Submerged vegetation has a significant impact on water flow velocity.Current investigations include the impact through adding drag resistance and increasing bottom roughness coefficient,which cannot elucidate the char...Submerged vegetation has a significant impact on water flow velocity.Current investigations include the impact through adding drag resistance and increasing bottom roughness coefficient,which cannot elucidate the characters of real submerged vegetation.To evaluate the effects of submerged vegetation on water currents at different velocities,a laboratory experiment was conducted using three kinds of vegetations.The effective heights of these vegetations on varying flow velocities were evaluated.An equation describing the relationship between the normalized resistance of the submerged plants and the Reynolds number based on the plant effective height was then established and used to calculate the hydraulic resistance parameters of submerged plants in different stages of growth.展开更多
Aquatic vegetation has significant effects on flow in waters. In this article, four types of water areas were analyzed according to the field survey on water depth and vegetation in the Nansi Lake for the East Line Pr...Aquatic vegetation has significant effects on flow in waters. In this article, four types of water areas were analyzed according to the field survey on water depth and vegetation in the Nansi Lake for the East Line Project of Water Transfer from South to North in China （WTSNC）. The depth-averaged 2-D hydrodynamic models with and without consideration of the effects of aquatic vegetation on flow were established to simulate flow fields in vegetated and non-vegetated zones in the Nansi Lake. With the established models, flow fields were predicted under the conditions of water transfer from south to north. The results indicate that when the drag force term exerted by aquatic vegetation is considered, the computed velocities agree well with the measured data, whereas as the drag term is taken into account, the computed velocities are obviously larger than the measured data in the vegetated zone and considerably smaller in the non-vegetated zone, and the error range between the two velocities is large if this problem is dealt with the method of increasing the roughness coefficient of the lake-bed to reflect the vegetation drag force. In addition, it is demonstrated that the emerged vegetation exerts larger effects on flow than submerged vegetation comparing the results in the Emerged Vegetation （reed） Zone （EVZ） and the Submerged Vegetation Zone （SVZ）.展开更多
基金supported by the National Basic Research Program of China (973 Program, Grant No. 2008CB418203)the National Water Project (Grant No. 2008ZX07101- 008)the Elitist Support Project of the Ministry of Education of China (Grant No. NCET-07-0524)
文摘Submerged vegetation has a significant impact on water flow velocity.Current investigations include the impact through adding drag resistance and increasing bottom roughness coefficient,which cannot elucidate the characters of real submerged vegetation.To evaluate the effects of submerged vegetation on water currents at different velocities,a laboratory experiment was conducted using three kinds of vegetations.The effective heights of these vegetations on varying flow velocities were evaluated.An equation describing the relationship between the normalized resistance of the submerged plants and the Reynolds number based on the plant effective height was then established and used to calculate the hydraulic resistance parameters of submerged plants in different stages of growth.
基金Project supported by the National Basic Research Program of China (Grant No: 2002CB412303) and the National Natural Science Foundation of China (Grant Nos: 50239010, 50379012).
文摘Aquatic vegetation has significant effects on flow in waters. In this article, four types of water areas were analyzed according to the field survey on water depth and vegetation in the Nansi Lake for the East Line Project of Water Transfer from South to North in China （WTSNC）. The depth-averaged 2-D hydrodynamic models with and without consideration of the effects of aquatic vegetation on flow were established to simulate flow fields in vegetated and non-vegetated zones in the Nansi Lake. With the established models, flow fields were predicted under the conditions of water transfer from south to north. The results indicate that when the drag force term exerted by aquatic vegetation is considered, the computed velocities agree well with the measured data, whereas as the drag term is taken into account, the computed velocities are obviously larger than the measured data in the vegetated zone and considerably smaller in the non-vegetated zone, and the error range between the two velocities is large if this problem is dealt with the method of increasing the roughness coefficient of the lake-bed to reflect the vegetation drag force. In addition, it is demonstrated that the emerged vegetation exerts larger effects on flow than submerged vegetation comparing the results in the Emerged Vegetation （reed） Zone （EVZ） and the Submerged Vegetation Zone （SVZ）.
