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2011年 第32卷 第4期    刊出日期：2011-03-29

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Articles

Modeling three-dimensional dynamic stall

吕超 王同光

2011, 32(4):  393-400.  doi:10.1007/s10483-011-1424-6

摘要 ( 547 )   PDF (305KB) ( 1311 )  

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The dynamic stall process in three-dimensional (3D) cases on a rectangular wing undergoing a constant rate ramp-up motion is introduced to provide a qualitative analysis about the onset and development of the stall phenomenon. Based on the enhanced understanding of the mechanism of dynamic stalls, a 3D dynamic stall model is constructed with the emphasis of the onset, the growth, and the convection of the dynamic stall vortex on the 3D wing surface. The results show that this engineering dynamic stall model can simulate the 3D unsteady aerodynamic performance appropriately.

论文

Approximate solutions to MHD Falkner-Skan flow over permeable wall

苏晓红 郑连存

2011, 32(4):  401-408.  doi:10.1007/s10483-011-1425-9

摘要 ( 451 )   PDF (302KB) ( 1858 )  

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The magnetohydrodynamic (MHD) Falkner-Skan boundary layer flow over a permeable wall in the presence of a transverse magnetic field is examined. The approximate solutions and skin friction coefficients of the MHD boundary layer flow are obtained by using a method that couples the differential transform method (DTM) with the Pad´e approximation called DTM-Pad´e. The approximate solutions are expressed in the form of a power series that can be easily computed with an iterative procedure. The approximate solutions are tabulated, plotted for the values of different parameters and compared with the numerical ones obtained by employing the shooting technique. It is found that the approximate solution agrees very well with the numerical solution, showing the reliability and validity of the present work. Moreover, the effects of various physical parameters on the boundary layer flow are presented graphically and discussed.

MHD stagnation-point flow and heat transfer towards stretching sheet with induced magnetic field

F. M. ALI R. NAZAR N. M. ARIFIN I.POP

2011, 32(4):  409-418.  doi:10.1007/s10483-011-1426-6

摘要 ( 582 )   PDF (317KB) ( 1793 )  

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The problem of the steady magnetohydrodynamic (MHD) stagnation-point flow of an incompressible viscous fluid over a stretching sheet is studied. The effect of an induced magnetic field is taken into account. The nonlinear partial differential equations are transformed into ordinary differential equations via the similarity transformation. The transformed boundary layer equations are solved numerically using the shooting method. Numerical results are obtained for various magnetic parameters and Prandtl numbers. The effects of the induced magnetic field on the skin friction coefficient, the local Nusselt number, the velocity, and the temperature profiles are presented graphically and discussed in detail.

Articles

Modelling two different therapy strategies for drug T-20 on HIV-1 patients

宋保军 娄洁 文清芝

2011, 32(4):  419-436.  doi:10.1007/s10483-011-1427-8

摘要 ( 411 )   PDF (610KB) ( 1027 )  

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A mathematical model describing the antiretroviral therapy of Enfuvirtide on HIV-1 patients is developed. The effect of Enfuvirtide (formerly called T-20) by impulsive differential equations is modeled by two different drug elimination kinetics, the first-order elimination kinetics and the Michaelis-Menten elimination kinetics. The model is a non-autonomous system of differential equations. For a time-dependent system, the disease-free equilibrium is mainly studied. Its stability, when the therapy is taken with perfect adherence, is obtained. To ensure the disease-free equilibrium remains stable, the analytical thresholds for dosage and dosing intervals are determined. The effects of supervised treatment interruption are also explored. It is shown that the supervised treatment interruption can be worse than no therapy at all.

Simulation of tumor microvasculature and microenvironment response to anti-angiogenic treatment by angiostatin and endostatin

吴洁 丁祖荣 蔡彦 许世雄 赵改平 龙泉

2011, 32(4):  437-448.  doi:10.1007/s10483-011-1428-7

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The effects of anti-angiogenesis treatment by angiostatin and endostatin on normalization of tumor microvasculature and microenvironment are investigated, based on mathematical modeling and numerical simulation of tumor anti-angiogenesis and tumor haemodynamics. The results show that after anti-angiogenesis treatment: (i) the proliferation, growth, and branching of neo-vessels are effectively inhibited, and the extent of vascularization in tumors is accordingly reduced. (ii) the overall blood perfusion inside of tumor is declined, the plateau of tumor interstitial fluid pressure (IFP) is relieved, the interstitial fluid oozing out from the tumor periphery into the surrounding normal tissue is reduced, the reduction of overall extravasation across vasculature to tumor interstium is much less than the decreased overall blood perfusion, due to the decline of IFP, the intravasations is remarkablely effected by the change, in some cases there are no intravasation flow appear.

Numerical studies on evolution of secondary streamwise vortices in transitional boundary layers

陈林 唐登斌 刘超群

2011, 32(4):  449-458.  doi:10.1007/s10483-011-1429-9

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Formation and evolution of secondary streamwise vortices in the compressible transitional boundary layers over a flat plate are studied using a direct numerical simulation method with high-order accuracy and highly effective non-reflecting characteristic boundary conditions. Generation and development processes of the secondary streamwise vortices in the complicated transitional boundary flow are clearly analyzed based on the of numerical results, and the effects on the formation of the ring-like vortex that is vital to the boundary layer transition are explored. A new mechanism forming the ring-like vortex through the mutual effect of the primary and secondary streamwise vortices is expressed.

Analytical solutions for transverse distributions of stream-wise velocity in turbulent flow in rectangular channel with partial vegetation

槐文信 耿川 曾玉红 杨中华

2011, 32(4):  459-468.  doi:10.1007/s10483-011-1430-6

摘要 ( 539 )   PDF (254KB) ( 846 )  

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The theory of poroelasticity is introduced to study the hydraulic properties of the steady uniform turbulent flow in a partially vegetated rectangular channel. Plants are assumed as immovable media. The resistance caused by vegetation is expressed by the theory of poroelasticity. Considering the influence of a secondary flow, the momentum equation can be simplified. The momentum equation is nondimensionalized to obtain a smooth solution for the lateral distribution of the longitudinal velocity. To verify the model, an acoustic Doppler velocimeter (ADV) is used to measure the velocity field in a rectangular open channel partially with emergent artificial rigid vegetation. Comparisons between the measured data and the computed results show that the method can predict the transverse distributions of stream-wise velocities in turbulent flows in a rectangular channel with partial vegetation.

Damage detection method in complicated beams with varying flexural stiffness

冯侃 励争 高桂云 苏先越

2011, 32(4):  469-478.  doi:10.1007/s10483-011-1431-x

摘要 ( 507 )   PDF (541KB) ( 954 )  

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A damage detection method for complicated beam-like structures is proposed based on the subsection strain energy method (SSEM), and its applicability condition is introduced. For a beam with the continuously varying flexural stiffness and an edge crack, the SSEM is used to detect the crack location effectively by numerical modal shapes. As a complicated beam, the glass fiber-reinforced composite model of a wind turbine blade is studied based on an experimental modal analysis. The SSEM is used to calculate the damage index from the measured modal parameters and locate the damage position in the blade model successfully. The results indicate that the SSEM based on the modal shapes can be used to detect the damages in complicated beams or beam-like structures for engineering applications.

Uniqueness theorem, theorem of reciprocity, and eigenvalue problems in linear theory of porous piezoelectricity

A. K. VASHISHTH V. GUPTA

2011, 32(4):  479-494.  doi:10.1007/s10483-011-1432-8

摘要 ( 718 )   PDF (204KB) ( 945 )  

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The uniqueness theorem and the theorem of reciprocity in the linearized porous piezoelectricity are established under the assumption of positive definiteness of elastic and electric fields. General theorems in the linear theory of porous piezoelectric materials are proved for the quasi-static electric field approximation. The uniqueness theorem is also proved without using the positive definiteness of the elastic field. An eigenvalue problem associated with free vibrations of a porous piezoelectric body is studied using the abstract formulation. Some properties of operators are also proved. The problem of frequency shift due to small disturbances, based on an abstract formulation, is studied using a variational and operator approach. A perturbation analysis of a special case is also given.

论文

Free vibration of circular cylindrical shell with constrained layer damping

曹雄涛 张志谊 华宏星

2011, 32(4):  495-506.  doi:10.1007/s10483-011-1433-7

摘要 ( 509 )   PDF (569KB) ( 1626 )  

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Free vibration characteristics of circular cylindrical shell with passive constrained layer damping (PCLD) are presented. Wave propagation approach rather than finite element method, transfer matrix method, and Rayleigh-Ritz method is used to solve the problem of vibration of PCLD circular cylindrical shell under a simply supported boundary condition at two ends. The governing equations of motion for the orthotropic cylindrical shell with PCLD are derived on the base of Sanders’ thin shell theory. Numerical results show that the present method is more effective in comparison with other methods. The effects of the thickness of viscoelastic core and constrained layer, the elastic modulus ratio of orthotropic constrained layer, the complex shear modulus of viscoelastic core on frequency parameter, and the loss factor are discussed.

Articles

Stresses in rotating heterogeneous viscoelastic composite cylinders with variable thickness

A. M. ZENKOUR

2011, 32(4):  507-520.  doi:10.1007/s10483-011-1434-9

摘要 ( 519 )   PDF (669KB) ( 1063 )  

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An analytical solution is presented for the rotation problem of a two-layer composite elastic cylinder under a plane strain assumption. The external cylinder has variable-thickness formulation, and is made of a heterogeneous orthotropic material. It contains a fiber-reinforced viscoelastic homogeneous isotropic solid core of uniform thickness. The thickness and elastic properties of the external cylinder are taken as power functions of the radial direction. By the boundary and continuity conditions, the radial displacement and stresses for the rotating composite cylinder are determined. The effective moduli and Illyushin’s approximation methods are used to obtain the viscoelastic solution to the problem. The effects of heterogeneity, thickness variation, constitutive, time parameters on the radial displacement, and stresses are investigated.

Two new predictor-corrector algorithms for second-order cone programming

曾友芳 白延琴 简金宝 唐春明

2011, 32(4):  521-532.  doi:10.1007/s10483-011-1435-x

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Based on the ideas of infeasible interior-point methods and predictor-corrector algorithms, two interior-point predictor-corrector algorithms for the second-order cone programming (SOCP) are presented. The two algorithms use the Newton direction and the Euler direction as the predictor directions, respectively. The corrector directions belong to the category of the Alizadeh-Haeberly-Overton (AHO) directions. These algorithms are suitable to the cases of feasible and infeasible interior iterative points. A simpler neighborhood of the central path for the SOCP is proposed, which is the pivotal difference from other interior-point predictor-corrector algorithms. Under some assumptions, the algorithms possess the global, linear, and quadratic convergence. The complexity bound O(rln(ε0/ε)) is obtained, where r denotes the number of the second-order cones in the SOCP problem. The numerical results show that the proposed algorithms are effective.