عنوان مقاله [English]
In this study, Investigation into temporal hydrodynamic forces on offshore Piggyback pipelines due to steady currents. All simulations are performed in 3D using ANSYS FLUENT16.0 and FLOW-3D v11.1 softwares environments. First, the capabilities of the above two softwares for the mentioned problem were investigated and after selecting the software with higher accuracy (ANSYS FLUENT), it was used for this research study. Also, after initial investigations, the model of large eddy simulation (LES) and regular cell formation were selected. By changing the fluid flow velocity and the diameter of the main cylinder, the effect of the Reynolds number variations on the coefficients of instantaneous hydrodynamic forces exerted on the piggyback pipelines was investigated. The effect of the relative distance of the main cylinder to the bed (e/D), the relative distance of the two cylinders from of other (G/D), and the relative diameter (d/D) were investigated.
Some important results are as follows:
As the fluid flow velocity increases, the number and amplitude of oscillations of the hydrodynamic force coefficients increase. Also, with the addition of sub pipelines, we see a decrease of about 65% has been found for the time averaged of the main cylinder.
By reducing the relative distance between the main cylinder and the bed (e/D), the number and range of oscillations of the hydrodynamic forces coefficients of the sub-cylinder have been reduced. Using the sub-pipeline,