Laminar flow in the gap between two rotating parallel frictional plates in hydro-viscous drive

The velocity,pressure and temperature distributions of the flow in the gap between hydro-viscous drive friction disks are the key parameters in the design of hydro-viscous drive and angular velocity controller.In the previous works dealing with the flow in the gap between disks in hydro-viscous drive,few authors considered the effect of Coriolis force on the flow.The object of this work is to investigate the flow with consideration of the effects of centrifugal force,Coriolis force and variable viscosity.A simplified mathematical model based on steady and laminar flow is presented.An approximate solution to the simplified mathematical model is obtained by using the iteration method assuming that the fluid viscosity remains constant.Then the model considering the effect of variable viscosity is solved by means of computational fluid dynamics code FLUENT.Numerical results of the flow are obtained.It is found that radial velocity profile diverges from the ideal parabolic curve due to inertial forces and tangential velocity profile is nonlinear due to Coriolis force,and pressure has two possible solution branches.In addition,it is found that variable viscosity plays an important role on pressure profiles which are significantly different from those of fluid with constant viscosity.The experimental device designed for this work consists of two disks,and one of them is fixed.Experimental pressure and temperature of the flow within test rig are obtained.It is shown that the trend of numerical results is in agreement with that of experimental ones.The research provides a theoretical foundation for hydro-viscous drive design.     

核能海水淡化源蒸汽质量流量的测量与新的密度补偿式

本采用汽液两相流均相流动的模型,分析了涡街流量计在核能海水淡化源汽的捏流量测量中的适用性,并结合低压和蒸汽的热物理性质,论述了涡街流量计测量低压饱和蒸汽质量流量的误差一蒸汽干度之间关系。给出了一个用于低压饱和蒸汽质量流量测量的变系数密度补偿式和该补偿式的特色。     

Experimental study on the vortex flow in a concentric annulus with a rotating inner cylinder

This experimental study concerns the characteristics of vortex flow in a concentric annulus with a diameter ratio of 0.52, whose outer cylinder is stationary and inner one is rotating. Pressure losses and skin friction coefficients have been measured for fully developed flows of water and of 0.4% aqueous solution of sodium carboxymethyl cellulose (CMC), respectively, when the inner cylinder rotates at the speed of 0-600 rpm. Also, the visualization of vortex flows has been performed to observe the unstable waves. The results of present study reveal the relation of the bulk flow Reynolds number Re and Rossby number Ro with respect to the skin friction coefficients. In somehow, they show the existence of flow instability mechanism. The effect of rotation on the skin friction coefficient is significantly dependent on the flow regime. The change of skin friction coefficient corresponding to the variation of rotating speed is large for the laminar flow regime, whereas it becomes smaller as Re increases for the transitional flow regime and, then, it gradually approach to zero for the turbulent flow regime. Consequently, the critical (bulk flow) Reynolds number Re_c decreases as the rotational speed increases. Thus, the rotation of the inner cylinder promotes the onset of transition due to the excitation of Taylor vortices.     

On the thermal expansion effects in the transverse direction of laminated composite plates by means of a global-local higher-order model

In this paper, a new efficient global-local higher-order model is proposed for the thermoelastic analysis of laminated composite and sandwich plates. The proposed model takes into account explicitly the contribution of thermal expansion in the transverse displacement component. To satisfy the transverse displacement continuity along the thickness direction, the continuity condition of transverse displacement at interfaces, which is not satisfied in many other schemes, has been a priori enforced. This model fully satisfies the free surface conditions and the geometric and stress continuity conditions at interfaces. As the number of variables of the proposed model is independent of the number of layers of laminates, compared to the 1,2-3 theory proposed by Li and Liu (1997) [20], the present model offers some significant improvements, and is able to predict accurately thermoelastic response of laminated plates under uniform temperature without a corresponding increase in the number of unknowns. The governing equations of equilibrium are derived by means of the principle of virtual displacements involving the thermal strain field. Applying Navier's technique, analytical solutions in terms of a double trigonometric series for simply supported laminated plates are presented. Results of benchmark examples are compared with the three-dimensional thermoelastic solutions as well as other published works. Numerical results show that the proposed model is more rigorous and can better predict the thermoelastic response in comparison with the 1,2-3 theory and other two-dimensional models.     

Micro- to macroscopic responses of a glass particle-blended polymer in the presence of an interphase layer

A multi-scale model which can be used to evaluate the interaction between a microstructure and the heterogeneous deformation behavior of ternary composites on the micro- to macroscopic scale has been developed based on the large deformation finite element homogenization method. Using four different interphases consisting of a rubber, two different types of polymer and an elastic material with intermediate stiffness of particle and matrix, the elasto-plastic behaviors of the composites have been confirmed to be markedly influenced by the interphase properties and the interphase with a stiffness well below that of the matrix shows a suitable effect on the micro- to macroscopic deformation behaviors of the composites. Therefore, a computational simulation has been performed for the present interphase to clarify the effects of the macroscopic strain ratio, interphase properties and particle volume fraction on macroscopic characteristics such as deformation resistance, elasticity modulus and yield stress, and on microscopic characteristics such as shear band pattern, mean stress in the matrix and normal stress on the particle surface. The results provide guidelines for selecting interphase properties and processing parameters to achieve desired overall composite characteristics.     

Investigation on the liquid water droplet instability in a simulated flow channel of PEM fuel cell

To investigate the characteristics of water droplets on the gas diffusion layer from both top-view and side-view of the flow channel, a rig test apparatus was designed and fabricated with prism attached plate. This experimental device was used to simulate the growth of a single liquid water droplet and its transport process with various air flow velocity and channel height. Not only dry condition but also fully humidified condition was also simulated by using a water absorbing sponge. The detachment height of the water droplet with dry and wet conditions was measured and analyzed. It was found that the droplet tends towards becoming unstable by decreased channel height, increased flow velocity or making a gas diffusion layer (GDL) dryer. Also, peculiar behavior of the water droplet in the channel was presented like attachment to hydrophilic wall or sudden breaking of droplet in case of fully hydrated condition. The simplified force balance model matches with experimental data as well.     

Experiments on the turbulent shear flow in a turn-around duct(II)—The structure of turbulence

Detailed measurements including two-component mean velocities (U andV), RMS of turbulent fluctuations (u′ andv′) and turbulent cross-correlation (uv) were made throughout a turn-around duct. Two-component velocity data were obtained using a Laser Doppler Velocimeter. With the aid of a digitized data acquisition system, energy spectra were estimated using a Fast Fourier Transform. Along the outer wall, the flow is affected more than the half across the channel height due to the centrifugal instability. The measured results are consistent with the turbulence production mechanism for stabilizing and destabilizing curved flows. Energy production and dissipation are reduced along the convex wall and amplified along the concave wall. In the quasi-laminar region, turbulent fluctuations and cross-correlations are damped. The mean flow and turbulence structure in this region are influenced mainly by the streamwise pressure gradient rather than curvature. The flow in the downstream part of the turn is dominated by the inertial effect. The turbulent large eddy motions along the concave wall are strongly anisotropic.