Iranica Journal of Energy & Environment 3 (1): 88-96, 2012 ISSN 2079-2115 IJEE an Official Peer Reviewed Journal of Babol Noshirvani University of Technology DOI: 10.5829/idosi.ijee.2012.03.01.3096 BUT Corresponding Author: Jafar Chapokpour, Department of Irrigation and Reclamation Engineering, University of Tehran, Karaj, Iran. Fax: +982612231787, E-mail: jafarchabokpour@yahoo.com 8 8 The Numerical Investigation on Vortex Flow Behavior Using FLOW-3D Jafar Chapokpour, Firouz Ghasemzadeh and Javad Farhoudi Department of Irrigation Engineering, Faculty of Agricultural Technology and Engineering, UTCAN, University of Tehran, Iran (Received: October 26, 2011; Accepted: November 28, 2012) Abstract: In this paper a numerical investigation is given for a Rankine type vortex flow inside the cylindrical vortex chamber using FLOW-3D. The FLOW-3D is a general purpose computational fluid dynamics (CFD) package. The fluid motion is described with non-linear, transient, second-order differential equations. Additionally the free surface also exists in many simulations carried out with FLOW-3D because flow parameters and materials properties, such as density, velocity and pressure experience a discontinuity at it. After analysis of the vortex by mentioned details, the finding of time-averaged velocity components, turbulent components, turbulence dissipation, in the 2D briefed sections of chamber were depicted. It was found that there are different flow patterns like clockwise/anticlockwise vortices and some sink points combined with each other in different time intervals, decaying and generating along the time. Also the turbulence intensity and dissipations around the boundary conditions of chamber like central flushing discharge are higher than the flow body. It was also found that this CFD package was not able to simulate thoroughly the central air core of chamber after filling of chamber. This analysis is validated by comparison with previous experimental data that was measured in vortex settling basin. Key words: Vortex flow; Flow 3D; Numerical Investigation; Turbulence INTRODUCTION installed at the center of the basin. Sediment particles A vortex-settling basin (VSB) is a fluidic device that from the basin periphery toward the orifice, to be uses only the vortices of the flow to extract the bed and eventually flushed out into a waste channel and suspended loads in the inlet canal. The size of a VSB is conveyed to some natural drainage, as is done in the case very small, compared with conventional settling basins of other sediment-extraction devices. The air core treating the same volume of water and sediment load [1]. developing at the center of the orifice reduces the Thus the cost of construction of a VSB is just a fraction flushing discharge. The trajectories described by of the cost required for the construction of a classical sediment particles make their settling lengths many times settling basin to extract comparable particles [2]. The VSB longer than the basin diameter, thereby permitting higher structure holds promise as an economical, efficient and inlet velocities compared with conventional settling water-conserving alternative to the other available basins. Because of the single-inlet port, the axis of the air sediment extraction devices. To remove sediment, a VSB core makes a small angle with the vertical and is slightly utilizes the secondary flow generated by the circulatory displaced with respect to the center of the orifice [4]. The flow induced in a circular basin of diameter. The understanding of the phenomenon of settling in a vortex secondary flow develops as a result of: (a) The basin requires knowledge of the mechanics of fluid flow deceleration of bottom layers of the fluid by friction and particle flow. between the basin floor and the fluid; and (b) cross-flow It is well known that when flow enters tangentially currents [3]. Maximization of the strength of circulation into a circular basin with an axial outlet pipe at its center, should be warranted by placing the basin tangentially to it is set into circulatory motion with respect to the vertical the inlet canal. The secondary flow moves the fluid layers axis through the center of basin. Experimental studies by near the basin floor toward the orifice of the flushing pipe, Cecen and Akmandor [5] and Cecen and Bayazit [6] heavier than the fluid are thus moved along spiral paths