Numerical Simulation On Local Resistance Based On CFD

In the actual production of oilfields,pipelines are usually used to transport liquid, gas and liquid mixture. In order to ensure safe and economic transportation, whether gathering & transportation pipelines or long-distance pipelines all need to properly solve the problem between energy consumption and supply. The friction loss is one of the main factors for the energy consumption, and it includes frictional head loss and local head loss. Now, the research for frictional head loss has been very widely and systematically. However, for the local resistance loss, the limitation, discreteness and inaccuracy of experiment lead to the error between experiment data and engineering practice. Since the 20th century, with the rapid development of mathematics, computer and CFD, a lot of local resistance problems that originally unable to test and cannot be solved through theoretical analysis have possibilities to obtain numerical solution.In this paper, some typical valves producing local resistance are studied through numerical simulation method of FLUENT respectively, for example, sudden-expansion pipe, three-way pipe and curved pipe. Firstly, their flow fields are simulated in laminar and turbulent conditions respectively, and then local resistance characteristics of three typical valves are analyzed. In the sudden-expansion pipe, Reynolds number and sudden expansion ratio play very important roles. With the increase of Reynolds number, After the sudden-expansion interface, the velocity of flow particle that is near slowing laminar gradually declines to zero, and then, the mainstream separates from the wall producing recirculation region. And the length of recirculation region is direct proportion to Reynolds number and sudden expansion. In the three-way pipe, local resistance generally produces at the rendezvous position of the mainstream and branch and becomes more subdued along the axial direction. When the level feed is constant, the local head loss will increase with the increment of vertical pipe diameter. In the curved pipe, the maximum pressure appears near the symmetry face of 90°elbow, and the pressure shows an obvious band across the whole pipeline. At the same time, the secondary flow gets the pressure gradually increases from inside to outside of curved pipe. In addition, local friction coefficients of sudden-expansion pipe and curved pipe are calculated respectively, and are in comparison to empirical values. The results show that calculated values go up or go down to empirical values without much difference. So the calculated values can be used to modify empirical values of engineering practice at a certain extent.