Precession Vibrations of the Two-Blade Rotor with the Elastic Weightless Shaft in Compound Rotation

The problem of precession vibrations of the rigid two-blade rotor with the elastic weightless shaft in compound rotation, when its axis executes an additional forced slew, was stated. The equations of vibrations of the system were derived, their periodic solutions for the case of steady motion were found at different values of the angular velocity of its own rotation. The resonance value of this velocity was determined, the amplitude-frequency characteristics in the pre- and postresonance states were plotted.     

Behavior of a Light Solid in a Rotating Horizontal Cylinder with Liquid Under Vibration

Dynamics of a cylindrical body in a rotating cavity is experimentally studied under transversal translational vibrations of the cavity rotation axis. Experiments are run at high rotation rate, when under the action of centrifugal force the body shifts to the rotation axis (the centrifuged state). In the absence of vibrations, the lagging rotation of the body is observed, due to the body radial shift from the axis of rotation caused by gravity. The body average rotation regime depends on the cavity rotation rate. The vibrations lead to the excitation of different regimes of body differential rotation (leading or lagging) associated with the excitation of its inertial oscillations. The dependence of the differential speed of the body rotation on the vibration frequency is investigated. The body dynamics has a complex character depending on the dimensionless vibration frequency. The analysis of body oscillation trajectory revealed that the body oscillatory motion consists of several modes, which contribute to the averaged dynamics of the body and the flows in the cavity.     

The vibration of rotating elastic membrane cylinders

Using membrane theory we first investigate the finite deformation of a right circular cylinder of compressible hyperelastic material rotating about its axis. A necessary and sufficient condition for axial shortening to accompany rotation is given. Secondly we consider small amplitude vibrations propogating on such a finitely deformed cylindrical membrane. The same equations are shown to govern both the compressible and incompressible cases. For axi-symmetric vibrations analytical results are obtained and are used to show that neither pure torsional nor pure longitudinal vibrations can propagate in a rotating cylinder. Numerical results are given for a variety of different forms of vibration for a particular realistic material model.     

Vortex configurations in a freely rotating superfluid drop

The equilibrium configurations of a single vortex in a freely rotating superfluid drop have been determined. The potential barrier to vortex nucleation has also been examined. A freely rotating drop is constrained to rotate at a fixed angular momentum, as opposed to fluid in a rotating vessel, where the vessel is usually constrained to rotate at fixed angular velocity. Vortex configurations that minimize the free energy have been found for a range of angular momenta. These configurations are not necessarily on the axis of rotation as is the case for a vessel rotating at a constant angular velocity. The nucleation of a vortex is shown to be opposed by a barrier in the free energy. This barrier narrows and decreases in height as the angular momentum of the drop is increased.     

Onset of vorticity in a rotating annulus of helium II

We present measurements of the critical angular velocity for the onset of vorticity in a rotating annulus. The measurements of the critical velocity were made over a temperature range from 1.5 to 2.165 K, and are consistently lower than theoretical predictions by about 20%. Nor do our results agree within experimental uncertainty with previous measurements of the critical velocity in an annulus. It appears that the discrepancies can be explained by the presence and growth of high concentrations of residual vorticity which prevent the system from achieving the lowest free energy state. We find that vorticity perpendicular to the axis of rotation grows as the angular velocity is increased and that the axial mutual friction coefficientB″ is 0.     

单轴气浮台低速自由转动规律分析

 根据单轴气浮台的结构及工作原理,通过对单轴气浮台核心部件静压气体轴承摩擦力矩和功率的分析,得出单轴气浮台的摩擦力矩和功率;在此基础上推导出单轴气浮台在不计外界空气阻尼条件下的低速自由转动规律,即单轴气浮台旋转的角速度及转速是一个随时间衰减的单指数函数;并通过运用Matlab曲线拟合工具箱将实验采集到的离散数据进行曲线拟合,结果表明：拟合曲线完全符合单轴气浮台低速自由转动规律.该规律对单轴气浮台的设计有一定的参考价值.     

Calculation of the thermodynamic parameters of helium in a centrifugal force field

The design of cooling systems for a cryoalternator's superconducting field windings must be based on the knowledge of the distribution of the thermodynamic parameters (primarily temperature) of the helium in both its liquid and gaseous phases in centrifugal force fields. This paper proposes a set of ordinary differential equations describing the distributions. By numerically solving the set, the effects of the angular velocity of rotation, filling factor and temperature (pressure) at the axis of rotation upon the pressure, temperature and density distributions in helium in rotating vessels have been studied. Formulee for the approximation of the distributions have been obtained, which are applicable to rotation axis temperatures from 3 to 4.6 K (corresponding to saturation pressures 0.24 × 10⁵ to 1.4 × 10⁵ Pa), angular velocities of rotation from 50 to 300 rad s^?1 and filling factors from 0.1 to 0.9.     

Influence of variations in the angular rotational velocity of a spacecraft on thermal convection under conditions of weightlessness

Unlike the conventional approach where it is assumed that liquid motion under conditions of weightlessness is caused by vibrations or residual quasisteady-state microaccelerations, the present paper examines convection caused by variations in the angular rotational velocity of a spacecraft. It is shown that although the level of microaccelerations caused by variations in the angular rotational velocity is extremely low for the Shuttle spacecraft, Mir space station, and unmanned spacecraft, of the order of 0.1–1 μg, the ensuing convection and nonuniformity in the impurity distribution during crystal growth may be very appreciable. Pis’ma Zh. Tekh. Fiz. 23, 6–13 (December 26, 1997)     

Measurement of viscoplastic properties of a liquid in experiments with a torsion viscosimeter

The results of a numerical solution of the problem of vibrations of a torsion viscosimeter filled with an incompressible viscoplastic liquid are presented. It has been shown that in the vicinity of the rotation axis there appears a dead zone, whose boundary changes in the process of vibrations. The influence of plastic properties of the liquid on the characteristics of viscosimeter vibrations has been determined. A method for identifying viscoplastic properties by the observed parameters of vibrations is proposed. __________ Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 80, No. 1, pp. 124–127, January–February, 2007.     

Calculation of the helium thermodynamic state in rotating cryostats

The present paper contains basic essential data for the design of rotating cryostats. The effect of the filling factor, angular velocity of rotation, reduced temperature at the axis of rotation and the method of helium supply to a rotating cryostat on temperature, pressure and density distribution is discussed. The maximum sub-cooling and distance from the axis of rotation at which the critical pressure is reached is studied theoretically. For vapour phase quasi-saturation there is a good agreement between the calculated data on temperature distribution and the experimental results available.     

微机电数字地震检波器设计及误差标定补偿方法

研制一种新型数字硅MEMS地震检波器,集成三支硅MEMS陀螺与加速度计,可提供三维加速度、速度、角速度及位移等振动信息,可提高检波器的信息量及效率;提出的基于无需指北单轴速率转台的硅MEMS地震检波器六位置正反速率标定方法,不仅可提高标定精度与效率,且可减小标定工作量。并经实验验证该数字硅MEMS地震检波器样机及标定补偿方法的可行性与适用性。     

Flow past an accelerated horizontal plate in a rotating fluid

Summary A semi-infinite mass of an incompressible viscous fluid bounded by an infinite flat plate is initially rotating with uniform angular velocity about an axis normal to the plate. An analysis is presented for the subsequent flow when the plate started impulsively from rest relative to the rotating fluid moves with uniform acceleration in its own plane. It is found that when 0, the velocity profiles for varying times are nonsimilar in contrast to the velocity profiles which are similar in the absence of rotation (=0). At a given instant, the velocity component along the direction of motion of the plate decreases with an increase in rotation but the transverse velocity component (induced by the Coriolis force) increases with increasing rotation. Due to the gradual thinning of the boundary layer with rotation, both the skin-friction components along and transverse to the direction of motion of the plate increase with increasing rotation. A study of the asymptotic behavior of the velocity field for large time reveals a novel feature of the flow; it develops inertial oscillations with frequency 2, which grow with time. This behavior has not been reported in the absence of rotation.     

Vibrations of a rotating flexible rod clamped off the axis of rotation

Summary We consider a fourth-order boundary value problem associated with the small vibrations of a uniform flexible rod which is clamped at one end and rotates in a plane perpendicular to the axis of rotation. A significant feature is that the axis of rotation does not pass through the clamped end itself. For rapid rotation rates, the governing equation involves a small parameter and must be treated by singular perturbation techniques. A second parameter fixes the relative location of two turning points. For a range of this second parameter, consistent approximations to the characteristic equation are derived, and the limiting behavior of the eigenvalues is obtained.     

Analysis and design of a CMOS angular velocity- and direction-selective rotation sensor with a retinal Processing circuit

This paper implements and analyzes a CMOS angular velocity- and direction-selective rotation sensor with a retinal processing circuit. The proposed rotation sensor has a polar structure and is selective of the angular velocity and direction (clockwise and counterclockwise) of the rotation of images. The correlation-based algorithm is adopted and each pixel in the rotation sensor is correlated with the pixel that is 45/spl deg/ apart. The angular velocity selectivity is enhanced by placing more than one pixel between two correlated pixels. The angular velocity selectivity is related to both the number and the positions of the edges in an image. Detailed analysis characterizes angular velocity selectivity for different edges. An experimental chip consisting 104 pixels, which form five concentric circles, is fabricated. The single pixel has an area of 91/spl times/84/spl mu/m/sup 2/ and a fill factor of 20%, whereas the area of the chip is 1812/spl times/1825/spl mu/m/sup 2/. The experimental results concerning the fabricated chip successfully verified the analyzed characteristics of angular velocity and direction selectivity. They showed that the detectable angular velocity and range of illumination of this rotation sensor are from 2.5/spl times/10/sup -3/ /spl pi//s to 40 /spl pi//s and from 0.91 lux to 366 lux, respectively.     

Statistical description of a turbulent gas suspension flow of large particles colliding with channel walls

Based on the particle distribution density function method over space, velocity, and angular rotational velocity, a closed system of equations for the first and second moments of the fluctuations of the characteristics of the particles and boundary conditions representing the process of the loss of momentum and onset of rotation of the particles caused by collisions with walls are found.     

Effects of Hall currents and Coriolis force on Hartmann flow under general wall conditions

Summary The influence of Hall currents and rotation on a generalized Hartmann flow and heat transfer is investigated. The channel is rotating with a constant angular velocity around an axis perpendicular to the walls in a uniform transverse magnetic field. The walls may have the same thickness, electrical and thermal conductivity as well as Hall parameter or different ones. The flow may be driven either by a pressure gradient or by motion of one of the walls. Exact solutions are derived for the velocity, magnetic field, viscous stress, current density, temperature distribution, yield components, electric current components, mean temperature as well as Nusselt numbers. Representative numerical results are presented in diagrams and effects of different parameters are discussed.     

Thermo-mechanical vibration analysis of rotating nonlocal nanoplates applying generalized differential quadrature method

In this study, thermal and small-scale effects on the flapwise bending vibrations of a rotating nanoplate, which can be the basis of nano-turbine design, have been analyzed. The nano-turbine is made of an orthotropic nanoplate with a setting angle that is modeled based on the classical plate theory (CPT) with cantilever boundary conditions. The axial forces are also included in the model as the true spatial variation due to the rotation and temperature change. The governing equations and boundary conditions are derived according to Hamilton's principle and the governing equations are solved with the aid of the generalized differential quadrature method. The effects of small-scale parameter, nondimensional angular velocity, temperature change, and setting angles in the first four nondimensional frequencies are discussed. Due to the consideration of the rotating effects, results of this study are applicable in nano-machines, such as nano-motors, nano-rotor, and other rotating nano-structures. Also, by considering the effect of thermal loading on rotation of a nanoplate, the results are useful in the design of nano-turbines.     

The Density Difference of Cupula and Endolymph Changes the Mechanics of Semicircular Canals

A precise balance of cupula and endolymph densities is key to the proper sensing of angular acceleration by the semicircular canals (SC). Estimates show that a density difference of cupula and endolymph (DD) as small as ~10^− 4 g/cm³ is sufficient to make the SC sensitive to gravity and centrifugal forces provided they are comparable with gravity. As a result this might cause vestibular disorders. There are conditions under which the DD may even exceed this value. One of them is a change of intra-labyrinth pressure (IP) that may take place during a spaceflight. Here, the effect of DD on SC dynamics is considered using a simplified one-dimensional toroidal mathematical model of a canal for rotation with constant or harmonically oscillating angular velocities. The DD results in: dependence of cupula dynamics on orientation of both the gravity vector relative to the SC plane and the axis of rotation, as well as on the distance between the axis of rotation and the center of SC; shift of the cupula to a new position of equilibrium that depends on both the gravity vector and the parameters of head rotation; and onset of cupula oscillations with multiple frequencies under harmonic stimulation. The DD effect may be important under conditions of artificial gravity where the directions of centrifugal forces, the values of which are comparable with Earth’s gravity, the orientations of the axis of rotation of a space station, and the axes of the SCs change during movements of the individuals and their habitat.     

Vibration and buckling of rotating flexible rods at transitional parameter values

Summary We consider the connection between vibration and buckling problems for a uniform flexible rod which is clamped at one end and rotates in a plane perpendicular to the axis of rotation. The rod is assumed off-clamped, i.e. the axis of rotation does not pass through the rod's clamped end. The resulting fourth-order boundary value problem with a turning point for the free vibrations is solved using uniform approximations in a transitional parameter range where high rotation rates balance small off-clampings. Second approximations to the vibration eigenvalues are used to determine critical buckling rotation rates for the slightly off-clamped rods. Buckling is unexpected in this situation as the rod is wholly under tension.     

NMR studies on vortices in rotating3He-A

NMR measurements are reported on rotating³He-A in a long cylindrical geometry of 5 mm diameter at a liquid pressure of 29.3 bar and in axial magnetic fields of 14.2, 28.4, and 56.9 mT. At 28.4 mT, NMR studies are also reported in fields inclined by 25° and 90° from the axis of rotation. The frequency shift, the width, and the intensity of the spin wave modes localized on the soft vortex cores, as well as the additional broadening of the main NMR line during rotation, were measured as a function of temperature, angular velocity , magnetic field intensity, and its inclination angle. Also observed were a critical angular velocity of vortex formation, hysteretic behavior in the number of vortices when comparing accelerating rotation to decelerating, and metastable vortex densities, presumably a vortex tangle after rapid oscillatory acceleration. The results can be understood in terms of the continuous 4 vortices first proposed by Seppälä and Volovik.