Theoretical Approach to the Flow Patterns in a Four-Branch Intersection

Abstract

In this paper, the hydraulic structure of flood flow on a four-branch urban road intersection with two adjacent input streets and two output streets was investigated theoretically. Not only were previous flow patterns investigated theoretically, but also two new flow patterns were introduced and discussed in this study: Flow Pattern Type 1, when the flows approaching the junction in the street were in subcritical condition and return to subcritical in output streets downstream of the junction; Flow Pattern Type 1 Sub-regime 1, when the flows approaching in the input streets were in supercritical condition and return to supercritical in output streets downstream of the junction. The deflection of supercritical flows was formulated and solved numerically through writing MATLAB codes and was investigated graphically. Nomo-graphs were generated for the case that two oblique hydraulic jumps formed in the junction, which can be used to predict the characteristics of flow downstream of the junction. For example, the jumps angle can be predicted from the known parameters of incoming flows by applying the Angle Model formulas.