Double-averaging concept for rough-bed open-channel and overland flows: Applications

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 typica 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 conventiona 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.