Experimental validation of the simulations of the flow around an impulsively started scaled clump weight using an overset dynamic mesh with OpenFOAM

The impulsive start of bluff bodies in viscous fluids might be crucial in engineering, such as sudden motions of floating offshore structures under extreme environmental conditions. This paper investigates the hydrodynamic forces and flow features caused by impulsive starts at Reynolds numbers near the transition regime, approached from three different perspectives – experimental, numerical and empirical predictions – illustrating their similarities and differences. Classical studies on circular cylinders with impulsive starts across Reynolds numbers are verified. The study’s implications extend to offshore mooring systems for floating wind turbines, where clump weights can experience similar impulsive motions. Here, a scaled clump weight undergoing constant acceleration with an impulsive start is numerically analyzed and validated against experiments. The overset mesh technique in OpenFOAM is explored to manage large body motions while maintaining high grid quality. The results validate the overset technique as a robust tool for simulating large amplitude motions capturing transient flow phenomena and hydrodynamic forces, advancing in the understanding of transition Reynolds number flows. This paper offers a comprehensive methodology for studying impulsive starts, validating numerical techniques with experiments. Additionally, a comparison with quasi-static empirical predictions is carried out, where the limitations of traditional models in predicting complex fluid–structure interactions are highlighted. • The effects of transient impulsive motions of a bluff body are determined with OpenFOAM simulations and experiments. • The use of the overset technique in impulsive motions is validated with experiments and verified with literature cases. • The influence in the results of the turbulence modeling of established literature cases is determined. • CFD and experimental results are compared with an empirical model for an application case: clump weights for the mooring lines of floating wind turbines.