Experimental study of gas entrainment by liquid falling film around a stationary Taylor bubble in vertical downward flow

Air entrainment by a liquid falling film was experimentally studied by means of videometry, image processing methods, and also by a measuring technique based on wire-mesh sensor. Air was entrained by a plunging liquid film around a stagnant Taylor bubble. Downstream of the impact point, a wire-mesh sensor was used to measure the total gas void fraction, gas void fraction distribution, and bubble size distribution. Results indicate that the gas void fraction increases and the bubble size decreases as the superficial liquid velocity increases. Good agreement was found by comparing video images with the images obtained by the wire-mesh sensor.