Ali Ahmed | University of BALOCHISTAN (original) (raw)

Papers by Ali Ahmed

This paper focuses on the analytical and numerical solutions of dynamic models for dengue fever. ... more This paper focuses on the analytical and numerical solutions of dynamic models for dengue fever. The considered model consists of a system of coupled non-linear differential equations. Homotopy Perturbation Method (HPM) and Runge Kutta Method of Order 4 (RK4) are applied to obtain analytical and numerical solutions, respectively. Moreover, the positivity of the solution is proved. The results of the suggested methods are validated with the exact solution for simplified model equations. Furthermore, the proposed methods are applied to the considered model using the real time data of Lahore (years 2011-2014), Pakistan. The results are found to be in agreement with the available exact solution and real time data. HPM results approach the exact solution by including higher order polynomials. The parametric study of dengue cases are performed. Moreover, the synchronization between the simulated results and real time data of dengue cases verifies the correctness of model formulation. On the

A numerical study is performed to analyze the effect of small control cylinders on fluid forces r... more A numerical study is performed to analyze the effect of small control cylinders on fluid forces reduction and vortex shedding suppression on the flow past three inline square cylinders using the lattice Boltzmann method (LBM). The Reynolds number Re = 160 is fixed while the spacing between the cylinders is taken in the range 1.0D ≤ g * ≤ 5.0D (where D is the size of the main cylinder) and the control cylinder size is varied from 0.1D to 0.5D. To systematically understand the effect of control cylinders on the forces a detailed analysis of Strouhal number (St), mean drag coefficient (C Dmean), root mean square values of drag and lift coefficients is presented in this paper. In this study, it is observed that the average mean drag coefficient (C Dmeanaverage) and Strouhal number reached either maximum or minimum values at different values of separation ratio (g *) and small control cylinder size (d). It is found that at (g * , d) = (5.0, 0.0) and (1.0, 0.5) the average C Dmean attains its maximum (C Dmeanaverage = 0.7813) and minimum (C Dmean = 0.0988) values. Furthermore, at (g * , d) = (5.0, 0.3) and (2.0, 0.0) the average St attains its maximum (St = 0.1780) and minimum (St = 0.041) values. It is found that the flow regimes completely changes in presence of control cylinders. Particularly, at g * = 4.0, there is a critical flow regime when the size of control cylinder changes from 0.1 to 0.5. The sudden jump in the mean drag coefficient and Strouhal number for the middle cylinder with their maximum and minimum values also confirm the critical flow regime. The effect of control cylinders within tandem square cylinders has not been studied before.

This work presents a numerical simulation performed to study the effect of Reynolds number (Re = ... more This work presents a numerical simulation performed to study the effect of Reynolds number (Re = 80-200) on fluid flow over a square rod attached to two small controlling rods using the Lattice Boltzmann method. For this reason, the spacing ratio between the control rods and main rod varies systematically from g = 0.5-5. Flow has been subdivided into three flow regimes based on spacing ratios. The first flow regime is considered at a small gap (g = 0.5, 1, and 1.5), the second flow regime is obtained at a moderate gap (g = 2, 2.5, and 3), and the third flow regime is considered a at large gap (g = 4-5). Five different types of flow modes were noticed in the given flow regimes. The values Re = 200 and g = 5 were found to be critical due to a sudden change in flow characteristics. The maximum value of Cd mean is 0.869 and the largest percent reduction (65.15%) in the mean drag coefficient was found at Re = 200 and g = 2.

Numerical simulations are carried out to study the flow around two tandem square cylinders (SC) u... more Numerical simulations are carried out to study the flow around two tandem square cylinders (SC) under the effect of spacing ratio(g/D) and splitter plate length (l/D) for a fixed Reynolds number (Re) � 100. e g/D is varied from 0 to 10 and l/D is varied from 0.5 to 10. e splitter plate length is found to have strong effect on vortex shedding and fluid forces. e maximum reduction in mean drag coefficient is observed at l/D � 8, that is 15% and 78% for upstream and downstream cylinders, respectively. e maximum reduction in root-mean-square value of lift coefficient is found at l/D � 10, that is 99%. e flow pattern at both of these points is steady flow. ere is 100% vortex shedding suppression for l/D > 5. e observed flow patterns for flow past tandem cylinders without splitter plate are; single bluff body (SBB), steady flow (SF), quasi-steady flow (QSF), fully developed flow (FDF) and fully developed two-row vortex street flow (FDTRVS) regimes. SBB, QSF and SF regimes were observed in presence of splitter plate.