Flow Velocity Distribution Near Curb-Opening Inlets: Experiments and Analysis

Abstract This paper presents an experimental investigation of the velocity distribution around curb-opening inlets using a laboratory channel model measuring 6.2 m in length, 2 m in width, and 1. 5 m in height. The flow system consisted of a base discharge supplemented by a spatially varied inflow generated through twelve nozzles uniformly arranged along the model’s length and width. Velocity measurements were carried out with a laser Doppler velocimeter (LDV) to examine the applicability of the universal velocity profile in accordance with the law of the wall. Dimensional analysis was employed to identify the governing parameters and construct a representative diagram for flow characterization. Under uniform flow conditions, without nozzle-induced inflow, the velocity distribution exhibited close agreement with the universal velocity profile. In contrast, the introduction of spatially varied inflow resulted in significant deviations, particularly within the buffer layer and logarithmic region, with discrepancies becoming more pronounced downstream as the cumulative influence of multiple nozzles increased. The measurements further revealed that the nozzle inflow generates a localized jet within the viscous sublayer, and the intensity of this jet was observed to increase in the downstream direction in response to higher inflow discharge. These findings highlight the complex interaction between localized inflow and classical velocity distribution laws.