针对飞行马赫数大于设计马赫数的情况,采用二维磁流体动力学方程对磁控进气道进行了数值模拟研究。数值模拟结果表明磁流体装置的电磁作用可以使非设计马赫数下进气道激波满足SOL(shock on lip)条件,并使出口处的流动变得均匀。分析了...针对飞行马赫数大于设计马赫数的情况,采用二维磁流体动力学方程对磁控进气道进行了数值模拟研究。数值模拟结果表明磁流体装置的电磁作用可以使非设计马赫数下进气道激波满足SOL(shock on lip)条件,并使出口处的流动变得均匀。分析了磁流体作用位置、宽度和深度等关键控制参数对该类进气道性能的影响,计算结果表明,磁流体作用区域越靠近飞行器前缘,而且在纵向越深,则进气道出口处的流动越均匀,但流率会有所下降;若磁流体作用区域较宽,则需较小的磁场就能使非设计马赫数下进气道的激波结构满足SOL条件。展开更多
In this work,a steady mixed convection in a two-dimensional enclosure filled viananoliquid Cu/H2O through a porous medium was numerically analyzed.The nanoliquid flow is designated utilizing the Brinkman-Forchheimer m...In this work,a steady mixed convection in a two-dimensional enclosure filled viananoliquid Cu/H2O through a porous medium was numerically analyzed.The nanoliquid flow is designated utilizing the Brinkman-Forchheimer model.The upper and the bottom horizontal walls are considered to be hot(Th)and cold temperature(Tc),respectively,whereas the other walls are thermally insulated.The impact of various dimensionless terms such as the Grashof number(Gr)in the ranges(0.01–20),the Reynolds number(Re)in the ranges(50–500),the Hartman number(Ha)in the ranges(0–20),and three different location cases(0.25,0.5,and 0.75)are carefully analyzed.The obtained outcomes are established in the form of isotherms,streamlines,and the average Nusselt number.It has been found that heat transport increases significantly through rising Reynolds number(Re).For the location cases L=0.25,Re=50,and Gr=105,the heat transfer is maximum.展开更多
基于理想磁流体动力学方程组,采用CTU(corner transport upwind)+CT(constrained transport)算法,数值研究了磁场控制下R22气柱界面Richtmyer-Meshkov不稳定性的演化过程.结果描述了平面激波冲击气柱界面过程中激波结构和界面不稳定性...基于理想磁流体动力学方程组,采用CTU(corner transport upwind)+CT(constrained transport)算法,数值研究了磁场控制下R22气柱界面Richtmyer-Meshkov不稳定性的演化过程.结果描述了平面激波冲击气柱界面过程中激波结构和界面不稳定性的发展;无磁场时,流场结构与Haas和Sturtevant(Hass J F,Sturtevant B 1987 J.Fluid Mech.18141)的实验结果相符;施加纵向磁场后,激波结构的演化基本无影响,但明显抑制了气柱界面的不稳定性.进一步研究表明,激波与界面的作用,使磁感线在界面上发生折射,改变流场的磁场梯度,在内外涡量层上形成磁张力.磁张力的形成,对界面流体产生一个与速度剪切相反的力矩,抑制了界面的失稳及主涡的卷起.另外,磁张力沿界面分布的不均匀,改变磁感线在界面上的聚集程度,放大磁能量,最终增强磁场对气柱界面不稳定性的抑制作用.展开更多
湍流模型参数的合理设置是气流场仿真中的要素之一。对于电流零区湍流模型的选择及湍流参数的设置,研究者持有不同的观点。文中针对零区气流场对标准k-epsilon湍流模型参数敏感度大小的问题,基于磁流体动力学原理,以252 k V压气式结构...湍流模型参数的合理设置是气流场仿真中的要素之一。对于电流零区湍流模型的选择及湍流参数的设置,研究者持有不同的观点。文中针对零区气流场对标准k-epsilon湍流模型参数敏感度大小的问题,基于磁流体动力学原理,以252 k V压气式结构燃弧阶段的动态仿真为基础,计算了电流过零阶段湍流模型参数C1e对气流场的影响偏差百分比。通过特定监测点处气压与温度的对比,分析讨论了引起敏感度数值差异较大的原因。研究表明,湍流模型参数C1e的改变对喷口区域内气体压力的影响较小,对于气体温度的影响相对较大。零区气流场对C1e的敏感度会受到气流场分布的制约,在激波存在的条件下,激波作用会增加湍流对气流场的影响程度,但在工程应用上,参数C1e变化所引起的气流场计算偏差是可以接受的。气流场对C1e敏感度的分析,对于湍流模型参数的设置具有一定的参考价值。展开更多
In this work, a numerical study for designing a new kind of MHD （Magneto-Hydrn-Dynamic） pumps is presented. This technique makes a compromise between electrolysis prevention and high flow rate performance. This tech...In this work, a numerical study for designing a new kind of MHD （Magneto-Hydrn-Dynamic） pumps is presented. This technique makes a compromise between electrolysis prevention and high flow rate performance. This technique should eliminate electrolytic bubble generation, electrodes wear and fluid propriety modification. All these side phenomena are prevented by considering isolated electrodes. The numerical presented results in this paper demonstrate that continuous MHD pumping is possible with isolated electrodes. The MHD excitation combines a high frequency altering current with a low frequency altering magnetic field. In order to validate our results, two independent theoretical methods for computing flow rate are followed. The two presented independent approaches show that high flow rate is possible even with isolated electrodes. To overcome the problem of dimensioning this kind of pumps, a generic numerical analysis is proposed. Hence, the pump performances as functions of the external parameter are studied and tools to calculate for a given fluid and the optimal high frequency regime are provided.展开更多
文摘针对飞行马赫数大于设计马赫数的情况,采用二维磁流体动力学方程对磁控进气道进行了数值模拟研究。数值模拟结果表明磁流体装置的电磁作用可以使非设计马赫数下进气道激波满足SOL(shock on lip)条件,并使出口处的流动变得均匀。分析了磁流体作用位置、宽度和深度等关键控制参数对该类进气道性能的影响,计算结果表明,磁流体作用区域越靠近飞行器前缘,而且在纵向越深,则进气道出口处的流动越均匀,但流率会有所下降;若磁流体作用区域较宽,则需较小的磁场就能使非设计马赫数下进气道的激波结构满足SOL条件。
文摘In this work,a steady mixed convection in a two-dimensional enclosure filled viananoliquid Cu/H2O through a porous medium was numerically analyzed.The nanoliquid flow is designated utilizing the Brinkman-Forchheimer model.The upper and the bottom horizontal walls are considered to be hot(Th)and cold temperature(Tc),respectively,whereas the other walls are thermally insulated.The impact of various dimensionless terms such as the Grashof number(Gr)in the ranges(0.01–20),the Reynolds number(Re)in the ranges(50–500),the Hartman number(Ha)in the ranges(0–20),and three different location cases(0.25,0.5,and 0.75)are carefully analyzed.The obtained outcomes are established in the form of isotherms,streamlines,and the average Nusselt number.It has been found that heat transport increases significantly through rising Reynolds number(Re).For the location cases L=0.25,Re=50,and Gr=105,the heat transfer is maximum.
文摘基于理想磁流体动力学方程组,采用CTU(corner transport upwind)+CT(constrained transport)算法,数值研究了磁场控制下R22气柱界面Richtmyer-Meshkov不稳定性的演化过程.结果描述了平面激波冲击气柱界面过程中激波结构和界面不稳定性的发展;无磁场时,流场结构与Haas和Sturtevant(Hass J F,Sturtevant B 1987 J.Fluid Mech.18141)的实验结果相符;施加纵向磁场后,激波结构的演化基本无影响,但明显抑制了气柱界面的不稳定性.进一步研究表明,激波与界面的作用,使磁感线在界面上发生折射,改变流场的磁场梯度,在内外涡量层上形成磁张力.磁张力的形成,对界面流体产生一个与速度剪切相反的力矩,抑制了界面的失稳及主涡的卷起.另外,磁张力沿界面分布的不均匀,改变磁感线在界面上的聚集程度,放大磁能量,最终增强磁场对气柱界面不稳定性的抑制作用.
文摘湍流模型参数的合理设置是气流场仿真中的要素之一。对于电流零区湍流模型的选择及湍流参数的设置,研究者持有不同的观点。文中针对零区气流场对标准k-epsilon湍流模型参数敏感度大小的问题,基于磁流体动力学原理,以252 k V压气式结构燃弧阶段的动态仿真为基础,计算了电流过零阶段湍流模型参数C1e对气流场的影响偏差百分比。通过特定监测点处气压与温度的对比,分析讨论了引起敏感度数值差异较大的原因。研究表明,湍流模型参数C1e的改变对喷口区域内气体压力的影响较小,对于气体温度的影响相对较大。零区气流场对C1e的敏感度会受到气流场分布的制约,在激波存在的条件下,激波作用会增加湍流对气流场的影响程度,但在工程应用上,参数C1e变化所引起的气流场计算偏差是可以接受的。气流场对C1e敏感度的分析,对于湍流模型参数的设置具有一定的参考价值。
文摘In this work, a numerical study for designing a new kind of MHD （Magneto-Hydrn-Dynamic） pumps is presented. This technique makes a compromise between electrolysis prevention and high flow rate performance. This technique should eliminate electrolytic bubble generation, electrodes wear and fluid propriety modification. All these side phenomena are prevented by considering isolated electrodes. The numerical presented results in this paper demonstrate that continuous MHD pumping is possible with isolated electrodes. The MHD excitation combines a high frequency altering current with a low frequency altering magnetic field. In order to validate our results, two independent theoretical methods for computing flow rate are followed. The two presented independent approaches show that high flow rate is possible even with isolated electrodes. To overcome the problem of dimensioning this kind of pumps, a generic numerical analysis is proposed. Hence, the pump performances as functions of the external parameter are studied and tools to calculate for a given fluid and the optimal high frequency regime are provided.
