Li Feipeng

Conceptual mechanism of hydrodynamic impacts on freshwater algae for flow management

Numerous studies have shown that low flow condition is the main trigger of algae bloom and flow management is widely acknowledged as a strategy for inhibiting bloom development based on critical flow velocity and replacement. Due to the underlying intervention mechanism is still not clear,long-term practices of flow management are not very effective. Based on the research progress and a series of studies through long-term observation,enclosure and laboratory experiments,we present the conceptual mechanism that there existed three different mechanisms of hydrodynamic impacts on freshwater algae:( 1) low turbulent flow results in the thickness of cell diffuse layer thinner in favor of nutrients transport from water phase to algae cell,which is preferred by algae growth;( 2) medium turbulent flow is harmful to nutrients absorption and light availability of algae and inhibits the algae growth;( 3) high shear force can damage the algae cell walls,which are individually determinant in different levels of flow intensity. According to theories,critical flow velocity should be applied from two different aspects of water replacement and cytology in flow management. The results will be of great scientific significance in order to control algle bloom and remain the water quality in flow management.

Layout and flow field optimization of a stormwater pumping station with FLUENT software

The flow patterns of forebay and outflow conduit are analyzed for a stormwater pumping station in Hongqiao Traffic Centre of Shanghai with FLUENT software based on Reynolds average N-S equations and standard k-εturbulence model. Geo-reconstruction VOF method is applied to track the free surface and the PISO algorithm is applied to calculated the flow filed. Taking the standard deviation of cross sectional velocities as the objective function and also based on the qualitative judgment of flow pattern and velocity distribution, the original design scheme of the pumping station is optimized. The results show that no unsatisfactory flow pattern will appear in the forebay and outflow conduct with the improved design.

Influencing Factors of Oil Slick Movement on Tidal Rivers

It is of vital importance for risk management and emergency response to understand the factors that may influence the slick movement in an oil spill accident. The influencing factors have been investigated based on a 2D numerical oil spill model, a laboratory physical model and a real spill accident on the Huangpu River. The results show that the combined effect of wind and river morphology is the determining factor dominating the movement of oil slick on narrow and meandering tidal rivers. Other important factors include the net flow rate which affects the drift velocity of oil slick and spill amount which affects the slick area. It is concluded that the real-time hydrometeorological information is a must for an effective emergency response.