Nonlinear motion equations for a non-Newtonian incompressible fluid in an orthogonal coordinate system

This paper describes the work carried out to investigate the pore pressures occurring in secondary consolidation. A theoretical approach and an experimental technique was developed in order to conduct the study. By considering compression to occur only due to water leaving the soil it was possible to derive an expression for the dissipation of pore pressure in the secondary phase. By further simplified assumptions which are based on experimental observations, the above general solution was reduced to a simple formula which predicted the observed behaviour of pore water pressures during secondary consolidation.     

The axisymmetric problem with initial conditions for the equations of motion of an ideal incompressible fluid

The present paper presents a proof of the existence and uniqueness theorem for the solution of the axisymmetric problem with initial conditions for the Euler equations in the case of an incompressible fluid. We consider the case of the nonporous wall, and also the transpiration problem in the formulation given in [1]. Global unique solvability is proved for assumptions only on the smoothness of the conditions and for all values of the time t. The existence theorem for a small time segment in the case of a nonporous wall has been proved for the general three-dimensional problem in [2, 3]. For the proof we use a method analogous to that developed in [1] for planar flows. The a priori estimate of the vorticity which is used in the present study was obtained previously in [4],The author wishes to thank V. I. Yudovich for continued interest in the study and many valuable suggestions.     

An equation of motion for an incompressible Newtonian fluid in a packed bed

The application of a volume average Navier-Stokes equation for the prediction of pressure drop in packed beds consisting of uniform spherical particles is presented. The development of the bed permeability from an assumed porous microstructure model is given. The final model is quasi-empirical in nature, and is able to correlate a wide variety of literature data over a large Reynolds number range. In beds with wall effects present the model correlates experimental data with an error of less than 10%. Numerical solutions of the volume averaged equation are obtained using a penalty finite element method.Nomenclatures d length of a representative unit cell - d _e flow length in Representative Unit Cell - d _p characteristic pore size - D _T column diameter - D _P equivalent particle diameter - e _v energy loss coefficient for elbow - f _app apparent friction factor - f _v packed bed friction factor, defined by Equation (30) - F term representing impermeability of the porous medium - I integral defined by Equation (3) - L length of packed column - N Number of RUC in model microstructure - P pressure - P interstitial pressure - P pressure deviation - Re_p Reynolds number,v _p d _p/ - Re_s Reynolds number,v _s d/gm - Re_b Reynolds number,v _s D _p/ - S _fs fluid solid contact area - T tortuosity - v fluid velocity - v velocity deviation - v _p velocity in a pore - v _s superficial velocity in the medium - v interstitial velocity - V _o total volume of representative unit cell - V pore volume of representative unit cell - change in indicated property - u normal vector onS _fs - porosity - viscosity - density - coefficient in unconsolidated permeability model     

Exact solutions of the equations of motion for an incompressible viscoelastic Maxwell medium

The unsteady plane-parallel motion of a incompressible viscoelastic Maxwell medium with constant relaxation time is considered. The equations of motion of the medium and the rheological relation admit an extended Galilean group. The class of solutions of this system which are partially invariant with respect to the subgroup of the indicated group generated by translation and Galilean translation along one of the coordinate axes is studied. The system does not have invariant solutions, and the set of partially invariant solutions is very narrow. A method for extending the set of exact solutions is proposed which allows finding solutions with a nontrivial dependence of the stress tensor elements on spatial coordinates. Among the solutions obtained by this method, the solutions describing the deformation of a viscoelastic strip with free boundaries is of special interest from a point of view of physics. __________ Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 50, No. 2, pp. 16–23, March–April, 2009.     

Three-dimensional motion of a viscous incompressible fluid in a narrow tube

An approximate solution of the problem of unsteady motion of a viscous incompressible fluid in a long narrow deformable tube at low Reynolds numbers is obtained. Pressure oscillations and tube deformation are shown to be related by an integrodifferential equation. The solution obtained extends the Poiseuille solution in elliptic tubes to the case of comparatively arbitrary small deformations in terms of the tube length and angle. __________ Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 50, No. 4, pp. 28–32, July–August, 2009.     

Analytical model of motion of turbulent vortex rings in an incompressible fluid

An analytical model describing the motion of vortex rings in an incompressible fluid is constructed. The model is valid both for homogeneous and inhomogeneous vortices buoyant in the gravity field, as well as for combined vortices. The expansion angle of a buoyant vortex is found from the characteristic parameters that define the flow rather than specified on the basis of experiments. Significant differences in the expansion angles of homogeneous and buoyant vortex rings are explained. The calculation results for the proposed model are compared with the results of laboratory experiments and data on the rise of the cloud produced by an atomic explosion.     

Finite element solutions of axisymmetric Euler equations for an incompressible and inviscid fluid

In this paper we present a finite element method for the numerical solution of axisymmetric flows. The governing equations of the flow are the axisymmetric Euler equations. We use a streamfunction angular velocity and vorticity formulation of these equations, and we consider the non-stationary and the stationary problems. For industrial applications we have developed a general model which computes the flow past an annular aerofoil and a duct propeller. It is able to take into account jumps of angular velocity and vorticiy in order to model the flow in the presence of a propeller. Moreover, we compute the complete flow around the after-body of a ship and the interaction between a ducted propeller and the stern. In the stationary case we have developed a simple and efficient version of the characteristics/finite element method. Numerical tests have shown that this last method leads to a very fast solver for the Euler equations. The numerical results are in good agreement with experimental data.     

Nonlinear equations of motion for orthotropic plates

Nonlinear equations of motion for orthotropic plates are proposed on the basis of the three dimensional nonlinear theory of elasticity. The resulting plate model provides a high accuracy, which is confirmed by solving the Vlasov static problem of bending a hinge-supported plate under sinusoidal load.     

On the self-similar solution to the Euler equations for an incompressible fluid in three dimensions

The equations for a self-similar solution to an inviscid incompressible fluid are mapped into an integral equation that hopefully can be solved by iteration. It is argued that the exponents of the similarity are ruled by Kelvin's theorem of conservation of circulation. The end result is an iteration with a nonlinear term entering a kernel given by a 3D integral for a swirling flow, likely within reach of present-day computational power. Because of the slow decay of the similarity solution at large distances, its kinetic energy diverges, and some mathematical results excluding non-trivial solutions of the Euler equations in the self-similar case do not apply.     

Small parameter method for determining motion of a viscous incompressible fluid in a thrust bearing

We consider the plane stationary motion of a viscous incompressible fluid between two surfaces. The fixed surface is given by the equation y=h[1+f(x/h)], where the functionf(x/h=h) characterizes the deviation of the fixed surface from the plane y=h(h and , are constants). The moving surface is a plane which moves with constant velocity along the x axis and remains parallel to the plane y=h. The small parameter method is used to solve the problem. The problem formulation is presented in the first section, the solvability of the linear equations obtained using the small parameter method is investigated in the second section, and the third section studies the convergence of the method and finds the radius of convergence of the constructed series.     

Finite-element analysis of slow incompressible viscous fluid motion

Summary The governing field equations and the constitutive relation are specialized to the boundary value formulation of incompressible viscous fluid motion excluding thermal effects. When choosing the velocities and the hydrostatic pressures as variables, the established non-linear matrix equation in terms of finite-element properties becomes valid for both two- and three-dimensional application. It is shown that a restricted class of problems readily fits within the scope of existing finite-element software designed for conventional structural mechanics analysis provided an effective Lagrange multiplier technique can be incorporated.Two curved triangular finite-element models are proposed for both two-dimensional and axisymmetric flow, based on a and order Lagrangian and 3rd order Hermitian interpolation set for the velocities. Some typical examples are attached including linear stationary and transient problems, as well as non-linear cavity flow at moderate Reynolds numbers.

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Übersicht Die Feldgleichungen und das Stoffgesetz werden für die Formulierung der Randwertaufgabe für inkompressible zähe Strömungen spezialisiert, wobei thermische Effekte unberücksichtigt bleiben. Die entwickelte nichtlineare Matrizenbeziehung in Termen der Finite-Element-Schreibweise gilt sowohl für zweidimensionale als auch für dreidimensionale Anwendungen, sofern die Geschwindigkeitskomponenten und der hydrostatische Druck als Strömungsvariablen gewählt werden. Es wird gezeigt, daß eine eingeschränkte Klasse von Problemen direkt im Rahmen bereits bestehender Finite-Element-Programme gelöst werden kann, die für herkömmliche Aufgaben der Strukturmechanik entwickelt wurden, sofern ein effektiver Einbau der Methode der Lagrangeschen Multiplikatoren möglich ist.Für zweidimensionale und achsensymmetrische Strömungen werden zwei krummseitige dreiecksförmige Finite-Element-Modelle vorgeschlagen, deren Geschwindigkeitsfelder mit Hilfe einer Lagrangeschen Interpolation zweiter Ordnung bzw. eines Hermiteschen Ansatzes dritter Ordnung approximiert werden. Einige typische Beispiele behandeln lineare stationäre und instationäre Probleme, sowie eine nichtlineare Hohlraumströmung bei kleineren Reynolds-Zahlen.

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Professor Dr. Ing. Dr. h. c. Eduard C. Pestel zu seinem 60. Geburtstag herzlichst gewidmet.     

An efficient algorithm for solving the incompressible fluid flow equations

The present paper reports on a modified pressure implicit predictor corrector type scheme for solving the flow governing equations, in which a consistent formulation is combined with a multi-grid solver for the pressure correction. In addition a parabolic sublayer (PSL) approach for the treatment of the flow in the vicinity of solid walls is critically evaluated in terms of accuracy and computational efficiency. The lid-driven cavity flow is chosen as the test case and results are presented for Reynolds numbers ranging from 100 to 1000. Predictions with the proposed scheme indicate substantial computational savings and fairly good agreement when compared with previous work. The PSL approach reduces the computing time, but with increasing Reynolds numbers the accuracy of the solutions tends to deteriorate.     

Exact solutions of equations of rotationally symmetric motion of an ideal incompressible liquid

A partially invariant solution of the Euler equations is considered, where the vertical component of velocity is a function of the vertical coordinate and time, whereas the remaining components of velocity and pressure are independent of the polar angle in a cylindrical coordinate system. Using the classification of equations obtained by analysis of an overdetermined system, we consider two hyperbolic systems: the first one describes the motion of a cylindrical layer of an ideal incompressible liquid under a punch, and the second system allows obtaining solutions in a halfcylinder with singularities at the axis of symmetry. A class of new exact solutions is obtained, which describe vortex motion of an ideal incompressible liquid, including the motion with singularities (sources of vortices) located along the axis of symmetry.