Numerical Analyses of High Reynolds Number Flow of High Pressure Fuel Gas Through Rough Pipes

In this paper, a CFD commercial code is used to evaluate the pressure drop through a pipe in a stream of high pressure gas. Preliminarily, a grid sensitivity analysis is carried out by comparing CFD results with analytical results. Hybrid grids are generated starting by a tetrahedral mesh by adding prism layers on the surface of the pipe. Each grid is characterized by different number and thickness of the layers in order to investigate the behavior of the grid with respect to the boundary layer. Then, the model based on the best performer grid is validated by using a literature test case, in which a high pressure gas flow through rough pipe is experimentally studied. Various equation of state (i.e. constant properties, ideal gas and Redlich Kwong equation) and boundary conditions (e.g. pressure, mass flow, etc.) are taken into consideration. Finally, the model is used to extrapolate the behavior of different gas (i.e. natural gas, biogas and hydrogen-methane mixture) flowing at high pressure through pipe characterized by different roughness.