An experimental study on the effect of splitter plate angle on the VIV behavior of submarine pipeline on an erodible bed under clear water condition

摘要

Pipeline is an appropriate method for transmission of oil and gas from seabed hydrocarbon reservoir to the land and platform or any other place where it is needed. Free spans in the line may occur initially by an uneven seabed or be created later due to under-scouring. Vortex Induced Vibration (VIV) may occur in these free spans at high Reynolds' numbers. Resonance can occur if the frequency of vortex shedding is close to the pipeline's natural frequency. Otherwise, it can cause pipeline's fatigue leading to its breakage and consequently economical and environmental losses. In literature, different methods are presented for decreasing the scouring depth due to the vortex shedding. One of them is the application of splitter plate. In this paper, the effect of splitter plate's angle with horizon (α) on the vibrating behavior of pipeline with two degrees of freedom over an erodible bed is studied experimentally. The experiments were performed for reduced velocity in the range of 2.45-5.06 and gap ratio of zero. Image processing technique as a non-contact method is used for measuring the vibrations of cylinder. Experimental results indicate that the splitter plate's angle is an important factor on the cylinder's vibration amplitude. According to these results, for the angle in the range of 0 ≤ α ≤ 30, the vibration amplitude is decreased while its frequency is increased, but the results are vice versa for the range of 60 ≤ α ≤ 90.