NUMERICAL STUDY OF REDUCTION OF ENERGY DISSIPATION USING MICRO BUBBLES IN A VERTICAL COUETTE-TAYLOR SYSTEM

This work focuses on studying of reduction of energy dissipation due to the presence of micro-bubbles in a vertical Couette-Taylor system. Flow is in theannular space between two concentric cylinders as the internal cylinder is rotating while the outer cylinder is stationary. Taylor vortices are formed between thecylinders and the rotational Reynolds number (Re ) also varies from 700 to 3000. Main flow is silicone while air bubbles are constantly injected to the siliconflow at the bottom of cylinder and rise through the flow. A discrete phase model and Euler-Lagrange Approachis employed in order to study a fully two phasesturbulent flow. At the first step the bubbles distribution or bubbles pattern through the flow, that is acquiredusing numerical method, shows a good agreement with those found via the experimental data for all Reynolds numbers. To investigate the changes of skin frictiondrag, the rate of energy dissipation in the system is calculated. The effect of injected air with constant flow rate on the total energy dissipation rate and the dragcoefficient is also investigated. The results confirmed reduction of energy dissipation and about 25% of drag reduction when micro bubbles were injected in the system. This reduction was the effect of the bubbles on the density of fluid and transformed momentum.Moreover, the acquired numerical results were in good agreement to those found in the previous experimental works, which maximum Rew is up to 3000.

کلیدواژه ها:

bubbly flow ، Taylor coquette system ، energy loss