Motion Of Incompressible Fluid Research Articles

Numerical Investigation of Tungsten Reduction Process

The subject of this research was a chemical reactor for the producing tungsten coverings by means of chemical vapor deposition. The physical and mathematical model of viscous incompressible fluid motion and heat and mass transfer in a vortex chamber has been described. The velocity field, the temperature and the concentration distributions in a vortex chamber were obtained. Calculations reliability was verified by different methods. Parametric studies on effects of the Reynolds, Prandtl and Rossbi criteria on the flow characteristics were performed.

Hydrodynamic permeability of a membrane built up by spheroidal particles covered by porous layer

This paper concerns the motion of a viscous steady incompressible fluid through a membrane, where the membrane is built up by impermeable spheroidal particles covered by a porous layer. In this work, we discuss the hydrodynamic permeability of a membrane built up by spheroidal particles. Cell model technique has been used to find the hydrodynamic permeability of the membrane. The emphasis is placed on the hydrodynamic permeability of the membrane and its controlling parameters like the permeability of the porous medium, particle volume fraction, deformation parameters, stress jump coefficient. The dependency of the hydrodynamic permeability of the membrane on the above controlling parameters is discussed graphically. Some previous results for hydrodynamic permeability and drag force are verified.

Asymptotics of Motions of Viscous Incompressible Fluids with Large Viscosity

We examine a nonstationary initial-boundary-value problem on the motion of a viscous incompressible fluid with large viscosity. We obtain estimates of the convergence of solutions of this problem to solutions of the corresponding linearized problems as the viscosity tends to infinity. We also consider the case of the problem periodic in time.

Global solvability of the Navier–Stokes equations with a free surface in the maximal Lp-Lq regularity class

We consider the motion of incompressible viscous fluids bounded above by a free surface and below by a solid surface in the N-dimensional Euclidean space for N≥2. The aim of this paper is to show the global solvability of the Navier–Stokes equations with a free surface, describing the above-mentioned motion, in the maximal Lp-Lq regularity class. Our approach is based on the maximal Lp-Lq regularity with exponential stability for the linearized equations, and also it is proved that solutions to the original nonlinear problem are exponentially stable.

On the qualitative theory of the rotating Boussinesq and quasi-geostrophic equations

The author studies the rotating Boussinesq equations describing the motion of a viscous incompressible stratified fluid in a rotating system which is relevant, e.g., a Lagrangian and Eulerian analysis of a geophysical fluid flow. This article focuses on the initial boundary value problem to the rotating Boussinesq equations. The equations are derived from conservation laws in continuum physics followed by the formulation of the problem as initial value problem on Hilbert spaces. By using Faedo-Galerkin approximation and semigroup technique, existence and uniqueness of solutions are proved. Additionally, the manuscript outlines how Lyapunov functions can be used to assess energy stability criteria. The author also addresses singular problems for which the equation has parabolic structure (rotating Boussinesq equations for the atmosphere and ocean) and the singular limit is hyperbolic (quasi-geostrophic equations for the atmosphere and ocean) in the asymptotic limit of small Rossby number. In particular, this approach gives as a corollary a constructive proof of the well-posedness of the problem of quasi-geostrophic potential vorticity equations governing modons or Rossby solitons.

Numerical estimation of various influence factors on a multipoint hydrostatic leveling system

Among various methods that allow controlling quasi-static vertical displacements of structures, the hydrostatic leveling method remains relevant. A multi-point hydrostatic leveling systems allows controlling the vertical displacement field with the required spatial resolution. It is assumed that the liquid level in the each measuring vessel has the same absolute elevation. However, it is influenced by various external factors, which are difficult to eliminate when implementing the method in real constructions. Consequently, it is necessary to assess the influence of these factors and develop methods aimed at their reduction or compensation. A mathematical model, describing the viscous incompressible fluid motion located in a multipoint level with absolutely rigid walls, is presented in the paper. The experiments performed with two point levels of different lengths, as well as analytical estimates of other authors, made it possible to estimate the degree of confidence of the model and the boundaries of applicability. The influence of non-uniform density of a liquid on the liquid level in a 4-point hydrostatic level of different topologies is numerically estimated using the model. An estimation of transient processes in the level, caused by an air pressure surge over one of the measuring vessels is carried out.

The existence theorem for the steady Navier–Stokes problem in exterior axially symmetric 3D domains

We study the nonhomogeneous boundary value problem for the Navier–Stokes equations of steady motion of a viscous incompressible fluid in a three-dimensional exterior domain with multiply connected boundary. We prove that this problem has a solution for axially symmetric domains and data (without any smallness restrictions on the fluxes). Our main tool is a recent version of the Morse–Sard theorem for Sobolev functions obtained by Bourgain et al. (Rev Mat Iberoam 29(1):1–23, 2013).

On the Motion of a Self-Gravitating Incompressible Fluid with Free Boundary

We consider the motion of the interface separating a vacuum from an inviscid, incompressible, and irrotational fluid, subject to the self-gravitational force and neglecting surface tension, in two space dimensions. The fluid motion is described by the Euler-Poission system in moving bounded simply connected domains. A family of equilibrium solutions of the system are the perfect balls moving at constant velocity. We show that for smooth data which are small perturbations of size $\epsilon$ of these static states, measured in appropriate Sobolev spaces, the solution exists and remains of size $\epsilon$ on a time interval of length at least $c\epsilon^{-2},$ where $c$ is a constant independent of $\epsilon.$ This should be compared with the lifespan $O(\epsilon^{-1})$ provided by local well-posdness. The key ingredient of our proof is finding a nonlinear transformation which removes quadratic terms from the nonlinearity. An important difference with the related gravity water waves problem is that unlike the constant gravity for water waves, the self-gravity in the Euler-Poisson system is nonlinear. As a first step in our analysis we also show that the Taylor sign condition always holds and establish local well-posedness for this system.

Numerical simulations of a third-grade fluid flow on a tube through a contraction

Based on a director theory approach related to fluid dynamics we reduce the nonlinear three-dimensional equations governing the axisymmetric unsteady motion of a non-Newtonian incompressible third-grade fluid to a one-dimensional system of ordinary differential equations depending on time and on a single spatial variable. From this new system we obtain the unsteady equation for the mean pressure gradient and the wall shear stress both depending on the volume flow rate, Womersley number and viscoelastic parameters over a finite section of a straight, rigid and impermeable tube with variable circular cross-section. We present some numerical simulations of unsteady flows regimes through a tube with a contraction using a nine-directors theory.

COAL DUST EMISSION PROBLEM

Purpose. The article aims to develop 2D numerical models for the prediction of atmospheric pollution during transportation of coal in the railway car, as well as the ways to protect the environment and the areas near to the mainline from the dust emission due to the air injection installation. Methodology. To solve this problem there were developed numerical models based on the use of the equations of motion of an inviscid incompressible fluid and mass transfer. For the numerical integration of the transport equation of the pollutant the implicit alternating-triangular difference scheme was used. For numerical integration of the 2D equation for the velocity potential the method of total approximation was used. The developed numerical models are the basis of established software package. On the basis of the constructed numerical models it was carried out a computational experiment to assess the level of air pollution when transporting bulk cargo by rail when the railway car has the air injection. Findings. 2D numerical models that belong to the class «diagnostic models» were developed. These models take into account the main physical factors affecting the process of dispersion of dust pollution in the atmosphere during transportation of bulk cargo. The developed numerical models make it possible to calculate the dust loss process, taking into account the use of the air injection of the car. They require a small cost of the computer time during practical realization at the low and medium power machines. There were submitted computational calculations to determine pollutant concentrations and the formation of the zone of pollution near the train with bulk cargo in «microscale» scale taking into account the air curtains. Originality. 2D numerical models taking into account the relevant factors influencing the process of dispersion of pollutants in the atmosphere, and the formation of the zone of pollution during transportation of bulk cargo by rail were created. A way to protect the atmosphere from pollution during the emission of bulk cargoes from the rail car, which is based on the principle of the air injection, was developed. Practical value. The efficient numerical models which can be used in the development of environmental protection measures in the operation of railway transport were considered. The proposed model allows calculating 2D dynamics of wind flow, taking into account the installed air injection, and mass transfer process of pollutants in the atmosphere.

On the Navier–Stokes system with the Coulomb friction law boundary condition

We propose a new model for the motion of a viscous incompressible fluid. More precisely, we consider the Navier–Stokes system with a boundary condition governed by the Coulomb friction law. With this boundary condition, the fluid can slip on the boundary if the tangential component of the stress tensor is too large. We prove the existence and uniqueness of weak solution in the two-dimensional problem and the existence of at least one solution in the three-dimensional case, together with regularity properties and an energy estimate. We also propose a fully discrete scheme of our problem using the characteristic method, and we present numerical simulations in two physical examples.

Controlled motion of a rigid body with internal mechanisms in an ideal incompressible fluid

We consider the controlled motion in an ideal incompressible fluid of a rigid body with moving internal masses and an internal rotor in the presence of circulation of the fluid velocity around the body. The controllability of motion (according to the Rashevskii–Chow theorem) is proved for various combinations of control elements. In the case of zero circulation, we construct explicit controls (gaits) that ensure rotation and rectilinear (on average) motion. In the case of nonzero circulation, we examine the problem of stabilizing the body (compensating the drift) at the end point of the trajectory. We show that the drift can be compensated for if the body is inside a circular domain whose size is defined by the geometry of the body and the value of circulation.

Global Existence of Heat-Conductive Incompressible Viscous Fluids

In this paper, we consider the Cauchy problem of non-stationary motion of heat-conducting incompressible viscous fluids in R2$\mathbb{R}^{2}$, where the viscosity and heat-conductivity coefficient vary with the temperature. It is shown that the Cauchy problem has a unique global-in-time strong solution (u,ź)(x,t)$(u, \theta)(x,t)$ on R2×(0,ź)$\mathbb{R}^{2}\times(0,\infty)$, provided the initial norm źźu0źL2$\|\nabla u_{0}\|_{L^{2}}$ is suitably small, or the lower-bound of the coefficient of heat conductivity (i.e. ź_$\underline{\kappa}$) is large enough, or the derivative of viscosity (i.e. |μź(ź)|$|\mu'(\theta)|$) is small enough.

Effects of Heat Transfer During Peristaltic Transport in Nonuniform Channel With Permeable Walls

In the present investigation, problem of heat transfer has been studied during peristaltic motion of a viscous incompressible fluid for two-dimensional nonuniform channel with permeable walls under long wavelength and low Reynolds number approximation. Expressions for pressure, friction force, and temperature are obtained. The effects of different parameters on pressure, friction force, and temperature have been discussed through graphs.

Global Well-Posedness for the Heat-conductive Incompressible Viscous Fluids

This paper is concerned with the Cauchy problem derived from the non-stationary motion of heat-conducting incompressible viscous fluids in three-dimensional whole space, where the viscosity and heat-conductivity coefficient vary with the temperature. We establish blow-up criteria and existence of global strong solution provided that the initial data is small enough.

Energetic variational approaches for incompressible fluid systems on an evolving surface

This paper considers the equations governing incompressible fluid-flow on an evolving surface. We employ an energetic variational approach to derive the dynamical system for the motion of incompressible fluid on such an evolving surface. The focus is to understand the coupling of an incompressible fluid-flow and the evolution of a moving surface, involving both the curvature and the motion of the surface.

Reproduction of solutions in the plane problem on motion of a free-boundary fluid

This study is devoted to finding exact solutions of the plane unsteady problem on the motion of an ideal incompressible free-boundary fluid. A certain procedure of reproduction making it possible to obtain a two-parametrical family of new exact solutions from one known solution is proposed.

Solutions of equations of motion of incompressible fluid with general function of degree five

Abstract Navier–Stokes Equations (NSE) are considered as basics of different fields of science and engineering. This study discusses exact solution of incompressible fluids with variable viscosity of specified fluid flow in the absence of external forces. Exact solutions of NSE describe the dynamics of fluid flow in a better way than other approximate methods. In this study fluid flow with the general function of degree five has been discussed through the solution of ordinary differential equations. Martin’s coordinates and von Mises variables are used to transform NSE into more simple system of ordinary differential equations, which then provide exact solutions subject to different cases. Final solutions are simplified using MATLAB routine. Streamline pattern for the fluid flows is also plotted for different cases.

Impermeability Through a Perforated Domain for the Incompressible two dimensional Euler Equations

We study the asymptotic behavior of the motion of an ideal incompressible fluid in a perforated domain. The porous medium is composed of inclusions of size \({\varepsilon}\) separated by distances \({d_{\varepsilon}}\) and the fluid fills the exterior. If the inclusions are distributed on the unit square, the asymptotic behavior depends on the limit of \({\frac{d_{\varepsilon}}\varepsilon}\) when \({\varepsilon}\) goes to zero. If \({\frac{d_{\varepsilon}}\varepsilon \to \infty}\), then the limit motion is not perturbed by the porous medium, namely, we recover the Euler solution in the whole space. If, on the contrary, \({\frac{d_{\varepsilon}}\varepsilon \to 0}\), then the fluid cannot penetrate the porous region, namely, the limit velocity verifies the Euler equations in the exterior of an impermeable square. If the inclusions are distributed on the unit segment then the behavior depends on the geometry of the inclusion: it is determined by the limit of \({\frac{d_{\varepsilon}}{\varepsilon^{2+\frac1\gamma}}}\) where \({\gamma \in (0,\infty]}\) is related to the geometry of the lateral boundaries of the obstacles. If \({\frac{d_{\varepsilon}}{\varepsilon^{2+\frac1\gamma}} \to \infty}\), then the presence of holes is not felt at the limit, whereas an impermeable wall appears if this limit is zero. Therefore, for a distribution in one direction, the critical distance depends on the shape of the inclusions; in particular, it is equal to \({\varepsilon^{3}}\) for balls.

Numerical simulation of wave and current interaction with a fixed offshore substructure

Offshore substructures have been developed to support structures against complex offshore environments. The load at offshore substructures is dominated by waves, and deformation of waves caused by interactions with the current is an important phenomena. Wave load simulation of fixed offshore substructures in waves with the presence of uniform current was carried out by numerical wave tank technique using the commercial software, FLUENT. The continuity and Navier–Stokes equations were applied as the governing equations for incompressible fluid motion, and numerical wavemaker was employed to reproduce offshore wave environment. Convergence test against grids number was carried out to investigate grid dependency and optimized conditions for numerical wave generation were derived including investigation of the damping effect against length of the damping domain. Numerical simulation of wave and current interactions with fixed offshore substructure was carried out by computational fluid dynamics, and comparison with other experiments and simulations results was conducted.