Análise numérica do efeito da oscilação e correnteza sobre coeficientes hidrodinâmicos de geometrias simples.

Abstract

In a launching/lifting operation of subsea equipment in the offshore industry, several factors are important for a safe and economical installation within an operating window. One of these factors is the hydrodynamic coefficients of the equipment to be installed. The coefficients can be obtained, experimentally or numerically, by applying an oscillatory motion that represents the effects of sea condition and vessel motion, but these applications simplify conditions during a real operation and disregard important effects such as ocean current. This work investigates numerically the effect of current together with forced oscillation on the hydrodynamic coefficients of disks. Analyzing two influence parameters, the Keulegan-Carpenter number (KC) and the reduced current velocity (V r ). A numerical model validation process was carried out in stages to overcome the lack of references on the subject. The model was compared with Direct Numerical Simulation (DNS) results for low Reynolds number (Re), in a qualitative and quantitative analysis, and then applied to broader conditions found in real operations, with KC up to 3, V r up to 0.3 , and for high Re, up to 240 thousand. The hydrodynamic coefficients of drag (C d ) and additional mass (C a ) had significant changes when added the current in the simulations. In summary, C d increases and C a decreases as V r increases. Considering real operating conditions, the same results are found, with variations of C d up to 300% and of C a up to 36% for low KC. The effects of the current are also perceived in the vortices. KC and V r directly influenced the generation of vortices and even shape changes occur by altering these parameters. Finally, the installation operation window in the water inlet region was compared using standard coefficients of the norm and the coefficients found in this work.