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Volume 1, Issue 2 (6-2014)
Abstract
In this paper, the impact of micro bubbles as the second phase in the turbulent flow inside the channel flow has been investigated. The developed turbulent flow inside channel containing micro bubbles has been solved using large eddy simulation. Numerical analysis has been done to survey the impact of micro bubbles on turbulent characteristics derived from carrier flow. Finally, the mechanism of reducing frictional drag force was illustrated. According to the results, increasing the volume fraction of bubbles in the constant diameter will decrease the frictional drag force. Also studying the energy spectrum showed that the energy in the small scales has increased and in the large scales decreased.
Amin Moosaie, Kourosh Goudarzi, Jalil Abbasi,
Volume 3, Issue 1 (9-2017)
Abstract
Drag reduction in turbulent flows allows achieving of higher speeds and reducing energy consumption in the motion of submerged objects. An efficient technique for drag reduction uses dilute solutions of microfibers. In this paper, a review of available methods for the simulation of turbulent drag reduction by microfiber additives is presented. To compute the turbulent flow, the direct numerical simulation (DNS) technique is employed. The effect of the fibers on the flow is described by a non-Newtonian stress tensor, involving the distribution of fiber position and orientation. The fiber dynamics is governed by a Fokker-Planck equation. The computation involves a numerical solution of three-dimensional, time-dependent Navier-Stokes equations for the incompressible flow of a non-Newtonian fluid. In this article, various methods for solving the Fokker-Planck equation are reviewed.
