# مقالههای Gholamali Atefi

**توجه:**محتویات این صفحه به صورت خودکار پردازش شده و مقالههای نویسندگانی با تشابه اسمی، همگی در بخش یکسان نمایش داده میشوند.

##### ۱Analysis of Couette and Poiseuille flows for fourth–grade fluids and Oldroyd 6–constant fluids with the perturbation technique

اطلاعات انتشار:
شانزدهمین کنفرانس سالانه مهندسی مکانیک،
سال ۱۳۸۷

تعداد صفحات:
۶

The steady laminar flow of a fourth–grade fluid and an incompressible Oldroyd 6–constant fluid, between two parallel plates is considered. Depending upon the relative motion of the plates we analyze three types of flows: Couette flow, Poiseuille flow and generalized Couette flow. In each case, the nonlinear differential equation describing the velocity field is solved using perturbation technique. The velocity profiles for each

non–Newtonian model are presented, moreover in several diagrams the accuracy of solutions are discussed. It is observed that the results of perturbation method for fluids with small ε are very exact.<\div>

non–Newtonian model are presented, moreover in several diagrams the accuracy of solutions are discussed. It is observed that the results of perturbation method for fluids with small ε are very exact.<\div>

##### ۲Investigation of Different Nuzzle Arrangements and ShapesEffects in Impingement Oven Performance

اطلاعات انتشار:
دوازدهمین کنفرانس دینامیک شاره ها،
سال ۱۳۸۸

تعداد صفحات:
۷

In this study, the effects of different kinds of nuzzles and their arrangement in a bread impingement oven have been considered. Modified V2 – f is employed for simulation of turbulent characteristics. This simulation has been done in a 3D domain with confinement walls. In this study slot nuzzles compared with round nuzzles. Results show that round jets produce maximum nusselt number more than slot jets but non uniform.<\div>

##### ۳An analytical solution of pulsatile micropolar flows in small tubes

اطلاعات انتشار:
هجدهمین کنفرانس سالانه مهندسی مکانیک،
سال ۱۳۸۹

تعداد صفحات:
۶

Pulsatile fully–developed flows of micropolar fluids whose elements can undergo rotations as well as translations in a straight circular tube are addressed. The governing field of equation for such flows turns out to be linear coupled partial differential system. The equations are subjected to boundary conditions of velocity and microrotation which were suggested by Kirawan. Because there is no singularity point in the field of solution, standard perturbation method has been used successfully to approach the problem. To apply this perturbation method, a small parameter must exist in the system of equation. Therefore a dimension analysis has been preformed and it has been observed that if the radius of the tube is small, the production of Reynolds and Womersley numbers is too small in compassion of the other terms that exist in the equations. In the first step first–order approximations have been obtained and then their solutions have been replaced in equations to find second iteration. The higher order approximations in small tubes could be neglected. By making use of this method of solution, higher order approximation terms could be calculated to accomplish more reliable answer. These solutions have the promise of application to many practically important physical situations such as flows of polymeric fluids with deformable spring suspensions and flows of biological fluids including blood with deformable cells suspension in small arteries.<\div>

##### ۴Estimating shear stress on the wall of arteries assuming Cosserat model for blood

اطلاعات انتشار:
هجدهمین کنفرانس سالانه مهندسی مکانیک،
سال ۱۳۸۹

تعداد صفحات:
۶

This study is to investigate a method for calculating shear stress on the wall of small arteries using Cosserat model for the blood flow. As it is mentioned in many articles, blood behavior in small arteries is non– Newtonian. Many models have been suggested to describe the treatment of non–Newtonian stress tensor such as Casson`s model, power–law and etc. Each model has its priorities and weaknesses for blood flow. Ericksen (1958) has presented Cosserat model which is suitable for fluids that contain suspended particles, like red cells in plasma. But this model has some coefficients those could not be measured experimentally. In this paper genetic–algorithm has been employed to obtain these coefficients for blood. This procedure contains four steps: Driving constitutive equation, solving these equations numerically and verifying the answer, applying GA to determine the viscosity coefficient and calculating the shear stress at the wall of artery. To make use of this algorithm some experimental information of blood velocity is needed. These data are taken in to account from the work done by Rubak K.Banejee (2001).<\div>

##### ۵THE THERMOELASTIC STRESS ANALYSIS OF A GAS TURBINE BLADE WITH COOLING

اطلاعات انتشار:
دهمین همایش انجمن هوافضای ایران،
سال ۱۳۸۹

تعداد صفحات:
۷

In some problems, the stress solution depends on a thermal solution without the inverse dependency. That means stress has no effect on the heat transfer solution. In current research the pure heat transfer problem has been solved as a predefined field for the purpose of stress analysis for a turbine blade with cooling. Since the blade is subjected to a hot pressurized flow which forces the rotor to rotate at its required speed therefore, the created stress by forces lead to fraction and corrosion on the blade. In this paper, temperature and stresses fields in a gas turbine rotor are investigated using finite element method (FEM). According to the complexity of the geometry, a two dimensional modeling of a group of blade is created using a commercial CAD software. The details of this new approach are presented while stresses developed due to the turbine operating conditions at high rotational speed and thermal gradient by taking into account the material behavior at elevated temperatures K(T), E(T), α(T).Finally, these results compared with the results of the material behavior at constant properties. The results of blade with constant material properties have a good agreement with experimental results<\div>

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