Flow Characteristics of a Round Jet Surrounded by Round Sub Jets

Abstract

An experimental study is conducted to investigate the flow characteristics of round jet which surrounded by multiple round sub jets at Reynolds number, Re (= U_cld₁/ν, U_cl ≈ 8.0 m/s, d₁: diameter of main nozzle) = 1.21×10⁴. Number of sub nozzles was varied between 2 to 10. The mean and fluctuating velocities were measured using cross-wire probe with constant-temperature type hot-wire anemometer. The length of potential core for the main round jet was x_c /d₁ ≈ 5, without influence the number of sub nozzles. Also, the centerline velocity decayed along x^-1/2 at 5 < x/d₁ ≲ 20, after the potential core region. At x/d₁ ≳ 20, the centerline velocity decayed along x^-1, similar to the single round jet.