The purpose of this experimental study was to investigate the effects of a rectangular canal on the hydrodynamics of turbulent surges before and after the canal by implementing a series of physical experiments. A dam-break wave model was used to simulate the tsunami-like turbulent waves passing over a smooth and horizontal surface, in the presence and absence of a canal. Three canal depths of [Formula: see text], 0.10 and 0.15[Formula: see text]m were used to model shallow, moderate and deep conditions and three canal widths of [Formula: see text], 1.60 and 3.0[Formula: see text]m were selected to model narrow to wide canals. The front velocity of the dam-break induced surges were controlled by rapidly releasing upstream impounded set volumes of water with depths of [Formula: see text], 0.30 and 0.40[Formula: see text]m. The dam-break wave propagation over a horizontal, dry and smooth bed revealed four regimes describing the variations of surge height with time. The arrival time to reach the maximum surge height and the quasi steady-state regime was correlated with each impoundment depth and an empirical formulation was proposed to estimate the onset of the quasi steady-state flow. The maximum surge heights measured before and after the mitigation canal location were compared with those recorded in the corresponding tests without the presence of the canal. It was found that the peak surge height upstream of the canal could increase up to 40% compared to the test without the presence of the canal in relatively small impoundment depth and in presence of a narrow canal due to momentum dissipation. The wave height downstream of the canal increased between 10% and 50% of the wave height without the presence of the canal and the minimum change in the wave height occurred for the canal width to depth ratio of 20. The time-history of surge velocity after the mitigation canal indicated a significant decay of between 40% and 60% in the presence of a canal due to the bed friction changes and momentum dissipation.

This companion paper presents the results of a series of numerical experiments examining the effects of a mitigation canal on the hydrodynamics of a tsunami-like turbulent bore proceeding over a horizontal bed. The hydraulic bores were generated by a dam-break setup which employed impoundment depths of do = 0.20 m, 0.30 m, and 0.40 m. The bore propagated downstream of the impoundments in the flume and interacted with a canal with varying geometry located downstream. The bore then left the flume through a drain located further downstream of the canal. In this study, the effect of the canal depth on the specific momentum and specific energy of hydraulic bores passing over a rectangular canal is numerically studied. The canal width was kept constant, at w = 0.6 m, while the canal depths were varied as follows: d = 0.05 m, 0.10 m, and 0.15 m. The time history of mean flow energy during the bore’s passing over the mitigation canal indicates that the jet stream of the maximum mean flow energy is controlled by the canal depth. The time required to dissipate the jet stream of the maximum vorticity, the turbulent kinetic energy, and the energy dissipation rate all increased as the canal depth decreased. The effect of canal orientation on the bore hydrodynamics was also numerically investigated, and it was found that the impulsive momentum and specific energy reached the highest values for canal orientations of 45 and 60 degrees. For the same canal depth, the highest peak specific momentum occurred with the highest degree of canal orientation (θ = 60°).

This companion paper investigates the hydrodynamics of turbulent bores that propagate on a horizontal plane and have a striking resemblance to dam break waves and tsunami-like hydraulic bores. The focus of this paper is on the propagation of a turbulent bore over a mitigation canal using both laboratory experiments and numerical simulations. In the first part of this paper, the effects of canal depth on the time histories of wave height and velocity were experimentally investigated, and the experimental results were used for the validation of the numerical model. The rapid release of water from an impoundment reservoir at depths of do = 0.30 m and 0.40 m generated bores analogous to tsunami-induced inundations. The time histories of the wave heights and velocities were measured at 0.2 m upstream and at 0.2 m and 0.58 m downstream of the canal to study the energy dissipation effect of the mitigation canal. The recorded time series of the water surface levels and velocities were compared with simulation outputs, and good agreement was found between the experimental and numerical water surface profiles, with a Root Mean Square Error (RMSE) of less than 6.7% and a relative error of less than 8.4%. Three turbulence models, including the standard k-ε, Realizable k-ε, and RNG k-ε, were tested, and it was found that all these models performed well, with the standard k-ε model providing the highest accuracy. The velocity contour plots of the mitigation canal with different depths showed jet streams of different sizes in the shallow, medium-depth, and deep canals. The energy dissipation and air bubble entrainment of the bore as it plunged downward into the canal increased as the canal depth increased, and the jet stream of the maximum bore velocity decreased as the canal depth increased. It was found that the eye of the vortex created by the bore in the canal moved in the downstream direction and plunged downward in the middle of the canal, where it then began to separate into two smaller vortices.