168 resultados para wave plate
Resumo:
An optical diagnostic system consisting of Michelson interferometer with image processor has been developed for study of the kinetics of thermal capillary convection and buoyancy convection. This optical interferometer has been used to observe and measure surface deformation and surface wave of capillary convection and buoyancy convection in a rectangular cavity with different temperature’s sidewalls. Fourier transformation is used to image processing. The quantitative results of surface deformation and surface wave have been calculated from the interference fringe pattern. With the increasing of temperature gradient, the liquid surface slant gradually. It’s deformation has been calculated, which is related directly with temperature gradient. This is one of the characters introducing convection. Another interesting phenomenon is the inclining direction, which is different when the liquid layer is thin or thick. When the liquid layer is thin, convection is mainly controlled by thermocapillary effect. However, When the liquid layer is thick, convection is mainly controlled by buoyancy effect. Surface deformation in the present experiment are more and more declining in this process. The present experiment proved that surface deformation appears before the appearance of surface wave on fluid convection, it is related with temperature gradient, and the height of liquid layer, and lies on capillary convection and buoyancy convection. The present experiment also demonstrates that the amplitude of surface wave of thermocapillary-buoyancy convection is much smaller than surface deformation, the wave is covered by deformation.
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In this paper the Deflagration to Detonation Transition (DDT) process of gaseous H-2-O-2 mixture and Mach reflection of gaseous detonation wave on a wedge have been conducted experimentally. The cellular pattern of DDT process and Mach reflection were obtained from experiments with wedge angle theta = 10(0) similar to 40(0) and initial pressure of gaseous mixture 16kPa similar to 26.7kPa. The 2-D numerical simulations of DDT process and Mach reflection of detonation wave were performed by using the simplified ZND model and improved space-time conservation element and solution element (CE/SE) method. The numerical cellular structures were compared with the cellular patterns of soot track. Compared results were shown that it is satisfactory. The characteristic comparisons on Mach reflection of air shock wave and detonation wave were carried also out and their differences were given.
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A shock tube method is introduced to study the ionization–recombination kinetics of high temperature gas, in which a test gas is heated and ionized by a reflected shock wave and subsequently quenched by a strong rarefaction wave reflected on the end wall of the driver section as the main cooling wave associated with a rarefaction wave incident back into region 5 when the reflected shock wave interacts with the contact surface. As the quenching rate of the strong rarefaction wave reaches 106 K/s, a nonequilibrium ionization-recombination process occurs, during which the ion recombination with electrons dominates.
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In this paper,focusing of a toroidal shock wave propagating from a shock tube of an- nular cross-section into a cylindrical chamber was investigated numerically with the dispersion- controlled scheme. For CFD validation, the numerical code was rst applied to calculate both viscous and inviscid ows at a low Mach number of 1.5, which was compared with the experi- ment results and got better consistency. Then the validated code was used to calculate several cases for high Mach numbers. From the result, several major factors that in uent the ow, such as the Mach number and the viscosity, were analyzed detailedly and along with the high Mach number some unusual ow structure was observed and explained theoretically
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Pressure wave refrigerators (PWR) refrigerate the gas through periodical expansion waves. Due to its simple structure and robustness, PWR may have many potential applications if the efficiency becomes competitive with existing alternative devices. In order to improve the efficiency, the characteristics of wave propagation in a PWR are studied by experiment, numerical simulation and theoretical analysis. Based on the experimental results and numerical simulation, a simplified model is suggested, which includes the assumptions of flux-equilibrium and conservation of the free energy. This allows the independent analysis of the operation parameters and design specifics. Furthermore, the optimum operation condition can be deduced. Some considerations to improve the PWR efficiency are also given.
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This paper deals with turbulence behavior inbenthalboundarylayers by means of large eddy simulation (LES). The flow is modeled by moving an infinite plate in an otherwise quiescent water with an oscillatory and a steady velocity components. The oscillatory one aims to simulate wave effect on the flow. A number of large-scale turbulence databases have been established, based on which we have obtained turbulencestatisticsof the boundarylayers, such as Reynolds stress, turbulence intensity, skewness and flatness ofturbulence, and temporal and spatial scales of turbulent bursts, etc. Particular attention is paid to the dependences of those statistics on two nondimensional parameters, namely the Reynolds number and the current-wave velocity ratio defined as the steady current velocity over the oscillatory velocity amplitude. It is found that the Reynolds stress and turbulence intensity profile differently from phase to phase, and exhibit two types of distributions in an oscillatory cycle. One is monotonic occurring during the time when current and wave-induced components are in the same direction, and the other inflectional occurring during the time when current and wave-induced components are in opposite directions. Current component makes an asymmetrical time series of Reynolds stress, as well as turbulence intensity, although the mean velocity series is symmetrical as a sine/cosine function. The skewness and flatness variations suggest that the turbulence distribution is not a normal function but approaches to a normal one with the increasing of Reynolds number and the current-wave velocity ratio as well. As for turbulent bursting, the dimensionless period and the mean area of all bursts per unit bed area tend to increase with Reynolds number and current-wave velocity ratio, rather than being constant as in steady channel flows.
Resumo:
An optical diagnostic system consisting of the Michelson interferometer with the image processor has been developed for studying of the surface wave in the thermal capillary convection in a rectangular cavity. In this paper, the capillary convection, surface deformation and surface wave due to the different temperature between the two sidewalls have been investigated. The cavity is 52mm?42mm in horizontal cross section and 4mm in height. The temperature difference is increased gradually and flow in liquid layer will change from steady convection to unstable convection. The optical interference method measures the surface deformation and the surface wave of the convection. The deformation of the interference fringes, which produced by the meeting of the reflected light from the liquid surface and the reference light has been captured, and the surface deformation appears when the steady convection is developed. The surface deformation is enhanced with the increasing of the temperature difference, and then several knaggy peeks in the interference fringes appear and move from the heated side to the cooled side, it demonstrates that the surface wave is existed. The surface deformation, the wavelength, the frequency, and the wave amplitude of the surface wave have been calculated.
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The induced flow fields by internal solitary waves and its actions on cylindrical piles in density stratified ocean with a basic density profile and a basic velocity profile are investigated. Some results, such as the time evolution of flow fields and hydrodynamic forces on the piles are yielded both by theoretical analysis and numerical calculation for general and specific cases. Several kinds of ambient sea conditions of the South China Sea are specified for numerical simulation. Moreover, the effects of relative density difference, depth ratio and wave steepness on maximal total force and total torque are analyzed.
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A recoverable plate impact testing technology has been used for studying the growth mechanisms of mode II crack. The results show that interactions of microcracks ahead of a crack tip cause the crack growth unsteadily. Failure mode transitions of materials were observed. Based on the observations, a discontinuous crack growth model was established. Analysis shows that the shear crack grows unsteady as the growth speed is between the Rayleigh wave speed c(R) and the shear wave speed c(s); however, when the growth speed approaches root 2c(s), the crack grows steadily. The transient microcrack growth makes the main crack speed to jump from subsonic to intersonic and the steady growth of all the sub-cracks leads the main crack to grow stably at an intersonic speed.
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A new method is presented here to analyse the Peierls-Nabarro model of an edge dislocation in a rectangular plate. The analysis is based on the superposition scheme and series expansions of complex potentials. The stress field and dislocation density field on the slip plane can be expressed as the first and the second Chebyshev polynomial series respectively. Two sets of governing equations are obtained on the slip plane and outer boundary of the rectangular plate respectively. Three numerical methods are used to solve the governing equations.
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Morison's equation is used for estimating internal solitary wave-induced forces exerted on SPAR and semi-submersible platforms. And the results we got have also been compared to ocean surface wave loading. It is shown that Morison's equation is an appropriate approach to estimate internal wave loading even for SPAR and semi-submersible platforms, and the internal solitary wave load on floating platforms is comparable to surface wave counterpart. Moreover, the effects of the layers with different thickness on internal solitary wave force are investigated.
Resumo:
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2 The flow of a compressible viscous fluid through a straight pipe.(可压缩黏性流体在直管中的流动1943年)
3 Two dimensional irrotational mixed subsonic and supersonic flow of a compressible fluid and the upper critical Mach number(可压缩流体二维无旋亚声速和超声速混合型流动及上临界马赫数1946年)
4 On the stability of transonic flows(论跨声速流的稳定性1947年)
5 The propagation of a spherical or a cylindrical wave of finite amplitude and the production of shock waves(有限振幅球面波或柱面波的传播及激波的产生1947年)
6 Two-dimensional irrotational transonic flows of a compressible fluid(可压缩流体二维无旋跨声速流动1948年)
7 On the hodograph method(关于速度图方法1949年)
8 Two-dimensional transonic flow past airfoils(绕翼型的二维跨声速流1951年)
9 On the stability of two-dimensional smooth transonic flows(论二元光滑跨声速流的稳定性1951年)
10 On the flow of an incompressible viscous fluid past a flat plate at moderate Reynolds numbers(中等雷诺数下不可压缩黏性流体绕平板的流动1953年)
11 Reflection of a weak shock wave from a boundary layer along a flat plate.I:Interaction of weak shock waves with laminar and turbulent boundary lavers analyzed by momentum-integral method(弱激波从沿平板的边界层的反射Ⅰ:用动量积分方法分析弱激波与层流和湍流边界层的相互作用1953年)
12 Reflection of weak shock wave from a boundary layer along a flat plate.Ⅱ:Interaction of oblique shock wave with a laminar boundary layer analyzed by differential-equation method(弱激波从沿平板的边界层的反射Ⅱ:用微分方程方法分析斜激波与层流边界层的相互作用1953年)
13 Plane subsonic and transonic potential flows(平面亚、跨音速势流1954年)
14 A similarity rule for the interaction between a conical field and a plane shock(锥型流和激波相互作用的相似律1955年)
15 Viscous flow along a flat plate moving at high supersonic speeds(沿高超声速运动平板的黏性流动【Ⅰ】1956年)
16 Viscous flow along a flat plate moving at high supersonic speeds(沿高超声速运动平板的黏性流动【Ⅱ】1956年)
17 The effects of Prandtl number on high-speed viscous flows over a flat plate(Prandtl数对绕平板高速黏性流的影响1956年)
18 Compressible viscous flow past a wedge moving at hypersonic speeds(楔的高超声速可压缩黏性绕流1956年)
19 Dissociation effects in hypersonic viscous flows(高超声速黏性流动中的离解效应1957年)
20 现代空气动力学的问题(1957年)
2l 在关于苏联发射成功第一颗人造卫星座谈会上的发言记录(1957年)
22 高超速钝体湍流传热问题(1963年)
23 宇宙飞船的回地问题(1965年)
24 激波的介绍
郭永怀生平
郭永怀传
Resumo:
A new type of sensor with the flexible substrate is introduced. It is applicable in measuring instantaneous heat flux on the model surface in a hypersonic shock tunnel. The working principle, structure and manufacture process of the sensor are presented. The substrate thickness and the dynamic response parameter of the sensor are calculated. Because this sensor was successfully used in measuring the instantaneous heat flux on the surface of a flat plate in a detonation-driven shock tunnel, it may be effective in measuring instantaneous heat flux on the model surface.