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MHD free convective flow past semi-infinite vertical permeable wall

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Applied Mathematics and Mechanics(English Edition) 2012年第9期33卷 1207-1222页

作者： r.k.singh A.k.singh Department of Mathematics Banaras Hindu University

In this paper, the basic equations governing the flow and heat transfer of an incompressible viscous and electrically conducting fluid past a semi-infinite vertical per- meable plate in the form of partial differential equations are reduced to a set of non-linear ordinary differential equations by applying a suitable similarity transformation. Approx- imate solutions of the transformed equations are obtained by employing the perturbation method for two cases, i.e., small and large values of the suction parameter. From the numerical evaluations of the solution, it can be seen that the velocity field at any point decreases as the values of the magnetic and suction parameters increase. The effect of the magnetic parameter is to increase the thermM boundary layer. It is also found that the velocity and temperature fields decrease with the increase in the sink parameter.

关键词： magnetohydrodynamics (MHD) suction source/sink prandtl number permeability boundary layer

poverty alleviation and resource conservation through development of cost effective technology at foot hill of Shivalik - A case study

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International Journal of Agricultural and Biological Engineering 2013年第3期6卷 34-40页

作者： r kumar p k singh B A Langoo Division of Agricultural Engineering Sher-e-Kashmir Univeristy of Agricultural Sciences and Techonology of KashmirSrinagar(J&K)India Department of soil and water Engineering College of Technology and EngineeringUdaipur(Raj)India

The study revealed the development of cost effective technology utilized as a practical tool for treatment of seasonal torrent and addressing erosion problems and land use *** was implemented in a small agricultural watershed located in foot hill of Shivalik,India,to assess its prediction capacity of runoff,peak runoff flow and sediment *** effective technology was evaluated at the event scale by using a database of hydrological,geomorphologic and land use data collected during a two-year *** the catchment,the gullies which are small to medium in size were treated with gully plugging by erecting loose boulder check dams and erected with different species of *** types of spur were constructed with vegetative reinforcement for channelization of stream *** sediments deposited in the first year at downstream was recorded 0.09-81.0 tons,while in the second year it was reduced up to 0.07-16.7 ***,up stream sediment deposition was recorded 1.0-72.0 tons and 0.37-13.1 tons in two consecutive *** D-50 analysis of sediment deposited was carried in three different places of torrent and it was found that deposited particle size material decreased after treatment undertaken in the torrent ***,the mechanical as well as vegetative measures helped in the channelization of water course towards the central line with the tune of 10-100 m,stabilization of torrent bed and reclamation of degraded land.

关键词： Integrated watershed management mechanical measures D-50 vegetative measures

Effect of induced magnetic field on natural convection in vertical concentric annuli

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Acta Mechanica Sinica 2012年第2期28卷 315-323页

作者： r.k.singh A.k.singh Department of Mathematics Central University of BiharPatnaIndia Department of Mathematics Banaras Hindu UniversityVaranasiIndia

In the present paper, we have considered the steady fully developed laminar natural convective flow in open ended vertical concentric annuli in the presence of a ra- dial magnetic field. The induced magnetic field produced by the motion of an electrically conducting fluid is taken into account. The transport equations concerned with the con- sidered model are first recast in the non-dimensional form and then unified analytical solutions for the velocity, induced magnetic field and temperature field are obtained for the cases of isothermal and constant heat flux on the inner cylin- der of concentric annuli. The effects of the various phys- ical parameters appearing into the model are demonstrated through graphs and tables. It is found that the magnitude of maximum value of the fluid velocity as well as induced magnetic field is greater in the case of isothermal condition compared with the constant heat flux case when the gap be- tween the cylinders is less or equal to 1.70 times the radius of inner cylinder, while reverse trend occurs when the gap between the cylinders is greater than 1.71 times the radius of inner cylinder. These fields are almost the same when the gap between the cylinders is equal to 1.71 times the radius of inner cylinder for both the cases. It is also found that as the Hartmann number increases, there is a flattening ten- dency for both the velocity and the induced magnetic field. The influence of the induced magnetic field is to increase the velocity profiles.

关键词： Natural convection Isothermal Heat flux Skin-friction Induced magnetic field Magnetohydrody- namics

reflection of three-dimensional plane waves at the free surface of a rotating triclinic half-space under the context of generalized thermoelasticity

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Applied Mathematics and Mechanics(English Edition) 2021年第9期42卷 1363-1378页

作者： p.singh A.k.singh A.CHATTOpADHYAY Department of Mathematics and Computing Indian Institute of Technology(ISM)Dhanbad-826004JharkhandIndia

The reflection of three-dimensional(3D) plane waves in a highly anisotropic(triclinic) medium under the context of generalized thermoelasticity is studied. The thermoelastic nature of the 3D plane waves in an anisotropic medium is investigated in the perspective of the three-phase-lag(TpL), dual-phase-lag(DpL), Green-Naghdi-III(GNIII), Lord-Shulman(LS), and classical coupled(CL) theories. The reflection coefficients and energy ratios for all the reflected waves are obtained in a mathematical form. The rotational effects on the reflection characteristics of the 3D waves are discussed under the context of generalized thermoelasticity. Comparative analyses for the reflection coefficients of the waves among these generalized thermoelastic theories are performed. The energy ratios for each of the reflected waves establish the energy conservation law in the reflection phenomena of the plane waves. The highly anisotropic materials along with the rotation may have a significant role in the phenomenon of the reflection behavior of the 3D waves. Numerical computations are performed for the graphical representation of the study.

关键词： reflection energy ratio triclinic thermoelasticity rotation three-dimensional(3D)wave

Heliospheric Effect on Solar Activity parameters during Maximum phase of Solar Cycle 24(2012–2015)

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research in Astronomy and Astrophysics 2024年第12期24卷 3-12页

作者： p.r.singh Upendra kr.singh kushwaha A.k.singh T.k.pant Department of physics University of Allahabad Department of physics Banaras Hindu University Space physics Laboratory VSSC

The time series of daily data on solar activity proxies, namely the sunspot number(SSN), sunspot area(SSA), solar radio flux(F10.7), modified coronal index(MCI), solar flare index(FI), and cosmic ray intensity(CrI), were analyzed to understand the solar activity modulations and short-term periodicities therein. rieger-type and other short-term periods include the solar rotational period that covers the maximum activity phase period(maximum phase of solar cycle 24). The wavelet power spectra and periodogram of SSN, SSA, F10.7, MCI, FI, and CrI exhibited a significant short-term period. The heliospheric effects exist for a particular period(～27 days) and they are related to the solar activity phenomena. The cross-correlation coefficients and time lags between the CrI and solar activity parameters were estimated to be ～200, 46, 281, 39, and 47 days for SSN, SSA, F10.7, MCI, and FI respectively during the time series 2012–2015(maximum phase of solar cycle 24).

关键词： (Sun:) sunspots Sun: activity Sun: flares Sun: heliosphere Sun: rotation

Nonlinear mixing-based terahertz emission in inclined rippled density plasmas

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Chinese physics B 2023年第6期32卷 384-390页

作者： k Gopal A p singh S Divya rajdhani College Department of Physics&ElectronicsUniversity of DelhiNew DelhiIndia Computational plasma Dynamics Laboratory Rajdhani CollegeDepartment of Physics&ElectronicsUniversity of DelhiNew DelhiIndia

We propose to investigate the THz field generation using nonlinear mixing mechanism of laser beat wave with inclined rippled density *** laser pulses with frequencies(ω_(1),ω_(2)) and wave vectors(k_(1),k_(2)) co-propagate and resultant laser beat wave forms at beat frequency(ω_(1)-ω_(2)).Laser beat wave imparts a nonlinear force on the ambient electrons and pushes them outward with nonlinear velocity v_(NL).Coupling of induced density perturbation and nonlinear velocity v_(NL)generates nonlinear currents at laser beat frequency that further generates electromagnetic field E_((ω_(1)-ω_(2))) in terahertz(THz)*** the present scheme,density ripples are introduced at an angle with respect to laser propagation and flat Gaussian index(f) is introduced in laser field profile that transform curved top of Gaussian field envelope into flat top field *** combined effect of flat laser pulses with inclined density ripples in plasmas shows 10-fold enhancement in THz field amplitude when flat-Gaussian index(f) varies from 1 to ***,the THz field intensifies when density ripples inclination increases upto a certain angle and then decreases.

关键词： terahertz inclined ripple flat laser laser plasma interaction

rayleigh-type wave propagation in incompressible visco-elastic media under initial stress

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Applied Mathematics and Mechanics(English Edition) 2018年第3期39卷 317-334页

作者： p.singh A.CHATTOpADHYAY A.k.singh Department of Applied Mathematics Indian Institute of Technology (ISM)

propagation of rayleigh-type surface waves in an incompressible visco-elastic material over incompressible visco-elastic semi-infinite media under the effect of initial stresses is discussed. The dispersion equation is determined to study the effect of differ- ent types of parameters such as inhomogeneity, initial stress, wave number, phase velocity, damping factor, visco-elasticity, and incompressibility on the rayleigh-type wave prop- agation. It is found that the affecting parameters have a significant effect on the wave propagation. Cardano＇s and Ferrari＇s methods are deployed to estimate the roots of dif- ferential equations associated with layer and semi-infinite media. The MATHEMATICA software is applied to explicate the effect of these parameters graphically.

关键词： rayleigh-type wave inhomogeneity initial stress visco-elasticity incom-pressible

Motion through spherical droplet with non-homogenous porous layer in spherical container

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Applied Mathematics and Mechanics(English Edition) 2020年第7期41卷 1069-1082页

作者： p.k.YADAV A.TIWArI p.singh Department of Mathematics Motilal Nehru National Institute of Technology AllahabadPrayagraj 211004India Department of Mathematics Birla Institute of Technology SciencePilani 333031Rajasthan Department of Mathematics National Institute of Technology PatnaPatna 800005India

The problem of the creeping flow through a spherical droplet with a non-homogenous porous layer in a spherical container has been studied ***’s model for the flow inside the porous annular region and the Stokes equation for the flow inside the spherical cavity and container are used to analyze the *** drag force is exerted on the porous spherical particles enclosing a cavity,and the hydrodynamic permeability of the spherical droplet with a non-homogeneous porous layer is *** is placed on the spatially varying permeability of a porous medium,which is not covered in all the previous works related to spherical *** variation of hydrodynamic permeability and the wall effect with respect to various flow parameters are presented and discussed *** streamlines are presented to discuss the kinematics of the *** previous results for hydrodynamic permeability and drag forces have been verified as special limiting cases.

关键词： non-homogenous porous medium Stokes equation Darcy’s law perme-ability parameter wall effect

Strength and deformation characteristics of steel fibrous concrete beams

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Journal of Zhejiang University-Science A(Applied physics & Engineering) 2007年第2期8卷 257-263页

作者： singh Bhupinder singh S.p. kAUSHIk S.k Department of Civil Engineering Indian Institute of Technology Roorkee 247 667 India Department of Civil Engineering National Institute of Technology Jalandhar 144 011 India

The results of an analytical investigation of the flexural behaviour of Steel Fibre reinforced Concrete （SFrC） beams are presented. The complete response of the SFrC beams under displacement controlled static loading was obtained using nonlinear Finite Element （FE） techniques implemented with the help of ATENA 2D sorware. Issues relating to the behaviour of SFrC which have a direct bearing on the FE modelling are discussed with relevance to the software employed for the nonlinear analysis. Constitutive models amenable to numerical analysis for steel fibrous concrete are presented. The structural response throughout the loading regime was captured in terms of the load-deflection behaviour, which in addition to the post-peak response characterized the failure mode of the test beams. The crack patterns at crack initiation and at the end of the tests were also recorded. Experimental results from the specimens of two other investigators were used as control values for this investigation. The response of the specimens of this investigation was evaluated in terms of initial tangent stiffness, peak loads and toughness. Good match was obtained between the results from this investigation and corresponding experimentally obtained values, wherever available. The influence of the fibre content is reflected in the observed trends in peak loads, deflection at peak loads and toughness, which are in broad agreement with known behavioral patterns of SFrC.

关键词： Analysis Deformation Strength Steel Fibre reinforced Concrete (SFrC) Toughness