios is carried out from both the technical and economic perspectives. The effects of a CO2-water ratio, an injection rate and a flow scheme are comprehended. Followed by the determination of an optimal operating strategy. In the results, by reasonably selecting a CO2 mass ratio and an injection rate, CO2-water-EGS can recover more geothermal energy and earn more profits than water-EGS and CO2-EGS. The injection rate shows positive correlations to heat mining, carbon storage, and economic performance, while the impact of a flow scheme is negligible when the total volume of injected fluids remains consistent. From the optimization study, the CO2-water-EGS with the 110 kg/s injection rate and 20%wt CO2 ratio shows the highest Net Present Value (NPV) of 42.4 M$. This study proposes theoretical guidance to operators in their decision-making processes on the development of CO2-water-EGS.

Comment on the Paper “Seminumerical Scheme for Mixed Convection Flow of Hybrid Nanofluids with Viscous Dissipation and Dynamic Viscosity, BioNanoScience, doi.org/10.1007/s12668-023-01271-2”

Some serious errors exist in the above paper.

Implicit high-order gas-kinetic schemes for compressible flows on three-dimensional unstructured meshes I: Steady flows

In the previous studies, the high-order gas-kinetic schemes (HGKS) have achieved successes for unsteady flows on three-dimensional unstructured meshes. In this paper, to accelerate the rate of convergence for steady flows, the implicit non-compact and compact HGKSs are developed. For non-compact scheme, the simple weighted essentially non-oscillatory (WENO) reconstruction is used to achieve the spatial accuracy, where the stencils for reconstruction contain two levels of neighboring cells. Incorporate with the nonlinear generalized minimal residual (GMRES) method, the implicit non-compact HGKS is developed. In order to improve the resolution and parallelism of non-compact HGKS, the implicit compact HGKS is developed with Hermite WENO (HWENO) reconstruction, in which the reconstruction stencils only contain one level of neighboring cells. The cell averaged conservative variable is also updated with GMRES method. Simultaneously, a simple strategy is used to update the cell averaged gradient by the time evolution of spatial-temporal coupled gas distribution function. To accelerate the computation, the implicit non-compact and compact HGKSs are implemented with the graphics processing unit (GPU) using compute unified device architecture (CUDA). A variety of numerical examples, from the subsonic to supersonic flows, are presented to validate the accuracy, robustness and efficiency of both inviscid and viscous flows.

EXPERIMENTAL STUDY OF FLOW PATTERNS AND PRESSURE LOSSES IN VERTICAL FLOWS OF OIL-WATER MIXTURES

In this work the experimental results of the dynamics of the two-phase oil-water flow patterns and the pressure gradients due to friction that they produce when conducting them in a vertical ascending pipe are shown. For the study, an experimental facility and two types of injection nozzles were built, constructed and characterized. The selected fluids were oil (viscosity 90 cP, density 885 kg/m3 with 28.3 API) and water. The measurements were made in a range of superficial speeds from 0 to 0.257 m/s for oil and from 0 to 0.684 for water. The experimentation was carried out using the two nozzles and in accordance with a test matrix that has as parameters the superficial speed of the oil (USO) and the superficial speed of the water (USW) for which a fixed value of the USW was taken and it varied the USO, although it was also worked in reverse. From the experimental results, the effect of the nozzles to induce the group of flow patterns and their respective pressure gradient is shown, which reaches its lowest value when conducting the oil in the annular flow scheme. The numerical results showed that there is a notable energy saving, since the pressure loss due to friction is up to 5 times lower when conducting the same amount of oil in the annular flow pattern. Key Words: Experimental installation, oil-water mixture, injection nozzle, flow patterns, annular flow, pressure gradient.

Using natural gas content of groundwater to improve the understanding of complex thermo-mineral spring systems

The varied gaseous composition of thermo-mineral waters emerging in a non-active zone reflects the diversity and complexity of groundwater pathways and provides important insights into their hydrogeological behaviours. The investigated geochemical content of complex thermo-mineral springs revealed the need to use dissolved gas contents as part of a multi-tracer approach to discriminate processes, geogenic (water–gas-rock interactions), abiotic (geological confinement, flow paths) and biotic activity influencing geochemical of groundwater along regional pathways. Irrespective of the dissolved element content or the water type, examining the overall concentration of dissolved gases enables an effective delineation of regional groundwater flow paths. Using dissolved gas content further contributed to the circumvention of some analytical challenges associated with conventional isotopic or geochemical techniques, often linked to the high concentration of elements such as iron, sulfate, sulfide or other naturally occurring elements content. The primary objectives are to analyse the gas composition of individual springs, to identify the origin of these gases in the groundwater, and to use this gas composition to improve the understanding of the flow patterns contributing to the geochemical diversity observed at the surface. From field investigations in a geologically and structurally complex area of Eastern Corsica (France), three types of gas contents are identified: (type 1) CH4 & H2S-rich, (type 2) N2-rich and (type 3) CO2-rich. The study of these dissolved gases highlights that the wide geochemical diversity of thermo-mineral waters observed here is not only related to the mineralogical composition of the local aquifer but also involves strong and cumulative interactions along deep regional circulation pathways. This approach also reveals a common deep crustal gaseous influence characterised by N2 production, which interacts during up flow with groundwater and then with the local metamorphic or sedimentary rock matrix. The groundwater’s isotopic and geochemical contents are then altered by local lithologies encountered through both abiotic and biotic interactions. Finally, at shallow depths, phreatic groundwater can add its geochemical and isotopic footprint and dilute this complex mixture before groundwater emerges as mineral spring. This paper answers the primary objectives yet further demonstrates that using dissolved gas as a tracer of groundwater flow paths allows a deeper interpretation of surface geochemical and isotopic observations, distinguishes local from regional flow paths, and provides information about processes at the origin of groundwater diversity.The combination of tools presented in this paper (i.e., geochemical, dissolved gas, and isotopic tools) allows the establishment of a reliable regional groundwater flow scheme for thermo-mineral waters in a non-active zone. This scheme is essential to improve thermo-mineral water management, and protection to ensure their sustainable quality in front of increasing anthropogenic and climatic pressures.

Physical feature preserving and unconditionally stable SAV fully discrete finite element schemes for incompressible flows with variable density

In this paper, we construct new positive preserving, unconditionally stable and fully discrete finite element schemes for incompressible flows with variable density. The proposed schemes employ the positive function transform ρ=F(ϕ) for the density equation and scalar auxiliary variable (SAV) q=exp(−t/T) for the momentum equation in its reformulation system. The SAV schemes are unconditionally energy stable and second-order accurate in time and lead to two decoupled generalized Stokes equations for the momentum equation to be solved at each time step. Thus, it is easy to implement and extremely efficient for these schemes when combined with an adaptive time stepping method. Numerical experiments demonstrate the stability of computations and verify the second-order accuracy of the proposed schemes.

Multiphase simulations of nonlinear fluids with SPH

A modified apparent viscosity approach has been implemented for a weakly compressible SPH scheme for two-phase flows where a nonlinear phase must yield under erosive dynamics but also maintain a pseudosolid behaviour under the right conditions. The final purpose is to provide a means to model both dam-break dynamics and erosive interactions between different phases simultaneously while also keeping smooth pressure fields in spite of discontinuities introduced by viscosity variations of a nonlinear phase along with significant differences in mean density. Key contributions include purposeful avoidance of nonphysical elastic behaviour and the integration of a specific particle shifting technique that allows for proper replication of erosion and scouring. In this work, the method is validated by applying it to model a silted-up dam that collapses over a static water bed, effectively including all main elements of interest. Although the formulation is inherently three dimensional, validation is done by direct comparison with data from physical experiments of a dominant two-dimensional nature, assuming variable yield stress of medium-grain quartz sand according to the Drucker–Prager equation. Overall results show most of the expected interface dynamics, such as erosion and transportation of the nonlinear phase, sustained piling of the non-yielded volume of silt, and good correspondence of both granular and water surface position with experimental data. Finally, a series of modelling assumptions and implications for future developments are explicitly stated because of their direct impact on stability and versatility for multiphase, nonlinear flows in general.

A two‐stage reliable computational scheme for stochastic unsteady mixed convection flow of Casson nanofluid

AbstractResearchers can incorporate uncertainties in computational fluid dynamics (CFD) that go beyond the inaccuracies caused by numerical discretization thanks to stochastic simulations. This study confirms the validity of current stochastic modeling tools by providing examples of stochastic simulations in conjunction with numerical solutions for incompressible flows. A numerical technique for solving deterministic and stochastic models is developed in this work. Our approach employs the Euler‐Maruyama method for stochastic modeling, representing a stochastic version of the third‐order explicit‐implicit scheme. For the deterministic model, the scheme is third‐order accurate. The consistency and stability of the constructed scheme are provided in the mean square sense. The scheme is the predictor–corrector type that is built on two time levels. Moreover, a mathematical model of the Casson nanofluid flow with variable thermal conductivity is given with the effect of the chemical reaction. The appropriate transformations are used to condense the set of partial differential equations (PDEs) down to one that is dimensionless. The scheme is applied for the deterministic and stochastic models of dimensionless flow problems. The velocity profile's deterministic and stochastic behavior are shown using contour plots. Results show that growing values of the thermal mixed convection parameter enhance the velocity profile. This article presents the progress made in stochastic computational fluid dynamics (SCFD) and highlights the energy‐related aspects of our discoveries. Our computational approach and stochastic modeling techniques provide new insights into the energy properties of Casson nanofluid flow, specifically regarding the variability of thermal conductivity and chemical processes. Our objective is to clarify the complex interaction of these factors on energy dynamics. This article presents a contemporary summary of the latest SCFD advancements. Additionally, it highlights potential directions for future research and unresolved issues that require attention from the members of the field of computational mathematics.

Staggered Schemes for Compressible Flow: A General Construction

Staggered Schemes for Compressible Flow: A General Construction

A modification of explicit time integrator scheme for unsteady power-law nanofluid flow over the moving sheets

This paper introduces an exponential time integrator scheme for solving partial differential equations in time, specifically addressing the scalar time-dependent convection-diffusion equation. The proposed second-order accurate scheme is demonstrated to be stable. It is applied to analyze the heat and mass transfer mixed convective flow of power-law nanofluid over flat and oscillatory sheets. The governing equations are transformed into a dimensionless set of partial differential equations, with the continuity equation discretized using a first-order scheme. The proposed time integrator scheme is employed in the time direction, complemented by second-order central discretization in the space direction for the momentum, energy, and nanoparticle volume fraction equations. Quantitative results indicate intriguing trends, indicating that an increase in the Prandtl number and thermophoresis parameter leads to a decrease in the local Nusselt number. This modified time integrator is a valuable tool for exploring the dynamics of unsteady power-law nanofluid flow over moving sheets across various scenarios. Its versatility extends to the examination of unstable fluid flows. This work improves engineering and technological design and operation in nanofluid dynamics. Improving numerical simulations’ precision and computational efficiency deepens our comprehension of fundamental physics, yielding helpful information for enhancing systems that rely on nanofluids.

Quad-SAV scheme for gradient systems

In this work we develop a new Scalar Auxiliary Variable scheme for general gradient flows. The main novelty of our scheme is that it always produces positive approximations for the nonlinear part of the free energy without any stabilizations. We prove unconditional stability of our scheme for general gradient systems and establish error estimates for the fully discrete scheme in the case of Allen–Cahn and Cahn–Hilliard equations. Several representative numerical examples are presented to demonstrate the accuracy and the efficiency of the proposed scheme.

Computational study of numerical flux schemes for mesoscale atmospheric flows in a Finite Volume framework

Abstract We develop, and implement in a Finite Volume environment, a density-based approach for the Euler equations written in conservative form using density, momentum, and total energy as variables. Under simplifying assumptions, these equations are used to describe non-hydrostatic atmospheric flow. The well-balancing of the approach is ensured by a local hydrostatic reconstruction updated in runtime during the simulation to keep the numerical error under control. To approximate the solution of the Riemann problem, we consider four methods: Roe-Pike, HLLC, AUSM+-up and HLLC-AUSM. We assess our density-based approach and compare the accuracy of these four approximated Riemann solvers using two classical benchmarks, namely the smooth rising thermal bubble and the density current.