Flow Configure in Vertical 180 Degree Turning Duct

Abstract Bend is applied in many industries, which exert an influence on fluid and make the flow complicate. The second flow caused by the bend is strong enough that the flow behind it very long can be affected, so it is hard to make the flow in it steady. The long-term unsteady flow can make the pipe fatigue, so make the tube crack and leak. It is important to improve this situation. In this paper a throttle is built in the exit of the bend to control the non-homogeneous flow inside the bend, which can overcome the disadvantage of bend in industrial application. Through computed the flow field behind the bend by water, we can see that the throttle can improve the flow situation and make the flow steady behind it. Applying this method to the gas-liquid flow, the experimental result showed that the void fraction behind the bend is alike the fully developed flow. It means that the throttle can improve the two-phase flow situation in the invert U bend. At last the gas-liquid flow pattern in-bend was studied by experiment and built the flow pattern map in the vertical parts of the invert U bend. It was found that the flow pattern in the vertical part of invert U bend is different from the fully developed gas-liquid flow in vertical tube. The throttle built in the bend make the unsteady region of two-phase flow being reduced.