基于高速摄像技术的流体作用力试验

针对颗粒在动水中的流体作用力问题,采用高速摄像技术对颗粒的运动过程进行观测,通过求解圆球及天然泥沙跃移运动过程中的力学方程,得到拖曳力系数及上举力系数。试验结果表明:①动水中颗粒非匀速运动时的拖曳力系数、静水中颗粒非匀速运动时的拖曳力系数与匀速运动时的拖曳力系数均随着雷诺数的增加而减小,颗粒与水流之间的相对运动速度越接近于颗粒沉速,三者间的差异越小;当颗粒与水流之间的相对运动速度等于颗粒沉速时,三者近似相等。②形状对上举力系数的影响较对拖曳力系数的影响更明显,天然泥沙的拖曳力系数大于圆球的拖曳力系数,天然泥沙的上举力系数小于圆球的上举力系数。最后,构建了圆球及天然泥沙的拖曳力系数及上举力系数公式,公式计算值与实测值符合较好。

搅拌槽内横向流体作用力特性的测试与研究

采用应变片测量技术和数据采集系统，测量了搅拌轴上端部所受的弯矩，得到了搅拌桨的流体作用力特性曲线及横向流体作用力的频谱图。

水压球阀在不同阀口形式下的流体作用力研究

针对水液压直驱球阀,研究了球阀的阀座上是否存在倒角的2种不同阀口形式对阀芯所受稳态流体作用力特性的影响;采用基于COMSOL Multiphysics的CFD仿真的方法,分别对2种阀口形式下,阀芯在不同阀口开度、不同进出口压差下所受稳态流体作用力进行了数值求解,并对比了2种阀口形式下的通流流量大小,最后,对仿真结果进行了网格无关性验证。结果表明,阀口形式不同时,阀芯所受的稳态流体作用力的大小和方向不同,阀口的通流流量不同;网格无关性验证仿真结果是可信的,此研究可用于指导直驱球阀的结构优化设计。

地震时任意截面大尺度垂直柱群上的流体作用力

大尺度垂直柱体是海洋工程结构物的一种典型结构型式。地震时它们遭受的水动作用力是抗震设计中的一个重要考虑因素。尤其当多柱共存且相距不远时,柱间的干扰将导致柱体振动时流体动力特性的改变。本文发展了地震作用下单柱振动的奇点分布法,可用于计算地震时大尺度垂直柱群振动的流体作用力,并初步探讨了柱间间距对流体作用力变化的影响。在我们的讨论中,柱的截面可以是任意的,柱与柱间截面也可以不同。

任意截面大尺度垂直柱体的波浪力和水动作用力

许多海洋工程结构物和水工结构物,如海上贮油罐、各种支墩等,具有等截面柱状体外形,或在足够精确的工程近似意义上可视为这类柱体。它们的下端固置于水底,上端穿透水面,它们的波浪载荷是设计中的一个重要考虑因素;在许多场合,它们与周围流体的耦联振动也是相当重要的。 对大尺度结构物而言,我们可在势流理论的范围内求解这一问题。通用的三维源汇分布法无疑是适用的,但对这类特殊的结构形式显得极不经济。

流体黏性对受迫振荡水平圆柱受力的影响

【目的】准确预测显著黏性效应下结构物所受流体作用力。【方法】采用有限体积(FVM)方法构建两相流数值波浪水槽模型。首先,通过半潜水平圆柱受波浪力数值结果与前人实验数据的对比,验证数值模型的准确性。其次,对不同流体黏性下,受迫振荡淹没水平圆柱上的流体作用力进行数值计算,通过黏性流结果和势流结果的对比,分析流体黏性对圆柱受力的影响特征。最后,通过将黏性流和势流理论压力结果对比,并结合对圆柱周围黏性涡量场分布特征分析,解释不同流体黏性下,黏性流与势流结果之间出现差异的原因。【结果】在不同流体黏性条件下,圆柱所受各倍频流体作用力均出现一定程度上的差别,表明流体黏性的影响明显。【结论】相比势流理论,采用黏性流理论对受迫振荡水平圆柱受力的影响的研究更为准确。

集液管及其内部导流板对旋喷泵性能的影响

为研究集液管对旋喷泵性能的影响,本文对旋喷泵内部流场进行了数值模拟,获得了整泵流道内的速度、静压强和湍动能分布。本文对比了不同流量工况下的流动参数分布特征,重点讨论了集液管及内部导流板对流动的影响及集液管受到的流体作用力。结果表明:旋喷泵转子腔内的流动参数分布规律性强,在集液管入口处及集液管内流道转弯处存在着较高的静压强梯度;未设置导流板时集液管内流体湍动能较高,但泵性能较设置导流板时高;集液管所受的流体作用力合力随流量增加而下降,其中沿泵轴的作用力分量占主导地位,加装导流板后集液管的受力略下降。

Research on Pressure Drop Performance of the Packing-Flotation Column

A packing-flotation column was proposed to optimize the flotation environment A research system was es- tablished using a 100 mm diameter cyclonic micro-bubble flotation column to study fluid properties. Dry-plate and wet- plate pressure drops were studied and the corresponding pressure drop equations developed. The results show that the dry-plate pressure drop of the packing cyclonic micro-bubble flotation column is 10–15 times less than that of the chemical tower, which is principally shown in its relatively small resistance coefficient, ξ ≈0.0207. The wet-plate pressure drop is 2–3 times higher than that of the chemical tower, which is largely caused by the separation materials and characteristics of the equipment. With flotation, the greater the pressure drop, the better the flotation environment.

Performance of dynamically loaded journal bearings lubricated with couple stress fluids considering the elasticity of the liner

To take into account the couple stress effects, a modified Reynolds equation is derived for dynamically loaded journal beatings with the consideration of the elasticity of the liner. The numerical results show that the influence of couple stresses on the bearing characteristics is significant. Compared with Newtonian lubricants, lubricants with couple stresses increase the fluid film pressure, as a result enhance the load-carrying capacity and reduce the friction coefficient. However, since the elasticity of the liner weakens the couple stress effect, elastic liners yield a reduction in the load-carrying capacity and an increase in the friction coefficient. The elastic deformation of the bearing liner should be considered in an accurate performance evaluation of the journal bearing.

A Coupled Analysis of Nonlinear Sloshing and Ship Motion

Nonlinear interactions among incident wave, tank-sloshing and floating body coupling motion are investigated. The fully nonlinear sloshing and body-surface nonlinear free surface hydrodynamics is simulated using a Non-Uniform Rational B-Spline （NURBS） higher-order panel method in time domain based on the potential theory. A robust and stable improved iterative procedure （Yan and Ma, 2007） for floating bodies is used for calculating the time derivative of velocity potential and floating body motion. An energy dissipation condition based on linear theory adopted by Huang （2011） is developed to consider flow viscosity effects of sloshing flow in nonlinear model. A two-dimensional tank model test was performed to identify its validity. The present nonlinear coupling sway motion results are subsequently compared with the corresponding Rognebakke and Faltinsen （2003）＇s experimental results, showing fair agreement. Thus, the numerical approach presented in this paper is expected to be very efficient and realistic in evaluating the coupling effects of nonlinear sloshing and body motion.

Laser Light Scattering Study on Aggregation of Cellulose Diacetate in Acetone

We have investigated the properties of cellulose diacetate in solution by using laser light scattering. The cellulose diacetate molecules can form micelles and micellar clusters in acetone besides the individual chains. As the concentration increases, the average hydrodynamic radius （Rh） linearly increases, whereas the ratio of gyration radius to hydrodynamic radins 〈Rg〉/〈Rh〉 linearly decreases. It indicates that the micelles associate and form micellar clusters due to the intermolecular interactions.

A Two-Layer Model for Superposed Electrified Maxwell Fluids in Presence of Heat Transfer

Based on a modified-Darcy-Maxwell model, two-dimensional, incompressible and heat transfer flow of two bounded layers, through electrified Maxwell fluids in porous media is performed. The driving force for the instability under an electric field, is an electrostatic force exerted on the free charges accumulated at the dividing interface. Normal mode analysis is considered to study the linear stability of the disturbances layers. The solutions of the linearized equations of motion with the boundary conditions lead to an implicit dispersion relation between the growth rate and wave number. These equations are parameterized by Weber number, Reynolds number, Marangoni number, dimensionless conductivities, and dimensionless electric potentials. The case of long waves interfaciaJ stability has been studied. The stability criteria are performed theoreticaily in which stability diagrams are obtained. In the limiting cases, some previously published results can be considered as particular cases of our results. It is found that the Reynolds number plays a destabilizing role in the stability criteria, while the damping influence is observed for the increasing of Marangoni number and Maxwell relaxation time.

A CFD Based Investigation of the Unsteady Hydrodynamic Coefficients of 3-D Fins in Viscous Flow

The motion of the fins and control surfaces of underwater vehicles in a fluid is an interesting and challenging research subject.Typically the effect of fin oscillations on the fluid flow around such a body is highly unsteady, generating vortices and requiring detailed analysis of fluid-structure interactions.An understanding of the complexities of such flows is of interest to engineers developing vehicles capable of high dynamic performance in their propulsion and maneuvering.In the present study, a CFD based RANS simulation of a 3-D fin body moving in a viscous fluid was developed.It investigated hydrodynamic performance by evaluating the hydrodynamic coefficients (lift, drag and moment) at two different oscillating frequencies.A parametric analysis of the factors that affect the hydrodynamic performance of the fin body was done, along with a comparison of results from experiments.The results of the simulation were found in close agreement with experimental results and this validated the simulation as an effective tool for evaluation of the unsteady hydrodynamic coefficients of 3-D fins.This work can be further be used for analysis of the stability and maneuverability of fin actuated underwater vehicles.

Computational Study on Interaction Between Swimming Fish and Drifting Vortices Behind the Cylinder

To predict the flow evolution of fish swimming problems,a flow solver based on the immersed boundary lattice Boltzmann method is developed.A flexible iterative algorithm based on the framework of implicit boundary force correction is used to save the computational cost and memory,and the momentum forcing is described by a simple direct force formula without complicated integral calculation when the velocity correction at the boundary node is determined.With the presented flow solver,the hydrodynamic interaction between the fish-induced dynamic stall vortices and the incoming vortices in unsteady flow is analyzed.Numerical simulation results unveil the mechanism of fish exploiting vortices to enhance their own hydrodynamic performances.The superior swimming performances originate from the relative movement between the“merged vortex”and the locomotion of the fishtail,which is controlled by the phase difference.Formation conditions of the“merged vortex”become the key factor for fish to exploit vortices to improve their swimming performance.We further discuss the effect of the principal components of locomotion.From the results,we conclude that lateral translation plays a crucial role in propulsion while body undulation in tandem with rotation and head motion reduce the locomotor cost.

CFD aided investigation of single droplet coalescence

This article describes the development of a coalescence model using various CFD work packages,and is validated using as toluene water model system.Numerical studies were performed to describe droplet interactions in liquid–liquid test systems.Current models use adjustable parameters to describe these phenomena.The research in the past decades led to different correlations to model coalescence and breakage depending on the chemical system and the apparatus geometry.Especially the complexity of droplet coalescence requires a detailed investigation of local phenomena during the droplet interaction.Computational fluid dynamics(CFD) studies of single droplet interactions were performed and validated with experimental results to improve the understanding of the local hydrodynamics and film drainage during coalescence.The CFD simulations were performed for the interaction of two differently sized droplets at industrial relevant impact velocities.The experimental verification and validation of the numerical results were done with standardized high-speed imaging studies by using a special test cell with a pendant and a free rising droplet.An experimental based algorithm was implemented in the open source code OpenF OAM to account for the contact time and the dimple formation.The standard European Federation of Chemical Engineering(EFCE) test system toluene/water was used for the numerical studies and the experimental investigations as well.The results of the CFD simulations are in good accordance with the observed coalescence behavior in the experimental studies.In addition,a detailed description of local phenomena,like film rupture,velocity gradients,pressures and micro-droplet entrainment could be obtained.

Parallel Open Source CFD-DEM for Resolved Particle-Fluid Interaction

A parallelized resolved method for the simulation of the dynamics of immersed bodies within fluids is presented. The algorithm uses a FDM （fictitious domain method） and combines the Lagrangian DEM （discrete element method） for tracking the bodies with a CFD （computational fluid dynamics） method for calculating the dynamics of the fluid phase. First the CFD-calculation is carried out, disregarding the solid bodies. Afterwards, the velocity information from the bodies is included and the force, the fluid imposes onto the bodies, is computed. The last step consists of a correction-operation which ensures the fulfillment of the conservation equation. Dynamic local mesh refinement is used for minimizing the number of fluid cells. The CFD-DEM coupling is realized within the Open Source framework CFDEMcoupling （www.cfdem.com）, where the DEM software LIGGGHTS （www.liggghts.com） is linked against an OpenFOAM^-based CFD solver. While both LIGGGHTS and the CFD solver were already parallelized, only a recent improvement of the algorithm permits the fully parallel computation of resolved problems. This parallelization permits the treatment of large-scale problems. The enclosed validation and application examples show the dynamics of the flow around settling and rotating spheres as well as an investigation of the settling of spheres regarding the Boycott effect.

Corona-Support for the Entirety of High Energetic Disk

Based on results obtained from the study for MHD （magneto-hydrodynamics） of advective accretion disk, which are applied to real source showing typical values for CBS （close binary star-system）, it will investigate on self-structuring in the disk under the impact of the distribution of leading parameters （density, velocity ...）. The paper is considering the problem of development of the corona and will analyze the process of interaction of the plasma with the magnetic field in connection to support for the instabilities.

Groundwater Dating and Its Application to Earthquake Monitoring

Monitoring and study of dynamic characteristics of groundwater are significant methods of earthquake monitoring and forecasting. For research on groundwater dynamics,groundwater dating can qualitatively and quantitatively provide scientific analysis on the characteristics of groundwater recharge and runoff as well as renewal capacity. This article illustrates the methods used globally and summarizes the main advances and achievements in groundwater dating. It also focuses on the relationships between groundwater renewal capacity and seismic monitoring,groundwater movement and seismic activity,shallow groundwater recharge and abnormal interference elimination. The studies show that groundwater dating plays an important role in water-rock interaction,and geological tectonic and seismic activity evaluation. Therefore,groundwater dating can be widely used to monitor and analyze the precursor information in seismic underground fluid observations in the near future.

对与流体压强相关的一些问题的梳理分析

本文针对中学物理教学中与流体压强相关的一些典型问题,从压强的产生机制进行相关梳理分析,同时针对流体产生的作用力作出简要说明,在此基础上对教学提出一些具体建议.

搅拌釜稳定器性能的验证实验

大中型搅拌釜如发酵罐等为了避免染菌和消毒彻底,常采用取消搅拌轴中间轴承和底部轴承,而在搅拌桨上方或下方加装稳定器的方法。本文通过实验方法验证了稳定器的稳定性能及其影响因素,推算出了搅拌轴轴端挠度与实测挠度的关系式及挠度与流体力的关系式。