The effect of viscosity on liquid curtain stability was explored by high-speed visualization. Measurements of the velocity within the curtain revealed the presence of a viscous boundary layer along the edge guides. The critical condition at the onset of curtain breakup was determined by identifying the flow rate below which the curtain broke for two different edge guide geometries: parallel and convergent. Curtain breakup was initiated by the expansion of a hole within the curtain. For low viscosity liquid, the measured hole retraction speed is independent of the viscosity and equal to the Taylor-Culick speed. For high viscosity liquids, the retraction speed is lower than the Taylor-Culick speed due to viscous forces that resist the flow. The results also show the effect of liquid viscosity on the curtain stability is a strong function of the edge guide design.
Bibliographical noteFunding Information:
The authors would like to acknowledge the financial support from the Dow Chemical Company. The authors also would like to thank William B. Griffith, Saswati Pujari, John R. Reffner, and Vinita Yadav for their valuable discussions through this research.
© 2017 American Institute of Chemical Engineers
- coating flows
- fluid mechanics