Nonstationary spherical wave diffraction by a circular cylinder in a fluid

Institute of Mechanics, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Prikladnaya Mekhanika, Vol. 25, No. 6, pp. 3–9, June, 1989.     

Motion of a circular cylinder near a vertical wall

We consider the arbitrary motion of a circular cylinder in an ideal fluid near a vertical wall. This problem is usually solved in the approximate formulation with a degree of error which is difficult to assess, increasing with approach of the cylinder to the wall [1, 2], The exact solution has previously been carried out only for the case of purely circulatory flow about the cylinder [3].     

Effect of irregular gravitational waves on a vertical circular cylinder

We examine the question of three-dimensional irregular waves acting on a vertical circular cylinder. Pilings in the form of circular cylinders are used as support elements for such hydrotechnical structures as offshore piers and stationary moorings.A theoretical-empirical approach to the solution of the problem for the action of swells was developed in [1].The account for irregularity is based on the hypotheses which are adopted in spectral theory of waves. Examples are presented for particular cases of the sea-state spectral density.     

Combined convection on a vertical slender cylinder in a micropolar fluid

An analysis is presented for the steady state mixed convective boundary layer flow of a micropolar fluid along vertical slender cylinders. The governing equations have been solved numerically. Results for the friction factor, Nusselt number as well as the details of flow and temperature fields are displayed for a range of values of the transverse curvature and material parameters for the micropolar fluid. It is observed that micropolar fluids display drag reduction as well as heat transfer rate reduction when compared to Newtonian fluids.

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Mischkonvektion an einem senkrechten schlanken Zylinder in einem mikropolaren Fluid

Zusammenfassung Die Untersuchung bezieht sich auf stationäre Mischkonvektion in der Grenzschicht einer mikropolaren Flüssigkeit entlang eines senkrechten schlanken Zylinders. Die bestimmenden Gleichungen wurden numerisch gelöst. In einem gewissen Bereich des Krümmungsverhältnisses und der Stoffparameter des mikropolaren Fluids werden Ergebnisse für den Widerstandsbeiwert, die Nusselt-Zahl sowie Besonderheiten des Strömungs- und Temperaturfeldes mitgeteilt. Wie sich zeigte, weisen mikropolare Fluide gegenüber Newtonschen Fluiden sowohl geringeren Widerstand als auch niedrigere Wärmeübertragungsintensität auf.

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FVM与LBM分区耦合模拟圆柱绕流

构造了用于模拟远场边界下圆柱绕流的有限容积法(FVM)与格子Boltzmann方法(LBM)的分区耦合模型.模型中,靠近圆柱处采用多块网格的LBM,远离圆柱处采用FVM,并将计算结果同适体网格LBM以及多块网格LBM进行了比较.结果表明,耦合模型能在保证计算精度的前提下,显著提高计算效率.     

Flow of non-Newtonian fluid contained in a fixed circular cylinder due to the longitudinal oscillation of a concentric circular cylinder

Summary The flow of a Reiner-Rivlin fluid between two coaxial porous circular cylinders has been studied. The inner cylinder performs a steady oscillation while the outer one is fixed.The exact solution of this problem has been obtained and approximate solutions for the two extreme cases, very small and very high frequencies, have been derived.     

AN ANALYTICAL SOLUTION OF SECOND－ORDER WAVE FORCE ON A VERTICAL CIRCULAR CYLINDER

ＡＮＡＮＡＬＹＴＩＣＡＬＳＯＬＵＴＩＯＮＯＦＳＥＣＯＮＤ－ＯＲＤＥＲＷＡＶＥＦＯＲＣＥＯＮＡＶＥＲＴＩＣＡＬＣＩＲＣＵＬＡＲＣＹＬＩＮＤＥＲＺｈｏｕＺｈｉ－ｌｉ（邹志利）（ＤａｌｉａｎＵｎｉｖｅｒｓｉｔｙｏｆＴｅｃｈｎｏｌｏｇｙ,Ｄａｌｉａｎ）Ｄａｉ...     

Nonlinear problem of a circular cylinder rising vertically to an interface between liquid media

The nonlinear initial-boundary-value problem of a contour approaching an interface between two liquid media is considered. A solution is constructed using a previously developed numerical method that is based on reducing the original problem to a system of integrodifferential equations for singularities simulating liquid and rigid boundaries and a function that describes the interface between the media. Calculation results for the perturbations generated by a circular cylinder approaching a free surface are presented. The dependences of the flows obtained and the hydrodynamic characteristics of the contour on the Froude number are estimated. Omsk Branch of the Sobolev Institute of Mathematics, Siberian Division, Russian Academy of Sciences, Omsk 644099. Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 41, No. 2, pp. 84–89, March–April, 2000.     

The effect of air-water interface on the vortex shedding from a vertical circular cylinder

The flow past an interface piercing circular cylinder at the Reynolds number Re=2.7×10⁴ and the Froude numbers Fr=0.2 and 0.8 is investigated using large-eddy simulation. A Lagrangian dynamic subgrid-scale model and a level set based sharp interface method are used for the spatially filtered turbulence closure and the air-water interface treatment, respectively. The mean interface elevation and the rms of interface fluctuations from the simulation are in excellent agreement with the available experimental data. The organized periodic vortex shedding observed in the deep flow is attenuated and replaced by small-scale vortices at the interface. The streamwise vorticity and the outward transverse velocity generated near the edge of the separated region, which enforces the separated shear layers to deviate from each other and restrains their interaction, are primarily responsible for the devitalization of the periodic vortex shedding at the interface. The lateral gradient of the difference between the vertical and transverse Reynolds normal stresses, increasing with the Froude number, is the main source of the streamwise vorticity and the outward transverse velocity at the interface.     

Deformation by the external flow of the surface of a magnetic fluid covering a circular cylinder

As one of the methods of controlling separation of a flow and reducing hydrodynamic resistance in flow round the body, [1] proposes covering the surface of the body with a layer of magnetic fluid maintained by a inhombgeneous field. The effectiveness of the method is studied in the example of flow rounda circular cylinder covered with a uniform layer of a magnetic fluid the surface of which is also assumed to be cylindrical and not dependent on the external flow. The resistance of the cylinder falls (if the viscosity of the magnetic fluid is not too high) and can be greatly reduced. It is of interest to determine the nature of the deformation produced in the surface of the magnetic fluid by the external flow, since the degree to which the boundary can be deformed determines whether the proposed method can be realized in practice. Moreover, the magnitude of the deformation evidently affects the resistance of the cylinder and determines the limits of the applicability of the approximation adopted in [1] for the nondeformed state of the surface.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 1, pp. 28–31, January–February, 1988.     

Natural convection of a viscoplastic fluid in vertical circular channels

In contrast to a Newtonian fluid, a viscoplastic fluid can be in a state of mechanical equilibrium when heat is supplied from the side. Therefore, natural convection in a viscoplastic fluid heated from the side occurs only when the determining parameters exceed certain threshold values. The threshold conditions for the onset of convection for a flat vertical layer have been investigated several times [1–4]. The present paper is an investigation of the conditions of occurrence of plane-parallel natural convection of a viscoplastic fluid in regions with cylindrical symmetry: in a vertical annular layer and in a vertical circular tube.     

The indentation of a Newtonian fluid in a finite cylindrical container by a right circular cylinder

The indentation of the free surface of a Newtonian fluid in a finite cylindrical container by a right circular cylinder is considered. It is assumed that weight and inertia effects are negligible compared to viscous effects. A finite difference technique is used to obtain approximate values for initial velocities, pressures, and stresses at any point in the fluid as well as an estimate of the force required to indent the fluid with a given velocity. The solution obtained forms the basis for a primary indenter viscometer for very viscous fluids which have viscosities in the range of 10⁴–10¹⁰ poises.     

SH波入射时垂直半空间中双相介质界面附近圆孔的动力分析

利用复变函数和Green函数法研究了垂直半空间中双相介质界面附近圆孔对SH波的散射与动应力集中问题。该问题的解答采用镜像法,首先构造出含有圆孔的直角平面区域出平面问题的Green函数,然后利用契合技术,并根据界面处位移连续性条件将解答归结为具有弱奇异性的第一类Fredholm积分方程组的求解,结合散射波的衰减特性,直接离散该方程组,把积分方程组转化为线性代数方程组可得到该问题的数值结果。最后,通过算例分析了圆孔的动应力集中情况。结果表明,与全空间中界面附近圆孔对SH波的散射相比,由于垂直半空间自由边界的存在,孔边动应力集中系数明显增大;另外,入射波由硬介质(波速大)进入到软介质(波速小)时,与均匀介质相比,孔边动应力集中更显著,最不利的参数组合,孔边动应力集中系数几乎提高了一倍,入射波由软介质进入到硬介质时,情况相反。     

Heat transfer in a second-order fluid for flow around a circular cylinder

The temperature distribution within the thermal boundary layer region due to the flow of an incompressible second-order fluid around a heated circular cylinder, maintained at a constant temperature higher than that of the fluid at infinity, has been obtained near the forward stagnation point by series expansion. The graph of the Nusselt number Nu for the Prandtl number P = 25 and the Eckert number E = 0.1 indicates that the non-Newtonian effect is to increase the heat flux from the cylinder to the liquid in the region 0° ? θ ? 15.7° and to decrease it in the region 15.7° < θ ? 0₀ where θ is the angular distance on the cylinder measured from the forward stagnation point. The critical point θ₀ at which Nu = 0, that is, where the effect of the frictional heating balances the effect of the temperature difference and there is no heat flux either from the cylinder or from the liquid, shifts towards the forward stagnation point with the increase of non-Newtonian effects.     

A note on the unsteady flow of a fractional Maxwell fluid through a circular cylinder

In this note the velocity field and the adequate shear stress corresponding to the unsteady flow of a fractional Maxwell fluid due to a constantly accelerating circular cylinder have been determined by means of the Laplace and finite Hankel transforms.The obtained solutions satisfy all imposed initial and boundary conditions.They can easily be reduced to give similar solutions for ordinary Maxwell and Newtonian fluids.Finally,the influence of pertinent parameters on the fluid motion,as well as a comparison between models,is underlined by graphical illustrations.     

Incompressible fluid flow past a circular cylinder with linear relation between the vorticity and the stream function

Incompressible fluid flow with a linear relationship between the vorticity and the stream function past a circular cylinder is studied.Vortical flows about profiles have been considered in several studies [1–15], but in all these studies with the exception of [15] a constant vorticity was assumed (in [15] an approximate solution is found of the problem of incompressible fluid flow about a Zhukovskii profile with parabolic distribution of the velocities in the approaching stream).A freestream velocity profile similar to that considered below occurs, for example, in a planar jet (laminar or turbulent), in the wake behind a bluff body, in the boundary layer along an infinite plane [4,13], in turbulent jet flows with reverse fluid currents [16]. A similar situation also arises in the flow past an array of cylinders with large spacing which is located in the wake of another array.The author wishes to thank V. E. Davidson for posing the problem and for guidance in its solution.