Experimental investigation of bubbly flow and air entrainment discharge downstream of chute aerators

Abstract

In a chute aerator flow, a large air discharge that is introduced through an air supply duct is entrained into the flow and transported to the downstream zone. In this study, a series of experiments were conducted to quantify the two–phase flow properties, including air concentration, bubble frequency, and bubble diffusivity, and air entrainment flux for a wide range of Froude numbers (3.3 ≤ F0 ≤ 7.4) at relatively large Reynolds numbers (5 × 105 ≤ R ≤ 1.2 × 106). The distributions of air concentration and bubble frequency, which demonstrated two competitive turbulent processes, were presented. The air transport process of the chute aerator flow was quantitatively described based on the approach flow conditions and the aerator geometry. According to the characteristics of air discharge in the equilibrium zone, and based on the previous equation, qa = KV0L, the experimental results indicated that the dimensionless coefficient K was independent of the aerator structure and significantly increases with the flow Froude number.