This paper reports an experimental and numerical investigation of stratified gas-liquid two-phase flow in downwardinclined circular pipes. Reynolds averaged Navier-Stokes equations with the κ-ω turbulence model were solved by using the least-square finite-element method to simulate the stratified gas-liquid flow. Experiments were carried out in an air-water two-phase flow loop with a test section of 7.8-m-long circular pipe with 1 inch inner diameter for 3 downward-inclined angles, −2.5 • , −5.0 • , and −10.0 • . The height of the liquid layer was measured by using a pulse-echo ultrasonic technique with a single fast transducer and a visualization technique with a high-speed digital camera. Numerical results for the liquid height and hold-up as a function of inclination angles were compared favorably with experimental results of the present study and literature data.
This paper reports an experimental study of the measurement of elongated bubbles velocities and their longitudinal shapes using a high speed ultrasonic system in concurrent horizontal and at 5° and 10° inclined upward flow. The circular pipe test section is made of 25.6 mm stainless steel, followed by a transparent acrylic pipe with the same diameter. The high speed ultrasonic system consists of two transducers (10 MHz/6.35 mm diameter), a generator/multiplexer board that convert analog signals into digital data at a rate of 100 million frames per second, and a software that stores all the frames and the results of the time of flight of each signal. The results are compared with a visualization technique that consists of a high-speed digital camera recording images at rates of 125 and 250 frames per second. This range of liquid superficial velocity is from 0.2 to 1.1 m/s and that of the gas superficial velocity is from 0.35 to 1.0 m/s. The results obtained with the two experimental techniques show a good agreement among them for the elongated bubbles lengths and velocities, while having great statistics dispersion. The measured bubble shape is in agreement with literature data.
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