The present work examines the downstream vortex evolution behind a cascade of vortex generators producing counter-rotating vortices in a boundary layer of negligible streamwise pressure gradient. For the current study, which is an extension of the model presented in [4], these parameters are all seen to vary linearly in the downstream direction. Based on the experimental observations triggered by a previous study, the vortices generated by vortex generators have been observed to be self-similar for both the axial ($u_z$) and azimuthal ($u_θ$) velocity profiles. The previous model, which is based merely on $u_z$ and $u_θ$ at one single downstream location, can therefore be extended to include the downstream development of the vortex using self-similarity scaling arguments. This knowledge is important for fundamental understanding as well as for the aspect of applications, for which parametric experiments can be substantially reduced in terms of required time and cost by facilitating engineering models.
Possible Implications of a Vortex Gas Model and Self-Similarity for Tornadogenesis and Maintenance
我们用Chorin（1994）提出的三维涡旋气体模型描述了龙卷风的发生和维持，Flandoli和Gubinelli（2002）进一步发展了该模型。我们认为，Fiedler和Rotunno（1986）研究过的Benjamin（1962）意义上的高能超临界涡旋，具有Onsager（1949）意义上的负温度，在模型中起着重要作用。我们推测高温涡旋的形成与它们形成或倾斜到垂直方向时所继承的螺旋度以及它们与表面和边界层的相互作用有关。我们还利用自相似性的概念来证明Cai（2005）; Wurman and Gill（2000）; Wurman and Alexander（2005）中提出的从弱龙卷风和强龙卷风的观测中得出的幂律。分析布赖恩云模型（CM 1）模拟的龙卷风超级单体揭示了与观测研究一致的缩放。
Dynamic similarity of vortex shedding in a superfluid flowing past a penetrable obstacle
Seoul National University（首尔大学）；NextQuantum, Seoul National University（NextQuantum，首尔大学）；Institute of Applied Physics, Seoul National University（首尔大学应用物理研究所）
Initial evolution of 3D turbulence en route to the Kolmogorov state: emergence and transformations of coherent structures, self-similarity and instabilities
In the seminal work [39], Leray demonstrated the existence of global weak solutions to the Navier-Stokes equations in three dimensions. We exhibit two distinct Leray solutions with zero initial velocity and identical body force. Our approach is to construct a `background' solution which is unstable for the Navier-Stokes dynamics in similarity variables; its similarity profile is a smooth, compactly supported vortex ring whose cross-section is a modification of the unstable two-dimensional vortex constructed by Vishik in [43,44]. The second solution is a trajectory on the unstable manifold asso…
Helical structure of longitudinal vortices embedded in turbulent wall-bounded flow
研究了平板湍流附壁流动中的嵌入涡，该涡是由被动矩形叶片涡发生器在低雷诺数流动（$β$，基于进口网格尺寸$L=0.039\;$ m和自由流速度$U_{\infty} = 1.0\;$ m s $^{-1}$）中与来流形成的。这些研究是在低速闭路风洞中利用立体粒子图像测速仪（SPIV）进行的。涡流已被证明具有螺旋对称性，允许以简单的方式描述流动。轴向涡度等值线图显示$20^{\circ} \leq β\leq 40^{\circ}$的主涡占优势，次涡较弱。对于该范围之外的角度，由于出现额外的流动效应，螺旋对称性受损。描述的流动模型已被利用，显示出很强的并发性与测量，即使该模型是解耦的外部流动过程，可能会扰乱螺旋对称性。涡的螺距、涡核尺寸、环流和平流速度都随装置角度$β$线性变化。这对于流动控制是重要的，因为由此可以确定由螺旋涡流以及对于给定的装置角度$β$重新分配轴向速度分量的涡流引起的轴向速度。这也简化了理论研究，\eg理解和预测的稳定性的旋涡和模拟的流动数值。
Neural Operator-Based Surrogate Model for CFD:Helical Coil Steam Generator in Small Modular Reactor
Department of Quantum System Engineering, Jeonbuk National University（全子系统工程系，全州国立大学）；Department of Nuclear Engineering, Hanyang University（核工程系，翰阳大学）；Graduate School of Integrated Energy-AI, Jeonbuk National University（整合能源-人工智能研究生院，全州国立大学）
