Browsing by Author "Asif Ali"

Now showing 1 - 9 of 9
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    Comparative analysis for the performance of diesel engine using blends of biodiesel from neem oil & distilled neem oil
    (UMT Lahore, 2025-09-19) Asif Ali; Ali Ashfaq; Muhammad Sohail
    This study investigates Neem oil biodiesel as a sustainable alternative to conventional diesel, focusing on Pakistan where Neem (Azadirachta indica) is abundant as a non-edible feedstock. To address the high free fatty acid content of raw Neem oil, a distillation pre-treatment was applied prior to biodiesel production. Blends of raw and distilled Neem biodiesel (B05–B30) were tested in a single-cylinder, four-stroke diesel engine to evaluate performance and emission behavior. Experimental results showed that distilled Neem biodiesel blends outperformed raw biodiesel in both efficiency and emissions. Brake thermal efficiency increased by up to 88.96% for DNB25D75, while brake-specific fuel consumption was reduced by over 40% compared to diesel. Emission analysis revealed notable decreases in carbon monoxide (CO) and sulfur oxides (SO₂), along with a downward trend in nitrogen oxides (NOₓ), contrary to typical biodiesel behavior. These improvements were attributed to the enhanced viscosity, volatility, and combustion quality of distilled Neem biodiesel. Overall, distilled Neem biodiesel demonstrated superior fuel efficiency and lower pollutant emissions, confirming its potential as a technically viable and environmentally preferable alternative to diesel. Its adoption could reduce Pakistan’s dependence on imported petroleum while supporting cleaner energy solutions for agricultural and rural applications.
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    Entropy generation in hydrodynamic slip flow over a vertical plate with convective boundary
    (Springer, 2012) Adnan Saeed Butt; Sufian Munawar; Asif Ali; Ahmer Mehmood
    The present article aims to report the effects of hydrodynamic slip on entropy generation in the boundary layer flow over a vertical surface with convective boundary condition. Suitable similarity transformations are used to transform the fundamental equations of hydrodynamic and thermal boundary layer flow into ordinary differential equations. The governing equations are then solved numerically using the shooting method and the velocity and the temperature profiles are obtained for various values of parameters involved in the governing equations. The expressions for the entropy generation number and the Bejan number are presented and the results are discussed graphically and quantitatively for the slip parameter, the local Grashof number, the Prandtl number, the local convective heat transfer parameter, the group parameter and the local Reynolds number. It is observed that due to the presence of slip, entropy production in a thermal system can be controlled and reduced.
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    Extensions, integrations and applications of best worst method
    (UMT Lahore, 2022-04-01) Asif Ali
    This research consists of two-part; one is the extensions of the classical Best-Worst Method (BWM) in the context of hesitant fuzzy information and generalized interval-valued trapezoidal fuzzy (GITrF) information, and the other is the applications of classical and fuzzy BWM and hybrid methodologies for industrial robot selection. Fuzzy extensions of BWM are proposed using hesitant and GITrF multiplicative preference relations. The linguistic terms are used to express the reference comparisons of the best criterion and the worst criterion. These linguistic terms are expressed in hesitant fuzzy elements and GITrF numbers, respectively. The non-linear constrained mathematical models are constructed to obtain the hesitant and GITrF weights of criteria that are converted to crisp weights. The consistency ratio of both extensions is proposed to check the reliability of the methods. The results of comparative case analysis show the advantage and suitability of the proposed methods due to higher comparison consistency as compared to BWM and fuzzy BWM. For different applications, there are different robots having capabilities and specifications accordingly. For a particular application and industrial requirement, proper and suitable selection of a robot is a difficult task. Numerous robot selection methods are available. Considering the research works on industrial robot selection, three Multiple Criteria Decision Making (MCDM) methodologies are proposed. (1) Group BWM is employed for the proper selection of robots. Weighing the decision-makers by considering their past experience is an important factor considered for expert and reliable selection of robots. Objective weights to describe the importance of the attributes along with the decision-makers’ subjective preferences to describe the weights of the attribute are considered. (2) A hybrid MCDM methodology is proposed by integrating BWM with the evaluation based on distance from average solution method. (3) GITrF best-worst method is integrated with extended Technique for Order of Preference by Similarity to Ideal Solution and extended VlseKriterijumska Optimizacija I Kompromisno Resenje methods for the selection of the optimal industrial robot using fuzzy information. For this study, both subjective and objective criteria are considered. The preferences of decision-makers are provided with the help of linguistic terms that are then converted into fuzzy information. Comparative studies and sensitivity analysis are performed to check the stability and reliability of the proposed methodologies. The proposed hybrid and fuzzy methodologies are not limited to robot selection; instead, they are general and can be used for any criteria-based selection problems.
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    Thermal analysis of the flow over an oscillatory stretching cylinder
    (IOP Publishing, 2012) Sufian Munawar; Asif Ali; Ahmer Mehmood
    An investigation has been conducted on the convective heat transfer and the entropy production attributable to the presence of an infinitely long cylinder in a viscous fluid exhibiting oscillatory motion. The heat transfer analysis is carried out by assuming that the surface of the cylinder is isothermal. The entropy generation is caused by heat transfer attributable to the finite temperature difference MT and viscous effects produced in the fluid. The number of independent variables in the governing equations is reduced by using a proper set of similarity variables. To obtain the solution of the nonlinear partial differential equation, we use a well-known finite difference scheme by transforming the semi-infinite domain to a finite domain. The numerical results have been analyzed by means of a comprehensive parametric study. It is observed that the entropy production intensifies in the presence of the oscillatory motion of the cylinder.
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    Time dependent flowin a composite channel with heat transfer
    (Begell House, Inc. Publishers, 2013) Muhammad Nasir; Sufian Munawar; Asif Ali
    In this article, unsteady oscillatory flow and heat transfer in a horizontal composite porous channel is discussed. The Darcy-Brinkman model is used to develop the governing equations for the flow in a porous medium. The upper plate is oscillating with the constant amplitude while the lower plate is stationary. The viscous and Darcian dissipation terms are included in the energy equation. At the interface of both regions the velocity, shear stress, and temperature profiles are assumed to be continuous. The governing equations for momentum and heat transfer are solved analytically using the series solution in terms of harmonic and nonharmonic functions in both regions of the channel. The effects of various physical parameters on the velocity and the temperature profiles are analyzed with the help of graphs and tables.
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    Time-dependent flow and heat transfer over a stretching cylinder
    (The Physical Society of Republic of China, 2012) Sufian Munawar; Ahmer Mehmood; Asif Ali
    The unsteady laminar boundary-layer flow and heat transfer of a viscous fluid over a stretching cylinder is discussed in this work. To normalize the governing system of equations a proper set of similarity variables is used. Two types of thermal boundary conditions, prescribed surface temperature (PST) and prescribed heat flux (PHF), are taken into account for thermal analysis. The governing equations are solved using the homotopy analysis method, and the obtained series solution is found to be valid for the entire temporal and spatial domains and for certain ranges of the other physical parameters. The effects of various material parameters on different physical quantities, such as the coefficient of skin friction and the Nusselt number, are illustrated through graphs and tables.
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    Time-dependent stagnation-point flow over rotating disk impinging oncoming flow
    (Shanghai University and Springer-Verlag, 2013) Sufian Munawar; Ahmer Mehmood; Asif Ali
    The unsteady stagnation point flow of an incompressible viscous fluid over a rotating disk is investigated numerically in the present study. The disk impinges the oncoming flow with a time-dependent axial velocity. The three-dimensional axisymmetric boundary-layer flow is described by the Navier-Stokes equations. The governing equations are solved numerically, and two distinct similarity solution branches are obtained. Both solution branches exhibit different flow patterns. The upper branch solution exists for all values of the impinging parameter and the rotating parameter . However, the lower branch solution breaks down at some moderate values of . The involvement of the rotation at disk allows the similarity solution to be transpired for all the decreasing values of . The results of the velocity profile, the skin friction, and the stream lines are demonstrated through graphs and tables for both solution branches. The results show that the impinging velocity depreciates the forward flow and accelerates the flow in the tangential direction.
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    Unsteady Boundary-Layer Flow over Jerked Plate Moving in a Free Stream of Viscoelastic Fluid
    (The Scientific World Journal, 2014) Sufian Munawar; Ahmer Mehmood; Asif Ali; Najma Saleem
    This study aims to investigate the unsteady boundary-layer flow of a viscoelastic non-Newtonian fluid over a flat surface.The plate is suddenly jerked to move with niform velocity in a uniform stream of on-Newtonian fluid. Purely analytic solution to governing nonlinear equation is obtained. The solution is highly accurate and valid for all values of the dimensionless time 0 ≤ 𝜏 < ∞. Flow properties of the viscoelastic fluid are discussed through graphs.
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    Unsteady flow and heat transfer in a composite porous annulus with time-dependent injection
    (VERLAG Z NATURFORSCH, 2012) Muhammad Nasir; Sufian Munawar; Ahmer Mehmood; Asif Ali
    In the present study, we deal with the momentum and heat transfer analysis in a horizontal annulus of a composite porous medium. The Darcy–Brinkman model is used to develop the governing equations for the flow and heat transfer phenomenon. The annulus injects the time dependent oscillatory velocity normal to its surface. Both the regions of the flow have their own viscosities, and the heat transfer analysis is carried out by retaining viscous dissipation. The governing equations for flow and heat transfer are solved analytically using a perturbation series for solutions in both regions of the annulus. A brief parametric analysis is performed for the velocity and the temperature profiles through graphs.