Number Density Distribution of Bubbles Forming Near a Wall in a Beverage

Abstract

To clarify the spatial structure of number density distribution of bubbles in stout beer poured into a container, we investigated local time development of the void fraction and velocity of bubbles. The propagation velocity of the texture, i.e. the number density distribution, appearing near the inclined wall of the container is measured by the images analysis. We measured the local void fraction using brightness of images while the velocity of bubbles by means of Particle Tracking Velocimetry. As the result of measurements, we found the local void fraction and the bubbles advection velocity increase and decrease repeatedly with a time delay. We conclude the pattern of the number density distribution of bubbles is composed of fluid blobs which contain less bubbles; extruding and suction flows respectively toward and from the interior of the container form respectively in front and back of the blobs.