Superconducting cylinder in a static longitudinal magnetic field

A study of the calculation of the magnetic field forces acting on a superconducting cylinder in a longitudinal magnetic field is reported. A computation algorithm and the results of field calculation by means of the boundary integral method, taking account of the cylinder edge singularity, are presented. The method makes it possible to compute the forces pressing the cylinder with a relative error below 1%     

An experimental investigation of capillary breakup of a liquid metal jet

The limits of influence of oxidation on the capillary breakup of a liquid metal jet is investigated. It is shown that in a region of weak oxidation the disruption of the jet proceeds as is usual for a Newtonian fluid.Translated from Inzhenerno-fizicheskii Zhurnal, Vol. 60, No. 4, pp. 554–557, April, 1991.     

低温绝热气瓶真空丧失后内容器热流场分析

建立了真空丧失后低温液体在金属表面上的核态沸腾模型,并用于计算液氮充满率为90%的175L立式低温绝热气瓶真空丧失后容器内的液体流动、传热及沸腾过程.研究表明,真空丧失后液体温度出现明显分层,且温度分层的方向会随着时间的增加而发生变化;容器内液体在整个容器内形成环状自然循环,而沸腾产生的汽泡主要集中在近壁区和气液界面.     

Laminar flow of a liquid in a rotating cylinder in a gravitational field

The laminar flow of a viscous liquid in a vertical rotating cylinder is studied.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 54, No. 2, pp. 198–202, February, 1988.     

Stokes flow past a smooth cylinder

Summary Ranger's solution of the two-dimensional Stokes flow past a smooth body is analyzed in detail. The body can be made convex or concave depending on the choice of its two parameters and concavity is found to be necessary but not sufficient for separation to occur. A relationship exists between the formation of a Stokesian wake and the curvature at the concave end of the body. Particular attention is given to the case when the body degenerates to a circular arc. The two-dimensional Stokes flow past a circular arc is strikingly similar to the axisymmetric Stokes flow past a spherical cap.     

Steady magnetohydrodynamic flow past a circular cylinder

The steady two-dimensional, viscous, electrically conducting flow around a circular cylinder is investigated. The flow and magnetic field are uniform and parallel at large distances from the cylinder. The equations and boundary conditions are derived for arbitrary values of R, R_mand β, where R is the Reynolds number, R_m the magnetic Reynolds number and β, the ratio of the square of the Alfvén speed to the square of the main stream speed. Because of the large number of parameters involved, the numerical solution is restricted to R = 40, R_m = 1 and infinity and 0 ? β ? 4. Also the cylinder is taken to be a perfect conductor, this avoids having to compute the magnetic field within the cylinder. The numerical computations for the non-magnetic case, i.e. β = 0, are presented and are found to be in good agreement with existing results. The effect of increasing the strength of the magnetic field (i.e. increasing β) on the drag coefficient, the size and position of the standing vortex and the increasing effect of the upstream propagation of disturbances are examined.     

Steady viscous flow past a tapered cylinder

The three-dimensional nature of the viscous flow past a linearly tapered circular cylinder is examined at low Reynolds numbers. The numerical solution of the unsteady Navier–Stokes equations converges to a steady state. The primary flow in planes perpendicular to the cylinder axis is practically indistinguishable from the two-dimensional flow past a uniform cylinder. A secondary spanwise flow is observed in the stagnation zone going from the wide end towards the narrow end, whereas a secondary motion on the rear side goes in the opposite direction. In spite of this secondary flow, the length of the separation zone varies linearly with the local Reynolds number.     

Uniform shear flow past a circular cylinder

Summary This paper solves the two-dimensional problem of the unsteady shear flow of a viscous incompressible fluid past a circular cylinder. The flow is calculated using two methods. The first takes the form of a double series solution where an expansion is carried out in powers of the time, t, and in powers of the parameter where R is the Reynolds number. This approximate analytical solution is valid for small times following the start of the motion and for large Reynolds numbers. The second method involves a spectral-finite difference procedure for numerically integrating the full Navier-Stokes equations expressed in terms of a stream function and vorticity. Our results demonstrate that for small times and moderately large R the two methods of solution are in good agreement. Results are presented for a wide range of Reynolds numbers. Comparisons with previous studies are also carried out and discussed.     

Stability of viscous flow past a circular cylinder

A spectral method which employs trigonometric functions and Chebyshev polynomials is used to compute the steady, incompressible laminar flow past a circular cylinder. Linear stability methods are used to formulate a pair of decoupled generalized eigenvalue problems for the growth of symmetric and asymmetric (about the dividing streamline) perturbations. We show that, while the symmetric disturbances are stable, the asymmetric perturbations become unstable at a Reynolds number about 40 with a Strouhal number about 0.12. The critical conditions are found to depend on the size of the computational domain in a manner similar to that observed in the laboratory.     

Steady flow of a power-law fluid past a cylinder

Summary Considered in this paper is the two-dimensional steady flow of a power-law fluid past a stationary circular cylinder. The governing nonlinear equations, expressed in terms of a stream function and vorticity, were solved by finite differences for Reynolds numbers (based on the radius of the cylinder)R=5,20, 40 for various power-law indices,n. Parameters such as the drag coefficient, separation angle, wake length and critical Reynolds number are presented and contrasted with those of a Newtonian fluid (n=1) to illustrate the non-Newtonian effects. For a given-Reynolds number a consistent behaviour withn was observed in the parameters for the ranges considered. The results obtained for the Newtonian case agree well with documented results.     

Bimetallic cylinder in a pulsed magnetic field

The magnetic field diffusion into a bimetallic cylinder comprising a central rod and the outer shell made of different conducting materials is analytically described. In the case of an external field pulse representing a half-wave B _e = B _msin(πt/T), the cylinder exhibits delamination, which is caused by the shell expansion under the action of a residual magnetic field present in its internal cavity. The pressure of this residual field nonmonotonically depends on the conductivity of the rod.     

Turbulent pipe flow of electrically conducting liquid in longitudinal magnetic field in the region of hydrodynamic stabilization

Numerical simulation is performed of turbulent pipe flow in the vicinity of entry to longitudinal magnetic field. Use is made of the model of turbulence developed by the present author and previously employed for performing calculations in the region of stabilized flow and heat transfer. 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 the hydraulic drag coefficient and longitudinal component of velocity vector.     

The initial oscillatory flow past a circular cylinder

This paper presents results obtained from an initial approximation for the flow around a circular cylinder in two-dimensional oscillating flow. The analysis is developed in terms of the scalar vorticity and stream function. An expansion in powers of time from the start of the motion is obtained using an exact analysis which extends the results of boundary-layer theory by taking into account corrections for finite Reynolds number. The time development of the physical properties of the flow are determined both by means of analytical expressions and by an accurate numerical procedure. The surface pressure, drag and surface vorticity are calculated and various estimates of the time of separation and the distance moved in this time are obtained. The phenomenon of steady streaming is not considered in this paper since the time of validity of the expansions is small. The agreement between the analytical and numerical results at small times is excellent.     

An experimental investigation of dynamic crack growth past a stiff inclusion

The mechanics of transient crack growth past stiff inclusions embedded in a relatively compliant matrix are studied optically under stress wave dominant loading conditions. An ultra high-speed rotating mirror-type CCD digital camera is used to record gray scales in the crack–inclusion vicinity at rates of up to 300,000 frames per second and 1000 × 1000 pixel resolution in real time. By analyzing the images before and after deformations, crack-tip deformation histories from the time of impact up to complete fracture are mapped and fracture parameters are extracted. The effects of inclusion–matrix adhesion strengths (weak and strong) and eccentricity of the inclusion relative to the crack path in the crack-tip vicinity are examined. A weakly bonded inclusion attracts and traps a dynamically growing mode-I crack momentarily whereas the same is deflected away by the inclusion if it is bonded strongly to the matrix. As a result, significantly higher re-initiation crack velocities are seen in weakly bonded inclusion cases upon re-initiation when compared to the strongly bonded counterparts. The effective stress intensity factor histories extracted from measured full-field displacements show a spike in values corresponding to higher crack velocities. Further, crack-tip mode-mixities correlate well with crack attraction and deflection mechanisms. The measured surface roughness is found to be consistently higher for weakly bonded inclusion specimens compared to the strongly bonded ones.     

Shear flow past a square cylinder near a wall

A numerical study on the wake behind a square cylinder placed parallel to a wall has been made. The cylinder is considered to be within the boundary layer of the wall, so that the outside flow is taken to be due to uniform shear. Flow has been investigated in the laminar Reynolds number (based on the cylinder height) range. The interaction of wall boundary layer on the vortex shedding at Reynolds number up to 1400.0 has been investigated for cylinder to wall gap height 0.5 and 0.25 times the cylinder height. The gap flow between the cylinder and wall during a period of vortex shedding has been obtained. The governing unsteady Navier–Stokes equations are discretised through the finite volume method on staggered grid system. An algorithm SIMPLE has been used to compute the discretised equations iteratively. Our results show that at the gap height 0.5 times the cylinder height the vortex shedding occurs at a Strouhal number greater than for an isolated cylinder. Vortex shedding suppression occurs and wake becomes steady up to a certain value of Reynolds number at gap height 0.25 time the cylinder height. At higher Reynolds number the formation of a single row of negative vortices behind the cylinder when it is in close proximity to wall is noteworthy. Due to the shear, the drag experienced by the cylinder is found to decrease with the reduction of gap height.     

The longitudinal electrical conductivity of metal matrix composites at cryogenic temperature in the presence of a longitudinal magnetic field

In this paper we use the results of Part I to derive two integral expressions for the electrical conductivity of metal matrix composite materials when a magnetic field, B, is added to a small electric field also parallel to fibres. One expression applies to strong magnetic fields meaningR ₀/a < 1, whereR ₀ =m ^* v _F/eB when the Fermi velocity is perpendicular to the magnetic field. WhenB , the integral expression reduces to the well known conductivity value = ₀(1 -V _f), where ₀ is the bulk matrix conductivity andV _f is the fibre volume fraction. For weak magnetic fields,R ₀/a > 1, then the electrical conductivity is expressed by the sum of two integrals. When B 0, the electrical conductivity reduces to the integral expression obtained in our earlier results when there is only a longitudinal electric field. In this paper we correct an incorrect derivation of the composite conductivity in the absence of a magnetic field published earlier [J. Mater. Sci.21 (1986) 2409].     

Wall effects on separation of flow past a circular cylinder

Abstract

The nature of the flow past a circular cylinder has been a classical problem, raising many questions concerning the various wake phenomena that have been observed. This study focused on the critical Reynolds number for the onset of the recirculation region for a flow restricted in a channel. The influence of the bounded walls is examined. The trend is that larger critical Reynolds numbers are accomplished with larger values of blockage ratio (defined as the ratio of cylinder diameter to the channel width). Furthermore, as the blockage ratio tends to zero, the trend seems to imply that the critical Reynolds number approaches the experimental value for flows in an unbounded domain.     

Free-surface flow of liquid oxygen under non-uniform magnetic field

The paramagnetic property of oxygen makes it possible to control the two-phase flow at cryogenic temperatures by non-uniform magnetic fields. The free-surface flow of vapor-liquid oxygen in a rectangular channel was numerically studied using the two-dimensional phase field method. The effects of magnetic flux density and inlet velocity on the interface deformation, flow pattern and pressure drop were systematically revealed. The liquid level near the high-magnetic channel center was lifted upward by the inhomogeneous magnetic field. The interface height difference increased almost linearly with the magnetic force. For all inlet velocities, pressure drop under 0.25 T was reduced by 7–9% due to the expanded local cross-sectional area, compared to that without magnetic field. This work demonstrates the effectiveness of employing non-uniform magnetic field to control the free-surface flow of liquid oxygen. This non-contact method may be used for promoting the interface renewal, reducing the flow resistance, and improving the flow uniformity in the cryogenic distillation column, which may provide a potential for enhancing the operating efficiency of cryogenic air separation.     

A new branch of instability of the magnetohydrodynamic Poiseuille flow in a longitudinal magnetic field

We have studied the stability of the flow of a conducting viscous fluid in a flat channel in the presence of a longitudinal magnetic field. A new branch of instability has been found and a jumplike change in the critical Reynolds number has been observed.