What is the effect of surface tension in gas-water mixture in inclined pipe in Ansys?
 

Dear All,

Currently I am evaluating the effect of surface tension in gas-water mixture in inclined pipe in 2D model. (*the gas I am using is methane)

The project consists of two, which are in case at 72 mN/m and 0.01 mN/m, while each case is divided into three inclination, which are 0° (horizontal), 45°, and 90° (vertical). There are three phases included, which are water, gas (methane), and air. (So total models are 12).

Case of 72 mN/m means I put the surface tension of water-gas and water-air both in 72 mN/m, and case of 0.01 mN/m means I put the surface tension of water-gas and water-air both in 0.01 mN/m. (Without considering adhesion walls)

Moreover, as a geometry description, the model consists of two inlets that are located underneath (right for gas inlet and left for water inlet), and two outlets at the top. The flow moves upward from the inlets toward the outlets.

My question is; in case at 72 mN/m, when the inclination increases from horizontal (0°) to 45°, the gas fraction decreases at its minimum. Then, when the inclination increases further from 45° to 90°, the gas fraction increases yet it is not as high as when it is horizontal. This is surely correct as based on Beggs and Brill's correlation as a liquid holdup tends to increase, allowing the gas fraction to decrease if the inclination is increased until it reaches the maximum point (approximately 50°). After that point, it behaves oppositely.

However, in case at 0.01 mN/m, the gas fraction decreases linearly when the inclination increases. (0° to 45°, it decreases, then 45° to 90°, it decreases more)

Does anyone know why does this happen? Please someone kindly explain as this is very important to my dissertation. I attached some supportive figures in this forum.

Sincerely

Stefano