Round Turbulent Air Jet Submitted to a Pulsed Coflow

Abstract

Mean and turbulent properties of an unsteady round air jet submitted to a pulsed coflowing airstream were studied from laser Doppler Velocimetry measurements. The ejection velocity of the jet is kept at a constant value, whereas the coflowing stream is pulsed. These measurements revealed that the unsteadiness leads to a longitudinal partition of the jet. Near the jet exit, the flow is a quasi-steady jet flow. Farther downstream, the flow is unsteady with the creation of a large and propagative structure in the jet flow. The objective of the study is comprehen- sive understanding of the main physical mechanisms induced by the coflow unsteadiness. Consequences of the entrainment process are also discussed.