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THE WALL EFFECT ON VENTILATED CAVITATING FLOWS IN CLOSED CAVITATION TUNNELS

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Journal of Hydrodynamics 2008年第5期20卷 561-566页

作者： chen xin lu chuan-jing LI Jie PAN Zhan-cheng Department of Engineering Mechanics Shanghai Jiao Tong University Shanghai 200240 China

For ventilated cavitating flows in a closed water tunnel, the wall effect may exert an important influence on cavity shape and hydrodynamics, An isotropic mixture multiphase model was established to study the wall effect based on the RANS equations, coupled with a natural cavitation model and the RNG k-ε turbulent model. The governing equations were discretized using the finite volume method and solved by the Gauss-Seidel linear equation solver on the basis of a segregation algorithm. The algebraic multigrid approach was carried through to accelerate the convergence of solution. The steady ventilated cavitating flows in water tunnels of different diameter were simulated for a conceptual underwater vehicle model which had a disk cavitator. It is found that the choked cavitation number derived is close to the approximate solution of natural cavitating flow for a 3-D disk. The critical ventilation rate falls with decreasing diameter of the water tunnel. However, the cavity size and drag coeflicient are rising with the decrease in tunnel diameter for the same ventilation rate, and the cavity size will be much different in water tunnels of different diameter even for the same ventilated cavitation number.

关键词： ventilated cavitation water tunnel choked cavitation number critical ventilation rate

水下航行体尾喷燃气与通气超空泡相互作用的研究

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水动力学研究与进展（A辑） 2008年第4期23卷 438-445页

作者：胡勇陈鑫鲁传敬潘展程郭建红上海交通大学船舶海洋与建筑工程学院上海200240

基于Reynolds平均Navier-Stokes方程和Mixture多相流模型,耦合自然空化模型,采用有限体积法,建立了气、汽、液多相通气空泡流和燃气射流的数值模拟方法,模拟了超空泡航行体尾部燃气射流与通气空泡的相互作用,研究了通气量和燃烧室总压... 详细信息

基于Reynolds平均Navier-Stokes方程和Mixture多相流模型,耦合自然空化模型,采用有限体积法,建立了气、汽、液多相通气空泡流和燃气射流的数值模拟方法,模拟了超空泡航行体尾部燃气射流与通气空泡的相互作用,研究了通气量和燃烧室总压对它的影响。计算结果表明:燃气射流对于通气空泡流具有引射作用,使得空泡尺度特别是其后部明显收缩,空泡变短,"颈缩"位置前移,航行体阻力系数变大,导致泄气截面面积减小,并影响泡内的压力分布。

关键词：水下航行体通气超空泡燃气射流多相流

Numerical Study on the Unsteady Characteristics of the Propeller Cavitation in Uniform and Nonuniform Wake Flows

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China Ocean Engineering 2020年第5期34卷 688-696页

作者： GONG Zhao-xin chen Ying LI Jie chen xin lu chuan-jing Key Laboratory of Hydrodynamics(Ministry of Education) School of Naval ArchitectureOcean and Civil EngineeringShanghai Jiao Tong UniversityShanghai 200240China

Propeller cavitation is a problematic issue because of its negative effects, such as performances losses, noise,vibration and erosion. Numerical methodology is an effective and efficient technical tool for the study of propeller cavitation, however, it is hard to capture tip-vortex cavitation in the previous work by using common turbulence models based on turbulent-viscosity hypothesis. In this work, the Reynolds-Averaged Naiver-Stokes(RANS)approach, adopting the Reynolds stress turbulence model(RSM), is taken to study the unsteady characteristics of the cavitation on the four-bladed INSEAN E779 A model propeller. The numerical simulation was carried out using the commercial CFD software ANSYS Fluent 14.0. One kind of uniform wake flow and two kinds of nonuniform wake flows are considered here. The results in the uniform flow show a good agreement with previous experimental results on both the sheet cavitation and the tip vortex cavitation and prove the ability of the RSM on capturing the tip vortex cavitation. Two kinds of nonuniform wake flows are designed based on the previous experimental researches and the unsteady characteristics of the propeller cavitation are analyzed by comparing the results in the uniform and two nonuniform wake flows together.

关键词： propeller cavitation wake flow Reynolds stress model

APPLICATION OF QUADRATIC AND CUBIC TURBULENCE MODELS ON CAVITATING FLOWS AROUND SUBMERGED OBJECTS

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Journal of Hydrodynamics 2012年第6期24卷 823-833页

作者： chen Ying lu chuan-jing CAO Jia-yi chen xin Department of Engineering Mechanics Shanghai Jiao Tong University Department of Engineering Mechanics and State Key Laboratory of Ocean Engineering Shanghai Jiao Tong University

Quadratic and cubic Non-Linear Eddy-Viscosity Models （NLEVMs） at low Reynolds number （Re） correction were introduced into the present Computational Fluid Dynamics （CFD） framework, to provide better numerical treatment about the anisotropic turbulence stress in cavitating flows, which have large density ratio and large-scaled swirling flow structures. The applications of these NLEVMs were carried out through a self-developed cavitation code, coupled with a cavitation model based on the transport equation of liquid phase. These NLEVMs were firstly validated by the benchmark of disk supercavity, and found able to obtain more accurate capture of the hydrodynamic properties than the linear models. One of such models was further applied on the cavitation problem of submerged vehicles. Ultimately, the supercavitating flows around an especially designed underwater vehicle were predicted using the cubic k - e turbulence model, and its cavitation behaviors were studied.

关键词： cavitating flow Non-Linear Eddy-Viscosity Model (NLEVM) submerged object cavitation model

NUMERICAL SIMULATIONS OF 2D PERIODIC UNSTEADY CAVITATING FLOWS

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Journal of Hydrodynamics 2006年第3期18卷 341-344页

作者： WU Lei lu chuan-jing LI Jie chen xin Department of Engineering Mechanics Shanghai Jiaotong University Shanghai 200240 China

A two-phase mixture model was established to study unsteady cavitating flows. A local compressible system of equations was derived by introducing a density-pressure function to account for the two-phase flow of water/vapor and the transition from one phase to the other. An algorithm for solving the variable-density Navier-Stokes equations of cavitating flow problem was put forward. The numerical results for unsteady characteristics of cavitating flows on a 2D NACA hydrofoil coincide well with experimental data.

关键词： unsteady cavitating flow variable-density Navier-Stokes equations periodic cavity break-off and shedding hydrofoil

CHARACTERIZATIONS ON THE THIXOTROPY-LOOP TESTS USING UCM MODEL WITH A RATE-TYPE KINETIC EQUATION

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Chinese Journal of Polymer Science 2006年第6期24卷 609-617页

作者： Shu-xin Huang chuan-jing lu Department of Engineering Mechanics Shanghai Jiao Tong University Shanghai 200030 China

The theoretical characterizations on the triangular-form thixotropy-loop tests of an LDPE melt （PE-FSB- 23D022/Q200） were conducted in the present paper by using a new thixotropy model, which is constituted by the upper convected Maxwell model and a rate-type kinetic equation. The new thixotropic Maxwell model can partially describe well three reported thixotropy-loop experiments by comparison with the previous calculations of the variant form of the thixotropy-type Huang model. It is noted that the stress deviations between the experiments and the predictions of the new thixotropic Maxwell model are much slighter than those deviations obtained by using the variant Huang model at the same condition, although both models include five parameters. The constitution of the new thixotropic Maxwell model is more reasonable than that of the variant Huang model.

关键词： Thixotropy-loop tests Theoretical characterization Thixotropy models.

RESEARCH ON THE BASE CAVITY OF A SUB-LAUNCHED PROJECTILE

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Journal of Hydrodynamics 2012年第2期24卷 244-249页

作者： CAO Jia-yi lu chuan-jing chen Ying chen xin LI Jie Department of Mechanics Shanghai Jiao Tong University Shanghai 200240 China MOE Key Laboratory of Hydrodynamics Shanghai Jiao Tong University Shanghai 200240 China

The finite volume method based on a multiphase model is adopted to solve the Reynolds-Averaged Navier-Stokes （RANS） equations,which takes into account the effects of fluid compressibility,viscosity,gravity,medium mixture and energy transfer of water and combustion *** program Fluent User Define Function （UDF） module combined with the dynamic mesh method is employed to simulate the coupling flow field of combustion gas,water field and trajectory of *** results show that the volume of gas cavity at the bottom of projectile and tail pressure will fluctuate after bottom of the projectile leaving the launch *** cause of the fluctuation is analyzed and its effects on the trajectory of projectile are *** numerical and experimental results agree well with each other.

关键词： sub-launched projectile gas cavity trajectory

THE THIXOTROPY-LOOP BEHAVIORS OF AN LDPE MELT:EXPERIMENT AND SIMPLE ANALYSIS

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Journal of Hydrodynamics 2006年第6期18卷 666-675页

作者： HUANG Shu-xin lu chuan-jing Department of Engineering Mechanics Shanghai Jiaotong University Shanghai 200030 China

The time-dependent viscoelastic behaviors of an Low-Density-Pdyethyene（LDPE）（PE-FSB-23D022） melt were experimentally investigated using two types of thixotropy-loop test i.e., the triangular- and the trapezoidal-loop shear test. The shear strengthening was noted in the thixotropy-loop tests not only at high shear rate but also at low shear rate, and it was found that the dimensionless stress amplitude of shear strengthening at low shear rate is larger than that at high shear rate. Moreover, the shear strengthening is a time-dependent viscoelastic behavior that is observed during the initial stage of shearing, and it cannot be found when the time interval corresponding to the increase in shear rate is sufficiently long, The remarkable shear-weakening phenomenon was noticed at higher shear rate when shearing time is prolonged. Five types of the triangular thixotropy-loop results were marked in terms of the configurations of the stress-rate curves, which indicate the complex features of the time-dependent viscoelasticity. A simple model was used to describe the thixotropy-loop tests, and the fitted results showed good agreement with the experimental results.

关键词： thixotropy-loop test time-dependent viscoelasticity LDPE shear strengthening shear weakening

A HOMOGENOUS-EQUILIBRIUM-MODEL BASED NUMERICAL CODE FOR CAVITATION FLOWS AND EVAluATION BY COMPUTATION CASES

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Journal of Hydrodynamics 2008年第2期20卷 186-194页

作者： chen Ying lu chuan-jing Department of Engineering Mechanics Shanghai Jiaotong University Shanghai 200240 China

A computer code, ELANEX, including several Homogenous-Equilibrium-Model （HEM） type cavitation models, were developed, to numerically simulate natural cavitation phenomena. The effectiveness of the code was checked by cavitation flows around the disk and cylinder body for a wide range of different cavitation numbers. Cavity profiles were compared with the analytic solution of disk and empirical formulae fitted from the experiment data, and contrast between different cavitation models were fulfilled as well. The cavity length and maximal cavity diameter were found to agree well with the analytic solutions, and detailed cavity profiles were in accordance with the experimental formula. Comparison with the hemisphere headed cylinder body presented a good agreement of the pressure coefficient with the experiment data. Reasonable drag-force coefficient variation and drag-force reduction effect were obtained.

关键词： cavitation numerical code disk hemisphere cavity profile pressure coefficient