# Influence of Right Triangular Prism Rough Beds on Hydraulic Jumps
## 1 Introduction  
Flood flow from a reservoir over spillways has a large amount of kinetic energy. If this energy is not dissipated downstream of the spillway, there is a danger of scouring the riverbed, which may threaten the dam's stability. Through a hydraulic jump phenomenon, almost all of the kinetic energy of the flood flow was dissipated just downstream of the spillway. Therefore, the hydraulic jump was widely applied in hydraulic works as the primary method to dissipate energy for low-head dams and highway sewers. Climate change is becoming increasingly erratic, and flood flows are indeed changing. Many low-head irrigation works or highway sewers have low-energy dissipation efficiency, making it challenging to control floods. A flow carrying large amounts of energy downstream will cause many significant consequences. In that case, it will easily damage the downstream structures and cause erosion downstream of the flood discharge works. Therefore, the need to renovate and repair to improve the working capacity of sewers and limit harmful effects downstream is becoming increasingly urgent. Recently, a new research approach to hydraulic jump on rough beds featured a rather special arrangement of roughness elements on the surface of the channel bed [1; 2; 3; 4; 5; 6]. The crests of the roughness elements were at the same level as the channel bed surface. Therefore, under the impact of supercritical flow, it avoids the phenomenon of cavitation causing damage to the rough bed structure and, at the same time, achieves the benefit of reducing the downstream water depth and jump length compared to a smooth bed. This has been confirmed by several researchers and published in high-quality scientific journals [1; 2; 4; 7; 8; 9; 10]. Rough bed shapes,including sinusoidal, triangular, rectangular, and trapezoidal, have been studied. These rough beds are generally mainly studied by physical models performed in the experimental laboratory through flow measurement and visualization. This approach may provide helpful information on flow properties and raise an experiment's expense. Thus, the rapid development of computer technology has opened new avenues for developing computational fluid dynamics (CFDs). Consequently, computational models and turbulence methods have been significantly improved. The CFD method records and stores specific data from a research hydraulic phenomenon's evolution process and is also appropriate for observing the flow structure detail. Therefore, the CFD method has become a powerful tool for approaching and studying complex hydraulic phenomena [11]. Until now, many researchers in hydraulics have successfully used the CFD method to study the hydraulic jump on a smooth and rough bed. The numerical model results have been compared to experimental results and show good agreement [3; 5; 12]. These researchers applied the VOF method and turbulent models (k-\(\varepsilon\) or renormalization group (RNG) k-\(\varepsilon\)) to simulate a hydraulic jump. Therefore, in this study, the author chooses the VOF method in combination with the RNG k-\(\varepsilon\) model as the primary tool for research due to the significant advantages of the CFD method over the traditional experimental method. Recently, the hydraulic jump phenomenon on rough beds was studied using experiments and numerical models. [PERSON] and [PERSON] [1] studied hydraulic jumps on sinusoidal corrugated beds using the experimental method, with the range of initial Froude numbers (\(F_{\rm{r1}}\)) of \(4.0\leq F_{\rm{r1}}\leq 10.0\). The values of the relative roughness \(t/y_{1}\) (\(t\) is the height of sinusoidal corrugations, and \(y_{1}\) is the depth flow just before a hydraulic jump) were \(0.25\leq t/y_{1}\leq 0.50\). The results showed that the jump length was reduced by about 50% compared with a classical jump.