Investigation of dynamic mixedness characteristics of a transverse acoustically excited turbulent jet by high-repetition-rate acetone tracer Planar laser-induced fluorescence technique

Abstract

Abstract The dynamic mixedness characteristics of a bluff-body stabilized turbulent jet under transverse acoustic excitations are investigated using high-repetition-rate acetone planar laser-induced fluorescence (PLIF) at 7 kHz and multipoint scanning hot-wire measurements. Acetone mixedness imaging is made for the turbulent jet to assess the interaction between the turbulent jet and the imposed transverse acoustic excitations at a driving frequency of 50 Hz. The high-repetition-rate acetone PLIF images show that the acetone mixedness distribution swings left and right frequently under the transverse acoustic excitation, and the deflection angle can reach about 6°. The mixedness area of a turbulent jet flow can also be increased by 13.3% when excited by a transverse acoustic wave. Meanwhile, the sequence of acetone instantaneous PLIF images illustrates how the wrinkled edges are generated when acoustic excitations are imposed. The curvature of the acetone PLIF interface shows that the portion of large curvatures increases to 1.6 times after applying an acoustic wave of 123 dB. Multipoint hot-wire measurements further stress that the turbulence intensity at the transverse acoustic excitation of 123 dB increases to be about 1.3 times the natural turbulence. The proper orthogonal decomposition results show that the large and small scales of the jet wrinkles both increase with the sound pressure level. RANS transient simulation also implies that a stronger turbulent kinetic energy distribution and distorted velocity streamlines can be achieved inside the turbulent jet due to the transverse acoustic excitation. They can further lead to increased mixing between the turbulent jet and the surrounding air.