On Generating Uniform Bottom Shear Stress. Part I: A quantitative study of microcosm chambers

Arzhang      Khalili; Khodayar      Javadi; Arash      Saidi; Afshin      Goharzadeh; Markus      Huettel; Bo   B.   Jorgensen

Abstract

Generating uniform shear stress planes finds a variety of applications in different disciplines such as process engineering, medicine and marine sciences. The focus of this study is to quantify the potential of microcosm chambers, applied in marine applications, in producing shear stress uniformity at the chamber bottom. To do this, computational fluid dynamics was used to simulate the flow pattern, velocity profiles, and shear stress distribution at chamber bottom. The study revealed that the microcosm chambers, such as those presented in the patent of Gust, produce a fully vortical flow, containing acceleration-deceleration zones near the central axis and the outer wall. The results show that the presence of these acceleration-deceleration zones is the major reasons for non-uniform shear stress formation at the chamber bottom. Utilizing a suction-injection mechanism and-or attached skirt provides better bottom shear stress profiles compared to a conventional disk-cylinder. In spite of this partial improvement, the addition of a suction-injection device or a skirt attached to the disk provide a partial shear stress uniformity only over the 72% of the bottom area, and are therefore of limited use.

Keywords: Benthic chamber, microcosm chamber, shear stress uniformity, bottom shear stress