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1.
The effects of elastic anisotropy in piping materials on fluid–structure interaction are studied for water-filled carbon-fiber reinforced thin plastic pipes. When an impact is introduced to water in a pipe, there are two waves traveling at different speeds. A primary wave corresponding to a breathing mode of pipe travels slowly and a precursor wave corresponding to a longitudinal mode of pipe travels fast. An anisotropic stress–strain relationship of piping materials has been taken into account to describe the propagation of primary and precursor waves in the carbon-fiber reinforced thin plastic pipes. The wave speeds and strains in the axial and hoop directions are calculated as a function of carbon-fiber winding angles and compared with the experimental data. As the winding angle increases, the primary wave speed increases due to the increased stiffness in the hoop direction, while the precursor wave speed decreases. The magnitudes of precursor waves are much smaller than those of primary waves so that the effect of precursor waves on the deformation of pipe is not significant. The primary wave generates the hoop strain accompanying the opposite-signed axial strain through the coupling compliance of pipe. The magnitude of hoop strain induced by the primary waves decreases with increasing the winding angle due to the increased hoop stiffness of pipe. The magnitude of axial strain is small at low and high winding angles where the coupling compliance is small. 相似文献
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Two long tubes each of aluminum and polymethyl methacrylate, with two different wall thicknesses, were subjected to transverse impact by two different steel spheres when in an empty or a fluid-filled condition. Water and a high-density electric capacitor liquid were emplaced in the interior, usually under stationary, but occasionally under streaming, conditions. Input-force history and response of the system at two gage stations involving single axial and hoop, as well as coupled symmetric and antisymmetric strain histories, were recorded from the response of strain gages, while fluid pressures were measured by means of small tourmaline crystals suspended at the tube center line. The effect of parameter variation in input and system material and geometry on these quantities was studied. The measured signal speed and frequency of the breathing mode of the system were compared with corresponding analytical predictions. 相似文献
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In simulations of propagating blast waves the effects of artificial reflections at open boundaries can seriously degrade the accuracy of the computations. In this paper, a boundary condition based on a local approximation by a plane traveling wave is presented. The method yields small artificial reflections at open boundaries. The derivation and the theory behind these so-called plane-wave boundary conditions are presented. The method is conceptually simple and is easy to implement in two and three dimensions. These non-reflecting boundary conditions are employed in the three-dimensional computational fluid dynamics (CFD) solver FLACS, capable of simulating gas explosions and blast-wave propagation in complex geometries. Several examples involving propagating waves in one and two dimensions, shock tube and an example of a simulation of a propagating blast wave generated by an explosion in a compressor module are shown. The numerical simulations show that artificial reflections due to the boundary conditions employed are negligible. © 1998 John Wiley & Sons, Ltd. 相似文献
5.
The formation of a secondary shock wave behind a shock wave diffracting at a convex corner 总被引:3,自引:0,他引:3
This paper deals with the formation of a secondary shock wave behind the shock wave diffracting at a two-dimensional convex
corner for incident shock Mach numbers ranging from 1.03 to 1.74 in air. Experiments were carried out using a 60 mm 150 mm shock tube equipped with holographic interferometry. The threshold incident shock wave Mach number () at which a secondary shock wave appeared was found to be = 1.32 at an 81° corner and = 1.33 at a 120° corner. These secondary shock waves are formed due to the existence of a locally supersonic flow behind
the diffracting shock wave. Behind the diffracting shock wave, the subsonic flow is accelerated and eventually becomes locally
supersonic. A simple unsteady flow analysis revealed that for gases with specific heats ratio the threshold shock wave Mach number was = 1.346. When the value of is less than this, the vortex is formed at the corner without any discontinuous waves accompanying above the slip line. The
viscosity was found to be less effective on the threshold of the secondary shock wave, although it attenuated the pressure
jump at the secondary shock wave. This is well understood by the consideration of the effect of the wall friction in one-dimensional
duct flows. In order to interpret the experimental results a numerical simulation using a shock adaptive unstructured grid
Eulerian solver was also carried out.
Received 1 May 1996 / Accepted 12 September 1996 相似文献
6.
We study possible steady states of an infinitely long tube made of a hyperelastic membrane and conveying either an inviscid, or a viscous fluid with power-law rheology. The tube model is geometrically and physically nonlinear; the fluid model is limited to smooth changes in the tube’s radius. For the inviscid case, we analyse the tube’s stretch and flow velocity range at which standing solitary waves of both the swelling and the necking type exist. For the viscous case, we first analyse the tube’s upstream and downstream limit states that are balanced by infinitely growing upstream (and decreasing downstream) fluid pressure and axial stress caused by fluid viscosity. Then we investigate conditions that can connect these limit states by a single solution. We show that such a solution exists only for sufficiently small flow speeds and that it has a form of a kink wave; solitary waves do not exist. For the case of a semi-infinite tube (infinite either upstream or downstream), there exist both kink and solitary wave solutions. For finite-length tubes, there exist solutions of any kind, i.e. in the form of pieces of kink waves, solitary waves, and periodic waves. 相似文献
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This study examined the instability of mistuned tube-array structures with axial loads. The tube-array structures were used to simulate a heat exchanger. In a heat exchanger, the tubes are frequently affected by hot and cold fluid shock waves. Therefore, the tubes often wear out. This wear may affect the dynamic properties of the tubes and introduce mode localization in the system. This study examined the instability caused by mode localization in a heat exchanger. A system consisting of periodic cooling tubes was used to simulate a coupled periodic structure system. Because each tube is coupled to the adjacent tube through the water, the system can be regarded as a weakly coupled system. The equations of the mistuned system with reference to the fluid effect can be derived using the Galerkin method. The numerical results indicated that the wear may introduce mode localization and instability into a mistuned heat exchanger with fluid. 相似文献
9.
正向爆轰驱动高焓激波风洞的数值模拟 总被引:5,自引:1,他引:4
对充满氢氧可燃气体、带扩容腔的正向爆轰驱动的激波风洞进行了数值模拟。计算采用了欧拉方程,频散可控耗散差分格式(DCD)和改进的二阶段化学反应模型。在扩容腔附近采用二维轴对称计算模型,而在驱动段和被驱动段的直管道部分则采用一维计算模型。本文分析了爆轰波在管道中的传播、反射和绕射过程。计算结果表明扩容腔的尺寸对爆轰波的传播、反射、汇聚等起着决定性的作用;带扩容腔的正向爆轰驱动的激波风洞能够得到平稳的持续时间较长的气流,提高了实验的精确度和可重复性。 相似文献
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《Journal of Fluids and Structures》2007,23(1):117-142
A submerged fluid-filled circular cylindrical shell subjected to a shock wave propagating in the external fluid is considered. The study focuses on a number of acoustic and structural effects taking place during the interaction. Specifically, the influence of the acoustic phenomena in the fluid on the stress–strain state of the shell is analysed using two different visualization techniques. The effect that the parameters of the shell have on the internal acoustic field is addressed as well, and the ‘shock transparency’ of various shells is discussed. Special attention is paid to the analysis of the contribution of the terms in the shell equations representing bending stiffness, and the limits of applicability of the membrane theory of thin shells are discussed in the fluid–structure interaction context. The possibility of cavitation in the internal fluid is investigated, and the effect that cavitation could have on the structural dynamics of the shell is discussed. The present paper is a follow-up of the author's earlier study of the interaction between fluid-filled cylindrical shells and external shock waves. 相似文献
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Abstract. This paper reports on the characteristics of a compact vertical diaphragmless shock tube, which was constructed and tested
in the Shock Wave Research Center to study experimentally the behavior of toroidal shock waves. It is 1.15 m in height and
has a self-sustained co-axial vertical structure consisting of a 100 mm i.d. outer tube and an 80 mm o.d. inner tube. To create
a ring shaped shock wave between the inner and outer tubes, a rubber sheet is inserted to separate a high pressure driver
gas from a test gas, which is bulged with auxiliary high pressure helium from the behind. When the rubber membrane is contracted
by the sudden release of the auxiliary gas so as to break the seal, shock waves are formed. Special design features of the
shock tube are described and their role in producing repeatable shock waves is discussed. Its special opening characteristics
make possible the production of annular shaped shock waves that are unlikely met with a conventional tube that uses rupturing
diaphragms. Performance of the shock tube is evaluated in terms of the shock wave Mach numbers and the measured flow properties.
It eventually showed a higher degree of repeatability and the scatter in the shock wave Mach numbers Ms was found to be 0.2%
for Ms ranging from 1.1 to 1.8. The shock wave Mach number so far measured agreed very well with the simple shock tube theory.
Received 3 February 1999 / Accepted 6 April 2000 相似文献
14.
The propagation of elastic stress waves in a conical shell subjected to axial impulsive loading is studied in this paper by
means of the finite element calculation and model experiments. It is shown that there are two axisymmetrical elastic stress
waves propagating with different velocities, i.e., the longitudinal wave and the bending wave. The attenuation of these waves
while propagating along the shell surface is discussed. It is found in experiments that the bending wave is also generated
when a longitudinal wave reflects from the fixed end of the shell, and both reflected waves will separate during the propagation
due to their different velocities.
Southwest Institute of Structural Mechanics 相似文献
15.
The propagation of harmonic waves through a system formed of coaxial tubes filled with incompressible continua is considered as a model of arterial pulse propagation in the craniospinal cavity. The inner tube represents a blood vessel and is modelled as a thin-walled membrane shell. The outer tube is assumed to be rigid to account for the constraint imposed on the vessels by the skull and the vertebrae. We consider two models: in the first model the annulus between the tubes is filled with fluid; in the second model the annulus is filled with a viscoelastic solid separated from the tubes by thin layers of fluid. In both models, the elastic tube is filled with fluid. The motion of the fluid is described by the linearized form of the Navier–Stokes equations, and the motion of the solid by classical elasticity theory. The results show that the wave speed in the system is lower than that for a fluid-filled elastic tube free of any constraint. This is due to the stresses generated to satisfy the condition that the volume in the system has to be conserved. However, the effect of the constraint weakens as the radius of the outer tube is increased, and it should be insignificant for the typical physiological parameter range. 相似文献
16.
A Free-Lagrange method for unsteady compressible flow: simulation of a confined cylindrical blast wave 总被引:1,自引:0,他引:1
G. J. Ball 《Shock Waves》1996,5(5):311-325
A Free-Lagrange numerical procedure for the
simulation of two-dimensional inviscid compressible flow
is described in detail. The
unsteady Euler equations are solved on an unstructured
Lagrangian grid based on a density-weighted Voronoi mesh.
The flow solver is of the Godunov type, utilising either the
HLLE (2 wave) approximate Riemann solver or the more recent HLLC
(3 wave) variant, each adapted to the Lagrangian frame.
Within each mesh cell, conserved properties are
treated as piece-wise linear, and a slope limiter of the MUSCL type
is used to
give non-oscillatory behaviour with nominal
second order accuracy in space.
The solver is first order accurate in time.
Modifications to the slope limiter to minimise
grid and coordinate dependent
effects are described.
The performances of the HLLE and HLLC solvers are compared for
two test problems; a one-dimensional
shock tube and a two-dimensional blast wave confined
within a rigid cylinder. The blast wave is initiated by impulsive
heating of a gas column whose centreline is parallel to,
and one half of the cylinder radius from,
the axis of the cylinder.
For the shock tube problem, both solvers predict shock and expansion
waves in good agreement with theory.
For the HLLE solver, contact resolution
is poor, especially in the blast wave problem. The HLLC solver achieves
near-exact contact capture in both problems.
Received May 25, 1995 / Accepted September 11, 1995 相似文献
17.
A one-dimensional model for the numerical simulation of transport effects in small-scale, i.e., low Reynolds number, shock
tubes is presented. The conservation equations have been integrated in the lateral directions and three-dimensional effects
have been introduced as carefully controlled sources of mass, momentum and energy, into the axial conservation equations.
The unsteady flow of gas behind the shock wave is reduced to a quasi-steady flow by choosing a coordinate system attached
to the shock. The boundary layer problem is thereby reduced to a laminar solution, similar to the Blasius solution, with the
exception that the wall velocity can be nonzero. The resulting one-dimensional equations are then solved numerically using
a two-step Lax-Wendroff/ MacCormack scheme with flux correction transport. For validation purposes, comparisons are performed
against previously published shock structure and low Reynolds number shock tube experiments; good agreement is observed. The
model has been used to predict the performance of a 10μm shock tube and the result of this simulation shows the possibility
of shock wave disappearance at lower pressure ratios for a micro-scale shock tube.
相似文献
18.
Basic design scheme for wave rotors 总被引:2,自引:0,他引:2
Pressure wave devices use shock waves to transfer energy directly between fluids without additional mechanical components,
thus having the potential for increased efficiency. The wave rotor is a promising technology which uses shock waves in a self-cooled
dynamic pressure exchange between fluids. For high-pressure, high-temperature topping cycles, it results in increased engine
overall pressure and temperature ratio, which in turn generates higher efficiency and lower specific fuel consumption. Designing
a wave rotor mainly focuses on predicting the behavior of shock and expansion waves. The extant literature presents numerous
examples of wave rotor designs, but most of them rely on complicated numerical analyses as well as computer code developed
specifically for this application. This paper presents an initial scheme used for designing wave rotors employing thermodynamic
and gasdynamic analysis as well as computational fluid dynamic analysis. Basic theory and a simplified model of the wave rotor
are used to predict the travel time and strength of waves. The model is then refined using a more advanced numerical scheme
on the basis of the Lax–Wendroff method and FLUENT, a commercial CFD code.
Research was conducted while F. Iancu was a Ph.D. candidate at Michigan State University. 相似文献
Research was conducted while F. Iancu was a Ph.D. candidate at Michigan State University. 相似文献
19.
An investigation was made of the reflection of planar shock waves from cones. 86 cones, the half apex angle of which varied
from 10° to 52° at every 0.5°, were installed in a 60 mm×150 mm diaphragmless shock tube equipped with holographic interferometry.
The diaphragmless shock tube had a high degree of reproducibility with which the scatter of shock wave Mach number was within
±0.25% for shock wave Mach number ranging from 1.16 to approximately 2.0. The reflection of shock waves over cones was visualized
using double exposure holographic interferometry. Whitham's geometrical shock wave dynamics was used to analyse the motion
of Mach stems over cones. It is found that for relatively smaller apex angles of cones trajectory angles of resulting irregular
reflections coincide with the so-called glancing incidence angles and their Mach stems appear to be continuously curved from
its intersection point with the incident shock wave, which shows the chractericstic of von Neumann reflection. The domain
of the existence of the von Neumann reflection was analytically obtained and was found to be broadened much more widely than
that of two-dimensional reflections of shock waves over wedges. 相似文献
20.
薄壁圆柱壳流体冲击振动响应是一个复杂的流固耦合(FSI)动力学问题,对于薄壳状态监测与缺陷识别具有重要意义。基于Flügge壳体应力理论,得到壳体运动的高阶偏微分方程组(PDE),利用波传播方法获得圆柱壳系统振动响应。将壳体周围流体定义为理想声学介质,通过亥姆霍兹方程描述声压场,得到流固耦合条件下的薄壁圆柱壳受迫振动响应演变规律。针对薄壳裂纹损伤识别问题,基于断裂力学理论建立局部柔度矩阵,结合呼吸型线弹簧模型(LSM),构造裂纹附近应力及位移连续条件,获得含裂纹损伤充液圆柱壳的振动响应,进而给出一种基于振动能量流的裂纹损伤识别方法。研究结果表明:充液圆柱壳耦合系统在非线性激励下,位移响应在沿轴向、周向和径向的传播特性差异明显;裂纹的存在会导致结构局部柔度的降低和耦合系统固有频率下降;归一化输入功率流能够有效地对充液圆柱壳耦合系统进行结构裂纹损伤识别。研究结果可为充液薄壳振动响应方面的研究提供有益参考,也可为流固耦合条件下的结构裂纹损伤识别方面提供技术支持。 相似文献