Near-bottom currents play important roles in the formation and dynamics of deep-water sedimentary systems.This study examined the characteristics and temporal variations of near-bottom currents, especially the tidal c...Near-bottom currents play important roles in the formation and dynamics of deep-water sedimentary systems.This study examined the characteristics and temporal variations of near-bottom currents, especially the tidal components, based on two campaigns(2014 and 2016) of in situ observations conducted southeast of the Dongsha Island in the South China Sea. Results demonstrated near-bottom currents are dominated by tidal currents, the variance of which could account for ~70% of the total current variance. Diurnal tidal currents were found stronger than semidiurnal currents for both barotropic and baroclinic components. The diurnal tidal currents were found polarized with predominantly clockwise-rotating constituents, whereas the clockwise and counterclockwise constituents were found comparable for semidiurnal tidal currents. It was established that diurnal tidal currents could induce strong current shear. Baroclinic tidal currents showed pronounced seasonal variation with large magnitude in winter and summer and weak magnitude in spring and autumn in 2014. The coherent components accounted for ~65% and ~50% of the diurnal and semidiurnal tidal current variances,respectively. The proportions of the coherent and incoherent components changed little in different seasons. In addition to tidal currents, it was determined that the passing of mesoscale eddies could induce strong nearbottom currents that have considerable influence on the deep circulation.展开更多
Rapid changes in the near-bottom water temperature are important environmental factors that can significantly affect the growth and development of species in the bottom culture.The object of this research is to invest...Rapid changes in the near-bottom water temperature are important environmental factors that can significantly affect the growth and development of species in the bottom culture.The object of this research is to investigate the mechanism causing these rapid changes within a bottom culture area near the Zhangzi Island.The hydrographic transects observations in the North Yellow Sea(NYS)suggest that our mooring station is very close to the tidal mixing front.The horizontal advection of the tidal front has induced the observed tidal change of bottom temperature at the mooring station.Analysis of the mooring near-bottom temperature and current measurements show that the angle between the tidal current horizontal advection and the swing of the tidal front is crucial in determining the variation trend of temperature.When the angle equals 90°,the horizontal tidal current advects along the isotherms so the temperature remains the same.When the angle is between 0°and 90°,the seawater moves from deep water to the warmer coastal zone and the temperature decreases.In contrast,the horizontal tidal advection moves the coastal warm water to the mooring station and the water temperature increases when the angle is between 90°and 180°.The amplitude of the temperature change is proportional to the magnitude of the horizontal temperature gradient and the tidal excursion in the direction of the temperature gradient.This study may facilitate the choice of culture area in order to have a good aquaculture production.展开更多
采用求解RANS方程的方法,结合RNG k-ε湍流模型,对于某潜艇模型近海底和近水面绕流进行了数值模拟。计算了不同海底深度下潜艇模型的阻力、垂向力和俯仰力矩,也计算了同一海底深度下潜艇阻力随傅氏数的变化,研究表明当海底深度超过二分...采用求解RANS方程的方法,结合RNG k-ε湍流模型,对于某潜艇模型近海底和近水面绕流进行了数值模拟。计算了不同海底深度下潜艇模型的阻力、垂向力和俯仰力矩,也计算了同一海底深度下潜艇阻力随傅氏数的变化,研究表明当海底深度超过二分之一艇长时,海底对阻力的影响可忽略不计。自由液面捕捉采用VOF(Volume of Fluid)方法。计算了不同浸深下潜艇模型的阻力和自由液面波型,同时又研究了同一浸深下阻力和波型随傅氏数的变化趋势。研究表明,当浸深超过三分之一艇长时,自由液面波高迅速减小,自由液面对阻力的影响可忽略不计。计算结果与试验结果吻合较好。展开更多
基金The National Key Research and Development Program of China under contract No.2017YFC1404201the National Natural Science Foundation of China under contract Nos 41706035 and 41876029+2 种基金the NSFC-Shandong Joint Fund for Marine Science Research Centers under contract No.U1606405the Laboratory for Regional Oceanography and Numerical Modeling,Qingdao National Laboratory for Marine Science and Technology under contract No.2017A01the China Postdoctoral Science Foundation under contract No.2017M622111
文摘Near-bottom currents play important roles in the formation and dynamics of deep-water sedimentary systems.This study examined the characteristics and temporal variations of near-bottom currents, especially the tidal components, based on two campaigns(2014 and 2016) of in situ observations conducted southeast of the Dongsha Island in the South China Sea. Results demonstrated near-bottom currents are dominated by tidal currents, the variance of which could account for ~70% of the total current variance. Diurnal tidal currents were found stronger than semidiurnal currents for both barotropic and baroclinic components. The diurnal tidal currents were found polarized with predominantly clockwise-rotating constituents, whereas the clockwise and counterclockwise constituents were found comparable for semidiurnal tidal currents. It was established that diurnal tidal currents could induce strong current shear. Baroclinic tidal currents showed pronounced seasonal variation with large magnitude in winter and summer and weak magnitude in spring and autumn in 2014. The coherent components accounted for ~65% and ~50% of the diurnal and semidiurnal tidal current variances,respectively. The proportions of the coherent and incoherent components changed little in different seasons. In addition to tidal currents, it was determined that the passing of mesoscale eddies could induce strong nearbottom currents that have considerable influence on the deep circulation.
基金The National Key Research and Development Program of China under contract Nos 2017YFC1404403 and2016YFC1401602。
文摘Rapid changes in the near-bottom water temperature are important environmental factors that can significantly affect the growth and development of species in the bottom culture.The object of this research is to investigate the mechanism causing these rapid changes within a bottom culture area near the Zhangzi Island.The hydrographic transects observations in the North Yellow Sea(NYS)suggest that our mooring station is very close to the tidal mixing front.The horizontal advection of the tidal front has induced the observed tidal change of bottom temperature at the mooring station.Analysis of the mooring near-bottom temperature and current measurements show that the angle between the tidal current horizontal advection and the swing of the tidal front is crucial in determining the variation trend of temperature.When the angle equals 90°,the horizontal tidal current advects along the isotherms so the temperature remains the same.When the angle is between 0°and 90°,the seawater moves from deep water to the warmer coastal zone and the temperature decreases.In contrast,the horizontal tidal advection moves the coastal warm water to the mooring station and the water temperature increases when the angle is between 90°and 180°.The amplitude of the temperature change is proportional to the magnitude of the horizontal temperature gradient and the tidal excursion in the direction of the temperature gradient.This study may facilitate the choice of culture area in order to have a good aquaculture production.
文摘采用求解RANS方程的方法,结合RNG k-ε湍流模型,对于某潜艇模型近海底和近水面绕流进行了数值模拟。计算了不同海底深度下潜艇模型的阻力、垂向力和俯仰力矩,也计算了同一海底深度下潜艇阻力随傅氏数的变化,研究表明当海底深度超过二分之一艇长时,海底对阻力的影响可忽略不计。自由液面捕捉采用VOF(Volume of Fluid)方法。计算了不同浸深下潜艇模型的阻力和自由液面波型,同时又研究了同一浸深下阻力和波型随傅氏数的变化趋势。研究表明,当浸深超过三分之一艇长时,自由液面波高迅速减小,自由液面对阻力的影响可忽略不计。计算结果与试验结果吻合较好。