Tannin foam is a new functional material.It can be widely applied to the automobile industry,construction industry,and packaging industry due to its wide range of raw materials,renewable,easily degraded,low cost and a...Tannin foam is a new functional material.It can be widely applied to the automobile industry,construction industry,and packaging industry due to its wide range of raw materials,renewable,easily degraded,low cost and almost no pollution.Preparing tannin foam is a very complex process that includes high temperature,two phases,mechanical agitation,and phase change.To investigate the influence of the stirring velocity and paddle shape,simulation was calculated by making use of the volume of fluid(VOF)method and multiple reference frame(MRF)method in a three-dimensional flow field of tannin-based foaming precursor resin.The gas holdup and velocity magnitude were analysed with various conditions of mechanical velocities and paddle shape in the stirring flow field.The result shows the higher the velocity,the greater the disturbance and paddle shape between the eggbeater and the Rushton turbine,obviously the paddle shape of the eggbeater with a wider range of agitation,which can entrap more air into the tannin-based foaming precursor resin in a short time.Especially when the speed is 1500 rpm,the flow field of the Rushton turbine comes out of a ditch,which decreases the efficiency of mass transfer;there is less air to mix into the tannin-based foaming precursor resin,which causes unevenness.At the same time,the eggbeater shows the marvelous capability of hybrid as it has two vortexes and multiple cycles that make a difference from the Rushton turbine,which has only one vortex and two upper and lower loops;the structure makes the flow field more stable allowed evenness of flow field tannin-based foaming precursor resin.The results reveal that it is beneficial for tannin-based foaming precursor resin to use an eggbeater with a speed of 1500 rpm to reduce the consumption of resources while obtaining a uniform flow field.展开更多
文章基于RANS方程,对计及自由面影响的双桨转动情况下的舰船旋臂试验(RAT)粘性流场数值模拟方法进行了研究。在旋臂试验的数值模拟中,根据旋臂试验的特点,采用分区混合网格,结合MRF方法和滑移网格方法,解决船体圆运动及螺旋桨定轴旋转...文章基于RANS方程,对计及自由面影响的双桨转动情况下的舰船旋臂试验(RAT)粘性流场数值模拟方法进行了研究。在旋臂试验的数值模拟中,根据旋臂试验的特点,采用分区混合网格,结合MRF方法和滑移网格方法,解决船体圆运动及螺旋桨定轴旋转运动的叠合难题。文中以ITTC推荐的MARIN model no.7967船模为对象,对其在四组转动半径下的旋臂试验进行了数值计算,并将结果与权威水池试验结果进行了对比,吻合良好。文中提出的方法可获得全附体船模旋转流场水动力性能参数,可以较真实地模拟其流场特性,获取包括船—舵—桨干扰在内的流场信息。该文的工作是可行的、有效的,可为深入研究舰船自由旋回试验及非定常操纵运动的数值模拟提供基础。展开更多
基于Euler-Euler双流体模型和群体平衡模型,应用多重参考坐标系(MRF)方法,运用Fluent分析发酵罐内由圆盘涡轮式搅拌器和翼型轴流式的三层搅拌器内部的流体特性,计算发酵罐内部的氧气气含率及气泡大小。结果表明:上两层搅拌器产生轴向流...基于Euler-Euler双流体模型和群体平衡模型,应用多重参考坐标系(MRF)方法,运用Fluent分析发酵罐内由圆盘涡轮式搅拌器和翼型轴流式的三层搅拌器内部的流体特性,计算发酵罐内部的氧气气含率及气泡大小。结果表明:上两层搅拌器产生轴向流动,最下层搅拌器产生径向流动,相互作用形成循环流场。氧气分布比较均匀,在搅拌轴和换热管附近有氧气集中的现象;罐内部的整体气含率为2.22%,模拟计算得到发酵罐的搅拌功率为117.81 k W。采用计算流体动力学方法对发酵罐的研究结果具有工业应用价值,而在研究过程中用到的理论方法在解决问题时具有一定的理论意义。展开更多
基金supported by the Key Program of Applied and Basic Research in Yunnan Province(Grant No.202101AS070008)the National Natural Science Foundation of China(NSFC 31760187)+4 种基金supported by the 111 Project(D21027)the Yunnan Provincial Academician Workstation(YSZJGZZ-2020052)the Foreign Expert Workstation(202305AF150006)supported by the Scientific Research Foundation of Education Department of Yunnan Province(Grant Nos.2023J0696,2023Y0699)Foreign Talent Introduction Program of Science and Technology Department of Yunnan Province(Grant No.202305AO350002).
文摘Tannin foam is a new functional material.It can be widely applied to the automobile industry,construction industry,and packaging industry due to its wide range of raw materials,renewable,easily degraded,low cost and almost no pollution.Preparing tannin foam is a very complex process that includes high temperature,two phases,mechanical agitation,and phase change.To investigate the influence of the stirring velocity and paddle shape,simulation was calculated by making use of the volume of fluid(VOF)method and multiple reference frame(MRF)method in a three-dimensional flow field of tannin-based foaming precursor resin.The gas holdup and velocity magnitude were analysed with various conditions of mechanical velocities and paddle shape in the stirring flow field.The result shows the higher the velocity,the greater the disturbance and paddle shape between the eggbeater and the Rushton turbine,obviously the paddle shape of the eggbeater with a wider range of agitation,which can entrap more air into the tannin-based foaming precursor resin in a short time.Especially when the speed is 1500 rpm,the flow field of the Rushton turbine comes out of a ditch,which decreases the efficiency of mass transfer;there is less air to mix into the tannin-based foaming precursor resin,which causes unevenness.At the same time,the eggbeater shows the marvelous capability of hybrid as it has two vortexes and multiple cycles that make a difference from the Rushton turbine,which has only one vortex and two upper and lower loops;the structure makes the flow field more stable allowed evenness of flow field tannin-based foaming precursor resin.The results reveal that it is beneficial for tannin-based foaming precursor resin to use an eggbeater with a speed of 1500 rpm to reduce the consumption of resources while obtaining a uniform flow field.
文摘文章基于RANS方程,对计及自由面影响的双桨转动情况下的舰船旋臂试验(RAT)粘性流场数值模拟方法进行了研究。在旋臂试验的数值模拟中,根据旋臂试验的特点,采用分区混合网格,结合MRF方法和滑移网格方法,解决船体圆运动及螺旋桨定轴旋转运动的叠合难题。文中以ITTC推荐的MARIN model no.7967船模为对象,对其在四组转动半径下的旋臂试验进行了数值计算,并将结果与权威水池试验结果进行了对比,吻合良好。文中提出的方法可获得全附体船模旋转流场水动力性能参数,可以较真实地模拟其流场特性,获取包括船—舵—桨干扰在内的流场信息。该文的工作是可行的、有效的,可为深入研究舰船自由旋回试验及非定常操纵运动的数值模拟提供基础。
文摘基于Euler-Euler双流体模型和群体平衡模型,应用多重参考坐标系(MRF)方法,运用Fluent分析发酵罐内由圆盘涡轮式搅拌器和翼型轴流式的三层搅拌器内部的流体特性,计算发酵罐内部的氧气气含率及气泡大小。结果表明:上两层搅拌器产生轴向流动,最下层搅拌器产生径向流动,相互作用形成循环流场。氧气分布比较均匀,在搅拌轴和换热管附近有氧气集中的现象;罐内部的整体气含率为2.22%,模拟计算得到发酵罐的搅拌功率为117.81 k W。采用计算流体动力学方法对发酵罐的研究结果具有工业应用价值,而在研究过程中用到的理论方法在解决问题时具有一定的理论意义。
