ali kargar - Academia.edu (original) (raw)

Papers by ali kargar

AIAA Journal, 1976

ABSTRACT

Two-dimensional heat conduction within a composed solid material with a constant internal heat ge... more Two-dimensional heat conduction within a composed solid material with a constant internal heat generation has been investigated numerically in a sector of the rotor a generator. The heat transfer between two adjacent materials is assumed to be purely conduction. Boundary conditions are assumed to be forced convection on the fluid side and adiabatic on symmetry lines. The control volume method is applied for the diffusion energy equation. Physical coordinates are transformed to the general curvilinear coordinates. Then by using a line-by-line method, the temperature distribution in a sector of the rotor has been determined. Finally, the results are normalized and the effect of cooling fluid on the maximum temperature of insulation is investigated.

Fourth International Conference On Advances in Civil, Structural and Mechanical Engineering -ACSM 2016, 2016

In this research, numerical analysis of corners of square cylinder on following parameters of the... more In this research, numerical analysis of corners of square cylinder on following parameters of the turbulence and changing pressure and drag coefficient in air flow has been discussed. Selected models were made of Plexiglas that side length is 15mm and high of this is 400mm. To investigate effect of different corners on following parameters of square cylinder, these cylinders with sharp, rounded and beveled corners are used. Amount of bevel and radius of rounded edges are selected 25.5mm. Type of grid (mesh) around each square is structured and for other parts of solution range, unstructured mesh was used. The result of this research, shows angle of attack and figure of corners of cylinder, causes significant changes in turbulence parameters of square cylinder and value of drag coefficient. Rounding and bevel corners of square cylinder, decrease mean (average) and maximum turbulence in the wakes of cylinder. Drag coefficient by rounding and beveling corners of square cylinder with sharp edges can be considerably reduced.

An analysis has been performed to study the natural convection of a non-Newtonian fluid between t... more An analysis has been performed to study the natural convection of a non-Newtonian fluid between two infinite parallel vertical flat plates and the effects of the non-Newtonian nature of fluid on the heat transfer are studied. The governing boundary layer and temperature equations for this problem are reduced to an ordinary form and are solved by Homotopy perturbation method (HPM) and numerical method. Velocity and temperature profiles are shown graphically. The obtained results are valid for the whole solution domain with high accuracy. These methods can be easily extended to other linear and non-linear equations and so can be found widely applicable in engineering and science.

In this paper numerical analysis of compressible fluid in a convergent- divergent nozzle in super... more In this paper numerical analysis of compressible fluid in a convergent- divergent nozzle in supersonic- subsonic flow, semi-one dimensional conditions and long with the shock has been investigated. Shock occurrence point is considered in X/L=3/4, and its results are compared with analytical amounts. Governing equations written in conservation form and artificial non-viscosity term is used to prevent high vibrations in shock area in momentum equation. Because of changing cross section along the flow, all fluid characteristics would be considered a function of x. so by choosing an appropriate control volume, the main equations include continuity, momentum and energy were discrete .To solve the main equations, McCormack explicit method are used.

International journal of advanced computer science, 2012

Advanced Studies in Theoretical Physics

A modified variational approach called Global Error Minimization (GEM) method is developed for ob... more A modified variational approach called Global Error Minimization (GEM) method is developed for obtaining an approximate closed-form analytical solution for nonlinear oscillator differential equations. The proposed method converts the nonlinear differential equation to an equivalent minimization problem. A trial solution is selected with unknown parameters. Next, the GEM method is used to solve the minimization problem and to obtain the unknown parameters.