Field Of Mass Forces Research Articles

Exact solutions to the NAVIER–STOKES equations for unidirectional flows of micropolar fluids in a mass force field

Exact solutions to the NAVIER–STOKES equations for unidirectional flows of micropolar fluids in a mass force field

Measurement of mass force field driving water refilling of cuttage

Cuttage is a common plant cultivation method, and the key to its survival is the restoration of water refilling, which remains unclear up to now. We report 3D dynamic imaging of water refilling of cuttage without resorting to any contrast agent. Hydrodynamics of the refilled water flow over time reveals the existence of a unit mass force field with a gradient along the refilling direction, which means that cutting plants also have a gradient force field to drive the recovery of water refilling, as predicted by Cohesion-Tension theory in normal plants. We found that force fields of different functional regions are isolated and independently distributed, which is conducive to ensure the safety of water transmission. At the same time, we also found that there is a so-called "inchworm effect" in the mass force field, which contributes to the force transfer inside the cutting through local force accumulation. Results of this paper demonstrate that the developed method for the measurement of mass force field in-vivo is applicable to help decipher the mechanism of plant water refilling.

ВПЛИВ ТЕМПЕРАТУРИ НА ПРАЦЕЗДАТНІСТЬ ПАЛИВНОЇ СИСТЕМИ КОСМІЧНИХ ЛІТАЛЬНИХ АПАРАТІВ

The tasks that modern spacecraft must solve during the flight task are constantly becoming more complicated. Accordingly, the conditions for the functioning of all systems and, above all, the fuel system are complicated. This system should provide the engines of the aircraft with fuel components when they start and operate under conditions of action of a variable field of mass forces, that is, in conditions of practical weightlessness. In these conditions, the nature of the impact on the performance of the fuel system of various external and internal factors changes significantly.
 The paper analyzes the degree of influence of the temperature of the structural elements of the spacecraft and liquid fuel on the performance of individual components of the fuel system. Some existing approaches to this issue are considered and it is concluded that it is necessary to conduct further research in this direction in order to improve existing and create new, more modern, fuel systems of multipurpose spacecraft and acceleration units.

Горение заряда металлизированного смесевого твердого топлива с плоским каналом в поле массовых сил

In this paper, combustion of a channel charge of a metallized composite solid chunk fuel in the field of mass forces is modeled. We have investigated the influence of the g-force on the total mass influx from the combustion surface of two parallel plates of the metallized solid fuel. The combustion rate of the fuel is calculated based on the nonstationary model of the metallized solid fuel combustion. The conducted computational and theoretical analysis has provided the data on the influence of the mass forces and the composition of the fuel on the total mass influx from the combustion surface. The g-force values are ranged from -650 to 650 m/s2. It is assumed that the g-force is directed along the normal to the combustion surface; otherwise, the projection of the g-force onto the normal to the combustion surface is considered. The obtained results have shown that the effect of the g-force is not symmetric - the g-forces, which are identical in magnitude but different in sign, lead to a different response of the combustion rate. The character of the dependence between the combustion rate and g-force for the particles with the radius greater than 7.5 pm is nonmonotonic. The obtained results demonstrate the importance of taking into account the effect of the g-force on the combustion rate when simulating nonstationary processes in solid propellant engines at the stages of start, maneuvering, and deceleration.

Gravitational principle of minimum pressure for incompressible flows

We consider the flows of ideal (Euler equations) and Newtonian viscous (Navier–Stokes equations) incompressible fluids in the gravitational field of mass forces. In this case, the gravitational field created by the liquid itself (self-gravity) is also taken into account. It is shown that some well-known principles of maximum pressure, according to which either the pressure is constant in the flow region, or the minimum pressure is reached at the boundary of this region if the forces of self-gravity are taken into account, exclude the case of constant pressure. It is also demonstrated that self-gravity makes it impossible for waves and solitons to pass with pressure minima to the surface of a body flown around by a viscous fluid.

A class of exact solutions with spatial acceleration for the description of viscous incompressible fluid flows in the field of mass forces

The article presents a new class of exact solutions to the system of Navier–Stokes equations, which allows one to take into account the nonlinear distribution of the pressure field and the influ-ence of external volumetric forces, as well as the possibility of horizontal fluid outflow/inflow when modeling its vertical motion. This class is a generalization of the Lin–Sidorov–Aristov class, which assumes the linear distribution of two projections of the fluid flow velocity vector along a part of the coordinates and the independence of the third projection of the velocity vector from these coor-dinates.

Решение комбинированных краевых задач для анизотропных тел вращения с массовыми силами

The aim of the work is to determine the stress-strain state of anisotropic bodies of revolution under the action of mass forces and external conditions of a physical and geometrical nature in a combined formulation. The task is ensured by the development of the method of boundary states, based on the concepts of spaces of internal and boundary states. The theory of the formation of the basis of the space of internal states, which includes displacements, deformations, stresses and mass forces, is constructed. A common basis is a combination of two bases. The first is formed for the case of plane deformation from the action of only mass forces, based on the application of the application of fundamental polynomials. Further, on its basis, according to the method of integral overlays, a basis of internal spatial states is induced. The second is the basis of internal states in the classical boundary value problem for transversely isotropic bodies. After orthogonalization of the common basis, where the inner energy of elastic deformation acts as the scalar product, the desired state is determined by a Fourier series, the coefficients of which are defined integrals. Checking the adequacy of the solution is carried out by comparing a given field of mass forces with that obtained, as well as by comparing the specified boundary conditions with the resulting solutions. Solutions of problems with different combinations of boundary conditions for a circular cylinder of rock with the corresponding conclusions are given. Presents a graphical visualization of the results.

Analytical investigation of free vibrations of a bounded nonlinear bulk-elastic medium in a field of mass forces

Analytical investigation of free vibrations of a bounded nonlinear bulk-elastic medium in a field of mass forces

Technology of Gasification of Liquefied Natural Gas

A flow diagram of gasification of a cryogenic liquid, which is based on the utilization of the liquid′s internal energy to obtain a vapor phase, has been presented. The limiting steam fractions of the two-phase flow in a gasifier have been evaluated as applied to the problems of gasification of methane. Consideration has been given to the conditions of phase separation in the field of mass forces. A numerical scheme of solution of a system of gasdynamic equations for the two-phase flow in a cylindrical coordinate system in a three-dimensional formulation has been implemented. The results of numerical modeling of the conditions of precipitation of particles with a diameter of 2 to 10 μm from a swirling dispersed flow have been presented; the role of the particle size in the dynamics of the process of phase separation has been established.

Boiling process in oil coolers on porous elements

Holography and high-speed filming were used to reveal movements and deformations of the capillary and porous material, allowing to calculate thermo-hydraulic characteristics of boiling liquid in the porous structures. These porous structures work at the joint action of capillary and mass forces, which are generalised in the form of dependences used in the calculation for oil coolers in thermal power plants (TPP). Furthermore, the mechanism of the boiling process in porous structures in the field of mass forces is explained. The development process of water steam formation in the mesh porous structures working at joint action of gravitational and capillary forces is investigated. Certain regularities pertained to the internal characteristics of boiling in cells of porous structure are revealed, by means of a holographic interferometry and high-speed filming. Formulas for calculation of specific thermal streams through thermo-hydraulic characteristics of water steam formation in mesh structures are obtained, in relation to heat engineering of thermal power plants. This is the first calculation of heat flow through the thermal-hydraulic characteristics of the boiling process in a reticulated porous structure obtained by a photo film and holographic observations.

The integral invariant of the equations of motion of a viscous gas

An expression for the velocity of motion of a simple vortex contour for which the circulation of the fluid velocity is preserved in it is obtained in the general three-dimensional case for the flow of a viscous gas or liquid. The velocity of motion of the contour at each point is calculated from the values of the flow parameters and their derivatives at the same point. This result extends Thomson's theorem, which is well known for an ideal barotropic fluid. A previously unknown conservation property is found, which consists of the fact that the circumferential circulation of the swirling axisymmetric flow in the potential field of mass forces is the first integral of the equations of unsteady flow of a non-barotropic ideal gas.

Pumping Action of Heat Transfer for Free Convection Flow in a Ventilated Facades

The flows generated by lifting force can be met as in environment as in a number of technical devices. These flows emerge due to volume force which depends on the difference in densities caused by transfer of thermal energy as a result of temperature non-uniformity. Convection flows, which cause heat transfer between surfaces and air, emerge near heated or cooled surfaces. The densities of both liquid and gas depend on temperature. Therefore with the temperature gradient in liquid or gas mass forces are different at different points. This causes motion of gas or liquid which can be defined by direction of the field of mass forces, distribution of temperature in liquid and geometric shape of volume.

On the theory of combustion and synthesis of composite materials in the field of mass forces

The formation of a composite material during combustion of a two-layer sample in a centrifugal device was studied by mathematical modeling. The liquid combustion products of the upper layer flow into the lower porous layer under the action of the centrifugal force and initiate its combustion to form a composite material. The critical conditions for the passage of the combustion wave from the upper to the lower layer of the sample are determined depending on the gravitational overload and initial porosity. Dependences of the burning velocity and the impregnation depth of the lower layer on its porosity and overload are obtained.

An approximation method for estimation of the residual stress relaxation in a face-hardened blade in a mass-force field under creep

An approximation method for the evaluation of the residual stress relaxation in face-hardened blades of gas turbine engines under creep is reported. A hypothesis that allows for the blade to be decomposed into the blade “body” and a thin hardened surface layer underlies this method, which enables one to divide the problem under consideration into a series of boundary value problems that are solved in sequence. A model analysis of the residual stress relaxation in the face-hardened layers of a number of blades is made, in particular, for the first stage of the high-pressure turbine of the GTK-10-4.

Magnetic fluid separation of gold-containing products in the vibration field

New data on the process of the magnetic fluid (MF) separation, which is based on the ponderomotive effect of the magnetized separation medium—or ferromagnetic fluid (FMF) on the nonmagnetic bodies arranged in it—are obtained. The magnetization of the FMF in a nonuniform magnetic field increases the strength of the field of mass forces affecting the FMF and, as a consequence, the pressure gradient in the FMF. This phenomenon can be considered pseudoweighting of the FMF and, when controlling the magnetic field force, it can be used to separate nonmagnetic materials according to their specific weights. The behavior of the FMF in the vibration field is investigated theoretically, and the dependence of energy absorbed by it on the amplitude and frequency of vibrations is revealed. Under industrial conditions, a series of tests on separation of free gold from the products of washing the goldfields by the method of MF separation is performed. The results of these tests prove the prospects of including secondary Au-containing resources with difficult-to-recover gold in processing.

The calculation of heat transfer and resistance under conditions of stabilized turbulent pipe flow of electrically conducting liquid in longitudinal magnetic field

The model of turbulence, developed previously for a flow in the field of mass forces (buoyancy, Coriolis) and for an unsteady flow, is applied to the case of liquid flow in magnetic field. The model describes the suppression of turbulence by the magnetic field and the laminarization of turbulent (at the pipe inlet) flow. The calculation results agree well with the experimental data on heat transfer and resistance obtained in the region of stabilized flow and heat transfer.

Sedimentation acceleration of remanent iron oxide by magnetic flocculation

Sedimentation based processes are widely used in industry to separate particles from a liquid phase. Since the advent of the “Nanoworld” the demand for effective separation technologies has rapidly risen, calling for the development of new separation concepts, one of which lies in hybrid separation using the superposition of a magnetic field for magnetic particles. Possible product portfolio of such separation consists of pigment production, nanomagnetics production for electronics and bio separation. A promising step in that direction is magnetic field enhanced cake filtration, which has by now progressed from batch to continuous operation. In sedimentation processes in a mass force field the settling behaviour of particles strongly depends on physico-chemical properties, concentration and size distribution of the particles. By adjusting the pH, the interparticle forces, in particular the electrostatic repulsion, can be manipulated. For remanent magnetic particles such as magnetite, pre-treatment in a magnetic field could lead to a change of interparticle interactions. By magnetizing the particles apart from van der Waals attraction and electrostatic repulsion, an additional potential is induced, the magnetic attraction, which could easily dominate the other potentials and result in agglomeration in the primary minimum. By sedimentation analysis, a wide spectrum of parameters like pH, magnetic field strength and concentration have been investigated. The results show a strong increase of sedimentation velocity by magnetic flocculation of the raw suspension. This leads to a rise in throughput due to the acceleration of sedimentation kinetics by imparting a non-chemical interaction to the physico-chemical properties in the feed stream of the separation apparatus.

Problem of Critical Convective Flows in Horizontal-Cylindrical Cavities

The results of an analysis of the linear perturbations of equilibrium of a viscous heat-conducting fluid or gas in cavities with simple geometric cross-sections are given. Both plane motions and motions periodic in the direction of the horizontal generator of the boundary surface are considered. Variants in which the acceleration of the mass force field can be both constant and periodically modulated are calculated. The solutions of the problem for the stream function (or the vertical velocity component) and the temperature are represented in the form of double or triple Fourier series. For the coefficients in the expansions an infinite system of equations which admits reduction is obtained. The results are found to be in good agreement with the known data.

Thermo-gravitational and vibrational convection in a near-critical gas in microgravity

The flow and heat transfer in a medium near the critical point (second-kind liquid-gas phase transition) in a stationary and oscillating mass force field is considered in relation to the experiments conducted in microgravity. The conditions of onset of a mean convective flow and the characteristic nondimensional parameters describing the vibrational and thermo-gravitational convection in the medium are analyzed. It is shown that even low-frequency and small-amplitude vibrations or steady microaccelerations can induce appreciable convective flows.

Experimental study of variations in the thickness of a liquid film moving over the inner surface of a rotating cylinder

The behavior of a liquid layer moving in a mass-force field on the inner surface of a rotating vertical cylinder is studied experimentally. Free-surface profiles of the liquid moving under these conditions are constructed. An empirical dependence for the mean thickness of the film is obtained in criterial forms. The presence of a hydraulic jump in the lower part of the cylinder behind the entrance of the liquid onto the vertical surface is revealed.