# Influence of Right Triangular Prism Rough Beds on Hydraulic Jumps
## 4 Conclusions  
This research evaluated and investigated the effects of four right triangular prism rough bed types arranged in a channel bed (stilling basin) on hydraulic jumps. The considerable variation in boundary conditions, including supercritical flow conditions and geometry characteristics of the roughness elements, were provided by the initial Froude number (\(Fr_{1}\)) from 4.8 to 9.4, the wave steepness values (\(t/s\)) of 0.67 \(\leq t/s\leq\) 1.33, and the relative distance of roughness elements of 0.0 \(\leq L_{\rm s}/y_{1}\leq\) 4.0. The hydraulic jump characteristics, such as sequent depth, jump length, energy loss, and bed shear stress, primarily depended on \(Fr_{1}\). These hydraulic parameters increase with the increase in \(Fr_{1}\) and vice versa. Meanwhile, the rough bed models' two main geometry parameters (\(t/y_{1}\) and \(L_{\rm s}/y_{1}\)) do not have much of an influence on directly reducing the sequent depth and jump length. However, they affect increased bed shear stress on the channel bottom and energy loss in flow.  
This study indicated that the arrangement of the right triangular prism rough elements on the stilling basin increased bed shear stress from 6 to 17 times compared with a smooth bed, and the energy loss also increased from 6% to 24%. Therefore, the result leads to conjugate depth and jump length, which are about 22% and 50% shorter than on a smooth bed, respectively. The study results show that the effective jump length reduction is more significant with a high Froude number (\(Fr_{1}\)).  
Entropy production was used to demonstrate the energy dissipation in the hydraulic jump. The study results indicated that the energy dissipation was more substantial in the hydraulic jump zone. The triangular rough elements shaped with \(m_{1}=0\), which conflicts with the flow direction, have a better energy dissipation effect than in the flow direction shape (\(m_{2}=0\)). Therefore, the character shape of a rough bed has a significant effect on reducing hydraulic jump length. The results indicated that arranging rough beds within the jump length region reduced the conjugate depth and jump length. The rough bottom area arranged after the hydraulic jump has a minimal influence on the energy dissipation of the flow; this may be because the downstream flow has changed into a subcritical flow with a small amount of energy. Therefore, it needs a suitable rough bed structure solution with a rough bed region of about \(2L_{\rm j}/3\).  
The results of this study indicate that these rough beds have a positive effect on hydraulic jumps, such as reduced conjugate depth and jump length. Therefore, this work recommends that right triangular prism rough bed models be used as an alternative method to control the location of free and steady hydraulic jumps for energy dissipation work. It is necessary to renovate the small and medium irrigation work types or urban sewer systemsthat do not have the stilling basin and use the classical jump under the impact of increasing flood discharge due to climate change.  
Writing--original draft, C.T.T. (Cong Ty Trinh), J.Z. and C.T.T. (Cong Trieu Tran). All authors have read and agreed to the published version of the manuscript.  
This research received no external funding.  
Not applicable.  
The data presented in this study are available in article.  
The authors declare no conflicts of interest.