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Current designs of sanitary collection systems normally only consider the transport of wastewater without attention on the air movement in the sewer airspaces. Under anaerobic conditions, hydrogen sulfide (H 2 S) can be generated in the liquid phase in sewer systems. H 2 S is corrosive to concrete and steel structures and odorous or even toxic to human, which can cause corrosion and sewer odor issues. To develop a feasible sewer corrosion and odor control strategy, it is necessary to understand the mechanisms of air flow in sewer systems for developing practical tools to predict and control the air flow. This paper comprehensively reviewed previous efforts on modeling the air flow in sewer systems and provided recommendations on predicting the air flow for engineering applications. The air flow in a single pipe was firstly reviewed followed by the air flow in sewer structures as well as air flow models in sewer networks. Some other considerations such as temperature driven flow, transient water flow, and wind effect were also reviewed. The knowledge gaps were then identified, and recommendations on the further studies were provided. [ABSTRACT FROM AUTHOR]

Hydropower operations can induce significant variation of velocity field upstream of intakes and may lead to fish entrainment into turbines. In this study, the flow fields upstream of a high dam in China under different intake and spillway operation patterns were investigated theoretically using potential flow solution and computational fluid dynamic modeling, and experimentally in a 1:50-scale physical model. Flow fields induced by multiple intakes and by a line sink tends to be the same at about two times of the distance of adjacent operating intake upstream of the intakes. Different operation scenarios were analyzed to improve the general understanding of characteristics of upstream flow and to reduce the risk of fish entrainment. The extent of the risk zone for fish entrainment defined by specified thresholds of velocity and acceleration indicate that smaller water depth over submerged intake means a higher risk of fish entrainment. [ABSTRACT FROM AUTHOR]