Viscous flow through sudden contractions

Abstract

Despite efforts since the 1950s, laminar flow through pipe fittings is still a topic that needs investigation (Jacobs, 1993). Most experimental studies on this topic include fittings such as contractions, expansions, elbows, valves and orifices (Edwards et aI., 1985; Turian et al., 1998; Pal & Hwang, 1999). Although sudden contractions are not often found in industry, most researchers included these fittings as part of their experimental investigation. The volume of work done on flow through sudden contractions over the last 50 years (e.g. Bogue, 1959; Christian et aI., 1972; Vrentas & Duda, 1973; Boger, 1987; Bullen et aI., 1996; Sisavath et aI., 2002), establishes its place of importance in the fundamental understanding offluid flow and fluid mechanics. There are inconsistent reports on the status ofthe study ofNewtonian fluids flowing through sudden contractions, i.e., that "it is a solved problem" (Boger, 1987) and "that it is far from being resolved" (Sisavath et aI., 2002). One reason for this apparent contradiction is the fact that most experimental studies do not agree with one another or with analytical and numerical studies. A state-of-the-art literature review by Pienaar et al. (2001) confirmed this and that further investigation of this topic is required. To explore these contradictions, it was necessary for one study to do both an experimental and numerical investigation and compare the results with existing literature. It was also important to find some basis for agreement of experimental work and not just add another data set to the existing scattered database. A test facility was built for testing three contraction ratios, i.e., ~ = 0.22, 0.50 and 0.85. A range ofNewtonian and non-Newtonian fluids was tested over a wide range ofReynolds number (Re = 0.01 - 100 000).