Laboratory Study of The Effect of V-shaped Structure on Changes in Fishway Roughness

In this study, a new overflow with a v-shaped structure was used as a barrier in the culvert. The main purpose of the present study was to investigate its performance on changes in flow resistance properties such as the square root of the Modi friction coefficient and the Manning roughness coefficient.

The present study experiments were performed on the physical model available in the hydraulic laboratory of the Faculty of Water and Environmental Engineering, Shahid Chamran University of Ahvaz. This physical model includes a laboratory flume 10 meters long, 0.25 meters wide, and 0.5 meters high. At the beginning of each experiment, the structures were glued to the flume bed at specified relative distances. After 24 hours of gluing the systems, the flume's flow rate and slope were adjusted. The desired flow rate was adjusted using a triangular overflow with an angle of 53 degrees located downstream of the flume and the slope through the jack. A point gauge with an accuracy of 0.1 mm was used to remove the water surface profile.

By increasing the dimensionless flow in a relative distance between structures and a certain slope, the manning roughness coefficient of the structure decreases. So that at a slope of 10%, the relative distance between the structures was 1.3, the value of the Manning roughness coefficient of the system from dimensionless flow decreased from 0.20 to 0.43 by 30%. By increasing the relative distance between structures at a certain flow rate, the manning roughness coefficient of the structure decreases, which is similar to the effect of the relative distance between structures on the square root of the friction drop coefficient of the structure.

In examining the impact trend of the V-fish structure, it was found that dimensionless flow has an inverse effect on the flow friction coefficient and the manning roughness coefficient of the structure. On the other hand, the inverse relationship between landing number and flow friction coefficient, and manning coefficient of the structure was determined. It was found that the relative distance between the structures also has an inverse effect on the flow friction coefficient and the manning coefficient of the structure. The inverse effect of the Reynolds number on current resistance parameters was also extracted. The best condition of the fish road structure with v-shaped overflow occurs in the relative distance between the 1.3 and 10% slope structures.