Exact solutions of problems of the three-dimensional flow of ideal viscous incompressible fluids near cylindrical surfaces

Three-dimensional flows of an incompressible fluid, the parameters of which depend on two coordinates and time, are considered. The stream surfaces of such flows are cylindrical. The equations of continuity and the Navier-Stokes equations can be transformed to relations, one of which is the equation for the stream function the other is the integral of the equations relating the pressure and the stream function, and the third is a linear equation for the projection of the velocity vector onto the axis parallel to the generatrix of the cylindrical surfaces. The problems of modelling the flows are considered on the basis of the exact solutions of the Navier-Stokes equations and Euler's equations using examples. Relations for the distribution of the flow parameters in the channel created by hyperbolical cylinders are derived for the case of unsteady inviscid flow. The streamlines of these flows are situated on the side surfaces of the hyperbolical cylinders and intercept the generatrices of the cylinders at certain indirect angles. The flow around a circular cylinder and the flow of fluid inside an elliptic cylinder are considered in the case of steady inviscid flow. The streamlines on the circular cylinder are arranged transverse to the cylinder (the projection of the velocity vector onto the coordinate axis, parallel to the generatrix of the cylinder, is equal to zero). Far from the cylinder the streamlines are also situated on a cylindrical surfaces, but not transverse to the cylinder, making certain indirect angles with the generatrix. Viscous three-dimensional flows, possessing a certain symmetry, are considered. In the case of radial symmetry the streamlines are helical lines. The non-planar Couette flow between parallel moving planes is characterized by the fact that the velocity vectors, being situated in the same plane, are collinear, while the velocity vectors in parallel planes are not collinear. Relations for viscous steady three-dimensional flows, using well-known relations, obtained for the stream function of two-dimensional flows, are given.     

The method of fundamental solutions for the Oseen steady‐state viscous flow past obstacles of known or unknown shapes

In this paper, the steady‐state Oseen viscous flow equations past a known or unknown obstacle are solved numerically using the method of fundamental solutions (MFS), which is free of meshes, singularities, and numerical integrations. The direct problem is linear and well‐posed, whereas the inverse problem is nonlinear and ill‐posed. For the direct problem, the MFS computations of the fluid flow characteristics (velocity, pressure, drag, and lift coefficients) are in very good agreement with the previously published results obtained using other methods for the Oseen flow past circular and elliptic cylinders, as well as past two circular cylinders. In the inverse obstacle problem the boundary data and the internal measurement of the fluid velocity are minimized using the MATLAB^© optimization toolbox lsqnonlin routine. Regularization was found necessary in the case the measured data are contaminated with noise. Numerical results show accurate and stable reconstructions of various star‐shaped obstacles of circular, bean, or peanut cross‐section.     

Stationary convection–diffusion equation in an infinite cylinder

We study the existence and uniqueness of a solution to a linear stationary convection–diffusion equation stated in an infinite cylinder, Neumann boundary condition being imposed on the boundary. We assume that the cylinder is a junction of two semi-infinite cylinders with two different periodic regimes. Depending on the direction of the effective convection in the two semi-infinite cylinders, we either get a unique solution, or one-parameter family of solutions, or even non-existence in the general case. In the latter case we provide necessary and sufficient conditions for the existence of a solution.     

Unsteady longitudinal flow of a generalized Oldroyd-B fluid in cylindrical domains

Considering a fractional derivative model the unsteady flow of an Oldroyd-B fluid between two infinite coaxial circular cylinders is studied by using finite Hankel and Laplace transforms. The motion is produced by the inner cylinder which is subject to a time dependent longitudinal shear stress at time t = 0⁺. The solution obtained under series form in terms of generalized G and R functions, satisfy all imposed initial and boundary conditions. The corresponding solutions for ordinary Oldroyd-B, generalized and ordinary Maxwell, and Newtonian fluids are obtained as limiting cases of our general solutions. The influence of pertinent parameters on the fluid motion as well as a comparison between models is illustrated graphically.     

Modelling two-dimensional flow past arbitrary cylindrical bodies using boundary element formulations

This paper presents an efficient method of solving Queen's linearized equations for steady plane flow of an incompressible, viscous Newtonian fluid past a cylindrical body of arbitrary cross-section. The numerical solution technique is the well known direct boundary element method. Use of a fundamental solution of Oseen's equations, the ‘Oseenlet’, allows the problem to be reduced to boundary integrals and numerical solution then only requires boundary discretization. The formulation and solution method are validated by computing the net forces acting on a single circular cylinder, two equal but separated circular cylinders and a single elliptic cylinder, and comparing these with other published results. A boundary element representation of the full Navier-Stokes equations is also used to evaluate the drag acting on a single circular cylinder by matching with the numerical Oseen solution in the far field.     

On the hydrodynamic interaction of two circular cylinders oscillating in a viscous fluid

The present paper deals with the plane flow fields induced by two parallel circular cylinders with radiia andb oscillating in a direction which is i) parallel or ii) perpendicular to the plane containing their axes. The effect of the cylinders' hydrodynamic interaction on steady streaming has been studied analytically at high frequency by the method of matched asymptotic expansions.It is found that ifa=b the steady streaming is directed symmetrically to the cylinders while whenab (in the case i)) the secondary steady flow is directed towards the larger cylinder and one of the outer steady vortices disappears.It is shown in case i) that the drag force acting on each cylinder is smaller than the same force experienced on a single cylinder with the same radius which is placed in an unbounded oscillating flow. When the cylinder radii are equal, the drag is greater on the forward cylinder than on the rear one.In contrast, in case ii), wherea=b, it is shown that the drag on each of the two cylinders is greater than the drag acting on a single cylinder with the same radius placed in an unbounded oscillating stream and also each of the cylinders experiences a repulsive force in a direction perpendicular to the oscillating flow.     

Two-dimensional viscous flow between circular cylinders: application to damping devices for seismic isolation

A detailed analysis of the fluid dynamics of the two-dimensional viscous flow between circular cylinders is dealt with in this paper. Analytic solutions are found on the basis of asymptotic expansions with respect to a small parameter defined by the ratio between the difference of the radii and the radius of the internal cylinder. The analysis is related to the study of recently developed devices for seismic isolation of buildings based on modified pile foundation, separated from the soil, in which a viscous fluid is inserted in the void space between the pile and the lining of the surrounding soil. The availability of this analytical solution contributes to obtaining accurate predictions of the force on the pile.     

Linear oscillatory hydromagnetic flow between two coaxial cylinders

Hydromagnetic flow between two coaxial circular cylinders is discussed when the inner cylinder oscillates axially under a radial magnetic field. Exact solution is given for the case of a perfectly conducting fluid. Expressions for velocity, induced magnetic field, current density, electric field, viscous drag and energy transfer are derived and expressed in polar forms so as to facilitate the study of magnitude and phase variations. Current sheets are found to exist on the two boundaries.     

Exact solutions of starting flows for a fractional Burgers’ fluid between coaxial cylinders

This paper deals with the unsteady flows of a viscoelastic fluid between two infinitely long concentric circular cylinders. The fractional calculus approach in the constitutive relationship model of a Burgers’ fluid is introduced. With the help of integral transforms (the Laplace transform and the Weber transform), exact solutions are constructed for the following two problems: (i) when the outer cylinder makes a simple harmonic oscillation; and (ii) when the outer cylinder suddenly begins rotating while the inner cylinder remains stationary. Some previous and classical results can be recovered from the presented results, such as starting solutions for second grade, Maxwell, Oldroyd-B, and Burgers’ fluids.     

Multi‐periodic eigensolutions to the Dirac operator and applications to the generalized Helmholtz equation on flat cylinders and on the n‐torus

In this paper, we study the solutions to the generalized Helmholtz equation with complex parameter on some conformally flat cylinders and on the n‐torus. Using the Clifford algebra calculus, the solutions can be expressed as multi‐periodic eigensolutions to the Dirac operator associated with a complex parameter λ∈?. Physically, these can be interpreted as the solutions to the time‐harmonic Maxwell equations on these manifolds. We study their fundamental properties and give an explicit representation theorem of all these solutions and develop some integral representation formulas. In particular, we set up Green‐type formulas for the cylindrical and toroidal Helmholtz operator. As a concrete application, we explicitly solve the Dirichlet problem for the cylindrical Helmholtz operator on the half cylinder. Finally, we introduce hypercomplex integral operators on these manifolds, which allow us to represent the solutions to the inhomogeneous Helmholtz equation with given boundary data on cylinders and on the n‐torus. Copyright © 2009 John Wiley & Sons, Ltd.     

Effects of slip on the non-linear flows of a third grade fluid

The present analysis considers the non-linear problems of steady flow of a third grade fluid between the concentric cylinders. A complete analysis of mathematical modeling is made when no-slip condition is no longer valid. Exact analytic solutions of the following two non-linear problems are derived: (i) when inner cylinder moves and outer cylinder remains stationary and (ii) for inner cylinder at rest and outer cylinder in motion. Graphical results are presented to illustrate the analytic solutions. The corresponding results of no-slip condition are deduced as the limiting cases when the slip parameter is equal to zero.     

Couette flow of dipolar fluids

An exact solution for the problem of steady flow of an incompressible, isothermal and homogeneous dipolar fluid in the annular space between two concentric circular cylinders rotating with uniform angular velocities is obtained. The effect of the material constants on the torque acting on the cylinders is studied particular cases.     

Viscoelastic flow in a curved channel: A similarity solution for the Oldroyd-B fluid

A similarity solution is used to analyse the flow of the Oldroyd fluid B, which includes the Newtonian and Maxwell fluids, in a curved channel modelled by the narrow annular region between two circular concentric cylinders of large radius. The solution is exact, including inertial forces. It is found that the non-Netonian kinematics are very similar to the Newtonian ones, although some stress components can become very large. At high Reynolds number a boundary layer is developed at the inner cylinder. The structure of this boundary layer is asymptotically analysed for the Newtonian fluid. Non-Newtonian stress boundary layers are also developed at the inner cylinder at large Reynolds numbers.     

Extension of the Lamé–Gadolin problem for large deformations and its analytical solution

The formulation and solution of the axisymmetric static problem of the stress-strain state of two hollow circular elastic cylinders, one of which is predeformed and inserted into the other cylinder, is considered in the case of large plane deformations (an extension of the Lamé–Gadolin problem to large deformations). Using the theory of the superposition of large deformations, an exact analytical solution of the static problem for cylinders made of incompressible Treloar and Bartenev–Khazanovich materials is obtained, including the case when the cylinders are made of dissimilar materials. An analytical solution is obtained in parametric form for a compressible Blatz–Ko material. Non-linear effects are investigated.     

Circular oscillations of a cylinder in a viscous fluid

Summary The steady streaming velocity induced by the circular motion of a cylinder of elliptic cross-section in a viscous fluid is considered. The amplitude of this circular motion is supposed small compared with a typical diameter of the cylinder, which maintains a fixed orientation throughout the motion. Outside the Stokes shear-wave layer Reynolds stresses contribute to the induced steady streaming. The outer flow is calculated in the case of large streaming Reynolds numbers for two particular cylinders.

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Zusammenfassung Es wird die stationäre Strömung untersucht, die durch die kreisförmige Bewegung eines Zylinders mit elliptischem Querschnitt in einer zähen Flüssigkeit induziert wird. Die Amplitude dieser Kreisbewegung wird als klein angenommen gegenüber den Halbachsen der Ellipse, deren Orientierung während der Bewegung unverändert bleibt. Ausserhalb der Stokes-Schicht tragen die Reynolds-Spannungen zur Induzierten stationären Strömung bei. Die äussere Strömung wird im Falle von grossen Reynolds-Zahlen der Strömung für zwei besondere Zylinder berechnet.

     

Inversion transformation of Stokes flows bounded by parallel planes

The positive inversion transformation applied to a two-dimensional Stokes flow around bodies leads alike to a Stokes flow. This fact can be exploited to find new two-dimensional Stokes flow solutions around inverse bodies. Some features of this method, such as the relations between the reference and inverse fluid velocity fields, are presented followed by an application to examples of cellular flow between two parallel plates induced by rotating or translating cylinder. Thus hydrodynamic characteristics of flow around circular bodies obtained by inversion of the plates are straightforward deduced. Typical fluid flow patterns around two circular cylinders in contact placed in the centre of a rotating or a translating circular cylinder are thus illustrated.     

Inversion transformation of Stokes flows bounded by parallel planes

The positive inversion transformation applied to a two-dimensional Stokes flow around bodies leads alike to a Stokes flow. This fact can be exploited to find new two-dimensional Stokes flow solutions around inverse bodies. Some features of this method, such as the relations between the reference and inverse fluid velocity fields, are presented followed by an application to examples of cellular flow between two parallel plates induced by rotating or translating cylinder. Thus hydrodynamic characteristics of flow around circular bodies obtained by inversion of the plates are straightforward deduced. Typical fluid flow patterns around two circular cylinders in contact placed in the centre of a rotating or a translating circular cylinder are thus illustrated.     

Global regularity of a class of p-fluid flows in cylinders

We consider the motion of an incompressible non-Newtonian fluid with shear dependent viscosity. We extend and improve the results obtained in the recent paper by Crispo [F. Crispo, Shear thinning viscous fluids in cylindrical domains. Regularity up to the boundary, J. Math. Fluid Mech., in press], concerning the case of the motion between two coaxial cylinders, to the case of a full cylinder. Actually we prove boundary regularity for solutions to the stationary Dirichlet problem with zero boundary data.     

Exact solutions for the flow of a viscoelastic fluid induced by a circular cylinder subject to a time dependent shear stress

The velocity field and the adequate shear stress corresponding to the flow of a Maxwell fluid with fractional derivative model, between two infinite coaxial cylinders, are determined by means of the Laplace and finite Hankel transforms. The motion is due to the inner cylinder that applies a longitudinal time dependent shear to the fluid. The solutions that have been obtained, presented under integral and series form in terms of the generalized G and R functions, satisfy all imposed initial and boundary conditions. They can be easy particularizes to give the similar solutions for ordinary Maxwell and Newtonian fluids. Finally, the influence of the relaxation time and the fractional parameter, as well as a comparison between models, is shown by graphical illustrations.     

Packing cylinders on a cylinder with contact constraints

The problem of cylinder packing is investigated. The specific problem is to determine the maximum number of congruent cylinders that can be packed around a core cylinder of arbitrary dimensions. The constraint is that their circular face must keep in contact with the core cylinder and there may be no overlapping. Only right circular cylinders are considered. Mathematically, a lower and upper bound is determined. A quantitative result is also found using a modified genetic algorithm. The algorithm was found to reproduce the published results for the top and bottom circular faces of the core which reduces to the problem of packing congruent circles within a circle. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)