从现代实验技术的发展和数据处理方法的应用到科学发现

From Modern Experimental Technology Development and Advanced Data Processing Methods to Scientific Discovery

本文介绍了近年来北京大学团队开发实验流体力学新技术和数据处理方法,以及如何利用国际上新的实验技术和数据处理方法来研究复杂流动现象。基于这些技术和方法发现新的科学现象和原理:利用改进的氢气泡技术发现了孤立波拟序结构(SCS)在转捩/湍流边界层中对湍流发生起决定性作用,利用拉格朗日追踪法对不同形式的转捩边界层和湍流边界层的实验和数值结果进行分析证实SCS是普适结构;近壁粒子图像测速(PIV)技术的发展解决了旋转叶片测量的世界难题。对龙洗现象、大迎角旋成体非对称效应等长期未解决重大科学问题给予合理而简捷的解释;结合近壁PIV测量和瑞利散射流动显示技术,在高超声速流动中揭示转捩的非线性作用机制,发现气动加热的新原理,并基于该原理建立了新的热防护准则;六自由度测量技术解析了圆盘下落的模态转换相关的动力学过程,发现zigzag-spiral-zigzag现象并发现此与不同分离形式相对应。

New experimental technologies and data processing methods developed by the Peking University team were introduced in recent years.These technologies and data processing methods were used to study complex flows,and new scientific phenomena and principles have been discovered.Using improved hydrogen bubble technology,it was discovered that the Soliton-like Coherent Structure(SCS)plays a decisive role in the transition/turbulence boundary layer.Lagrangian tracing method was used for different types of transitional boundary layers and turbulent boundary layers.The analysis of experimental and numerical results confirmed that SCS is a universal structure.The development of near-wall Particle Image Velocimetry(PIV)technology has solved the world problem of rotating blade measurement,and has given reasonable and simple explanations to long-term unresolved major scientific problems such as the phenomenon of dragon washbasin and the asymmetric effect of slender revolutionary body at a large angle of attack.Combining near-wall PIV measurement and Rayleigh scattering flow display technology,the nonlinear mechanism of transition was revealed in hypersonic flow,a new principle of aerodynamic heating was discovered,and a new thermal protection criterion was established based on this principle.The six-degree-of-freedom measurement technology was used to analyze the dynamic process related to the modal conversion of a falling disc.Zigzag-spiral-zigzag phenomenon was found to correspond to different forms of separation.