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2021年 第42卷 第10期    刊出日期：2021-10-01

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论文

Two-phase nonlocal integral models with a bi-Helmholtz averaging kernel for nanorods

Pei ZHANG, Hai QING

2021, 42(10):  1379-1396.  doi:10.1007/s10483-021-2774-9

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In this work, the static tensile and free vibration of nanorods are studied via both the strain-driven (StrainD) and stress-driven (StressD) two-phase nonlocal models with a bi-Helmholtz averaging kernel. Merely adjusting the limits of integration, the integral constitutive equation of the Fredholm type is converted to that of the Volterra type and then solved directly via the Laplace transform technique. The unknown constants can be uniquely determined through the standard boundary conditions and two constrained conditions accompanying the Laplace transform process. In the numerical examples, the bi-Helmholtz kernel-based StrainD (or StressD) two-phase model shows consistently softening (or stiffening) effects on both the tension and the free vibration of nanorods with different boundary edges. The effects of the two nonlocal parameters of the bi-Helmholtz kernel-based two-phase nonlocal models are studied and compared with those of the Helmholtz kernel-based models.



Effect of inertial acoustic cavitation on antibiotic efficacy in biofilms

M. GHASEMI, S. SIVALOGANATHAN

2021, 42(10):  1397-1422.  doi:10.1007/s10483-021-2776-7

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Bacterial biofilms can lead to chronic infections, increase tolerance to antibiotics and disinfectants, resistance to phagocytosis, and other components of the body's immune system. Biofilm formation is implicated in the persistence of staphylococcal infections and chronic Pseudomonas aeruginosa lung infections in cystic fibrosis (CF) patients (which can result from biofilm-growing mucoid strains). Conventional treatments utilize aggressive antibiotic prophylaxis/therapy to prevent/eliminate biofilms, followed by chronic suppressive therapy. Recently, the use of enzymes to dissolve the biofilm matrix was investigated, in addition to quorum sensing inhibitors to increase biofilm susceptibility to antibiotics. Here, we propose a novel strategy, utilizing ultrasound-induced inertial cavitation, to increase antibiotic efficacy. The wall shear stress at the biofilm interface is calculated, and viscoplastic constitutive equations are used to examine the biofilm response to the mechanical stress. Our simulations suggest that the maximum biofilm detachment occurs at high pressure/low frequency, and the mechanical disruption can affect the biochemical processes inside the biofilm resulting in vulnerability to antibiotics.

Clamped-end effect on static detection signals of DNA-microcantilever

Junzheng WU, Nenghui ZHANG

2021, 42(10):  1423-1438.  doi:10.1007/s10483-021-2780-6

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Boundary constraint induced inhomogeneous effects are important for mechanical responses of nano/micro-devices. For microcantilever sensors, the clamped-end constraint induced inhomogeneous effect of static deformation, so called the clamped-end effect, has great influence on the detection signals. This paper is devoted to developing an alternative mechanical model to characterize the clamped-end effect on the static detection signals of the DNA-microcantilever. Different from the previous concentrated load models, the DNA adsorption is taken as an equivalent uniformly distributed tangential load on the substrate upper surface, which exactly satisfies the zero force boundary condition at the free-end. Thereout, a variable coefficient differential governing equation describing the non-uniform deformation of the DNA-microcantilever induced by the clamped-end constraint is established by using the principle of minimum potential energy. By reducing the order of the governing equation, the analytical solutions of the curvature distribution and static bending deflection are obtained. By comparing with the previous approximate surface stress models, the clamped-end effect on the static deflection signals is discussed, and the importance of the neutral axis shift effect is also illustrated for the asymmetric laminated microcantilever.

Effective elastic properties of one-dimensional hexagonal quasicrystal composites

Shuang LI, Lianhe LI

2021, 42(10):  1439-1448.  doi:10.1007/s10483-021-2778-8

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The explicit expression of Eshelby tensors for one-dimensional (1D) hexagonal quasicrystal composites is presented by using Green's function method. The closed forms of Eshelby tensors in the special cases of spheroid, elliptic cylinder, ribbon-like, penny-shaped, and rod-shaped inclusions embedded in 1D hexagonal quasicrystal matrices are given. As an application of Eshelby tensors, the analytical expressions for the effective properties of the 1D hexagonal quasicrystal composites are derived based on the Mori-Tanaka method. The effects of the volume fraction of the inclusion on the elastic properties of the composite materials are discussed.

Numerical solution to the Falkner-Skan equation: a novel numerical approach through the new rational a-polynomials

S. ABBASBANDY, J. HAJISHAFIEIHA

2021, 42(10):  1449-1460.  doi:10.1007/s10483-021-2777-5

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The new rational a-polynomials are used to solve the Falkner-Skan equation. These polynomials are equipped with an auxiliary parameter. The approximated solution to the Falkner-Skan equation is obtained by the new rational a-polynomials with unknown coefficients. To find the unknown coefficients and the auxiliary parameter contained in the polynomials, the collocation method with Chebyshev-Gauss points is used. The numerical examples show the efficiency of this method.

Flow of Eyring-Powell liquid due to oscillatory stretchable curved sheet with modified Fourier and Fick's model

M. IMRAN, Z. ABBAS, M. NAVEED

2021, 42(10):  1461-1478.  doi:10.1007/s10483-021-2779-9

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This study deals with the features of the mass and heat transport mechanism by adopting a modified version of Fourier and Fick's model known as the CattaneoChristov double diffusive theory. The time-dependent magnetohydrodynamic (MHD) flow of the Eyring-Powell liquid across an oscillatory stretchable curved sheet in the presence of Fourier and Fick's model is investigated. The acquired set of flow equations is transformed into the form of nonlinear partial differential equations (PDEs) by applying appropriate similarity variables. A convergent series solution to the developed nonlinear equations is accomplished with the help of an analytical approach, i.e., the homotopy analysis method (HAM). The consequences of diverse parameters, including the dimensionless EyringPowell liquid parameter, the radius of curvature, the Schmidt/Prandtl numbers, the ratio of the oscillatory frequency of the sheet to its stretchable rate constant, the mass and thermal relaxation variables involved in the flow, and the heat and mass properties, are displayed through graphs and tables. It is noted from this study that the amplitude of the pressure distribution rises for the high parametric values of the Eyring-Powell parameter.

Amplification mechanism of perturbation energy in controlled backward-facing step flow

Yadong HUANG, Desheng ZHANG, Fadong GU

2021, 42(10):  1479-1494.  doi:10.1007/s10483-021-2775-6

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A body force resembling the streamwise Lorentz force which decays exponentially in the wall-normalwise direction is applied in the primary and secondary separation bubbles to modify the base flow and thereby adjust the amplification rate of the perturbation energy. The amplification mechanisms are investigated numerically via analyzing the characteristics of the terms in the Reynolds-Orr equation which describes the growth rate of the perturbation energy. The results demonstrate that the main convective term always promotes the increase in the growth rate while the viscous terms usually play the reverse role. The contours of the product of the wall-normalwise and streamwise perturbation velocities distribute on both sides of the isoline, which represents the zero wall-normalwise gradient of the streamwise velocity in the base flow, due to the Kelvin-Helmholtz (KH) instability. For the case without control, the isoline downstream the reattachment point of the primary separation bubble is closer to the lower wall, and thus the viscous term near the lower wall might suppress the amplification rate. For the case in which the body force only acts on the secondary separation bubble, the secondary separation bubble is removed, and the magnitude of the negative wall-normalwise gradient of the base flow streamwise velocity decreases along the streamwise direction, and thus the growth rate of the perturbation energy is smaller than that for the case without control. For the case where the body force acts on both the separation bubbles, the secondary separation bubble is removed, the isoline stays in the central part of the channel, and thereby the viscous term has less effects on the amplification rate of which the peak value could be the maximum one for some control number.

Reiner-Rivlin nanomaterial heat transfer over a rotating disk with distinct heat source and multiple slip effects

A. S. SABU, J. MACKOLIL, B. MAHANTHESH, A. MATHEW

2021, 42(10):  1495-1510.  doi:10.1007/s10483-021-2772-7

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The thermodynamic features of the Reiner-Rivlin nanoliquid flow induced by a spinning disk are analyzed numerically. The non-homogeneous two-phase nanofluid model is considered to analyze the effect of nanoparticles on the thermodynamics of the Reiner-Rivlin nanomaterial, which also includes a temperature-dependent heat source (THS) and an exponential space-dependent heat source (ESHS). Further, the transfer of heat and mass is analyzed with velocity slip, volume fraction jump, and temperature jump boundary conditions. The finite difference method-based routine is used to solve the complicated differential equations formed after using the von-Karman similarity technique. Limiting cases of the present problem are found to be in good agreement with benchmarking studies. The relationship of the pertinent parameters with the heat and mass transport is scrutinized using correlation, which is further evaluated based on the probable error estimates. Multivariable models are fitted for the friction factor at the disk and heat transport, which accurately predict the dependent variables. The Reiner-Rivlin nanoliquid temperature is influenced comparatively more by the ESHS than by the THS. The Nusselt number is decreased by the ESHS and THS, whereas the friction factor at the disk is predominantly decremented by the wall roughness aspect. The increment in the non-Newtonian characteristic of the liquid leads more fluid to drain away in the radial direction far from the disk compared with the fluid nearby the disk in the presence of the centrifugal force during rotation. The increased thermal and volume fraction slip lowers the nanoliquid temperature and nanoparticle volume fraction profiles.

Unsteady flow of a Maxwell hybrid nanofluid past a stretching/shrinking surface with thermal radiation effect

N. A. ZAINAL, R. NAZAR, K. NAGANTHRAN, I. POP

2021, 42(10):  1511-1524.  doi:10.1007/s10483-021-2781-7

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The non-Newtonian fluid model reflects the behavior of the fluid flow in global manufacturing progress and increases product performance. Therefore, the present work strives to analyze the unsteady Maxwell hybrid nanofluid toward a stretching/shrinking surface with thermal radiation effect and heat transfer. The partial derivatives of the multivariable differential equations are transformed into ordinary differential equations in a specified form by applying appropriate transformations. The resulting mathematical model is clarified by utilizing the bvp4c technique. Different control parameters are investigated to see how they affect the outcomes. The results reveal that the skin friction coefficient increases by adding nanoparticles and suction parameters. The inclusion of the Maxwell parameter and thermal radiation effect both show a declining tendency in the local Nusselt number, and as a result, the thermal flow efficacy is reduced. The reduction of the unsteadiness characteristic, on the other hand, considerably promotes the improvement of heat transfer performance. The existence of more than one solution is proven, and this invariably leads to an analysis of solution stability, which validates the first solution viability.

Entropy generation analysis of tangent hyperbolic fluid in quadratic Boussinesq approximation using spectral quasi-linearization method

C. SRINIVAS REDDY, B. MAHANTHESH, P. RANA, K. S. NISAR

2021, 42(10):  1525-1542.  doi:10.1007/s10483-021-2773-8

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In many industrial applications, heat transfer and tangent hyperbolic fluid flow processes have been garnering increasing attention, owing to their immense importance in technology, engineering, and science. These processes are relevant for polymer solutions, porous industrial materials, ceramic processing, oil recovery, and fluid beds. The present tangent hyperbolic fluid flow and heat transfer model accurately predicts the shear-thinning phenomenon and describes the blood flow characteristics. Therefore, the entropy production analysis of a non-Newtonian tangent hyperbolic material flow through a vertical microchannel with a quadratic density temperature fluctuation (quadratic/nonlinear Boussinesq approximation) is performed in the present study. The impacts of the hydrodynamic flow and Newton's thermal conditions on the flow, heat transfer, and entropy generation are analyzed. The governing nonlinear equations are solved with the spectral quasi-linearization method (SQLM). The obtained results are compared with those calculated with a finite element method and the bvp4c routine. In addition, the effects of key parameters on the velocity of the hyperbolic tangent material, the entropy generation, the temperature, and the Nusselt number are discussed. The entropy generation increases with the buoyancy force, the pressure gradient factor, the non-linear convection, and the Eckert number. The non-Newtonian fluid factor improves the magnitude of the velocity field. The power-law index of the hyperbolic fluid and the Weissenberg number are found to be favorable for increasing the temperature field. The buoyancy force caused by the nonlinear change in the fluid density versus temperature improves the thermal energy of the system.