Effect of the Coriolis force on the onset of convection in a layer with a fixed heat flux on the boundaries

The effect of the Coriolis force on the onset of convection in a plane horizontal layer of viscous fluid with a fixed heat flux on the rigid lower and free upper boundaries is investigated. Expressions for the critical Rayleigh numbers and wave number are obtained analytically in the rapid rotation limit.Perm'. Translated from Izvestiya Rossiiskoi Akademii Nauk, Mekhanika Zhidkosti i Gaza, No. 3, pp. 42–46, May–June, 1994.     

Investigation of the effect of the Coriolis force on a thin fluid film on a rotating disk

The effect of the Coriolis force on the evolution of a thin film of Newtonian fluid on a rotating disk is investigated. The thin-film approximation is made in which inertia terms in the Navier–Stokes equation are neglected. This requires that the thickness of the thin film be less than the thickness of the Ekman boundary layer in a rotating fluid of the same kinematic viscosity. A new first-order quasi-linear partial differential equation for the thickness of the thin film, which describes viscous, centrifugal and Coriolis-force effects, is derived. It extends an equation due to Emslie et al. [J. Appl. Phys. 29, 858 (1958)] which was obtained neglecting the Coriolis force. The problem is formulated as a Cauchy initial-value problem. As time increases the surface profile flattens and, if the initial profile is sufficiently negative, it develops a breaking wave. Numerical solutions of the new equation, obtained by integrating along its characteristic curves, are compared with analytical solutions of the equation of Emslie et al. to determine the effect of the Coriolis force on the surface flattening, the wave breaking and the streamlines when inertia terms are neglected.     

Two-layer turbulent flow over a rough rotating surface

A model of turbulent incompressible fluid flow over a rough surface under the action of the Coriolis force with a turbulent transfer coefficient corresponding to the Prandtl mixing length is proposed. A solution of the problem, asymptotic in the small Coriolis parameter, is presented for horizontally uniform steady-state flow. It is shown that for a small Coriolis parameter the velocity profile and the turbulent transfer coefficient can differ substantially from the limiting expressions known from Prandtl theory. The smaller the roughness coefficient, the greater the difference.Moscow. Translated from Izvestiya Rossiiskoi Akademii Nauk, Mekhanika Zhidkosti i Gaza, No. 4, pp. 61–67, July–August, 1995.     

Vortex intensification in convective cells

The intensification of single vortices in convective flows swirled by the Coriolis force is studied numerically. The initial disturbances, specified against the background of a steady cell, are coaxial with the cell flow and have various swirl directions, intensities, and dimensions. It is shown that the vortices are intensified no matter whether the direction of disturbing vortex rotation is co- or counter-directional with the Coriolis force. If the disturbance intensity is small as compared with that of the convective-cell flow, the growth of the azimuthal velocity circulation in the perturbing vortices depends linearly on their initial circulation. For such vortices, the energy increase is proportional to the characteristic vortex radius to the power –5/3.Translated from Izvestiya Rossiiskoi Academii Nauk, Mekhanika Zhidkosti i Gaza, No. 5, 2004, pp. 62–68. Original Russian Text Copyright © 2004 by Ivanov and Povarnitsyn.     

MODEL VERIFICATION ON 3D TIDAL CURRENT ANALYSIS IN TOKYO BAY

The results of a research project to verify the newly improved multiple- level model for 3D tidal current analysis in Tokyo Bay are presented. The improved multiple-level model includes additional effects due to Coriolis force, river inflows and wind shear stresses. Furthermore, a new numerical treatment of the open boundary condition was applied which effectively eliminated the spurious reflective waves often generated by various numerical methods simulating free surface flows. The mean (time-averaged or residual) and tidal currents in Tokyo Bay were simulated as examples to demonstrate the validity and capability of the newly improved multiple-level model. A series of numerical experiments was conducted to carefully examine the tidal circulations affected by the forcing factors of Coriolis force, river inflows and wind shears, both individually and combined. The numerical results demonstrated that the effects of each forcing term are physically reasonable, with the wind shear effect being the most significant and the case including all forcing terms being in best overall agreement with the field data collected in Tokyo Bay by the Ministry of Transportation. This study has contributed not only to the verification of the newly improved multiple-level model but also to the enhancement of the accuracy of numerical simulations of three-dimensional flow in coastal waters by this model.     

Effect of the coriolis force on convection in a deep lake: Numerical experiment

Convection in a deep lake at temperatures close to the temperature of maximum density (TMD) is studied on the basis of a quasi-two-dimensional nonhydrostatic model of hydrothermodynamics with allowance for the compressibility of water. The rotation of the Earth is accounted for in the model by two components of the Coriolis force. Convection in deep lakes is influenced by the fact that theTMD is found to be dependent on pressure and salinity. Results are compared from three numerical experiments: without allowance for the Coriolis force, and with one and two Coriolis parameters. The results demonstrate the substantial effect of the Coriolis force, which shows the need to account for it in modeling convective processes in natural objects. Computer Center, Siberian Division, Russian Academy of Sciences, Novosibirsk 630090. Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, No. 4, pp. 127–134, July–August, 1998.     

On the dynamical structure of the wind field of Jupiter's Great Red Spot

Based on the geographic approximation the two-dimensional dynamical structure of the wind fields of Jupiter's Great Red Spot and White Oval BC is obtained. The results of calculation are in good agreement with the observations. Thus, an explanation of the observed dispersion of the velocities along the horizontal streamline is given. The major physical mechanism of this dispersion is as follwos: The distance between two adjacent elliptical streamlines varies along the elliptical streamline, leading to the variance of the normal pressure gradient. Thus, the horizontal velocity V_t has to vary correspondingly so that the Coriolis force can approximately balance the normal pressure gradient Another less important factor, i. e., the change of the Coriolis force parameter with the latitude, is also taken into account.The distributions of the vorticities of GRS and White Oval BC are also calculated.     

Effect of flow contraction on the level of turbulence

The results of an experimental investigation of the effect of flow contraction in the convergent nozzle of a subsonic wind tunnel on the level of turbulence are reported. The method of conducting the experiments and analyzing the data, which makes it possible to eliminate the effect of secondary factors on the results, is explained.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 2, pp. 146–152, March–April, 1987.     

风力机叶片的三维非定常气动特性估算

结合动量-叶素理论、非定常空气动力和动态失速模型来计算风力机叶片的二维非定常气动特性,并在此基础上经过适当修正后考虑三维旋转效应的非定常气动特性。分析比较二维和三维两种计算结果,给出更为合理的计算叶片非定常气动特性的方法。计算结果表明,风力机叶片的三维非定常气动特性计算结果与二维时的计算结果相比有较大改善。     

Experimental study of the effect of riblets and LEBU-devices on the drag of a body of revolution

The effect of ribbed coatings and large-eddy-breakup devices (LEBUs) on the turbulent friction and total drag of a body-of-revolution model has been studied in a low-speed wind tunnel.Moscow. Translated from Izvestiya Rossiiskoi Akademii Nauk, Mekhanika Zhidkosti i Gaza, No. 3, pp. 154–157, May–June, 1996.     

ON THE DYNAMICAL STRUCTURE OF THE WIND FIELD OF JUPITER''''S GREAT RED SPOT

Based on the geographic approximation the two-dimensional dynamical structure of the wind fields of Jupiterls Great Red Spot and White Oval BC is obtained. The results of calculation are in good agreement with the observations. Thus, an explanation of the observed dispersion of the velocities along the horizontal streamline is given. The major physical mechanism of this dispersion is as follwos: The distance between two adjacent elliptical streamlines varies along the elliptical streamline; leading to the variance of the normal pressure gradient. Thus, the horizontal velocity V_T has to vary correspondingly so that the Coriolis force can approximately balance the normal pressure gradient Another less important factor, i.e., the change of the Coriolis force parameter with the latitude, is also taken into account. The distributions of the vorticities of GRS and White Oval BC are also calculated.     

风暴潮流运动的数值模拟

采用风暴潮全流运动方程组,对标准海域的风暴潮流运动进行数值模拟,利用以往的计算结果验证了数值模式,研究了开阔海域中,风暴气压、海域深度及底坡变化对风暴增水及流场的影响,分析了流速、潮位随时间和空间定量变化的规律。所建立的数值模型是进一步研究风暴潮流场中物质输运的基础。     

Dispersed phase motion in laminar boundary layer flow over a wedge

The motion of a dispersed phase in the laminar boundary layer on a wedge is considered with allowance for the effect of not only the Stokes force, which coincides in direction with the flow velocity, but also the transverse force (Saffman force) resulting from the transverse nonuniforrnity of the flow over the individual particle [1–3].Translated from Izvestiya Rossiiskoi Akademii Nauk, Mekhanika Zhidkosti i Gaza, No.6, pp. 34–42, November–December, 1993.In conclusion, the authors wishes to thank S. V. Manuilovich for assisting with the numerical calculations.     

Heat transfer in rotating cylindrical cells with partitions

A numerical analysis and an experimental study of heat transfer rate in rotating cylindrical cells with partitions are performed. The work is done mainly in the Ekman suction regime, where the Coriolis force dominates over centrifugal buoyancy. It is shown that the heat transfer rate increases substantially by placing partitions in the cell. The partitions suppress the Coriolis force so that convection induced by the centrifugal buoyancy becomes important. It is found that the Nusselt number correlates with the parameter PrβΔTEk^?1/2 with the partitions. The partitions have no effect on the heat transfer in the centrifugal buoyancy convection regime.     

Motion of a suspension in the laminar boundary layer on a flat plate

The boundary layer motion of a weak suspension is investigated with allowance for the effect on the particles not only of the Stokes force but also of the additional transverse force resulting from the transverse nonuniformity of the flow over the individual particle. As distinct from studies [1–3], in which the limiting values of the transverse force (Saffman force) were used [4], the velocity and density of the dispersed phase have been determined with allowance for the dependence of the Saffman force on the ratio of the Reynolds numbers calculated from the velocity of the flow over the individual particle and the transverse velocity gradient of the undisturbed flow, respectively [5, 6].Translated from Izvestiya Rossiiskoi Akademii Nauk, Mekhanika Zhidkosti i Gaza, No. 1, pp. 66–73, January–February, 1992.In conclusion the authors wishes to thank M. N. Kogan, N. K. Makashev, and A. Yu. Boris for useful discussions of the results.     

Experimental investigation of the separation of flow around a sphere

The results of an experimental investigation of the flow around a sphere over a broad range of Mach numbers M=0.3–3 and Reynolds numbers Re=3·10⁴–3·10⁷ are presented. The experiments were carried out on a ballistic test stand and in a wind tunnel. Flow patterns and pressure distributions were obtained. In particular, the effect of the Mach and Reynolds numbers on the position of the separation point and the edge shock was studied; the pressure distribution on the sphere was measured; and a nonmonotonic displacement of the flow separation point upon passage through the speed of sound was established.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 1, pp. 152–156, January–February, 1991.     

Effect of dust content of the flow on test results in hypersonic wind tunnels

The nature and character of the effect of dust content of the working flow of hypersonic wind tunnels on the results of aerodynamic tests are considered. It is shown that dustiness causes an increase of the drag of slender models and, conversely, a decrease of the drag and damping coefficient of the longitudinal moment of blunt models.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 4, pp. 187–189, July–August, 1970.     

Effect of the deformation in the inertia forces on the inverse dynamics of planar flexible mechanical systems

The inverse dynamics problem for articulated structural systems such as robotic manipulators is the problem of the determination of the joint actuator forces and motor torques such that the system components follow specified motion trajectories. In many of the previous investigations, the open loop control law was established using an inverse dynamics procedure in which the centrifugal and Coriolis inertia forces are linearized such that these forces in the flexible model are the same as those in the rigid body model. In some other investigations, the effect of the nonlinear centrifugal and Coriolis forces is neglected in the analysis and control system design of articulated structural systems. It is the objective of this investigation to study the effect of the linearization of the centrifugal and Coriolis forces on the nonlinear dynamics of constrained flexible mechanical systems. The virtual work of the inertia forces is used to define the complete nonlinear centrifugal and Coriolis force model. This nonlinear model that depends on the rate of the finite rotation and the elastic deformation of the deformable bodies is used to obtain the solution of the inverse dynamics problem, thus defining the joint torques that produce the desired motion trajectories. The effect of the linearization of the mass matrix as well as the centrifugal and Coriolis forces on the obtained feedforward control law is examined numerically. The results presented in this investigation are obtained using a slider crank mechanism with a flexible connecting rod.     

Resistance of rough plates in a rotating fluid

Generalizing Navier’s partial slip condition, the flow due to a rough or striated plate moving in a rotating fluid is studied. It is found that the motion of the plate, the fluid surface velocity, and the shear stress are in general not in the same direction. The solution is extended to the case of finite depth, or Couette slip flow in a rotating system. In this case an optimum depth for minimum drag is found. The solutions are also closed form exact solutions of the Navier–Stokes equations. The results are fundamental to flows with Coriolis effects.     

Thrust and slip of a track determined by the compression–sliding approach

Driving gear of a vehicle (here a track) generates thrust as a reaction to the opposite force taken by the ground. This force causes rearward soil deformation, which is associated with vehicle slippage. The presented compression–sliding (CS) approach, based on field measurements with the original double plate (DP) meter, states that the soil deformation as a consequence to the increasing thrust occurs in two principal stages: (a) primary horizontal soil compression, which steadily increases towards the back of the contact length forming virtual soil segments among neighboring grousers and (b) secondary slide of these sheared off segments referred to as soil blocks, which may collapse under specific conditions. These two stages are separated by a transient situation when both the compression and sliding occur simultaneously.The respective compression–sliding (CS) approach enables to analyze the effect of track arrangement, design and loading on its thrust–slip characteristics. The paper also deals with situation of the existing shear plane theory in view of the CS approach and finally suggests a practical thrust–slip function complying with the CS logic.