Purpose

This paper aims to study passive control techniques for transonic flow over a backward-facing step (BFS) using square-lobed trailing edges. The study investigates the efficacy of upward and downward lobe patterns, different lobe widths and deflection angles on flow separation, aiming for a deeper understanding of the flow physics behind the passive flow control system.

Design/methodology/approach

Large Eddy Simulation and Reynolds-averaged Navier–Stokes were used to evaluate the results of the study. The research explores the impact of upward and downward patterns of lobes on flow separation through the effects of different lobe widths and deflection angles. Numerical methods are used to analyse the behaviour of transonic flow over BFS and compared it to existing experimental results.

Findings

The square-lobed trailing edges significantly enhance the reduction of mean reattachment length by up to 80%. At Ma = 0.8, the up-downward configuration demonstrates increased effectiveness in reducing the root mean square of pressure fluctuations at a proximity of 5-step height in the wake region, with a reduction of 50%, while the flat-downward configuration proves to be more efficient in reducing the root mean square of pressure fluctuations at a proximity of 1-step height in the near wake region, achieving a reduction of 71%. Furthermore, the study shows that the up-downward configuration triggers early spanwise velocity fluctuations, whereas the standalone flat-downward configuration displays less intense crosswise velocity fluctuations within the wake region.

Practical implications

The findings demonstrate the effectiveness of square-lobed trailing edges as passive control techniques, showing significant implications for improving efficiency, performance and safety of the design in aerospace and industrial systems.

Originality/value

This paper demonstrates that the square-lobed trailing edges are effective in reducing the mean reattachment length and pressure fluctuations in transonic conditions. The study evaluates the efficacy of different configurations, deflection angles and lobe widths on flow and provides insights into the flow physics of passive flow control systems.

中文翻译：

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向后台阶跨音速流被动控制新探索

目的

本文旨在研究使用方瓣后缘的后向台阶（BFS）跨音速流的被动控制技术。该研究研究了向上和向下的波瓣模式、不同的波瓣宽度和偏转角度对流动分离的影响，旨在更深入地了解被动流动控制系统背后的流动物理原理。

设计/方法论/途径

大涡模拟和雷诺平均纳维-斯托克斯用于评估研究结果。该研究通过不同的波瓣宽度和偏转角度的影响，探讨了波瓣向上和向下的模式对流动分离的影响。数值方法用于分析 BFS 上的跨音速流动行为，并将其与现有的实验结果进行比较。

发现

方瓣后缘显着地将平均重新附着长度缩短了 80%。当 Ma = 0.8 时，向上向下配置在减少尾流区域 5 步高度附近的压力波动均方根方面表现出更高的效率，减少了 50%，而平底配置证明可以更有效地降低近尾流区域1级高度附近的压力波动均方根，实现降低71%。此外，研究表明，向上向下配置会触发早期的翼展速度波动，而独立的平坦向下配置在尾流区域内显示出不太强烈的横向速度波动。

实际影响

研究结果证明了方瓣后缘作为被动控制技术的有效性，对提高航空航天和工业系统设计的效率、性能和安全性具有重要意义。

原创性/价值

本文证明，方瓣后缘可有效减少跨音速条件下的平均重新附着长度和压力波动。该研究评估了不同配置、偏转角度和波瓣宽度对流量的影响，并提供了对被动流量控制系统的流动物理学的见解。