Application of pressure-sensitive paint to low-speed flow around a U-bend of strong curvature

Pressure measurements are traditionally made using pressure taps connected to a transducer. These measurements are labor-intensive, expensive and only yield discrete values. Pressure-sensitive paint is a method of optically measuring the pressure across an entire model. Originally designed for use in transonic flow, pressure-sensitive paints are absolute pressure sensors. Therefore, application of pressure-sensitive paint to low-speed flow represents a significant challenge to researchers. This study investigates the surface pressure distribution around a U-bend of sharp curvature with three different inlet velocities: 29.7, 21.5 and 12.0 ms−1. The absolute accuracy of the paint has been measured and compared with previously published literature and empirical relations. The paint was excited using two LED lamps, and full-field pressure maps have been gathered using a CCD camera. The absolute accuracy of the pressure measurements is ultimately limited by CCD shot noise, but is more commonly limited by the temperature-induced error and the microheterogeneity of the painted surface.

► Flow around a square section sharp U-bend has been investigated.
► Pressure-sensitive paint has been successfully applied to internal low-speed flow.
► Detailed descriptions of the experimental process is provided.
► Comparison with established results shows the applicability of the process.