Hydraulic jumps with intense turbulent mixing and air bubble entrainment are regarded as a change process from supercritical to subcritical flow [

1]. Free and submerged hydraulic jumps are usually suitable for energy loss under hydraulic structures such as gates, spillways and weirs. The characteristics of hydraulic jumps on the smooth bed have been widely studied [

2,

3,

4,

5,

6,

7,

8,

9]. Several experimental and numerical studies have been performed on the free and submerged hydraulic jumps over macroroughnesses to foresee how the roughness elements of the bed affect the characteristics of hydraulic jumps compared to the smooth bed. Ead and Rajaratnam [

10] investigated the properties of hydraulic jump on sinusoidal macroroughnesses and normalized the water surface profile and discharge with non-dimensional analysis. Tokyay et al. [

11] observed that the jump length ratio and energy loss over two sinusoidal macroroughnesses were 35% smaller and 6% higher than a smooth bed, respectively. Abbaspour et al. [

12] studied the properties of a hydraulic jump over six sinusoidal macroroughnesses. The results stated that the tailwater depth and jump length were lower than the smooth bed and the Froude number had a great impact on the jump length. Shafai-Bejestan and Neisi [

13] investigated the effects of lozenge macroroughnesses on the hydraulic jump. The results showed that the use of lozenge macroroughnesses reduced the tailwater depth and jump length compared with the smooth bed. Izadjoo and Shafai-Bejestan [

14] studied hydraulic jumps on various trapezoidal macroroughnesses. They observed that the shear stress coefficient was over ten times larger than that on the smooth bed, and the jump length decreased by 50%. Nikmehr and Aminpour [

15] investigated the properties of a hydraulic jump over macroroughnesses with trapezoidal blocks using the Flow-3D model Version 11.2 [

16]. The results stated that increasing the height and the distance of the macroroughnesses, the velocity decreases near the bed as well as the shear stress coefficient. Ghaderi et al. [

17] studied the free and submerged hydraulic jump characteristics over different shapes of macroroughness (triangular, square and semi-oval). The results stated that the shear stress coefficient, energy loss, the submerged depth, the tailwater depth and the relative length of jump in free and submerged jumps increase with the increasing Froude number. The highest shear stress and energy loss in the free and submerged jumps occurred in the presence of a triangular macroroughness. Elsebaie and Shabayek [

18] studied the properties of hydraulic jumps on five shapes of macroroughnesses (triangular, trapezoidal, sinusoidal with two side slopes and rectangular). The result showed that energy loss for all macroroughnesses was more than 15 times that on a smooth bed. Samadi-Boroujeni et al. [

19] investigated the hydraulic jump on six triangular macroroughnesses of various angles and showed that the triangular macroroughnesses reduce the jump length and increase the energy loss and the bed shear stress coefficient compared to the smooth bed. Ahmed et al. [

20] investigated the submerged hydraulic jump properties on a smooth bed and triangular macroroughnesses. The results stated that submerged depth and jump length decreased if compared to the smooth bed.

Table 1 lists the details of past experimental and numerical studies on hydraulic jumps presented by other researchers.

The major part of the previously discussed investigations are based on laboratory approaches and investigate how sinusoidal, lozenge, trapezoidal, square, rectangular and triangular macroroughnesses affect some free and submerged hydraulic jumps characteristics, e.g., conjugate depths, submerged depth, jump length, energy loss and bed shear stress coefficient. Moreover, with reference to a previous published paper about hydraulic jumps on different shapes of macroroughness by the authors [

17], it was observed that the triangular macroroughnesses have the highest bed shear stress coefficient and energy loss and also have the lowest submerged depth, tailwater depth and jump length compared to other rough shapes, i.e., square and semi-oval, and a smooth bed. Hence, in the present paper, using the triangular macroroughnesses (for different

T/I ratios with a constant roughness height of

T = 4 cm and a distance of triangular roughness of

I = 4, 8, 12, 16 and 20 cm), specific studies such as the flow patterns in the cavity region, turbulent kinetic energy (TKE) and streamwise velocity distribution are required. Computational fluid dynamics (CFD) methods arise as an important tool to undertake the modeling process of complex flows such as the free and submerged hydraulic jumps [

21] and the characteristics of a submerged hydraulic jump can be accurately predicted utilizing CFD simulations [

22,

23].

The present paper initially presents the main characteristics of a submerged hydraulic jump, the input parameters for the numerical model and a reference experimental investigation by Ahmed et al. [

20], reported for validation purposes. Furthermore, this study will investigate characteristics such as the longitudinal profile of streamlines, flow patterns in the cavity region, horizontal velocity profiles, thickness of the inner layer, bed shear stress coefficient, TKE and energy loss.