AI 中文总结
该研究通过三维直接数值模拟探究MHD管道流中涡旋促进器的作用，分析不同壁面条件、管道朝向及传热对流动的影响，构建了流动状态相图，明确了浮力与壁面电导比的关键作用。
AI 中文摘要
我们采用三维直接数值模拟（3D direct numerical simulations）研究液态金属管道流中涡旋促进器的作用，以维持强磁场下形成的准二维（Q2D）状态，这类状态存在于聚变反应堆的冷却包层等场景中，研究涵盖电绝缘壁与导电壁两种情况。对于绝缘壁，扰动会持续存在；对于导电壁，扰动可能立即消失，取而代之的是Walker型或Hunt型流动，伴随其自身的射流分离不稳定性。此外，我们通过在Shercliff壁施加恒定热通量引入传热过程，针对不同构型的湍流输运特性进行分类与比较：导电管道无额外效应，水平放置的绝缘管道仅产生微小效应，而垂直放置的绝缘管道中，浮力因驱动不稳定性产生间歇性波动，对流动有显著影响。对湍流动能（TKE）与努塞尔数（Nusselt number）的分析显示，湍流动能最大的流动未必具有最佳传热性能，原因是侧射流移除热量的速度快于主流体的混合速度。研究还在固定雷诺数（Reynolds）、哈特曼数（Hartmann）与普朗特数（Prandtl）下开展参数研究，最终构建了展示不同流动状态的相图。
英文摘要
We use 3D direct numerical simulations to study the effects of vortex promoters in liquid metal duct flow to sustain Q2D states which are formed in the presence of strong magnetic fields, such as those present in cooling blankets of fusion reactors. Both for electrically insulating and conducting walls. In case of insulating walls, disturbances are found to be sustained. For conducting walls, the disturbances may be extinguished immediately and replaced by a Walker- or Hunt-type flow with its own jet-detachment instability. Furthermore, we add heat transfer by imposing constant heat flux at the Shercliff walls. We classify and compare possible configurations with respect to their turbulent transport properties. For conducting ducts, no additional effect is observed. For insulating ducts in horizontal position, we observe a small effect. For vertical ducts, the buoyancy forces have a significant impact due to buoyancy-driven instabilities, which produce intermittent fluctuations. The analysis of the turbulent kinetic energy (TKE) and the Nusselt number show that flows with the largest TKE may not have the best heat transfer performance. This is caused by side jets removing heat faster than mixing the bulk flow. The buoyancy force and wall conductance ratio are found to play a key role in determining the flow structure. Part of our work is a parametric study at fixed Reynolds, Hartmann and Prandtl numbers, which allows us eventually to compose a phase diagram showcasing the different flow regimes.
