The Hydraulic Transient Simulation Analysis For Pipe Blockages

With China’s rapid economic development, pipeline transportation are playing an increasingly important role in the national economy, national defense industrial and people’s daily lives. Oil, natural gas, water pipelines have become the lifeblood of the country’s economic development. These pipelines are subject to blockage due to bending in the construction process and deformation due to mechanical pressure. The formation of gas hydrates in pipes in cold weather will lead blockage and cause economic losses for oil and gas pipelines. However, pipeline blockage detection is very complicated due to the diversity of media, pipelines environment and uncertainty of the blockage form. Therefore it is very important to find a simple and practical general reliable method for pipe blockage detection. A pipe blockage study is carried out to establish the mathematical model for pipeline blockage analysis under hydraulic transient, which will be a theoretical basis for future pipeline blockage detection. This study will be based on the finite volume method Godunov scheme introduced for water hammer equations and the transient model of pipe blockage is proposed and solved by using the Fortran programming language. The real-time pressure values are obtained with the transient flow simulation program. The current one-dimensional model results are validated with the results from ADINA numerical simulation, which is a two-dimensional model. The computational results are independent of the grid resolution, which is demonstrated by changing the size of the description grids. The numerical simulation results are also validated with the Wylie’s (1993) one-dimensional calculation of water hammer theory by examining several important points of the water hammer wave propagation process. Therefore it is validated that the current model can capture the complicated flow nature of the pipeline wave propagation and reflection. Unsteady friction of pipe flows are also included in the calculation process with the introduction of diffusion term into the governing equation of the one-dimensional water hammer, which represents the viscous effect due to the unsteady friction. Pressure traces for blockages with different lengths are calculated with and without diffusion terms. It is shown that shorter the pipe blockage length, more the viscous effect. The introduction of the diffusion term, which approximates the unsteady friction, is necessary in unsteady pipe flow. Pressure traces for blockages with different lengths are compared and the results show that the results for blockage length of1Om and5m are close to Wylie’s one-dimensional method of characteristics results. When the length of the blockage is small Wylie’s one-dimensional method of characteristics cannot capture the actual results. The study also shows that the thickness of wave front of the transient pressure wave is important to the peak of the pressure wave reflection. The results show that the shorter the length of blockage is, the smaller the amount of reflection.