This paper examines the steady thermocapillarybuoyant convection in a shallow annular pool subjected to a radial temperature gradient. A matched asymptotic theory is used to obtain the asymptotic solutions of the flow...This paper examines the steady thermocapillarybuoyant convection in a shallow annular pool subjected to a radial temperature gradient. A matched asymptotic theory is used to obtain the asymptotic solutions of the flow and thermal fields in the case of small aspect ratios,which is defined as the ratio of the layer thickness to the gap width. The flow domain is divided into the core region away from the cylinder walls and two end regions near each cylinder wall. Asymptotic solutions are obtained in the core region by solving the core and end flows separately and then joining them through matched asymptotic expansions. For the system of silicon melt,the asymptotic solutions are compared with the results of numerical simulations. It is found that the two kinds of solutions have a good agreement in the core region for a small aspect ratio. With the increase of aspect ratio,the applicability of the present asymptotic solutions decreases gradually.展开更多
Observational data obtained during the TOGA-COARE IOP in the "warm pool" area of the West-ern Tropical Pacific were used to analyze some characteristics of the intraseasonal variations in the mixedlayer. The...Observational data obtained during the TOGA-COARE IOP in the "warm pool" area of the West-ern Tropical Pacific were used to analyze some characteristics of the intraseasonal variations in the mixedlayer. The influence of westerly burst and rainfall on SST, salinity. and mixed layer depth are discussed.There are two pairs of counteracting processes in the "warm pool" mixed layer: (1) The increase of mixedlayer depth caused by local westerly bursts and the decrease of mixed layer depth caused by larger scaleeasterly relaxation;(2) the vertical mixing by local wind and the strong stratification due to rainfall in themixed layer. Some possible mechanisms through the interactions between the intraseasonal time scale varia-tions of the oceanic mixed layer and atmospheric low frequency oscillations are revealed.展开更多
This work is devoted to the study of steady thermocapillary-buoyant convection in a system of two horizontal superimposed immiscible liquid layers filling a lateral heated thin annular pool.The governing equations are...This work is devoted to the study of steady thermocapillary-buoyant convection in a system of two horizontal superimposed immiscible liquid layers filling a lateral heated thin annular pool.The governing equations are solved using an asymptotic theory for the aspect ratios ε→ 0.Asymptotic solutions of the velocity and temperature fields are obtained in the core region away from the cylinder walls.In order to validate the asymptotic solutions,numerical simulations are also carried out and the results are compared to each other.It is found that the present asymptotic solutions are valid in most of the core region.And the applicability of the obtained asymptotic solutions decreases with the increase of the aspect ratio and the thickness ratio of the two layers.For a system of gallium arsenide （lower layer） and boron oxide （upper layer）,the buoyancy slightly weakens the thermocapillary convection in the upper layer and strengthens it in the lower layer.展开更多
Using the 28℃ isotherm to define the Western Pacific Warm Pool （WPWP）, this study analyzes the seasonal variability of the WPWP thermohaline structure on the basis of the monthly-averaged sea temperature and salini...Using the 28℃ isotherm to define the Western Pacific Warm Pool （WPWP）, this study analyzes the seasonal variability of the WPWP thermohaline structure on the basis of the monthly-averaged sea temperature and salinity data from 1950 to 2011, and the dynamic and thermodynamic mechanisms based on the monthly-averaged wind, precipitation, net heat fluxes and current velocity data. A△T=-0.4℃ is more suitable than other temperature criterion for determining the mixed layer （ML） and barrier layer （BL） over the WPWP using monthly-averaged temperature and salinity data. The WPWP has a particular thermohaline structure and can be vertically divided into three layers, i.e., the ML, BL, and deep layer （DL）. The BL thickness （BLT） is the thickest, while the ML thickness （MLT） is the thinnest. The MLT has a similar seasonal variation to the DL thickness （DLT） and BLT. They are all thicker in spring and fall but thinner in summer. The temperatures of the ML and BL are both higher in spring and autumn but lower in winter and summer with an annual amplitude of 0.15℃, while the temperature of the DL is higher in May and lower in August. The averaged salinities at these three layers are all higher in March but lower in September, with annual ranges of 0.41-0.45. Zonal currents, i.e., the South Equatorial Current （SEC） and North Equatorial Counter Current （NECC）, and winds may be the main dynamic factors driving the seasonal variability in the WPWP thermohaline structure, while precipitation and net heat fluxes are both important thermodynamic factors. Higher （lower） winds cause both the MLT and BLT to thicken （thin）, a stronger （weaker） NECC induces MLT, BLT, and DLT to thin （thicken）, and a stronger （weaker） SEC causes both the MLT and BLT to thicken （thin） and the DLT to thin （thicken）. An increase （decrease） in the net heat fluxes causes the MLT and BLT to thicken （thin） but the DLT to thin （thicken）, while a stronger （weaker） precipitation favors thinner （thicker） MLT but thicker （thinner） BLT and DLT. In addition, a stronger （weaker） NECC and SEC cause the temperature of the three layers to decrease （increase）, while the seasonal variability in salinity at the ML, BL, and DL might be controlled by the subtropical cell （STC）.展开更多
为了探究渣层厚度对熔融热解炉底吹工艺过程中熔池流动性的影响,以200 kg熔融热解炉为研究对象,基于流体体积(volume of fluid,VOF)方法,构建了熔融热解炉底吹模型,通过模拟多元炉料的熔分过程,确定了不同原料配比下熔池中钢液/渣层与...为了探究渣层厚度对熔融热解炉底吹工艺过程中熔池流动性的影响,以200 kg熔融热解炉为研究对象,基于流体体积(volume of fluid,VOF)方法,构建了熔融热解炉底吹模型,通过模拟多元炉料的熔分过程,确定了不同原料配比下熔池中钢液/渣层与原料的质量比及渣层厚度.结果表明:使用70%废钢+30%直接还原铁(DRI),80%废钢+20%DRI,90%废钢+10%DRI进行熔分后,渣层厚度分别为118,74,41 mm,DRI占比越高,渣层厚度越大;在底吹流量(标准状况)为0.2 m^(3)/h的条件下,随着渣层厚度的增大,钢液上部及渣层的流场分布更均匀,流速也更高,钢液中下部的低流速区域逐渐扩大,熔池内流动死区体积也在增大,渣层上的渣眼面积逐渐减小直至消失,钢-渣界面的速度则先降低后升高;当以80%废钢+20%DRI作为冶炼原料时,熔池的流动性最优.展开更多
基金supported by the National Natural Science Foundation of China (50776102)the Fundamental Research Funds for the Central Universities (CDJXS10142248)
文摘This paper examines the steady thermocapillarybuoyant convection in a shallow annular pool subjected to a radial temperature gradient. A matched asymptotic theory is used to obtain the asymptotic solutions of the flow and thermal fields in the case of small aspect ratios,which is defined as the ratio of the layer thickness to the gap width. The flow domain is divided into the core region away from the cylinder walls and two end regions near each cylinder wall. Asymptotic solutions are obtained in the core region by solving the core and end flows separately and then joining them through matched asymptotic expansions. For the system of silicon melt,the asymptotic solutions are compared with the results of numerical simulations. It is found that the two kinds of solutions have a good agreement in the core region for a small aspect ratio. With the increase of aspect ratio,the applicability of the present asymptotic solutions decreases gradually.
基金Supported by National Natural Science Foundation of China (49276250) and LASG of Beijing.
文摘Observational data obtained during the TOGA-COARE IOP in the "warm pool" area of the West-ern Tropical Pacific were used to analyze some characteristics of the intraseasonal variations in the mixedlayer. The influence of westerly burst and rainfall on SST, salinity. and mixed layer depth are discussed.There are two pairs of counteracting processes in the "warm pool" mixed layer: (1) The increase of mixedlayer depth caused by local westerly bursts and the decrease of mixed layer depth caused by larger scaleeasterly relaxation;(2) the vertical mixing by local wind and the strong stratification due to rainfall in themixed layer. Some possible mechanisms through the interactions between the intraseasonal time scale varia-tions of the oceanic mixed layer and atmospheric low frequency oscillations are revealed.
基金supported by the National Natural Science Foundation of China (50776102)the Fundamental Research Funds for the Central Universities (CDJXS1041148)
文摘This work is devoted to the study of steady thermocapillary-buoyant convection in a system of two horizontal superimposed immiscible liquid layers filling a lateral heated thin annular pool.The governing equations are solved using an asymptotic theory for the aspect ratios ε→ 0.Asymptotic solutions of the velocity and temperature fields are obtained in the core region away from the cylinder walls.In order to validate the asymptotic solutions,numerical simulations are also carried out and the results are compared to each other.It is found that the present asymptotic solutions are valid in most of the core region.And the applicability of the obtained asymptotic solutions decreases with the increase of the aspect ratio and the thickness ratio of the two layers.For a system of gallium arsenide （lower layer） and boron oxide （upper layer）,the buoyancy slightly weakens the thermocapillary convection in the upper layer and strengthens it in the lower layer.
基金The National Basic Research Program(973 Program)of China under contract No.2012CB417402the CAS Strategy Pioneering Program under contract No.XDA10020104+1 种基金the Global Change and Air–Sea Interaction under contract No.GASI-03-01-01-02the National Natural Science Foundation of China under contract No.41406012
文摘Using the 28℃ isotherm to define the Western Pacific Warm Pool （WPWP）, this study analyzes the seasonal variability of the WPWP thermohaline structure on the basis of the monthly-averaged sea temperature and salinity data from 1950 to 2011, and the dynamic and thermodynamic mechanisms based on the monthly-averaged wind, precipitation, net heat fluxes and current velocity data. A△T=-0.4℃ is more suitable than other temperature criterion for determining the mixed layer （ML） and barrier layer （BL） over the WPWP using monthly-averaged temperature and salinity data. The WPWP has a particular thermohaline structure and can be vertically divided into three layers, i.e., the ML, BL, and deep layer （DL）. The BL thickness （BLT） is the thickest, while the ML thickness （MLT） is the thinnest. The MLT has a similar seasonal variation to the DL thickness （DLT） and BLT. They are all thicker in spring and fall but thinner in summer. The temperatures of the ML and BL are both higher in spring and autumn but lower in winter and summer with an annual amplitude of 0.15℃, while the temperature of the DL is higher in May and lower in August. The averaged salinities at these three layers are all higher in March but lower in September, with annual ranges of 0.41-0.45. Zonal currents, i.e., the South Equatorial Current （SEC） and North Equatorial Counter Current （NECC）, and winds may be the main dynamic factors driving the seasonal variability in the WPWP thermohaline structure, while precipitation and net heat fluxes are both important thermodynamic factors. Higher （lower） winds cause both the MLT and BLT to thicken （thin）, a stronger （weaker） NECC induces MLT, BLT, and DLT to thin （thicken）, and a stronger （weaker） SEC causes both the MLT and BLT to thicken （thin） and the DLT to thin （thicken）. An increase （decrease） in the net heat fluxes causes the MLT and BLT to thicken （thin） but the DLT to thin （thicken）, while a stronger （weaker） precipitation favors thinner （thicker） MLT but thicker （thinner） BLT and DLT. In addition, a stronger （weaker） NECC and SEC cause the temperature of the three layers to decrease （increase）, while the seasonal variability in salinity at the ML, BL, and DL might be controlled by the subtropical cell （STC）.
