Turbulence phenomena due to pure wave over the submerged horizontal cylinder

Abstract

Detailed investigation of turbulence flow characteristics due to mechanically generated regular water waves over a submerged cylinder is carried out. Regular waves are generated by a wave maker driven at three different frequencies. Prolonged measurements of the temporal variation in the instantaneous velocity in all three directions were carried out at multiple locations downstream of the cylinder. Particular attention is given to the change in flow characteristics downstream of the cylinder as a result of interaction of the surface wave and bottom mounted cylinder (radius, R = 2.5, 3.75, and 5.5 cm). The resulting flow field is studied in detail using quadrant and velocity spectra analysis. The results show that contributions to the total shear stress from ejection and sweep are prominent for the entire region. Furthermore, the probability density function is determined to describe the instantaneous turbulent velocity signal, which demonstrates a bimodal nature for bottom-normal velocity fluctuations and a sharp distribution for stream-wise velocity fluctuations. Power spectral density shows that the power spectral peak of surface wave is effectively reduced for both stream-wise and vertical velocities. In coastal zones, pipelines of cylindrical cross section are the most dependable and secure, economical, and efficient means of continually transporting natural gas and oil and this study will help in the improved design and implementation of such submarine pipelines.