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Surface-Piercing Truncated Cylinder

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.

Data, Equipment, and Conditions 

Data Equipment Fr Re (´105)
Free surface Servo gauges and capacitance wires 0.5, 1.1 1.4, 3.2
Surface pressure Differential pressure transducers 0.5, 1.1 1.5, 3.3
Flow field Stereo PIV 0.5, 1.1 1.5, 2.7

Sample Images

The following images show the underwater view of the SPIV setup (left) and the wall-mounted longitudinal wave-cut measurement setup (right).

The underwater view of the SPIV setup (left) and the wall-mounted longitudinal wave-cut measurement setup (right). The following images show the photos of the free surface waves around the cylinder model (left column) and the comparisons with the LES simulations (right) column) for the critical Re condition.

Towing tank experiments close up. Sample Data

The following images show the contours of the mean (top) and RMS fluctuation (bottom) of the free surface elevation for the sub-critical (left) and critical (right) Re conditions and their comparisons between the experiment (EFD) and the LES simulations.These images show the contours of the mean (top) and RMS fluctuation (bottom) of the free surface elevation for the sub-critical (left) and critical (right) Re conditions and their comparisons between the experiment (EFD) and the LES simulations.These images show the contours of the mean (top) and RMS fluctuation (bottom) of the free surface elevation for the sub-critical (left) and critical (right) Re conditions and their comparisons between the experiment (EFD) and the LES simulations.The following images show the streamwise profiles of the free surface mean elevation zAVG and RMS fluctuation sz along the cuts Y = 0 (top) and Y = 0.8 D (bottom) for the sub-critical (left) and critical (right) Re conditions and the comparisons between the experiment (EFD) and the LES simulations.These images show the streamwise profiles of the free surface mean elevation AVG and RMS fluctuation s along the cuts Y = 0 (top) and Y = 0.8 D (bottom) for the sub-critical (left) and critical (right) Re conditions and the comparisons between the experiment (EFD) and the LES simulations.The following images show the mean streamwise velocity U contours and the cross plane VW streamlines (top) and the turbulent kinetic energy k contours (bottom) at z = -0.75 D and the comparisons between the experiment (EFD) and the LES.

These images show the mean streamwise velocity U contours and the cross plane VW streamlines (top) and the turbulent kinetic energy k contours (bottom) at z = -0.75 D and the comparisons between the experiment (EFD) and the LES.Get Data: Truncated Cylinder

References

F. Stern, 2016, “Integrated High-Fidelity Validation Experiments and LES for a Surface-Piercing Truncated Cylinder for Sub and Critical Reynolds and Froude Numbers,” NATO Specialist Meeting

 

Last modified on December 4th, 2017
Posted on November 15th, 2017