• M IJAZ KHAN

      Articles written in Pramana – Journal of Physics

    • Theoretical investigation of chemically reactive flow of water-based carbon nanotubes (single-walled and multiple walled) with melting heat transfer

      TASAWAR HAYAT K MUHAMMAD M IJAZ KHAN A ALSAEDI

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      This study reports the chemically reacting flow of carbon nanotubes (CNTs) over a stretchable curved sheet. The flow is initialised due to a stretched surface. A heat source is present. Water is considered as the base liquid. The vital interest of this work is that heat phenomenon is studied via melting heat transfer. Xue relation of nanoliquid is implemented to explain the properties of both single- and multiwall CNTs. Mathematical systems (partial differential equations) for the flow field are obtained. Appropriate transformations are utilised in order to transform partial differential systems into nonlinear ordinary differential systems. Further, these systems are solved numerically. Variations in flow, temperature, concentration, skin friction coefficient and Nusselt number via the involved influential variables are illustrated graphically.

    • Entropy generation optimisation in the nanofluid flow of a second grade fluid with nonlinear thermal radiation

      TASAWAR HAYAT MEHREEN KANWAL SUMAIRA QAYYUM M IJAZ KHAN AHMED ALSAEDI

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      The flow of a second grade fluid by a rotating stretched disk is considered. Brownian motion and thermophoresis characterise the nanofluid. Entropy generation in the presence of heat generation/absorption, Joule heating and nonlinear thermal radiation is discussed. Homotopic convergent solutions are developed. The behaviour of velocities (radial, axial, tangential), temperature, entropy generation, Bejan number, Nusselt number, skin friction and concentration is evaluated. The radial, axial and tangential velocities increase for larger viscoelastic parameters while the opposite trend is noted for temperature. Concentration decreases when Schmidt number and Brownian diffusion increase. Entropy generation increases when the Bejan number increase while the opposite is true for the Brinkman number and the magnetic parameter.

    • Transportation of activation energy in the Oldroyd-B nanofluid by considering double stratification over a surface with variable thickness

      M IJAZ KHAN SUMAIRA QAYYUM SHAHID FAROOQ T HAYAT A ALSAEDI

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      In this communication, the impact of activation energy on the nonlinear binary chemically reactive flow of an Oldroyd-B nanofluid has been examined. Buongiorno’s nanofluid model is used in mathematical modelling. The flow behaviour is discussed over a nonlinear stretchable surface with variable thickness. Nonlinear mixed convection is considered. The energy equation is modelled subject to a heat source/sink and radiative flux. Furthermore, double stratification at the boundary of the sheet is considered for the heat and mass transfers. Important slip mechanisms such as Brownian and thermophoresis diffusions are accounted. The obtained flow expressions are analytically solved by using the optimal homotopy asymptotic method (OHAM). Computational analysis for concentration, temperature and velocity is obtained and discussed using plots. Nusselt and Sherwood numbers are discussed using a tabulated form. Total squared residual error is calculated for velocity, temperature andconcentration. The obtained results show that for increased values of Hartmann (magnetic parameter) and Deborah numbers, the fluid velocity decreases. The temperature field shows an increasing impact in the presence of larger radiative parameters. Sherwood and Nusselt numbers increase with higher values of thermophoresis and solutal stratified parameters.

    • Heat and mass transfer features of transient second-grade fluid flow through an exponentially stretching surface

      AAMIR ABBAS KHAN MUHAMMAD NAVEED KHAN NAVEED AHSAN M IJAZ KHAN TASEER MUHAMMAD AYESHA REHMAN

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      This paper deals with an unsteady magnetohydrodynamic (MHD) two-dimensional (2D) second-grade fluid flow towards a permeable exponentially stretching surface with homogeneous–heterogeneous reactions. The non-uniform heat source/sink, variable thermal conductivity and thermal radiation are considered to analyse the thermal attributes. The velocity slip effect is also taken into consideration at the boundary of the surface. The modelled equations of motions and energy are transformed into non-linear ODEs by suitable transformations. The Matlab Bvp4c approach is employed for the numerical solution of the equations. The impacts of various parameters are scrutinised using graphs. The physical quantities of interests such as Sherwood number,Nusselt number and skin friction are presented in the form of graphs and tables and discussed. The velocity profile diminishes by enhancing the values of the parameter of the porous medium. The temperature field rises with larger values of thermal radiation parameters. Decay in concentration profile is noted when the influence of homogeneous–heterogeneous reactions becomes larger. By increasing the values of the second-grade fluid parameter, the magnetic field parameter and the porous medium, the coefficient of skin friction increases, while it reduces by enhancing the values of the unsteady parameter.

    • Numerical simulations for optimised flow of second-grade nanofluid due to rotating disk with nonlinear thermal radiation: Chebyshev spectral collocation method analysis

      SHAMI A M ALSALLAMI USMAN SAMI ULLAH KHAN ABUZAR GHAFFARI M IJAZ KHAN M A EL-SHORBAGY M RIAZ KHAN

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      The optimised flow of nanofluids is quite essential to improve the thermal mechanism of various reacting materials. The entropy generation phenomenon is essential to avoid heat losses in thermal transport systems, heating processes and various engineering devices. In this theoretical analysis, the aspects of entropy generation is presented for time-independent second-grade nanomaterials for disk flow which shows rotating behaviours. The second-grade constitutive relations result in highly nonlinear differential equations. The effects of MHD, nonlinear radiation and chemical reaction are manifested in momentum, heat and concentration equations. Precise numerical treatmentfor a wide range of non-Newtonian fluid parameters was adopted to tackle the resulting similarity equations. The fluctuation against the heat transfer system, wall shear stress and mass changing phenomenon were also calculatedand examined for various parametrical values. The interesting Chebyshev spectral collocation numerical simulations were performed to present the solution. This research finds that the entropy generation and Bejan number show thesame trend for temperature and concentration difference parameters, whereas an opposite trend can be seen for the fluid and magnetic parameters. Also, entropy generation increases for diffusion parameter and Brinkman number,but Bejan number shows two trends.

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