01. Experimental/Computational Fluid Dynamics

We benefit from jet flow research in our daily lives in various fields, from electrical appliances, such as air conditioners and hair dryers, to large transportation equipment, such as airplanes, rockets, and ships. Jet flow research is active, particularly in the wake of the recent pandemic. For example, tabletop air curtains have been considered as effective countermeasures against droplet infection, and air walls have been developed to intercept aerosol particles without the need for rigid walls by appropriately controlling the airflow of the air curtain. However, the stiffness of the jet sheet against external disturbances, such as human coughing, running winds caused by surrounding humans, and air conditioner winds, have not been fully investigated. In this study, vortex pairs (pulse jets) were vertically impinged on a planar steady continuous jet as a disturbance, and their behavior was investigated through numerical simulations. The velocity fluctuation and time required for recovery after the vortex-pair impingement were evaluated. The main parameter was dimensionless frequency of the disturbance. The results show that the smaller the non-dimensional frequency of the disturbance, the more the disturbance changes the flow field of the continuous jet.