National Institute of Technology Delhi

Delhi, India

National Institute of Technology Delhi

Delhi, India

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Tripathi D.,National Institute of Technology Delhi | Anwar Beg O.,Gort Engovation Research Propulsion
Mathematical Biosciences | Year: 2014

A mathematical study of the peristaltic flow of complex rheological viscoelastic fluids using the generalized fractional Burgers' model through a non-uniform channel is presented. This model is designed to study the movement of chyme and undigested chyme (biophysical waste materials) through the small intestine to the large intestine. To simulate blockages and impedance of debris generated by cell shedding, infections, adhesions on the wall and undigested material, a drag force porous media model is utilized. This effectively mimicks resistance to chyme percolation generated by solid matrix particles in the regime. The conduit geometry is mathematically simulated as a sinusoidal propagation with linear increment in shape of the bolus along the length of channel. A modified Darcy-Brinkman model is employed to simulate the generalized flows through isotropic, homogenous porous media, a simplified but physically robust approximation to actual clinical situations. To model the rheological properties of chyme, a viscoelastic Burgers' fluid formulation is adopted. The governing equations are simplified by assuming long wavelength and low Reynolds number approximations. Numerical and approximate analytical solutions are obtained with two semi-numerical techniques, namely the homotopy perturbation method and the variational iteration method. Visualization of the results is achieved with Mathematica software. The influence of the dominant hydromechanical and geometric parameters such as fractional viscoelastic parameters, wave number, non-uniformity constant, permeability parameter, and material constants on the peristaltic flow characteristics are depicted graphically. © 2013 Elsevier Inc.


Tripathi D.,National Institute of Technology Delhi | Pandey S.K.,Indian Institute of Technology BHU Varanasi | Beg O.A.,Gort Engovation Research Propulsion and Biomechanics
International Journal of Thermal Sciences | Year: 2013

The present paper describes a mathematical study on peristaltic flow of viscoelastic fluids (with the robust Jeffrey model) through a finite length channel under the influence of heat transfer. The study is motivated by the need to further elucidate the mechanisms inherent in swallowing of diverse food bolus types (bread, fruit jam and almost all edible semi-solids) through the oesophagus, by taking account of the viscous and elastic effects. The expressions for temperature field, axial velocity, transverse velocity, volume flow rate, pressure gradient, local wall shear stress, mechanical efficiency, stream function, and reflux limit are obtained, when the Reynolds number is small and the wavelength is large, by using appropriate analytical and numerical methods. The computational results are presented in graphical form. The influence of thermophysical (heat transfer), relaxation time and retardation time parameters on pressure distribution, local wall shear stress profiles, temperature profiles and velocity profiles are studied in detail. Furthermore we investigate the effects of these parameters on two inherent phenomena (reflux and trapping) characterizing peristaltic flow using streamline plots. The present study emphasizes an important observation, namely that pressure along the entire length of the channel reduces when the magnitude of relaxation time (retardation time is fixed) or Grashof number or indeed thermal conductivity increase, whereas pressure is enhanced by increasing the magnitude of retardation time (relaxation time is fixed). © 2013 Elsevier Masson SAS. All rights reserved.


Tripathi D.,National Institute of Technology Delhi | Beg O.A.,Gort Engovation Research Propulsion and Biomechanics
International Journal of Heat and Mass Transfer | Year: 2014

This paper studies the peristaltic flow of nanofluids through a two-dimensional channel. The analysis is conducted based on the long wavelength and low Reynolds number approximations. The walls of the channel surface propagate sinusoidally along the channel. The Buongiornio formulation for nanofluids is employed. Approximate analytical solutions for nanoparticle fraction field, temperature field, axial velocity, volume flow rate, pressure gradient and stream function are obtained. The impact of the pertinent physical parameters i.e. thermal Grashof number, basic-density Grashof number, Brownian motion parameter and thermophoresis parameter on nanoparticle fraction profile, temperature profile, velocity profile and trapping phenomenon are computed numerically. The results of this study demonstrate good correlation with the Newtonian results of Shapiro et al. (1969) [4], which is a special case (Gr T = 0, GrF = 0) of the generalized model developed in this article. Applications of the study include peristaltic micro-pumps and novel drug delivery systems in pharmacological engineering. © 2013 Elsevier Ltd. All rights reserved.


Hofmann T.,Helmholtz Center Berlin | Kumar P.,National Institute of Technology Delhi | Enderle M.,Laue Langevin Institute | Wallacher D.,Helmholtz Center Berlin
Physical Review Letters | Year: 2013

The structure of solid deuterium confined in 9 nm wide tubular silicon nanochannels has been studied by means of elastic neutron scattering techniques. As a result we report the formation of fcc D2 as the stable solid phase in confinement in contrast to the hcp bulk structure. Further, a preferred alignment of D2 nanocrystals with respect to the surrounding crystalline silicon matrix is discussed in terms of heteroepitaxial growth of solid D2 on crystalline pore walls. © 2013 American Physical Society.


Sharma A.K.,National Institute of Technology Delhi | Mohr G.J.,Joanneum Research
Sensors and Actuators, B: Chemical | Year: 2016

A surface plasmon resonance (SPR) based optical sensor for the determination of refractive index of human skin tissue samples is proposed. Previous experimental results describing variation of refractive index of skin tissue samples with wavelength are considered for theoretical calculations. The angular interrogation method along with glass substrate and Au-Al bimetal layer is considered. The sensor's performance is closely analyzed in terms of well-defined performance indicators in order to achieve reliable and accurate sensing performance. The influence of operating wavelength on the performance of sensor scheme is investigated. Performance comparison for two different substrates (2S2G and SF10) is carried out. The proposed sensor has the potential to provide high sensitivity, precision, and resolution, thereby opening an easy and reliable window for dermatological applications. © 2015 Elsevier B.V. All rights reserved.


Tripathi D.,National Institute of Technology Delhi | Anwar Beg O.,Sheffield Hallam University
Mathematical Biosciences | Year: 2013

Magnetic fields are increasingly being utilized in endoscopy and gastric transport control. In this regard, the present study investigates the influence of a transverse magnetic field in the transient peristaltic rheological transport. An electrically-conducting couple stress non-Newtonian model is employed to accurately simulate physiological fluids in peristaltic flow through a sinusoidally contracting channel of finite length. This model is designed for computing the intra-bolus oesophageal and intestinal pressures during the movement of food bolus in the digestive system under magneto-hydro-dynamic effects. Long wavelength and low Reynolds number approximations have been employed to reduce the governing equations from nonlinear to linear form, this being a valid approach for creeping flows which characterizes physiological dynamics. Analytical approximate solutions for axial velocity, transverse velocity, pressure gradient, local wall shear stress and volumetric flow rate are obtained for the non-dimensional conservation equations subject to appropriate boundary conditions. The effects of couple stress parameter and transverse magnetic field on the velocity profile, pressure distribution, local wall shear stress and the averaged flow rate are discussed with the aid of computational results. The comparative study of non-integral and integral number of waves propagating along the finite length channel is also presented. Magnetic field and non-Newtonian properties are found to strongly influence peristaltic transport. © 2013 Elsevier Inc.


Tripathi D.,National Institute of Technology Delhi | Anwar Beg O.,Gort Engovation Propulsion and Biomechanics Research
Computer Methods in Biomechanics and Biomedical Engineering | Year: 2015

This paper studies the peristaltic transport of a viscoelastic fluid (with the fractional second-grade model) through an inclined cylindrical tube. The wall of the tube is modelled as a sinusoidal wave. The flow analysis is presented under the assumptions of long wave length and low Reynolds number. Caputo's definition of fractional derivative is used to formulate the fractional differentiation. Analytical solutions are developed for the normalized momentum equations. Expressions are also derived for the pressure, frictional force, and the relationship between the flow rate and pressure gradient. Mathematica numerical computations are then performed. The results are plotted and analysed for different values of fractional parameter, material constant, inclination angle, Reynolds number, Froude number and peristaltic wave amplitude. It is found that fractional parameter and Froude number resist the flow pattern while material constant, Reynolds number, inclination of angle and amplitude aid the peristaltic flow. Furthermore, frictional force and pressure demonstrate the opposite behaviour under the influence of the relevant parameters emerging in the equations of motion. The study has applications in uretral biophysics, and also potential use in peristaltic pumping of petroleum viscoelastic bio-surfactants in chemical engineering and astronautical applications involving conveyance of non-Newtonian fluids (e.g. lubricants) against gravity and in conduits with deformable walls. © 2014, © 2014 Taylor & Francis.


Badgujar H.F.,Central University of Gujarat | Sharma A.K.,National Institute of Technology Delhi
Optical and Quantum Electronics | Year: 2016

Aluminum nitride (AlN) possesses noble physical and optical properties at large ranges of wavelength and temperature. A new design of AlN substrate based surface plasmon resonance (SPR) sensor for the determination of temperature is proposed. Recent experimental results describing variation of refractive index of AlN with wavelength and temperature are considered for theoretical calculations. The angular interrogation method along with thermo-optic effect in metal and dielectric media is considered. The sensor’s performance is closely analyzed in terms of well-defined performance indicators in order to achieve reliable and accurate sensing performance. The influence of operating wavelength on the performance of temperature sensor is investigated. The proposed AlN-based temperature sensor has the capability to provide high performance. The stability of AlN at higher temperature is another added advantage that contributes to precise measurements even at higher temperatures with AlN-based SPR sensor. High refractive index of AlN in combination with SPR can make it a potential candidate for infrared sensing. © 2016, Springer Science+Business Media New York.


Sharma A.K.,National Institute of Technology Delhi
Sensing and Imaging | Year: 2014

Phase interrogation based surface plasmon resonance (SPR) biosensor is proposed for the determination of Hb concentration. Previous experimental results describing variation of refractive index of human blood with Hb concentration at different wavelengths are considered for design simulations. The biosensor design with silica substrate and gold layer is considered. The sensor’s performance is closely analyzed in terms of phase sensitivity and resolution. The influence of operating wavelength on biosensor’s performance for Hb measurement is critically investigated, which points to carry out the Hb measurement at a shorter wavelength as phase sensitivity and resolution increase significantly with decrease in wavelength. The results are explained in terms of suitable physical concepts such as radiation damping. Use of contamination-preventing biochemical layer ascertains the stability of measurement with the intended SPR biosensor probe. The simulation results also highlight that the resolution of Hb measurement achievable with the proposed biosensor is much higher compared with several existing methods. © 2015, Springer Science+Business Media New York.


Tripathi D.,National Institute of Technology Delhi
Mathematical and Computer Modelling | Year: 2013

Analytical and computational studies on transient peristaltic heat flow through a finite length porous channel are presented in this paper. Results for the temperature field, axial velocity, transverse velocity, pressure gradient, local wall shear stress, volume flow rate, averaged volume flow, mechanical efficiency, and stream function are obtained under the assumption of low Reynolds number (Re. →. 0) and long wavelength approximation (a≪. λ. →. ∞). The current two-dimensional analysis is applicable in biofluid mechanics, industrial fluid mechanics, and some of the engineering fields. The impact of physical parameters such as permeability parameter, Grashof number and thermal conductivity on the velocity field, pressure distribution, local wall shear stress, mechanical efficiency of peristaltic pump, and two inherent phenomena (reflux and trapping) are depicted with the help of computational results. The main conclusions that can be drawn out of this study is that peristaltic heat flow resists more porous medium whereas the peristaltic heat flow improves with increasing magnitude of Grashof number, and thermal conductivity. The results of Tripathi (2012). [42] can be obtained by taking out the effects of porosity from this model. © 2012 Elsevier Ltd.

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