Flow characterisation of diffusion flame in a standing wave

► Two-dimensional acoustic flow velocity maps and time resolved schlieren images are obtained. ► The velocity of cold fuel jet has a strong function of the acoustic phase angle. ► Flame is affected by the acoustic phase angle and the nozzle position in a tube. ► Flame dynamic is affected by both the ambient air and the acoustically induced fuel motion. ► The spatial variation and acoustic phase have to be considered in flame/acoustic wave coupling.