用液晶膜技术显示边界层转捩

VISUALIZATION OF BOUNDARY LAYER TRANSITION USED LIQUID-CRYSTAL-FOIL TECHNIQUE

液晶膜是一种新型液晶制成品,系三层结构。对温度敏感的液晶沉积在外层塑料膜和内层黑衬底之间。液晶膜的底面带胶,可直接贴在试验模型表面上。本文简要介绍了低速风洞中的液晶膜技术、液晶膜的构造和显示边界层转捩的原理,并将它应用于声激发控制边界层转捩研究。实验结果表明,液晶膜技术是一种简易可行的显示边界层转捩的新方法。它可以显示转捩过程的起始与结束以及转捩位置随试验条件的变化。与常规液晶技术相比,其优点是使用方便,无需熟练的液晶配制技能和喷涂经验,免受外界污染。液晶膜技术特别适合应用于二元模型。

The liquid-crystal foil is a new commercially availableliquid-crystal product.It consists of a three-layer arrangement.Theouter layer is a plastic foil.The inner layer is a black paint.Thermallysensitive liquid crystals are deposited between these two layers.Thisglue-on foil can be stuck directly on the model surface.A preliminaryinvestigation of flow visualization was conducted in the low speed windtunnel by means of the liquid-crystal-foil technique to study boundarylayer transition controlled by acoustic excitation.This paper describesbriefly the construction of liquid-crystal foil and the visualizationprinciple.The experimental results show that the liquid-crystal-foiltechnique as it was applied to visualize the.boundary layer transitionis a new,simple and reliable technique.It can be used to detect theonset and completion of transition as well as the shift of the transitionlocation due to the various test conditions.Its main advantages-comparedto the conventional liquid-crystal technique-are convenient for theapplication without requiring a sophisticated skill in the consistenceand spray of the liquid crystal.The crystals are protected againstcontamination.The application of this glue-on foil is obviously advan-tageous for two-dimensional models.