Visualization of Complex Flow Structures by Matched Refractive-Index PIV Method

With the development of computers and their surrounding equipments, the simulation of complicated flow structures around aircrafts will further become easier and cheaper by applying computational fluid dynamics. However, in order to judge whether the flow field obtained is reasonable or not, turbulent models and/or numerical schemes should be selected based on the comparison with experimental results. On the other hand, three-dimensional measurement of unsteady flow structures especially around obstacles with complicated geometry is still difficult due to some problems. For instance, where a three-dimensional flow structures around obstacles is visualized by a PIV technique, it is extremely difficult to grasp the whole flow-structure including the flow behind the obstacles even if transparent materials are used, because the difference of the refractive index between the working fluid and the transparent material causes distortion in the image. Therefore, in this chapter, I introduce a special visualization technique to match the refractive index of the working fluid with that of the transparent material that is called "matched refractive-index PIV measurement" and show some complicated flow fields visualized by this technique.