可压缩液体汽车减振器装置研究

对一种新型可压缩液体汽车减振器的基本结构和工作原理进行了分析，给出其内特性的数学模型．指出可压缩液体减振器由于腔内充满可压缩液体，其动作连续可靠，其外特性不会发生高频高速畸变，并提供了该减振器外特性试验．

可压缩液体反后坐装置的原理和应用

可压缩液体反后坐装置利用硅油(Dow corning 10cs)作为驻退液,这种液体在35MPa压力下相对体积压缩量为(3～4)%。因此该液体既能流过流液孔产生液压阻力消耗后坐能量,又能利用自身的可压缩性存储部份后坐能量,供火炮复进使用。所以这种反后坐装置可以省去复进机,使结构简单紧凑,动作可靠,并使后坐阻力的峰值大大减小,在一定程度上减小了后坐阻力。本文介绍了可压缩液体反后坐装置的发展现状,工作原理,典型结构和在一般后坐火炮和前冲火炮中的应用,并讨论了该技术的应用前景。

可压缩液体汽车减振器的基本结构和工作原理

对一种新型可压缩液体汽车减振器的基本结构和工作原理进行了分析,给出其内特性的数学模型。指出可压缩液体减振器由于腔内充满可压缩液体,其动作连续可靠,其外特性不会发生高频高速畸变。并提供了该减振器外特性试验。

可压缩液体中球形泡壁运动的研究

液体中气(或汽)泡在变压力场中的生长与崩溃现象导致固体材料的剥蚀,并向外辐射出强烈的空化噪声.研究泡的运动机制是一项重要的工作,文献[1]中介绍了几种泡壁运动方程式,基于不可压流体假设的Rayleigh 方程在大的泡壁运动马赫数下是不适用的,Gilmore 方程中对可压缩性的影响作了考虑.Lastman & Wentzell 作了进一步研究,指出Gilmore 方程在大马赫数场合的应用中存在问题,因此,关于可压缩性的处理还存在争议.

可压缩液体汽车减振器的动态特性分析和研究

对一种新型可压缩液体汽车减振器的基本结构和工作原理进行了详细分析 ,给出其内特性的数学模型 ,提供了该减振器外特性试验数据。可压缩液体减振器由于腔内充满可压缩液体 ,其动作连续可靠 ,增强了外特性的抗畸变能力。

可压缩液体反后坐装置液压阻力仿真研究

根据某火炮力学特性设计了一种可压缩液体反后坐装置,结构简单紧凑、动作可靠。采用某二甲基硅液作为驻退液,既能产生液压阻力消耗后坐动能,又能利用可压缩性储存部分能量以供火炮复进使用。针对基于一维准定常流动假设的液压阻力计算模型存在较大局限及误差的问题,建立三维双向流固耦合模型,对反后坐装置后坐复进过程中复杂流场性质及结构场动态特性进行了数值仿真,得到了内部流场及结构场相关数据并绘出液压阻力曲线,试验结果表明,上述法能够较真实地描述可压缩液体反后坐装置的工作特性,为进一步研究结构优化和故障分析提供了有效途径。

旋成体高速入水可压缩性影响研究

针对目前高速(≥100 m/s)跨水-气体界面多相流数值模拟中空化效应和水介质可压缩性影响等问题,建立一套高速入水数值模拟方法。以旋成体为计算模型,采用剪应力传递(SST)k-ω、标准(Standard)k-ε、重整化群(RNG)k-ε及可实现(Realizable)k-ε4种湍流模型进行数值模拟,得到速度衰减与入水深度随时间变化的结果及入水1 ms时的空泡形态,并与理论解比较。基于SST k-ω湍流模型与文献[15,17]实验开展对比研究,选取入水速度50 m/s、100 m/s、200 m/s、400 m/s、800 m/s进行计算。研究结果表明:采用SST k-ω湍流模型的数值模拟结果与理论解一致性最好,入水速度衰减、空泡发展与实验结果基本一致,证明该方法的有效性;在入水速度≤100 m/s时,液体可压缩性对入水冲击载荷基本没有影响;在入水速度≥200 m/s时,随着入水速度增加,液体可压缩性对入水冲击载荷影响越大,会弱化入水冲击载荷及延缓最大载荷出现的时间;在考虑液体可压缩性时,空泡形态有收缩现象;入水速度越大,入水过程速度衰减越快,加速度值在入水初期较大;在计算模型周围被超空泡包裹的航行阶段,随着入水深度增加,加速度逐渐减小,加速度的变化逐渐平缓。

火炮液体式复进机可行性研究

目前火炮复进机利用弹簧和气体作为储能介质。为减小复进机体积和质量,提出了一种利用可压缩液体作为储能介质的液体式复进机结构,并分析了其力学特性。依托某型火炮,给出了液体式复进机代替液气式复进机的设计方案,仿真结果证明了其可行性。

Analysis of semi-solid response under rapid compression tests using multi-scale modelling and experiments

Simulating semi-solid metal forming requires modelling semi-solid behaviour.However, such modelling is difficult because semi-solid behavior is thixotropic and depends on the liquid-solid spatial distribution within the material.In order to better understand and model relationships between microstructure and behavior, a model based on micromechanical approaches and homogenisation techniques is presented.This model is an extension of a previous model established in a pure viscoplastic framework to account for elasticity.Indeed, experimental load-displacement signals reveal the presence of an elastic-type response in the earlier stages of deformation when semi-solids are loaded under rapid compression.This elastic feature of the behaviour is attributed to the response of the porous solid skeleton saturated by incompressible liquid.A good quantitative agreement is found between the elastic-viscoplastic predicted response and the experimental data.More precisely, the strong initial rising part of the load-displacement curve, the peak load and the subsequent fall in load are well captured.The effect of solid fraction on mechanical response is in qualitative agreement with experiments.

ASTUDYONTHEDEVELOPMENTOFTHENUMERICALMETHODTOTRACKTHEMULTI┐FREESURFACESINLIQUID┐GASPHASEFLOW

This paper is concerned with a remedy for interface smearing,which is usable when fixed (i.e. non moving and so non conforming) grids are employed. It is simple to employ and has been found to be rather effective. The paper explains its principle, describes how it has been implemented and presents some results obtained with its assistance. The results are compared both with those of earlier methods of interface motion calculation and with experimental data.

Response of Microscopic Bubbles to Sudden Decrease of Ambient Pressure in Viscous Compressible Liquid

A shock tube is used to investigate the bubble dynamics under sudden decrease of ambient pressure. Both the oscillating and monotonously growl bubbles were simultaneously observed. Theoretical approach is based, on the Rayleigh-Plesset and Herring’s equations for incompressible and compressible liquids, respectively. Considering the linear approximation of these equations for the quasiequllibrium state, two critical Weber numbers are defined. They enable one to predict the following modes of the bubble expansion: (i) unbounded growth, (ii) asymptotic growth to limited volume and (iii) attenuated oscillations, depending on the pressure force, viscosity and compressibility of the liquid.

Simulating coupled dynamics of a rigid-flexible multibody system and compressible fluid

As a subsequent work of previous studies of authors, a new parallel computation approach is proposed to simulate the coupled dynamics of a rigid-flexible multibody system and compressible fluid. In this approach, the smoothed particle hydrodynamics(SPH) method is used to model the compressible fluid, the natural coordinate formulation(NCF) and absolute nodal coordinate formulation(ANCF) are used to model the rigid and flexible bodies, respectively. In order to model the compressible fluid properly and efficiently via SPH method, three measures are taken as follows. The first is to use the Riemann solver to cope with the fluid compressibility, the second is to define virtual particles of SPH to model the dynamic interaction between the fluid and the multibody system, and the third is to impose the boundary conditions of periodical inflow and outflow to reduce the number of SPH particles involved in the computation process. Afterwards, a parallel computation strategy is proposed based on the graphics processing unit(GPU) to detect the neighboring SPH particles and to solve the dynamic equations of SPH particles in order to improve the computation efficiency. Meanwhile, the generalized-alpha algorithm is used to solve the dynamic equations of the multibody system. Finally, four case studies are given to validate the proposed parallel computation approach.

On the global existence of weak solutions for the Cucker-Smale-Navier-Stokes system with shear thickening

We study the large-time dynamics of Cucker-Smale(C-S)flocking particles interacting with nonNewtonian incompressible fluids.Dynamics of particles and fluids were modeled using the kinetic Cucker-Smale equation for particles and non-Newtonian Navier-Stokes system for fluids,respectively and these two systems are coupled via the drag force,which is the main flocking(alignment)mechanism between particles and fluids.We present a global existence theory for weak solutions to the coupled Cucker-Smale-Navier-Stokes system with shear thickening.We also use a Lyapunov functional approach to show that sufficiently regular solutions approach flocking states exponentially fast in time.

Global existence for slightly compressible hydrodynamic flow of liquid crystals in two dimensions

In two dimensions, we study the compressible hydrodynamic flow of liquid crystals with periodic boundary conditions. As shown by Ding et al. （2013）, when the parameter λ→∞ oo, the solutions to the compressible liquid crystal system approximate that of the incompressible one. Furthermore, Ding et al. （2013） proved that the regular incompressible limit solution is global in time with small enough initial data. In this paper, we show that the solution to the compressible liquid crystal flow also exists for all time, provided that is sufficiently large and the initial data are almost incompressible.

Spherically Symmetric Solutions to Compressible Hydrodynamic Flow of Liquid Crystals in N Dimensions

The paper is concerned with the system modeling the compressible hydrodynamic flow of liquid crystals with radially symmetric initial data and non-negative initial density in dimension N(N ≥ 2).The authors obtain the existence of global radially symmetric strong solutions in a bounded or unbounded annular domain for any γ > 1.