Measures of mixing in laminar flow

✍ Scribed by David Bigio; William Stry

• Book ID: 104522654
• Publisher: Society for Plastic Engineers
• Year: 1990
• Tongue: English
• Weight: 874 KB
• Volume: 30
• Category: Article
• ISSN: 0032-3888
• DOI: 10.1002/pen.760300305

✦ Synopsis

Abstract

The general domain in which this work resides is that of mixing in creeping flows. Mixing, in this context, refers to the stretch of an interfacial line, or area in a strain field. The advancement of mixing technology is applied to the design of continuous mixers used in polymer processing. The geometric designs included single screw extruders, static motionless mixers, and co‐ and counter‐rotating twin screw extruders. The co‐rotating twin screw extruder was chosen to be studied in detail since it enjoys wide applications and, for which, little understanding of the contribution to mixing in the different screw geometries is known. In order to evaluate the rate of mixing for the non‐uniform strain history flows, the method for measuring mixing had to be reexamined and broadened. An automated method has been developed which incorporates a digital camera and a computer to analyze the cross‐sections of interest. Two measures of mixing—the correlation function and the distribution function—are developed to describe mixing in these regimes. These measures are applied successfully to the mixer geometries revealing subtle differences as to the nature of mixing in each.