The bimodal behavior of turbulent junction flows is associated with a low-frequency unsteadiness that can have implications for the overall performance of engineering applications. The literature suggests that the bimodal behavior may be correlated with upstream boundary-layer events. To test this hypothesis, large-eddy simulations of a generic junction flow with Rood wing geometry were performed for a Reynolds number of 7000 based on airfoil thickness and approach flow velocity. Pulsed disturbances were deliberately introduced upstream of the junction to generate deterministic boundary-layer events. The variable-interval time-averaging method was employed to evaluate the effectiveness of the forcing and track the downstream development of the boundary-layer events. Cross correlations of this quantity with the circulation of the junction flow horseshoe vortex were computed to quantify the dependence of the bimodal behavior on the upstream disturbances. Several of the observed boundary-layer events led to a loss of coherence of the horseshoe vortex. Overall, the present results provide support for the hypothesis that the bimodal behavior is related to upstream boundary-layer events.

湍流汇流的双峰行为与低频不稳定性有关，它可能对工程应用的整体性能产生影响。文献表明双峰行为可能与上游边界层事件有关。为了验证这一假设，基于翼型厚度和进近流速，对雷德数为7000的具有Rood机翼几何形状的通用节流进行了大涡模拟。故意在连接上游引入脉冲干扰，以产生确定的边界层事件。采用可变间隔时间平均法评估强迫作用的有效性并跟踪边界层事件的下游发展。计算该量与结流马蹄涡流的循环的互相关，以量化双峰行为对上游扰动的依赖性。观察到的几个边界层事件导致马蹄涡流的相干性丧失。总的来说，本结果为双峰行为与上游边界层事件有关的假设提供了支持。