The perforated breakwater is an environmentally friendly coastal structure, and dissolved oxygen concentration levels are an important index to denote water quality. In this paper, oxygen transport experiments with regular waves through a vertical perforated breakwater were conducted. The oxygen scavenger method was used to reduce the dissolved oxygen concentration of inner water body with the chemicals Na2SO3 and COC12. The dissolved oxygen concentration and wave parameters of 36 experimental scenarios were measured with different perforated arrangements and wave conditions. It was found that the oxygen transfer coefficient through wave surface, K1α1, is much lower than the oxygen transport coefficient through the perforated breakwater, K2α2. If the effect of K1α1 is not considered, the dissolved oxygen concentration computation for inner water body will not be greatly affected. Considering the effect of a permeable area ratio a, relative location parameter of perforations 6 and wave period T, the aforementioned data of 30 experimental scenarios, the dimensional analysis and the least squares method were used to derive an equation of K2α2 （K2α2=0.0042aσ56δ2T1）. It was validated with 6 other experimental scenarios data, which indicates an approximate agreement. Therefore, this equation can be used to compute the DO concentration caused by the water transport through perforated breakwater.
The dissolved oxygen （DO） concentration is an important index of water quality. This paper studies the dissolved oxygen recovery of the water and bubble mixture pipe flow through two sudden contractions and expansions. A 3-D computational fluid dy- namics model is established to simulate the water and bubble mixture flow with a DO transport model. An experiment is conducted to validate the mathematical model. The mathematical model is used to evaluate the effect of geometric parameters on the head loss coefficient, the relative saturation coefficient and the oxygen absorption efficiency. It is found that the contraction ratio is a signi- ficant influencing factor, other than the relative length and the relative distance. Given the same relative length and relative distance, the head loss coefficient, the relative saturation coefficient and the oxygen absorption efficiency increase with the decrease of the contraction ratio, respectively. Given the same relative length and contraction ratio, the head loss coefficient increases with the in- crease of the relative distance firstly, and then decreases gradually, in contrast, the relative saturation coefficient and the oxygen ab- sorption efficiency decrease with the increase of the relative distance firstly, and then increase gradually, the relative saturation coefficient and the oxygen absorption efficiency are inversely proportional to the head loss coefficient, respectively.
