Probing the velocity fields of gas and liquid phase simultaneously in a two-phase flow

The feasibility of simultaneous measurements of the instantaneous velocity fields of gaseous and liquid phase is demonstrated in a laminar, unsteady t wo-phase flow. Thus, the instantaneous relative velocity field can be measu red in such media. This is achieved by combining Particle Image Velocimetry (PIV) and a gas-phase velocimetry technique, which is based on laser-induc ed fluorescence (LIF) from a gaseous tracer. The wavelength shift of LIF is exploited to separate it from Mie scattering from the liquid phase. The ne w technique and the PIV measurement system work independently in this appro ach. Thus, the measurement accuracy and precision of the new technique can be validated by comparing it to the PIV results in regions of the flow fiel d where the relative velocity vanishes.