Round Turbulent Air Jet Submitted to a Pulsed Coflow

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 comprehensive understanding of the main physical mechanisms induced by the coflow unsteadiness. Consequences of the entrainment process are also discussed.