CFD Simulation of Pressure Drop in Line Pipe

Real fluid has viscosity. When fluid flows along a solid surface, the relative velocity between fluid and solid is zero on the solid surface. Getting away from the surface, velocity increases and shearing stress comes into being and forms a kind of friction. Fluid in a pipe losses pressure head when the friction happens as well as the pipe section area changes its size or the flow changes its direction. What is more, inlet box and outlet box will affect the results greatly together with boundary conditions. Namely, pressure drop is divided into 3 parts. They are inlet drop, outlet drop and inner drop of the pipe. Although there are many empiric formulas to estimate the pipe head loss and they are very easy to use, their accuracy is not high enough and the information is not detailed. Additionally these empiric formulas are limited to use for practical pipe with complex shapes. On the other hand, with the development of hardware and software of computer, CFD (Computational Fluid Dynamics) becomes a popular tool for duct designer to simulate their drafts. When CFD is used to simulate the head loss of pipe with complex shape, the error always varies according the pipe shape and the results must be checked by experiments. Little is known about how the accuracy should be improved and how the computational conditions such as boundary conditions affect the accuracy of duct simulation. In this paper, with version 5 of SC/Tetra ^[1], a commercial CFD tool developed by our company CRADLE, the effects to duct simulation accuracy of computational conditions including mesh shape, solver parameters and boundary conditions are discussed.