# مقالههای Ehsan Roohi

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

##### ۱Coalescence Collision of Two Droplets:Bubble Entrapment and the Effects of Important Parameters

اطلاعات انتشار:
چهاردهمین کنفرانس سالانه مهندسی مکانیک،
سال ۱۳۸۵

تعداد صفحات:
۸

In this study, coalescence collision of two water droplets is studied using a modified Volume of Fluid (VOF) method. The focus of this work is on head–on binary collision of two droplets; the effects of Reynolds number, drop size ratio and impact velocity on the coalescence process are investigated. In addition, air bubble entrapment phenomenon during droplet collision is discussed.<\div>

##### ۲Detailed Investigation of Rarefied Flow inMicro\Nano Lid–driven Cavities Using DSMC

اطلاعات انتشار:
نوزدهمین همایش سالانه مهندسی مکانیک،
سال ۱۳۹۰

تعداد صفحات:
۴

We use DSMC technique to investigate hydrodynamic and thermal characteristic of rarefied hydrogen flow in micro\nano lid–driven cavity. Flow behavior in all rarefaction regimes including slip, transition and free molecular ones has been studied. It is seen that center of primary vortex moves to the left and toward the drivenlid as Kn number increases. Moreover, wall shear stress and heat flux are decreased at higher degrees of rarefaction. It is also observed that wall slip motion is more pronounced in the slip regime and the slop smoothes as Kn grows.<\div>

##### ۳DSMC Simulation of Micro\Nano Shear Driven Flows

اطلاعات انتشار:
دهمین همایش انجمن هوافضای ایران،
سال ۱۳۸۹

تعداد صفحات:
۶

In the present work, compressible rarefied gas flow is considered between two parallel moving plates maintained at the same uniform temperature and analyzed by direct simulation Monte Carlo (DSMC) method. We compare our DSMC temperature and velocity profile with analytical solutions based on the NS equations subject to the velocity slip and temperature jump boundary conditions. We also study the behavior of shear stress and heat fluxes in the domain over a wide range of Knudsen numbers<\div>

##### ۴Simulation of Rarefied Gas Flow in Micro\Nano Cavity Using DSMC

اطلاعات انتشار:
دهمین همایش انجمن هوافضای ایران،
سال ۱۳۸۹

تعداد صفحات:
۸

Direct simulation Mont Carlo (DSMC) is a molecular approach which is widely used to model rarefied gas flow in a wide range of Knudsen numbers. Lid–driven cavity is a common geometry used in Micro\Nanoelectro– mechanical systems (MEMS\NEMS). In this paper, DSMC approach is utilized to compare hydrodynamic and thermal characteristic of monatomic and diatomic gasses, namely argon and nitrogen flow in micro\nano lid–driven cavity at transition and free molecular regimes. It is seen that compressibility effect for the monatomic gas is more pronounced. It is also seen that center of vortex is shifted downward to the right of the cavity as the non–equilibrium effects increase. Moreover, the heat transfer to the wall is higher for argon flow in comparison with nitrogen flow.<\div>

##### ۵Numerical Simulation of Cavitation around a Two–Dimensional Hydrofoil Using LES

اطلاعات انتشار:
بیستمین کنفرانس سالانه مهندسی مکانیک،
سال ۱۳۹۱

تعداد صفحات:
۴

In this paper simulation of cavitating flow over the Clark–Y hydrofoil is reported using computational fluid dynamics (CFD) technique. This simulation is performed using the large eddy simulation (LES) turbulence model. We applied an incompressible LES modeling approach based on an implicit method for the subgrid terms. To apply the cavitation model, the flow has been considered as a single fluid, two–phase mixture. A transport equation model for the local volume fraction of vapor is solved with the LES model and a finite rate mass transfer model is used for thevaporization and condensation processes. The volume of fluid (VOF) method is applied to track the interface of liquid and vapor phases. This simulation is performed using a two phase solver available in the framework of the OpenFOAM (open field operation and Manipulation) software package, namely interPhaseChangeFoam”. The solver is based on the finite volume method. Simulation is performed for the cloud and super cavitation regimes. The results of our simulation are compared with the experimental data and the accuracy of the simulation has been investigated<\div>

##### ۶STALL SIMULATION OF FLOW AROUND AN AIRFOIL USING LES MODEL AND COMPARISON OF RANS MODELS AT LOW ANGLES OF ATTACK

اطلاعات انتشار:
پانزدهمین کنفرانس دینامیک شاره ها (سیالات)،
سال ۱۳۹۲

تعداد صفحات:
۱۰

In this paper, the influence of turbulence modeling, Reynolds number and stall conditionon the fluid numerical solution over NACA0012 airfoil is studied by using the OpenFOAMpackage. Large–eddy simulation (LES) turbulence model is used to simulate flow at a highangle of attack in near–stall or stall condition. Some vortexes are formed and caused toappear a fluctuation behavior of pressure distribution on the upper surface of the airfoil.Three RANS turbulence models, i.e., K–ω SST, K–ε and RNG K–ε are used at low angles ofattack than stall condition and lift\drag coefficients of them are compared. Among differentturbulence models, the best result for lift coefficient is obtained once K–w SST turbulencemodel is used and the best drag coefficient is obtained by RNG K–ε turbulence model. K–ω SST turbulence model predicted the beginning of stall condition accurately whereas twoother models were not able to predict it. The effects of Reynolds number on the lift coefficienthave been investigated. It is observed that by increasing Reynolds number at constant Machnumber the lift coefficient is increased and stall phenomena is happened at a higher angle ofattack.<\div>

##### ۷Detailed Investigation of Hydrodynamics and Thermal Behaviors of Rarefied Shear Driven Flow Using DSMC

اطلاعات انتشار:
Scientia Iranica،
بيستم،شماره۴، ۲۰۱۳،
سال ۰

تعداد صفحات:
۱۳

In the present work we simulate rarefied gas flow between two moving parallel plates maintained at the same uniform temperature using direct simulation Monte Carlo (DSMC) method.We perform simulations for monatomic argon and diatomic nitrogen gas and compare mon\diatomic gas behaviors. For both gases, we study heat transfer and shear stress and investigate the effects of compressibility and rarefaction in the entire Knudsen regime and for a wide range of wall Mach number.Slip velocity, temperature jump, wall heat flux and wall shear stress are directly sampled from the particles striking the surfaces and reported for monatomic and diatomic cases for different rarefaction regimes. We also study deviation from theequilibrium using the probability density function for argon and nitrogen gas molecules.

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