Double-Averaging Concept for Rough-Bed Open-Channel and Overland Flows: Applications

Abstract

The paper briefly outlines the double-averaging methodology for studying environmental rough-bed flows. It focuses on the applications of this methodology in environmental hydraulics by providing several examples illustrating advantages of this methodology over conventional approaches. Examples include: (1) identification of specific flow layers and flow types; (2) vertical distribution of the double-averaged velocity between the roughness tops and troughs; (3) vertical distribution of momentum fluxes and sinks for typical roughness types due to turbulence, mean flow heterogeneity, secondary currents, form drag, and viscous drag; (4) estimates of form-induced (dispersive) stresses and evaluation of their structure using quadrant analysis; and (5) closure development for mass-transfer-uptake processes for stream periphyton. These examples illustrate the advantages of the double-averaging methodology over conventional approaches as well as highlight its potential for studying flows over very rough beds, highly mobile beds, permeable beds, and surface–subsurface exchanges of mass, heat, and momentum. This methodology may also significantly improve research tools for studying a wide range of flow–biota interaction phenomena such as those related to aquatic plants, mussel communities, biofilms, and many others.