Ahmad Izani Md. Ismail

Bio: Ahmad Izani Md. Ismail is an academic researcher from Universiti Sains Malaysia. The author has contributed to research in topics: Nanofluid & Boundary layer. The author has an hindex of 22, co-authored 151 publications receiving 1660 citations.

Radiative Convective Nanofluid Flow Past a Stretching/Shrinking Sheet with Slip Effects

Abstract: Steady two-dimensional laminar mixed convective boundary-layer slip nanofluid flow in a Darcian porous medium due to a stretching/shrinking sheet is studied theoretically and numerically. A thermal radiative effect is incorporated in the model. The governing transport, partial differential equations, along with the boundary conditions, are transformed into a dimensionless form and then, via a linear group of transformation, a system of coupled similarity differential equations is derived. The transformed equations are solved numerically using the Runge–Kutta–Fehlberg fourth–fifth-order numerical quadrature method from Maple symbolic software. The effects of the controlling parameters (namely, stretching/shrinking, velocity slip, thermal slip, mass slip, Darcy number, radiation conduction, buoyancy ratio parameter, and Lewis number) on the dimensionless velocity, temperature, nanoparticle volume fraction, velocity gradient, temperature gradient, and nanoparticle volume fraction gradient are shown in graphi...

Mechanical evaluation and thermal modelling of friction welding of mild steel and aluminium

Abstract: In friction welding of two dissimilar materials, two rods are welded together by holding one of them still while rotating the other under the influence of an axial load which creates frictional heat in the interface. In this study, mechanical properties of mild steel and aluminium welded rods were evaluated to understand the thermal effects, and an explicit one-dimensional finite difference method was used to approximate the heating and cooling temperature distribution of the joint. The thermal effects of the friction welding were observed to have lowered the welded materials hardness compared to the parent materials. The tensile strength of the welded rods is lower than the parent rods due to incomplete welding. The preliminary predictions were compared to actual thermocouple data from welds conducted under identical conditions and were shown to be in fair agreement. The finite difference method proposed in this work will provide guidance in weld parameter development and will allow better understanding of the friction welding process.

Unsteady forced bioconvection slip flow of a micropolar nanofluid from a stretching/shrinking sheet

Abstract: The unsteady forced bioconvection boundary layer flow of a viscous incompressible micropolar nanofluid containing microorganisms over a stretching/shrinking sheet is studied numerically. A mathematical model, with the aid of appropriate transformations, is presented. The transformed non-linear ordinary differential equations are solved numerically by the Runge–Kutta–Fehlberg fourth- to fifth-order numerical method. The effect of the governing parameters on the dimensionless velocity, micro-rotation, temperature, nanoparticle volume fraction and microorganism as well as the local skin friction coefficient, the heat transfer rate and microorganisms transfer rate is thoroughly examined. The findings show that the value of skin friction and Nusselt number are decreased and microorganism number is increased as velocity slip, thermal slip and microorganism slip parameter are increased, respectively. Results from this investigation were compared with previous investigations demonstrating very good correlation. T...

Analytical and numerical simulation of tsunami mitigation by mangroves in Penang, Malaysia

Abstract: The Andaman tsunami that occurred on 26 December 2004 killed about a quarter million people worldwide, of which 52 deaths happened in Penang, Malaysia. Mangrove forests fringing the shallow coastal seas of Penang Island and northwest of Peninsular Malaysia have been credited to have played a role in mitigating the tsunami waves. It is therefore relevant to assess the role of mangroves in tsunami mitigation by analytical model and numerical simulations. The role of mangrove forest in reducing tsunami wave energy, heights and velocities are simulated by the incorporation of the Morison Equation to represent friction provided by the mangrove forest for the coasts of Penang. Wave heights and velocities can be reduced in the presence of mangrove. However the degree of reduction varies significantly depending on several factors such as wave period and wavelength as well as mangrove characteristics including forest widths and density. For a wave of 10 km wavelength, with wave height and velocity of 1.0 m and 1.0 m/s, respectively at the shore without a mangrove forest, then a mangrove forest of 500 m width may provide a reduction ratio for wave height and wave velocity of about 0.55 and 0.50, respectively.

The numerical solution of advection–diffusion problems using new cubic trigonometric B-splines approach

Abstract: A new cubic trigonometric B-spline collocation approach is developed for the numerical solution of the advection–diffusion equation with Dirichlet and Neumann's type boundary conditions. The approach is based on the usual finite difference scheme to discretize the time derivative while a cubic trigonometric B-spline is utilized as an interpolation function in the space dimension with the help of θ-weighted scheme. The present scheme stabilizes the oscillations that are normally displayed by the approximate solution of the transient advective–diffusive equation in the locality of sharp gradients produced by transient loads and boundary layers. The scheme is shown to be stable and the accuracy of the scheme is tested by application to various test problems. The proposed approach is numerically verified to second order and shown to work for the Peclet number ≤ 5.

A Benchmark Study on the Thermal Conductivity of Nanofluids

Abstract: This article reports on the International Nanofluid Property Benchmark Exercise, or INPBE, in which the thermal conductivity of identical samples of colloidally stable dispersions of nanoparticles or “nanofluids,” was measured by over 30 organizations worldwide, using a variety of experimental approaches, including the transient hot wire method, steady-state methods, and optical methods. The nanofluids tested in the exercise were comprised of aqueous and nonaqueous basefluids, metal and metal oxide particles, near-spherical and elongated particles, at low and high particle concentrations. The data analysis reveals that the data from most organizations lie within a relatively narrow band (±10% or less) about the sample average with only few outliers. The thermal conductivity of the nanofluids was found to increase with particle concentration and aspect ratio, as expected from classical theory. There are (small) systematic differences in the absolute values of the nanofluid thermal conductivity among the various experimental approaches; however, such differences tend to disappear when the data are normalized to the measured thermal conductivity of the basefluid. The effective medium theory developed for dispersed particles by Maxwell in 1881 and recently generalized by Nan et al. [J. Appl. Phys. 81, 6692 (1997)], was found to be in good agreement with the experimental data, suggesting that no anomalous enhancement of thermal conductivity was achieved in the nanofluids tested in this exercise.

Kinetic Theory and Fluid Dynamics

Abstract: In this series of talks, I will discuss the fluid-dynamic-type equations that is derived from the Boltzmann equation as its the asymptotic behavior for small mean free path. The study of the relation of the two systems describing the behavior of a gas, the fluid-dynamic system and the Boltzmann system, has a long history and many works have been done. The Hilbert expansion and the Chapman–Enskog expansion are well-known among them. The behavior of a gas in the continuum limit, however, is not so simple as is widely discussed by superficial understanding of these solutions. The correct behavior has to be investigated by classifying the physical situations. The results are largely different depending on the situations. There is an important class of problems for which neither the Euler equations nor the Navier–Stokes give the correct answer. In these two expansions themselves, an initialor boundaryvalue problem is not taken into account. We will discuss the fluid-dynamic-type equations together with the boundary conditions that describe the behavior of the gas in the continuum limit by appropriately classifying the physical situations and taking the boundary condition into account. Here the result for the time-independent case is summarized. The time-dependent case will also be mentioned in the talk. The velocity distribution function approaches a Maxwellian fe, whose parameters depend on the position in the gas, in the continuum limit. The fluid-dynamictype equations that determine the macroscopic variables in the limit differ considerably depending on the character of the Maxwellian. The systems are classified by the size of |fe− fe0|/fe0, where fe0 is the stationary Maxwellian with the representative density and temperature in the gas. (1) |fe − fe0|/fe0 = O(Kn) (Kn : Knudsen number, i.e., Kn = `/L; ` : the reference mean free path. L : the reference length of the system) : S system (the incompressible Navier–Stokes set with the energy equation modified). (1a) |fe − fe0|/fe0 = o(Kn) : Linear system (the Stokes set). (2) |fe − fe0|/fe0 = O(1) with | ∫ ξifedξ|/ ∫ |ξi|fedξ = O(Kn) (ξi : the molecular velocity) : SB system [the temperature T and density ρ in the continuum limit are determined together with the flow velocity vi of the first order of Kn amplified by 1/Kn (the ghost effect), and the thermal stress of the order of (Kn) must be retained in the equations (non-Navier–Stokes effect). The thermal creep[1] in the boundary condition must be taken into account. (3) |fe − fe0|/fe0 = O(1) with | ∫ ξifedξ|/ ∫ |ξi|fedξ = O(1) : E+VB system (the Euler and viscous boundary-layer sets). E system (Euler set) in the case where the boundary is an interface of the gas and its condensed phase. The fluid-dynamic systems are classified in terms of the macroscopic parameters that appear in the boundary condition. Let Tw and δTw be, respectively, the characteristic values of the temperature and its variation of the boundary. Then, the fluid-dynamic systems mentioned above are classified with the nondimensional temperature variation δTw/Tw and Reynolds number Re as shown in Fig. 1. In the region SB, the classical gas dynamics is inapplicable, that is, neither the Euler

Mathematical Epidemiology Of Infectious Diseases Model Building Analysis And Interpretation

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