Investigation and evaluation of current resistance and kinetic energy of turbulence in W-W fish
It's important to live in a river. Structures in the present age Cross structures in the river can have negative effects on the environment, thus preserving the environment and preserving the aquatic ecosystem, which cross-section prevents the migration of fish upstream. Side effects of this problem include lack of spawning, reduced reproduction, and extinction of a species of fish. The fish route is a structure that allows fish to cross river barriers and provide fish access to their habitats. The hydraulic design of the fishway structure must be consistent with the characteristics of the fish's swimming behaviors in order to improve fish crossing efficiency (Castro et al., 2009; Kim et al., 2016).
On the other hand, turbulent kinetic energy (TKE), its distribution, and volume are the most important reasons for the low efficiency of fish (Puzdrowska & Heese, 2019). Therefore, it is necessary to study this variable along the flow path to determine the behavior of fish. Also, due to the fact that fish structure structures act as rough by colliding with the flow, it seemed that the study of hydrodynamic parameters such as TKE as well as knowledge of the performance of the fish structure as roughness under the new w-w structure is less studied. has taken. Therefore, in the present study, the strength of structures and turbulent kinetic energy (TKE) in the W-W path have been investigated and evaluated.
The present study was performed in the hydraulic laboratory of the Faculty of Water and Environmental Engineering, Shahid Chamran University, Ahvaz, in a 10 m long, 50 cm high, and 25 cm wide flume. The slopes tested in the present study were 4, 7, and 10%, the tested discharges were considered 0.025, 0.025, 0.029, 0.034, 0.043 liters per second, and the angle of the structure was 20. W-shaped overflow barriers were placed about 5 meters from the flume, and in order to reduce the effects of the initial turbulence caused by the inlet flow to them, the first overflow was placed at a distance of about 3.5 meters from the beginning of the flume. W-shaped overflows were placed as barriers at D / L = 3, D / L = 6 and D / L = 9 distances
Results and Discussion
With increasing dimensionless flow, the drop coefficients decrease; Because increasing the flow rate and consequently the flow depth, reduces the effect of the presence of obstacles as bed roughness on the flow conditions. On the other hand, with increasing slope, the flow depth is greatly reduced and this increases the effect of obstacles as roughness in the flow path.
The inverse effect of the Froude number is on the drop coefficients and thus reduces the resistance of the structures, which are roughness to flow..
It was observed that by increasing the relative distance between obstacles, the current resistance decreases. The reason for this is that as the distance between the obstacles increases, the density of the obstacles along the flow path and the effect of roughness actually decrease
At a constant slope, as the relative distance increases, the effect of relative depth changes on the flow resistance decreases. Increasing the depth of flow through the overflow of obstacles reduces the effect of the presence of obstacles as the roughness of the duct bed and reduces the flow resistance by about 53%. In contrast, increasing the slope and decreasing the flow depth increases the flow resistance.
After being aware of the roughness changes, in this section, when the flow rate is 0.029, the kinetic energy changes of the turbulence will be investigated. Longitudinal changes of TKE on the center line from the structure i to i + 1 relative to the relative longitudinal distance D / L = 3 It is clear that by increasing the relative longitudinal distance from the upstream structure by 50% near the center between two consecutive structures almost maximum TKE occurs.
The inverse effect of flow and slope on the reduction of drop coefficients and the ineffectiveness of the presence of obstacles as roughness.The inverse effect of the landing number on the drop coefficients and thus reduces the resistance of structures that are as roughness to flow.By increasing the relative distance between obstacles, the resistance to current decreases. Increasing the relative distance, the effect of relative depth changes on the flow resistance decreases. The formation position of the maximum TKE is independent of the slope of the path.The maximum amount of turbulent energy occurs near the water surface.The best distance for fish is D / L = 9.
Keywords: Flow turbulence, fish way, W-W overflow, TKE, flow resistance