Mahin Ghannadi - Ph.D. Student of Hydraulic Structures, Shahrood University of Technology, Shahrood, Iran
S.Fazlolah saghravani - Associate Professor, Department of Civil Engineering, Shahrood University of Technology, Shahrood, Iran
Hamid Niazmand - Professor, Department of Department of Mechanical Engineering, Ferdowsi University of Mashhad, Mashhad, Iran

The purpose of this paper is to study numerical analysis of the motion of a single bubble inside the venturi tube, collapse and shrink of it and formation of micro-nano bubble, using Computational Fluid Dynamics (CFD) technique. To study two-phase flow, venturi tube were modeled in Gambit software and for analyzing model OpenFOAM software that is open source has been used. From among many methods available for modeling the turbulent flow, the standard k-ε method has been used to model turbulent flow. To study two phase flow, the VOF method is used. Finite Volume method (FVM) is used for simulation. Pressure and velocity distribution, and Alpha (Void fraction) were calculated. Results show that large bubbles in the throat section are affected by intense turbulence and become deformed, and collapse after entering the diffusion section. Results show that the bubble, after exiting throat, enters diffusion section of venturi tube and when the venturi tube’s cross section gradually increases, flow speed starts to decline, and pressure increases, cavitation happens and large bubbles break into smaller bubbles. Bubbles deform as soon as they enter diffusion section and collapse there

Venturi, OpenFOAM, Two Phase Flow, Micro - Nano Bubble, VOF, FVM, k-ε