Characteristics of Monami Wave in Submerged Vegetated Flow

Abstract

Flow through submerged vegetation with inflection in the vertical profile of flow velocity exhibits instability at the interface of vegetation and overflow and causes generation of Kelvin-Helmholtz vortices. In case of flexible vegetation, the vortices cause periodic movement of stems called a monami wave. In this paper, the geometry of a bending stem is derived and the amplitude of the monami wave is calculated as a function of the bending angle. Using continuity and momentum equations, the stem geometry, combined with the temporal density stratification due to the periodic motion of stems, is analyzed to determine the frequency of the monami wave. The wave period, combined with the amplitude, explains the interfacial monami wave. The amplitude and period are derived in terms of easily measurable flow and vegetation parameters.