Simultaneous PIV–LIF measurements using RuPhen and a color camera

Abstract

Particle image velocimetry (PIV) and laser-induced fluorescence (LIF) are currently state-of-the-art, non-intrusive measurement techniques that help in our understanding of heat and momentum transfer in thermal fluid flow applications. We present a simplified, integrated PIV–LIF system which simultaneously measures velocity and temperature fields in aqueous flows by means of a novel fluorescent dye (RuPhen), a low-cost continuous-wave diode laser, and a single color camera. We demonstrate that RuPhen is well-suited for this approach due to its peak absorption at 450 nm, peak emission at 605 nm, and a strong temperature-dependent emission with a sensitivity coefficient of $$4\%/^{\circ }\hbox {C}$$ 4 % / ∘ C . The large Stokes shift between excitation (which also includes Mie scattering of the flow tracers) and the emission facilitates the handling of the signal components in the RGB channels of the camera. To correct the recordings for laser power fluctuations, we propose a novel method that jointly employs two photoluminescence signals. We provide a spectral characterization of the dye at different temperatures and discuss the choice of each component for our measurement system. We demonstrate the potential of our approach by two experimental test cases that focus on thermally driven and turbulent flow regimes.