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Stokes flow of micro-polar fluids by peristaltic pumping through tube with slip boundary condition

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Applied Mathematics and Mechanics(English Edition) 2011年第12期32卷 1587-1598页

作者： d.tripathi M.K.CHAUBE P.K.GUPTA department of Mathematics Indian Institute of Technology Ropar Punjab 140001 India department of Mathematics Raj Kumar Goel Institute of Technology Ghaziabad 201001 India department of Applied Mathematics Institute of Technology Banaras Hindu University Varanasi 221005 India

This paper studies the Stokes flow of micro-polar fluids by peristaltic pumping through the cylindrical tube under the effect of the slip boundary condition. The motion of the wall is governed by the sinusoidal wave equation. The analytical and numerical solutions for the axial velocity, the micro-polar vector, the stream function, the pressure gradient, the friction force, and the mechanical efficiency are obtained by using the lu- brication theory under the low Reynolds number and long wavelength approximations. The impacts of the emerging parameters, such as the coupling number, the micro-polar parameter, the slip parameter on pumping characteristics, the friction force, the velocity profile, the mechanical efficiency, and the trapping phenomenon are depicted graphically. The numerical results infer that large pressure is required for peristaltic pumping when the coupling number is large, while opposite behaviors are found for the micro-polar parameter and the slip parameter. The size of the trapped bolus reduces with the increase in the coupling number and the micro-polar parameter, whereas it blows up with the increase in the slip parameter.

关键词： Stokes flow slip boundary condition mechanical efficiency micro-polarfluid peristaltic pumping trapping

Cilia-assisted hydromagnetic pumping of biorheological couple stress fluids

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Propulsion and Power Research 2019年第3期8卷 221-233页

作者： K.Ramesh d.tripathi O.Anwar Bég department of Mathematics Symbiosis Institute of TechnologySymbiosis International UniversityPune412115India department of Mechanical Engineering Manipal University JaipurRajasthan303007India Fluid Mechanics/Propulsion Aeronautical/Mechanical Engineering DepartmentSalford UniversityManchesterUK

A theoretical study is conducted for magnetohydrodynamic pumping of electroconductive couple stress physiological liquids(***)through a two-dimensional ciliated channel.A geometric model is employed for the cilia which are distributed at equal intervals and produce a whip-like motion under fluid interaction which obeys an elliptic trajectory.A metachronal wave is mobilized by the synchronous beating of cilia and the direction of wave propagation is parallel to the direction of fluid flow.A transverse static magnetic field is imposed transverse to the channel *** Stokes’couple stress(polar)rheological model is utilized to characterize the *** normalized two-dimensional conservation equations for mass,longitudinal and transverse momentum are reduced with lubrication approximations(long wavelength and low Reynolds number assumptions)and feature a fourth order linear derivative in axial velocity representing couple stress contribution.A coordinate transformation is employed to map the unsteady problem from the wave laboratory frame to a steady problem in the wave *** slip conditions are imposed at the channel *** emerging linearized boundary value problem is solved analytically and expressions presented for axial(longitudinal)velocity,volumetric flow rate,shear stress function and pressure *** flow is effectively controlled by three geometric parameters,viz cilia eccentricity parameter,wave number and cilia length and two physical parameters,namely magnetohydrodynamic(MHd)body force parameter and couple stress non-Newtonian *** solutions are numerically evaluated with MATLAB *** velocity is observed to be enhanced in the core region with greater wave number whereas it is suppressed markedly with increasing cilia length,couple stress and magnetic parameters,with significant flattening of profiles with the latter two *** pressure gradient is decreased with eccentricity parameter whereas it is ele

关键词： Magneto hydrodynamics Metachronal waves Cilia Synchronous beating Polar couple stress fluid Physiological transport Magnetic blood pumps

Peristaltic flow of MHd Jeffrey fluid through finite length cylindrical tube

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Applied Mathematics and Mechanics(English Edition) 2011年第10期32卷 1231-1244页

作者： d.tripathi N.ALI T.HAYAT M.K.CHAUBE A.A.HENdI Birla Institute of Technology and Science Pilani Hyderabad CampusHyderabad 500078India department of Mathematics and Statistics International Islamic UniversityIslamabad 46000Pakistan department of Mathematics Quaid-i-Azam UniversityIslamabad 45320Pakistan department of Physics Faculty of ScienceKing Saud UniversityP.O.Box 1846Riyadh 11320Saudi Arabia department of Applied Mathematics IT-BHUVaranasi 221005India

The present investigation studies the peristaltic flow of the Jeffrey fluid through a tube of finite length. The fluid is electrically conducting in the presence of an applied magnetic field. Analysis is carried out under the assumption of long wavelength and low Reynolds number approximations. Expressions of the pressure gradient, volume flow rate, average volume flow rate, and local wall shear stress are obtained. The effects of relaxation time, retardation time, Hartman number on pressure, local wall shear stress, and mechanical efficiency of peristaltic pump are studied. The reflux phenomenon is also investigated. The case of propagation of a non-integral number of waves along the tube walls, which are inherent characteristics of finite length vessels, is also examined.

关键词： peristaltic flow magnetohydrodynamics Jeffrey fluid finite length tube mechanical efficiency reflux

3d radiative convective flow of ZnO-SAE50nano-lubricant in presence of varying magnetic field and heterogeneous reactions

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Propulsion and Power Research 2019年第4期8卷 339-350页

作者： M.K.Nayak J.Prakash d.tripathi V.S.Pandey department of Physics IHSESiksha"O"Anusandhan Deemed to be UniversityBhubaneswar751003OdishaIndia department of Mathematics Avvaiyar Government College for WomenKaraikal609602Puducherry-U.T.India department of Mathematics National Institute of TechnologyUttarakhand246174India department of Physics National Institute of Technology DelhiNew DelhiIndia

A numerical simulation is presented to investigate the effect of an exponentially varying magnetic field on three dimensional flow of Zinc Oxide-Society of Automotive Engineers 50 nanolubricant(ZnO-SAE50nano-lubricant)past a stretching *** the impact of homogenous and heterogeneous reactions on the flow of nanolubricant concerned has also taken into *** study has been strengthened by introducing the convection mechanism and the effect of thermal *** transformations are employed to transform the set of partial governing equations into the set of ordinary differential *** suitable boundary conditions are used to obtain the numerical *** numerical results are simulated using Matlab bvp4c solver and validated with the existing *** flow characteristics,thermal characteristics,nanoparticle concentration and some non-dimensional numbers are computed under the influence of the pertinent *** valuable outcome of the current study is that augmented magnetic field strength is the root cause of diminishing axial as well as transverse velocities and growing trend of fluid ***,the coeffi-cients of homogenous and heterogeneous reactions are boons for ascending concentration boundary layer.

关键词： MHd 3d flow ZnO-SAE50nanolubricant Exponential stretching sheet Convective heating mechanism Thermal radiation Heat generation/absorption

Indexing habitat suitability and human-elephant conflicts using GIS-MCdA in a human-dominated landscape

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Geography and Sustainability 2023年第4期4卷 343-355页

作者： W.K.N.C.Withanage M.d.K.L.Gunathilaka Prabuddh Kumar Mishra W.M.d.C.Wijesinghe Sumita tripathi department of Geography Faculty of Humanities and Social SciencesUniversity of Ruhun1Matara 81000Sri Lanka department of Geographical Information Science School of Geographical SciencesSouthwest UniversityBebei DistrictChongqing 400715China department of Geography University of ColomboColombo 300300Sri Lanka department of Geography Shivaji CollegeUniversity of DelhiNew Delhi 110027India department of Environment Studies Shri Lal Bahadur Shastri National Sanskrit UniversityNew Delhi 110016India

Concerns for biodiversity loss, wildlife conservation, and habitat destruction have dominated the policy agenda worldwide for decades. Unsustainable human-induced development and negative interaction between humans and wildlife have emerged as predominant issues globally. The present study deals with human and elephant conflicts (HEC) in the Polpitigama divisional Secretariat, Sri Lanka, which is located in the Kahalla-Pallekele elephant corridor and connects Wilpattu and Kaudulla wildlife sanctuaries. The research objectives are identifying spatial patterns of elephant habitat suitability and probable risk zones for HEC. The elephant habitat suitability and HEC risk zones were identified on spatial and temporal scales using Geographic Information System integrating Multi-Criteria decision Analysis. different factors, including habitat suitability, distance to roads, distance to croplands, distance to forests and protected areas, settlements, and population density, were considered to determine HEC risk zones in the area. Topography, water, and vegetation criteria are considered when determining elephant habitat suitability. The results of the Analytic Hierarchy Process run the spatially explicit model. The results revealed that of the total area, 15.3% is very highly suitable for elephant habitats, while the least suitable areas contribute only 4%. About 33.8% of the area is moderately suitable for elephants. The risk map indicates that 23.7% of the total area is under very high risk for HEC, and the least risk areas only account for 5.4%. About 26.2% of the area falls under the moderate risk zone for HEC. Since the model considered three aspects of HEC, it will help policymakers in wildlife conservation to avoid and minimize the HEC.

关键词： Analytic hierarchy process Geographic information system Human-elephant conflict Multi-criteria decision analysis Polpitigama

A two-dimensional analytical model for channel potential and threshold voltage of short channel dual material gate lightly doped drain MOSFET

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Chinese Physics B 2014年第11期23卷 620-625页

作者： Shweta tripathi department of Electronics & Communication Engineering Motilal Nehru National Institute of Technology

An analytical model for the channel potential and the threshold voltage of the short channel dual-material-gate lightly doped drain （dMG-Ldd） metal-oxide-semiconductor field-effect transistor （MOSFET） is presented using the parabolic approximation method. The proposed model takes into account the effects of the Ldd region length, the Ldd region doping, the lengths of the gate materials and their respective work functions, along with all the major geometrical parameters of the MOSFET. The impact of the Ldd region length, the Ldd region doping, and the channel length on the channel potential is studied in detail. Furthermore, the threshold voltage of the device is calculated using the minimum middle channel potential, and the result obtained is compared with the dMG MOSFET threshold voltage to show the improvement in the threshold voltage roll-off. It is shown that the dMG-Ldd MOSFET structure alleviates the problem of short channel effects （SCEs） and the drain induced barrier lowering （dIBL） more efficiently. The proposed model is verified by comparing the theoretical results with the simulated data obtained by using the commercially available ATLASTM 2d device simulator.

关键词： dual-material-gate MOSFET lightly doped drain short channel effect threshold voltage

A two-dimensional analytical modeling for channel potential and threshold voltage of short channel triple material symmetrical gate Stack(TMGS) dG-MOSFET

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Chinese Physics B 2016年第10期25卷 518-524页

作者： Shweta tripathi department of Electronics & Communication Engineering Motilal Nehru National Institute of Technology

In the present work, a two-dimensional（2d） analytical framework of triple material symmetrical gate stack（TMGS）dG-MOSFET is presented in order to subdue the short channel effects. A lightly doped channel along with triple material gate having different work functions and symmetrical gate stack structure, showcases substantial betterment in quashing short channel effects to a good extent. The device functioning amends in terms of improved exemption to threshold voltage roll-off, thereby suppressing the short channel effects. The encroachments of respective device arguments on the threshold voltage of the proposed structure are examined in detail. The significant outcomes are compared with the numerical simulation data obtained by using 2d ATLAS;device simulator to affirm and formalize the proposed device structure.

关键词： triple material symmetrical gate stack(TMGS) dG MOSFET gate stack short channel effect drain induced barrier lowering threshold voltage

Unsteady peristaltic transport of Maxwell fluid through finite length tube:application to oesophageal swallowing

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Applied Mathematics and Mechanics(English Edition) 2012年第1期33卷 15-24页

作者： S. K. PANdEY d. tripathi department of Applied Mathematics Institute of Technology Banaras Hindu University department of Mathematics Indian Institute of Technology Ropar

This paper analytically investigates the unsteady peristaltic transport of the Maxwell fluid in a finite tube. The walls of the tube are subjected to the contraction waves that do not cross the stationary boundaries. The analysis is carried out by a long wavelength approximation in the non-dimensional form. The expressions for the axial and radial velocities are derived. The pressures across the wavelength and the tubelength are also estimated. The reflux phenomenon is discussed, which culminates into the determination of the reflux limit. Mathematical formulations are physically interpreted for the flow of masticated food materials such as bread and white eggs in the oesophagus. It is revealed that the Maxwell fluids are favorable to flow in the oesophagus as compared with the Newtonian fluids. This endorses the experimental finding of Takahashi et al. （Takahashi, T., Ogoshi, H., Miyamoto, K., and Yao, M. L. Viscoelastic properties of commercial plain yoghurts and trial foods for swallowing disorders. Rheology, 27, 169- 172 （1999））. It is further revealed that the relaxation time does not affect the shear stress and the reflux limit. It is found that the pressure peaks are identical in the integral case while different in the non-integral case.

关键词： peristaltic transport Maxwell fluid oesophagus axisymmetric flow reflux

A novel approach towards molecular memory device in gate tunable structure of MoS_(2)-graphene

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Nano Research 2021年第1期14卷 177-184页

作者： Rahul tripathi Abha Misra department of Instrumentation and Applied Physics Indian Institute of Sciencey BangaloreKarnataka 560012India

Molecular interaction in two-dimensional(2d)van der Waals(vdW)interfaces has drawn tremendous attention for extraordinary materials *** sensing characteristics of molecular interaction has been exploited extensively to reach the detection limit to a few parts-per-billion(ppb)of molecules and far less attention is given to the evolution of persistent current state due to the molecular *** study focuses on molecular memory operation of MoS_(2)-graphene heterostructure based field effect *** resistance state of the device due to the external perturbation of molecules is tuned to get a nearly relaxation free current state at much lower molecular concentration of 10 ppb tofacilitate non-volatile memory features for molecular memory *** ultrafast switching operation in milli-second order is achieved at room temperature for the fastest recovery obtained sofar in any molecular *** process is co-controlled both by molecular as well as external charge density.

关键词： MoS_(2) graphene field effect transistor molecular memory trap charges