Statistical analysis of the hydrodynamic forces acting on pipe bends in gas-liquid slug flow and their relation to fatigue

In this paper, the resultant hydrodynamic force (FR, where FR=Fx2+Fy2) acting on pipe bends will be discussed. A hypothesis that the peak (resultant) forces, FR,peak acting on pipe bends can be described by the normal distribution function will be tested, with the purpose of predicting the mean of the FR,peak (FR,mean) and the standard deviations of the FR,peak (FR, standard deviation) generated. This in turn allows prediction of the probability of the largest forces that occasionally occur at various flow rates. This information is vital in designing an appropriate support for the piping system, to cater the maximum force over a long period of operation. Besides, this information is also important in selecting a pipe material or material for connections suitable to withstand fatigue failure, by reference to the S-N curves of materials. In many cases, large numbers of response cycles may accumulate over the life of the structure. By knowing the force distribution, 'cumulative damage' can also be determined; 'cumulative damage' is another phenomenon that can cause fatigue, apart from the reversal maximum force.