Instabilities in viscoelastic flow past a square cavity

Elastic flow transitions in viscoelastic flow past a square cavity adjacent to a channel are reported. The critical conditions for the onset of flow t ransitions and the qualitative and quantitative characterization of the sec ondary flows generated by the instability have been examined using streakli ne photography and instantaneous pressure measurements. Cellular type of in stabilities inside the cavity is observed for flow rates beyond a critical value. Small and large scale eddies are observed at high how rates. The flo w inside the cavity and in the channel upstream and downstream of the cavit y becomes weakly time-dependent for high flow rates. (C)2000 Elsevier Scien ce B.V. All rights reserved.