Experimental investigations on slug flow were carried out in horizontal helical rectangular channel by using high speed flow visualization. Evolution of slug in the whole helical rectangular channel was presented and the fine features of slug flow in different positions were illustrated. The slug characteristics changed along the axial direction due to the combined effects of gravitational and centrifugal force. Based on the experimental data

slug velocity

slug frequency and length distribution in different positions were given. The present topography measurement illustrated the evolution features of liquid film thickness

which was determined by the effect of centrifugal force and gravity. Liquid film falling velocity decreased as the slug moved upward and was visibly increasing in the downward flow.