A study on green water problem with dam break model and the BIV technique

Abstract

The green water generated by extreme waves is primarily an air-water mixture, which includes a continuous phase and a dispersed phase. The continuous phase is explored with the dam break model by three main approaches, namely analytical, experimental and numerical. Analytically, both the Eulerian and Lagrangian Stoker solutions are introduced to study the dam break wave in a dry horizontal channel. The two Stoker solutions have an intersection point at the dam section at instant t ∗ 1 = √ 10 3 . In the initial stages, the “sudden dam break” concept is revised. The dam may be considered break suddenly when the dimensionless gate removal period is smaller than 3t ∗ 1 5 ≈ 0.63. To include the bottom friction effects and the bed slope effects for green water problem, we proposed a simplified piecewise solution (PS). Numerically, the two fluid model with the Volume of Fluid (VOF) method implemented in the interFoam solver is used to simulate the dam break wave. The interFoam solves the RANS equations with a k − ε turbulence model. Experimentally, different dam break cases are carried out including one horizontal bed and four different downstream slope beds (upward 10◦ and 5◦ , downward 10◦ and 5◦ ). Each bed is tested with two different water levels (110 mm and 220 mm). By introducing a time compensation factor t ∗ c = t ∗ 1 3 into PS, the predicted downstream wave agree well with the experimental data and numerical results. In the dispersed phase, the present study mainly focus on the BIV technique. The special properties of bubbles are taken into consideration and a test BIV experiment is carried out to evaluate the BIV system capacity. Finally, the BIV technique is applied to the dam break experiment.