Experiment

Integrated high-fidelity validation towing tank experiments and LES are presented for a surface-piercing truncated cylinder for sub- and critical Reynolds and Froude numbers, as a unit problem case study.  The physics of interest are the effects of air-water interface on turbulence anisotropy and vortex shedding, 3D separation, transition to turbulence and the drag crisis; the effects of the truncated bottom; and ultimately bubble/droplet size distributions.  The integrated experiments and LES was successful in using preliminary LES to guide the experiments especially for local flow surface pressure and flow field measurements.  Experimental pacesetting issues were the difficulty of the PIV experiments; nonetheless, the data already collected is useful and valuable as the benchmark for LES validation.  The largest hurdle in achieving the desired outcomes, however, was the LES since the current grid design and sizes required large computational resources.  The experiments provide sufficient validation data for sub- and critical Re for many physics of interest.  Experiments for spray droplet and air bubble size distribution measurements are still required.  The LES at the current grid resolutions is able to fully-resolve the sub-critical but not the critical Re flow.  Code development for overset grids, conservative convection schemes, and air/water interface LES models are also required.  Future experiments and LES should focus on these issues along with extensions for VIV using towing tank PMM for pure sway motion.