Hydraulic characteristics of two-layered tidal flows in the Hiji River

Analysis on the characteristics of stratification based on field data

Abstract

The well mixed density flow in tidal river estuary through ebb and flood process during a tidal period includes both many kinds of hydraulic characteristics and unstability problems, because of the rapid transient stratification or disappearance of internal-surface.
This paper reports the results of an analytical consideration depended on field data and their measurement confirmation in the Hiji River.
A classification scheme to define the pattern of two layer flows given by the combination of two directions of currents and magnitudes of mean velocity is presented with field observations.
The verification of this algorithm proposal for eight kinds of flow patterns is derived from new measurements which are composed of the internal, the external and the stability Froude number and applied mass deficit law.
Two measurements of the latter facilitate a comprehensive understanding of the hydraulics for transient flows of both at the second part of flood flow and the seventh part of ebb flow.
After the above discussions, it is demonstrated that three kinds of two layer flows assumed to be quasi-steady state are approached by means of the internal surface resistance analysis for the exchange flow (wedge with counter current), the salt bottom wedge and the arrested surface wedge.
Two results of the former are sufficient to show the usefullness of the proposed scheme.