DOI: 10.1615/ICHMT.2009.TurbulHeatMassTransf
ISBN Print: 978-1-56700-262-1
ISSN: 2377-2816
Relation between an overshoot phenomenon and a vortex ring observed in a step-like wind speed variation generated by a wind tunnel
ABSTRACT
An overshoot phenomenon has been observed in time dependent variations of axial velocity of a step-like jet, expelled from the square nozzle of an unsteady wind tunnel. Vorticity maps in the horizontal plane, including the jet axis, obtained from velocity measurements using an ultrasonic anemometer, confirmed shedding of an isolated vortex ring from the nozzle exit. From an estimation of the axial induced velocities at an observation point on the jet axis, which was based on Biot-Savart’s law and a rough assumption of the non-rotation of the symmetric axes of the vortex ring, we concluded that the overshoot was caused by contributions from a growing free shear layer and unstable vortex shedding, in addition to the induced velocity from the isolated vortex ring.