共查询到12条相似文献,搜索用时 15 毫秒
1.
Xuecheng Wu Kefa Cen Zhongyang Luo Qinhui Wang Mengxiang Fang 《Experiments in fluids》2008,45(6):1117-1128
When a two-dimensional (2D) imaging system is used to visualize particle motion in a 3D gas–solid flow, the particle rotation
speed was found extremely difficult to be accurately measured due to the fact that the direction of rotation axis was usually
random and hard to be distinguished. The paper presents a method to calculate the particle rotation speed from particle images
based on the identification of its rotation axis using two or more characteristic points on its surface. The idea was analyzed
and realized in a mathematical way and based on which a calculation program was given. The measurement method was verified
with an experiment using a small sphere with known rotation axis and rotation speed. The effects of several factors, including
the direction of the particle rotation axis, the particle image resolution, the types and positions of characteristic points,
etc., on the measurement error are discussed. The error is found to be acceptable for most cases. The measurement method was
finally applied to those small glass beads in a real 3D gas–solid flow inside a cold circulating fluidized bed (CFB) riser,
which indicates that the problems of 2D imaging system applying to 3D particulate system could be solved by using this mathematical
method. 相似文献
2.
The present research experimentally studied the effect of pipe rotation on the flow patterns of downward gasliquid two-phase flow. Two-phase flow patterns and their transition boundaries were observed and analyzed at different pipe revolutions. The experimental setup was fabricated to show flow patterns in a downward direction. The setup includes a transparent vertical pipe with a diameter of 50 mm and an aspect ratio (L/d) of 80 that can rotate at different speeds. Eight flow maps were obtained at revolutions of 0, 60, 120, 180, 240, 300, 400 and 500 rpm by changing the air and water velocities at any revolution (a total of 2205 points). The gasliquid downward two-phase flow regimes were analyzed using image processing. The experimental results were compared with published flow maps for vertical flow. It was found that pipe rotation has major effect on flow patterns map and their transitions boundaries. Increasing pipe rotation cause slug and annular flow start at lower VSG. 相似文献
3.
《ournal of non Newtonian Fluid Mechanics》1999,84(1):45-64
A study is carried out for the flow of viscoelastic fluid contained between a stationary inner sphere and a rotating outer sphere. A sequence of flow transitions that is unique to viscoelastic fluids is observed in the experiments. It is found that a `traveling cell', with roll-cell-like characteristics, is generated in the polar region, and then propagates toward the equatorial region when a dimensionless parameter (a measure of strength of the elasticity against the shear viscosity) is increased. In order to investigate the structure and mechanism of the traveling cell, a numerical analysis is performed using a constitutive equation of the Giesekus model. Results of the numerical simulation revealed that the elasticity of the fluid strongly influences the flow in the polar region, where the inertia effect of the outer sphere rotation is minimal, destabilizing the flow forming a pair of weak vortices at the polar region. It was further shown that the pair travel toward the equatorial region in a different manner depending upon the speed of rotation. 相似文献
4.
5.
This paper deals with the problem of combined (forced and natural) convection from a horizontal cylinder performing oscillating
rotary motion in a quiescent fluid of infinite extent. While forced convection is caused by cylinder oscillation, the natural
convection is caused by the buoyancy driven flow. The heat transfer process is governed by Rayleigh number, Ra, Reynolds number,
Re, and the dimensionless frequency of oscillation, S. The study covers Ra up to 103, Re up to 400 and S up to 0.8. The results showed that, for the same Ra, the time-averaged rate of heat transfer lies in between two limiting
values. The first, is the steady state heat rate due to natural convection from a fixed cylinder and the second is the steady
state heat rate from a cylinder rotating steadily at a speed equal to the maximum speed of rotational oscillation. The smaller
the value of Re the nearer the time-averaged Nusselt number to that of fixed cylinder at the same Ra and the higher Re the
lower the average Nusselt number. The effect of frequency is only limited to changing the amplitude of the fluctuating Nusselt
number.
Received on 15 December 1997 相似文献
6.
《Comptes Rendus de l'Académie des Sciences》2001,329(5):351-356
A homogeneous and isotropic turbulence is suddenly subjected to a rigid body rotation, whose influence on the turbulent vorticity field is studied. It is shown that only the odd statistical moments are influenced by the rotation at the first order in time. This effect is shown in particular for triple correlations and should be more important for a small Rossby number. 相似文献
7.
Sergey V. Ershkov 《Archive of Applied Mechanics (Ingenieur Archiv)》2014,84(3):385-389
A new exact solution of Euler’s equations (rigid body dynamics) is presented here. All the components of angular velocity of rigid body for such a solution differ from both the cases of symmetric rigid rotor (which has two equal moments of inertia: Lagrange’s or Kovalevskaya’s case), and from the Euler’s case when all the applied torques are zero, or from other well-known particular cases. The key features are the next: the center of mass of rigid body is assumed to be located at meridional plane along the main principal axis of inertia of rigid body, besides, the principal moments of inertia are assumed to satisfy to a simple algebraic equality. Also, there is a restriction at choosing of initial conditions. Such a solution is also proved to satisfy to Euler–Poinsot equations, including invariants of motion and additional Euler’s invariant (square of the vector of angular momentum is a constant). So, such a solution is a generalization of Euler’s case. 相似文献
8.
The propagation of plane waves in fibre-reinforced, rotating thermoelastic half-space proposed by Lord-Shulman is discussed.
The problem has been solved numerically using a finite element method. Numerical results for the temperature distribution,
the displacement components and the thermal stress are given and illustrated graphically. Comparisons are made with the results
predicted by the coupled theory and the theory of generalized thermoelasticity with one relaxation time in the presence and
absence of rotation and reinforcement. It is found that the rotation has a significant effect and the reinforcement has great
effect on the distribution of field quantities when the rotation is considered. 相似文献
9.
Control of the flow around a circular cylinder is studied using Large Eddy Simulation. The influence of control by rotation and suction on the flow characteristics is considered for several Reynolds numbers. Comparisons with experiments were conducted at for the flow with and without control. A drag reduction up to 30% is obtained for an usual suction intensity. To cite this article: G. Fournier et al., C. R. Mecanique 333 (2005). 相似文献
10.
The time integration of strain rate tensor is a central problem in large transformations even if it is often an underlying one. The cumulated tensorial strains, obtained by the time integration of strain rate tensor , allow the tackling of this problem from a geometrical point of view, and independently of material behaviour considerations. The time integration here takes place in the local objective frame defined by the logarithmic spin proposed by Lehmann et al. and Xiao et al. The numerical results obtained in a closed deformation path are presented here. The advantages and drawbacks of this novel integration for the development of behaviour laws are described. To cite this article: V. Mora et al., C. R. Mecanique 332 (2004). 相似文献
11.
12.
《International Journal of Plasticity》1995,11(1):119-144