Visualization of Unsteady Flow on a Micro-Structured Cylindrical Surface Using Temperature-Sensitive Paint

Subaru has been developing fine texture, called HEXA, for streamlining the flow around the vehicle. Under given conditions, HEXA has shown drag reduction, however, it is still challenging to determine the optimal placement and structure of the HEXA for various flow conditions. In this research, three institutions – SUBARU, University of Notre Dame (UND), and Gunma University (GU) – have formed an international collaboration to elucidate the flow physics of the HEXA-induced flow. As a first step, the UND’s Temperature-Sensitive Paint (TSP) technique has implemented in the GU wind tunnel as a circular cylinder as a base model. The TSP measurement is utilized to understand the surface flow features with and without the HEXA in spatiotemporal manner. We have successfully measured the spatiotemporal changes in the temperature using TSP measurements that indicates the change in the surface flow. An obvious difference in the distribution of the HEXA cylinder to the smooth cylinder is confirmed, and that is thought to be transition to turbulence due to the HEXA.