基于离散型粗糙元的三维边界层横流失稳及其转捩特性研究

Discrete roughness,with a wide application prospect, will become a new type of boundary layer transition control technology.But because the complete theory system has not been set up,the engineering application and further development of this technology are restricted seriously. By means of the wind tunnel experiment,using the swept wing model with the typical characteristics of three-dimensional boundary layer flow,the boundary layer flow state disturbed by discrete roughness will be measured accurately through the sublimation and infrared thermography methods. The roughness scale boundary which affects the T-S wave and the cross flow transition will be determined.Also,this research project intends to investigate the disturbance characteristics of the span wise scale of roughness elements on transverse wave space mode.The response law of cross boundary layer to the roughness element configuration parameters and cross flow wave will be studied. As a result,the dominant factors of cross flow instability induced by the discrete roughness will be explored.In addition,the influencing characteristics of roughness element height on the receptivity of cross flow boundary layer will be probed.Finally,the coupled interaction law of flow conditions,roughness element shape parameters and roughness element location on the boundary layer transition will be studied systematically.This research project aims to find out the boundary layer instability mechanism and transition characteristics induced by the three-dimensional discrete roughness.The research results can provide an important evidence required for establishing the new boundary layer fixed transition and laminar flow control technology system based on the discrete roughness.

离散型粗糙元是一种具有广阔应用前景的新型边界层转捩控制技术，但目前尚未形成完善的理论体系，这严重制约了该项技术的工程应用和纵深发展。本项目拟采用风洞实验的方法，选用具有典型三维边界层流动特征的后掠翼模型，通过升华法和红外热像法精细测量离散型粗糙元扰动下的边界层流动状态，确定影响T-S波和横流转捩的粗糙元尺度边界，考察粗糙元横向尺度对横流波空间模态的扰动特性，研究横流边界层对粗糙元外形参数与横流波的响应规律，探寻粗糙元促发横流失稳的主导因素，摸索粗糙元高度对横流边界层感受性的影响特性，系统研究来流条件、粗糙元外形参数、粗糙元布置位置等因素对边界层转捩特性的耦合作用规律。本项目的研究旨在摸清基于离散型粗糙元的三维边界层横流失稳和转捩特性，为构建基于离散型粗糙元的新型边界层固定转捩技术和层流控制技术体系提供必要依据。

边界层固定转捩是风洞实验模拟真实飞行状态的必备技术之一。本项目重点研究了用于高速风洞实验的新型离散型粗糙带固定转捩技术及其作用机理。理论计算并确定了斑点型粗糙元的外形参数，研制成功了固化快、便于成型、易于研磨以及不易变形的粗糙元配方，建立了一套离散型粗糙带的高精度制作工艺。选用二维翼型和三维组合体模型，采用数值计算与风洞实验相结合的方法，通过升华法和红外热像法精细测量离散型粗糙元扰动下的边界层流动状态，研究了斑点型粗糙元的直径d、高度h 和间距l等参数对转捩特性的影响规律，确定了影响T-S波和横流转捩的粗糙元尺度边界，研究了粗糙元横向尺度对横流波空间模态的扰动特性，验证了该新型离散型粗糙带模拟边界层转捩的精准性和附加阻力特性。研究结果表明，该新型离散型粗糙带附加阻力小，转捩位置准确，性能可靠、稳定。本文所得结果为固定转捩风洞实验创建了一种新的技术手段，同时也为进一步开展离散型粗糙元的转捩机理研究提供了重要参考依据。