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Time-dependent viscoelastic behavior of an LDPE melt

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Acta Mechanica Sinica 2006年第3期22卷 199-206页

作者： Shuxin Huang chuanjing lu Yurun Fan Department of Engineering Mechanics Shanghai Jiao Tong University Shanghai 200030 China State Key Lab of Fluid Power Transmission and Control Zhejiang University Hangzhou 310027 China

Two differential constitutive equations, i.e. Giesekus model and Johnson-Segalman model were employed here to predict the time-dependent viscoelastic behavior of an LDPE melt in thixotropy-loop experiments and step shear rate experiment. Multiple relaxation modes were adopted, and the parameters used to describe the nonlinear viscoelasticity in the two models were obtained by fitting the shear-thinning viscosity. The predictions on those transient shear characteristics by the two models are found in qualitative agreement with our previous experiments. JohnsonSegalman model predicts oscillation behavior in the thixotropy-loop and step shear rate experiments, whereas Giesekus model does not. Both models predict higher shear stresses than the experimental data in the case of long time shearing, implying that both models are not able to completely characterize the time-dependent shear stress of the melt at high shear rate.

关键词： Transient shear tests LDPE Time-dependent viscoelastic Giesekus model Johnson-Segalman model

Fluid-structure interaction simulation of three-dimensional flexible hydrofoil in water tunnel

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Applied Mathematics and Mechanics(English Edition) 2016年第1期37卷 15-26页

作者： Shiliang HU chuanjing lu Yousheng HE Department of Engineering Mechanics Shanghai Jiao Tong University Ministry of Education (MOE) Key Laboratory of Hydrodynamics Shanghai Jiao Tong University

The closely coupled approach combined with the finite volume method （FVM） solver and the finite element method （FEM） solver is used to investigate the fluid-structure interaction （FSI） of a three-dimensional cantilevered hydrofoil in the water tunnel. The FVM solver and the coupled approach are verified and validated by compar- ing the numerical predictions with the experimental measurements, and good agreement is obtained concerning both the lift on the foil and the tip displacement. In the noncav- itating flow, the result indicates that the growth of the initial incidence angle and the Reynolds number improves the deformation of the foil, and the lift on the foil is increased by the twist deformation. The normalized twist angle and displacement along the span of the hydrofoil for different incidence angles and Reynolds numbers are almost uniform. For the cavitation flow, it is shown that the small amplitude vibration of the foil has limited influence on the developing process of the partial cavity, and the quasi two-dimensional cavity shedding does not change the deformation mode of the hydrofoil. However, the frequency spectrum of the lift on the foil contains the frequency which is associated with the first bend frequency of the hydrofoil.

关键词： closely coupled approach fluid-structure interaction (FSI) hydrofoil,cavitation

A new semi-empirical spectrum model for complex steady shear viscosity of complex fluids

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Acta Mechanica Sinica 2009年第6期25卷 897-901页

作者： Shuxin Huang chuanjing lu Yurun Fan Department of Engineering Mechanics Shanghai Jiaotong University 200240 Shanghai China State Key Laboratory of Fluid Power Transmission and Control Zhejiang University 310027 Hangzhou China State Key Laboratory of Ocean Engineering Shanghai Jiaotong University 200240 Shanghai China

A semi-empirical spectrum model is proposed to describe the experimental data of the steady shear properties of a Shengli waxy crude oil near its gel point, where sophisticated structural effects become apparent due to the existence of waxy crystals in the crude oil. The model, consisting of a time spectrum, can well fit the steady shear viscosities of the waxy crude oil over the whole experimental shear rate region from 10-4 to 102 s- 1. Two other experiments on complex fluids reported recently in the literature are also well described by this model demonstrating the applicability and accuracy of the model.

关键词： Sophisticated steady shear viscosityWaxy crude oil . Simple spectrum model

2008 Stability Analysis of the Immersed Boundary Method for a Two-Dimensional Membrane with Bending Rigidity

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Communications in Computational Physics 2008年第3期3卷 704-723页

作者： Zhaoxin Gong Huaxiong Huang chuanjing lu Department of Mechanics Shanghai Jiaotong UniversityShanghai 200240China Department of Mathematics and Statistics York UniversityTorontoOntario M3J 1P3Canada.

In this paper,we analyze the stability of the Immersed Boundary Methodapplied to a membrane-fluid system with a plasma membrane immersed in an incompressibleviscous *** show that for small deformations,the planar rest state isstable for a membrane with bending *** smoothed version,using a standardregularization technique for the singular force,is also shown to be ***,we show that the coupled fluid-membrane system is stiff and smoothing helpsto reduce the *** to the system of elastic fibers immersed in an incompressiblefluid,membrane with bending rigidity consist of a wider range of *** numerical instability could occur more easily for an explicit methodwhen the time step size is not sufficiently small,even though the continuous problemis stable.

关键词： Bending rigidity immersed boundary method membrane moving interface stability.

3-D NUMERICAL SIMULATION OF UNDERWATER EXPLOSION BUBBLE

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Chinese Journal of Aeronautics 1996年第1期9卷 38-42页

作者： lu chuanjing(Shanghai Jiao Tong University, Shanghai, China, 200030) Shanghai Jiao Tong University Shanghai 200030 China

The problem is solved by use of the boundary integral equation method and the high order finite element discretization on the assumption that the flow of water is inviscid, incompressible and irrotational, and the bubble gas obeys the isoentropic rule. The evolution of bubble is simulated by means of mixed Euler-Lagrangian method. The comparison of the numerical results with the 'exact solution' of a spheric bub ble and experimental data shows that the mathematical model is reasonable and the 3-D numerical method has high accuracy. Important behaviour of bubble, such as immigration and jetting, and dynamic load on an ellipsoid near explosion are derived.

关键词： underwater explosions bubbles potential flow boundary integral method

UNSTEADY THEORY OF THE HYDROFOIL OF FINITE SPAN

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Acta Mechanica Sinica 1985年第2期1卷 97-106页

作者： lu chuanjing He Yousheng Shanghai Jiao Tong University 1. Shanghai Jiao Tong University Shanghai China

A three-dimensional unsteady flow around the hydrofoil has been dealt with in thispaper. Under the assumption of infinitesimal wave and thin hydrofoil, analytic solution ofperturbation velocity potential induced by the unsteady flow of a hydrofoil which is simplified as aseries of rectangular vortex rings is achieved and then the unsteady forces can be evaluated.

关键词： hydrofoils unsteady flow vortex sheets water waves potential flow

Boger流体的松弛谱对非线性粘弹性表征的影响

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应用力学学报 2007年第1期24卷 37-41页

作者：黄树新鲁传敬上海交通大学上海200030

分析了一种Boger流体的松弛时间谱和该流体的粘弹性表征问题。文中采用带正约束的非线性规划方法得到了包含4个、5个、6个松弛时间的描述此Boger流体线性粘弹特性的时间谱。这些新时间谱比前文报道的含3个松弛时间的谱能更好地描述该流... 详细信息

分析了一种Boger流体的松弛时间谱和该流体的粘弹性表征问题。文中采用带正约束的非线性规划方法得到了包含4个、5个、6个松弛时间的描述此Boger流体线性粘弹特性的时间谱。这些新时间谱比前文报道的含3个松弛时间的谱能更好地描述该流体的储能模量G′。用PSM模型结合这些新松弛时间谱都不能很准确地描述这个Boger流体的第一法向应力差N1的实验数据。作者提出的3r模型描述此Boger流体的N1的结果比PSM模型的计算结果更接近实验值。

关键词： Boger流体松弛时间谱粘弹性 KBKZ积分型本构方程

A NEW TECHNIQUE IN SOLVING UNSTEADY AND STEADY WAVEMAKING PROBLEMS

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Journal of Hydrodynamics 1989年第1期1卷 22-30页

作者： lu chuanjing HE YOUSHENG, Shanghai Jiao Tong University, Shanghai, P.R. China

Under the' assumption of linearization of the free-surface condition, making use of Green's function method and the convolution theorem, analytic solutions of perturbation velocity potentials which correspond to three dimensional unsteady thickness problem and lifting problem caused respectively by arbitrary motions of a body and a hydrofoil beneath the water surface can be achieved in the closed form, In general, the whole perturbation velocity potential consists of three terms, namely φ=φ1+φ2+φ3 , where φ1 denotes the induced velocity potential of the surface singularity distribution in an unbounded fluid, φ2 denotes its mirror image and φ3 denotes that of wave formation which includes the memory effect of the action of the singularity distribution. Utilizing the polynomial expansion of sin[(t-τ)] , the similarity between φ2 and φ3 is discovered and thus a simpler differential relation between them is obtained. Applying this relation, the amount of work in calculation of φ3 which is the most time-consuming one will be reduced significantly. It is favorable not only for dealing with unsteady wave- making problems but also for solving the steady ones in virtue of evading a major difficulty which has to be encountered during the evaluation of an improper inte- gral containing a singularity in the Green's function. The limitation of this new technique turns out to be its slower convergence as the Froude number is lower.

关键词： A NEW TECHNIQUE IN SOLVING UNSTEADY AND STEADY WAVEMAKING PROBLEMS body

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三维小空化数空泡流数值方法

计算物理 2008年第2期25卷 163-171页

作者：陈瑛鲁传敬吴磊上海交通大学船舶海洋与建筑工程学院上海200240

采用均质平衡流空泡模型，引入基于求解液体质量份数输运方程的空泡流模型，提出新的压力密度耦合的压缩性方法和控制气液两相转换的源项，求解汽水混合介质的RANS方程和带低雷诺数修正的kε模型，实现了小空化数（σ=0．2～0．01）下... 详细信息

采用均质平衡流空泡模型，引入基于求解液体质量份数输运方程的空泡流模型，提出新的压力密度耦合的压缩性方法和控制气液两相转换的源项，求解汽水混合介质的RANS方程和带低雷诺数修正的kε模型，实现了小空化数（σ=0．2～0．01）下水下航行体的空泡流数值模拟．得到清晰的空泡形态特征与内部结构，以及空泡长度和最大直径随空化数的变化规律，给出航行体运动阻力系数与空化数之间的变化关系．将计算结果与解析结果及实验数据进行比较表明，该方法保证了极小空化数下自然空泡流计算的稳定性与收敛性，提高了空泡形态特性的预报精度．

关键词：空泡流小空化数数值模拟质量份数压缩性