Table of Content

01 September 2015, Volume 36 Issue 9

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Articles

Numerical investigation of turbulent channel flow controlled by spatially oscillating spanwise Lorentz force

Wentang WU, Yanji HONG, Baochun FAN

2015, 36(9):  1113-1120.  doi:10.1007/s10483-015-1972-6

Abstract ( 722 )   HTML   PDF (1014KB) ( 434 )  

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A formulation of the skin-friction drag related to the Reynolds shear stress in a turbulent channel flow is derived. A direct numerical simulation (DNS) of the turbulent control is performed by imposing the spatially oscillating spanwise Lorentz force. Under the action of the Lorentz force with several proper control parameters, only the periodically well-organized streamwise vortices are finally observed in the near-wall region. The Reynolds shear stress decreases dramatically, especially in the near-wall area, resulting in a drag reduction.

Study on local topology model of low/high streak structures in wall-bounded turbulence by tomographic time-resolved particle image velocimetry

Haiping TIAN, Nan JIANG, Yongxiang HUANG, Shaoqiong YANG

2015, 36(9):  1121-1130.  doi:10.1007/s10483-015-1978-6

Abstract ( 527 )   HTML   PDF (2395KB) ( 282 )  

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The relationship between the bursting event and the low/high-speed streak in the logarithmic law (log-law) region of a turbulent boundary layer is investigated. A tomographic time-resolved particle image velocimetry (TRPIV) system is used to measure the instantaneous three-dimensional-three-component (3D-3C) velocity field. The momentum thickness based Reynolds number is about 2 460. The topological information in the log-law region is obtained experimentally. It is found that the existence of the quadrupole topological structure implies a three-pair hairpin-like vortex packet, which is in connection with the low/high-speed streak. An idealized 3D topological model is then proposed to characterize the observed hairpin vortex packet and low/high-speed streak.

Second-order slip MHD flow and heat transfer of nanofluids with thermal radiation and chemical reaction

Jing ZHU, Liu ZHENG, Liancun ZHENG, Xinxin ZHANG

2015, 36(9):  1131-1146.  doi:10.1007/s10483-015-1977-6

Abstract ( 734 )   HTML   PDF (551KB) ( 417 )  

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The effects of the second-order velocity slip and temperature jump boundary conditions on the magnetohydrodynamic (MHD) flow and heat transfer in the presence of nanoparticle fractions are investigated. In the modeling of the water-based nanofluids containing Cu and Al₂O₃, the effects of the Brownian motion, thermophoresis, and thermal radiation are considered. The governing boundary layer equations are transformed into a system of nonlinear differential equations, and the analytical approximations of the solutions are derived by the homotopy analysis method (HAM). The reliability and efficiency of the HAM solutions are verified by the residual errors and the numerical results in the literature. Moreover, the effects of the physical factors on the flow and heat transfer are discussed graphically.

Theoretical analyses on hydrodynamic instability in narrow deep river with variable curvature

Haijue XU, Yuchuan BAI

2015, 36(9):  1147-1168.  doi:10.1007/s10483-015-1971-6

Abstract ( 599 )   HTML   PDF (612KB) ( 192 )  

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Bending river is the most common river type in nature, and it is also a typical example for river evolution. The transform of the flow pattern can affect the development of the riverbed form. In return, the variation in the riverbed form can affect the hydrodynamic characteristics of the flow, thereby leading to the continuous evolution of the bending river. Based on this, a theoretical model for the bending river is established. The hydrodynamic instability characteristics of the laminar flow in the channel with a variable curvature, a typical model as the meandering river, are studied, and the variations of some parameters such as the curvature, the wave number, and the wave frequency are also discussed.

Buoyant Marangoni convection of nanofluids in square cavity

H. SALEH, I. HASHIM

2015, 36(9):  1169-1184.  doi:10.1007/s10483-015-1973-6

Abstract ( 592 )   HTML   PDF (1290KB) ( 236 )  

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The buoyant Marangoni convection heat transfer in a differentially heated cavity is numerically studied. The cavity is filled with water-Ag, water-Cu, water-Al₂O₃, and water-TiO₂ nanofluids. The governing equations are based on the equations involving the stream function, vorticity, and temperature. The dimensionless forms of the governing equations are solved by the finite difference (FD) scheme consisting of the alternating direction implicit (ADI) method and the tri-diagonal matrix algorithm (TDMA). It is found that the increase in the nanoparticle concentration leads to the decrease in the flow rates in the secondary cells when the convective thermocapillary and the buoyancy force have similar strength. A critical Marangoni number exists, below which increasing the Marangoni number decreases the average Nusselt number, and above which increasing the Marangoni number increases the average Nusselt number. The nanoparticles play a crucial role in the critical Marangoni number.

Revised damage evolution equation for high cycle fatigue life prediction of aluminum alloy LC4 under uniaxial loading

Zhixin ZHAN, Weiping HU, Miao ZHANG, Qingchun MENG

2015, 36(9):  1185-1196.  doi:10.1007/s10483-015-1970-6

Abstract ( 635 )   HTML   PDF (246KB) ( 264 )  

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The fatigue life prediction for components is a difficult task since many factors can affect the final fatigue life. Based on the damage evolution equation of Lemaitre and Desmorat, a revised two-scale damage evolution equation for high cycle fatigue is presented according to the experimental data, in which factors such as the stress amplitude and mean stress are taken into account. Then, a method is proposed to obtain the material parameters of the revised equation from the present fatigue experimental data. Finally, with the utilization of the ANSYS parametric design language (APDL) on the ANSYS platform, the coupling effect between the fatigue damage of materials and the stress distribution in structures is taken into account, and the fatigue life of specimens is predicted. The outcome shows that the numerical prediction is in accord with the experimental results, indicating that the revised two-scale damage evolution model can be well applied for the high cycle fatigue life prediction under uniaxial loading.

P₁-nonconforming triangular finite element method for elliptic and parabolic interface problems

Hongbo GUAN, Dongyang SHI

2015, 36(9):  1197-1212.  doi:10.1007/s10483-015-1974-6

Abstract ( 575 )   HTML   PDF (181KB) ( 202 )  

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The lowest order P₁-nonconforming triangular finite element method (FEM) for elliptic and parabolic interface problems is investigated. Under some reasonable regularity assumptions on the exact solutions, the optimal order error estimates are obtained in the broken energy norm. Finally, some numerical results are provided to verify the theoretical analysis.

Moving line crack accompanied with damage zone subject to remote tensile loading

Minwei CHEN, Min LI, Xuesong TANG

2015, 36(9):  1213-1222.  doi:10.1007/s10483-015-1975-6

Abstract ( 461 )   HTML   PDF (411KB) ( 187 )  

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In the 1920s, a closed-form solution of the moving Griffith crack was first obtained by Yoffe. Based on Yoffe's solution, the Dugdale model for the moving crack case gives a good result. However, the Dugdale model fails when the crack speed is closed to the Rayleigh wave speed because of the discontinuity occurred in the crack opening displacement (COD). The problem is solved in this paper by introducing a restraining stress zone ahead of the crack tip and two velocity functions. The restraining stresses are linearly distributed and related to the velocity of the moving crack. An analytical solution of the problem is obtained by use of the superposition principle and a complex function method. The final result of the COD is continuous while the crack moves at a Rayleigh wave speed. The characteristics of the strain energy density (SED) and numerical results are discussed, and conclusions are given.

Generalized Bleustein-Gulyaev type waves in layered porous piezoceramic structure

A. K. VASHISHTH, A. DAHIYA, V. GUPTA

2015, 36(9):  1223-1242.  doi:10.1007/s10483-015-1976-6

Abstract ( 532 )   HTML   PDF (488KB) ( 221 )  

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The propagation of a Bleustein-Gulyaev (B-G) type wave in a structure consisting of multiple layers and a half-space of porous piezoelectric materials is theoretically studied. The solutions of the problem in terms of the mechanical displacements and electric potential functions are obtained for each layer and the half-space. The dispersion equation is obtained for electrically open and shorted boundary conditions by use of the transfer matrix method. A peculiar kind of B-G waves is investigated, which can propagate only in the layer over the half-space. The relationship between the piezoelectric constants and the dielectric constants is found for the existence of a peculiar kind of propagation modes. The numerical results in terms of the phase velocity and the electromechanical coupling factor with different thicknesses of the layer stack are presented.

Experimental research on grouser traction of deep-sea mining machine

Wenbo MA, Qiuhua RAO, Kang FENG, Feng XU

2015, 36(9):  1243-1252.  doi:10.1007/s10483-015-1979-6

Abstract ( 478 )   HTML   PDF (1966KB) ( 214 )  

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The traction characteristics of the grouser, cutting the simulative soil of deep-sea sediment, with different tooth widths, tooth heights, and ground pressures are studied with traction characteristic test apparatus. A traction-displacement model is obtained by combining the analysis of the cutting mechanism. The results show that the traction-displacement curves of grousers with different tooth widths, tooth heights, and ground pressures have the same changing trend, which matches the Wong traction model. Their sensitivity coefficient and shear modulus are slightly fluctuated. Therefore, the average values can be used as the traction model parameters. The maximum traction of the grouser with a two-side edge and a 10mm tooth width increment changing with the tooth height and ground pressure can be determined according to the grousers with different tooth widths. By combining the traction model parameters, the traction-displacement curve of the grouser with a certain group values of tooth width, tooth height, and ground pressure can be predicted. Therefore, the slip of the mining machine can be prevented to improve the mining efficiency.