Abstract
Along a wavy interface of a horizontal stratified flow in a closed channel, the gas flow over waves creates lift force on the wave crest due to local static pressure drop. This pressure drop, termed the Bernoulli effect, will prompt the wave growth and the flow regime transition from the stratified-wavy to slug flow slugging. The gas phase pressure during slugging was measured in a large-height (0.7m) rectangular duct for an air-water co-current horizontal two-phase flow under atmospheric pressure. The static pressure drop over waves was evaluated from measurement of air static pressure profile along a wave at different fetches. The pressure drop measured concurrently with the liquid level was comparable to the water static head corresponding to the wave height at vicinity of the crest of the slugging wave. The pressure drop profile along the wave agreed well with the prediction from the Bernoulli equation at the upstream side of the wave crest. Then, a considerable pressure drop occurred across the crest due to loss of air kinetic energy. Meanwhile, significant liquid entrainment occurred in the vicinity of the wave crest and tended to prevent the wave growth into a slug.
