# مقالههای ahmadreza pishevar

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

##### ۱A level –set approach for simulation of incompressible two –phase flows

اطلاعات انتشار:
هفدهمین کنفرانس سالانه مهندسی مکانیک،
سال ۱۳۸۸

تعداد صفحات:
۷

The numerical simulation of a two –dimensional bubble rising in a closed container filled by a liquid and also the simulation of falling droplet in a tank are presented.<\div>

##### ۲Numerical Investigation of Surfactants Behavior in the Poiseuille Flow Using Dissipative Particle Dynamics

اطلاعات انتشار:
بیستمین کنفرانس سالانه مهندسی مکانیک،
سال ۱۳۹۱

تعداد صفحات:
۵

Surfactants are defined as substances that can greatly reduce the water surface tension when used in very low concentrations. Recently, surfactant additives are considered as excellent drag reduction agents as well. They have very industrial applications in both chemical and consumer domains and have provided a quickly growing area of scientific research. In this paper, dissipative particle dynamics method is used for exploiting the behavior of surfactants under poiseuille flow. Morphology of micelles, velocity profile and density profile are examined and it will beshown that micelles migrate to the low shear rate regions and greatly stretched in the flow direction.<\div>

##### ۳Numerical Study on the Jet Dynamic through Centrifuge Spinning: Influence of Angular Velocity

نویسنده(ها):
Afsaneh Valipouri،
Seyed Abdolkarim Hosseini Ravandi*،
ahmadreza pishevar،
Emilian I Parau

اطلاعات انتشار:
Journal of Textiles and Polymers،
سوم،شماره۱، JAN ۲۰۱۵،
سال ۰

تعداد صفحات:
۶

Centrifuge spinning is a method that makes possible of fabrication nanofibers rapidly and at high yields. In the centrifugal spinning process, a polymer solution is delivered by the centrifugal force through small nozzle of a rapidly rotating cylindrical drum. Thereby, thin ﬁbers are formed and collected on a collector in the form of a web. In this study, a mathematical model of the dynamics of a viscous liquid jet, which emerges from rotating drum through centrifuge spinning, was derived. The Navier–Stokes equations were solved in this system with the usual viscous free surface boundary conditions. One–dimensional equations were derived using asymptotic methods based upon a slender jet assumption and solved numerically. The effect of angular velocity upon the trajectory, radius, and tangential velocity of the jet was simulated and presented. Increasing angular velocity resulted in a decrease in the size of the liquid jet. Also, increasing angular velocity tended to increase the jet velocity which translated to increase the production rate. The jet centerline became more tightly coiled when the angular velocity increased. In addition, simulated jet diameter was compared with some results reported in our previous work.

##### ۴Modeling active micromixers with multiple microstirrers using Smoothed Particle Hydrodynamics

اطلاعات انتشار:
Scientia Iranica،
بيست و يكم،شماره۴، ۲۰۱۴،
سال ۰

تعداد صفحات:
۱۳

Smoothed Particle Hydrodynamics method is used to explore the effects of design parameters on the mixing efficiency of two types of active micromixers. First, the complex flow field and the mixing process of two separated fluids in a square mixing chamber with nine symmetric microstirrers are simulated. The influence of design parameters such as the microstirrer rotation arrangement and the angular velocity of the microstirrer on the mixing performance are investigated. Mixing index parameter on ten control points is calculated and the average mixing index is compared for different cases. Simulations illustrate that the rotation arrangement of microstirrers is a key parameter in the mixing process. Then, a parametric study is performed for a horizontal and a Y–shape active micromixer where the influence of the length, the angular velocity, the rotation or the oscillation movement of the microstirrer, the inlet Reynolds number, and the inlet stream angle is investigated. It is also illustrated that the inlet Reynolds number and the Struhal number are the prominent parameters that affect the mixing efficiency of this type of active micromixers.

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