Phase-averaged Tomographic PIV Measurements for a Surface Combatant in Pure Sway Maneuver

Abstract

Forces and moment and phase-averaged Tomographic PIV (TPIV) local flow measurements are performed in a 3 m × 3 m × 100 m towing tank for a 3.048-m long geometrically similar model of surface combatant 5415 in pure sway maneuver. Test conditions are for maximum drift angle 𝛽max = 10° and Froude number Fr = 0.28. The TPIV enables fully volumetric flow measurements and the use of 𝑄-criteria enables vortex volume visualization and core analysis. The objective of the experiment is to extend the knowledge for the static condition vortex separation onset and progression to unsteady dynamic conditions, including integrated CFD. Test conditions meet the IITC criteria for sway frequency and restricted water restrictions. Both the present and previous uncertainty assessment (UA) for forces and moment show acceptable values. The uncertainty estimates for TPIV is done by using a practical approach and the results are comparable with the earlier UA using a conventional approach. Integrated CFD simulations are used to identify flow vortices. The comparison with the previous TPIV results for static maneuver conditions show improvements for the present TPIV using a more advanced algorithm. The pure sway measurements at phases corresponding to straight-ahead and 𝛽max = 10° show similarities and differences with the static maneuver measurements, whereas at intermediate phases substantial vortex interactions and unsteady separation onset and progression is shown. The vortex core analysis shows similarities and differences in the core strength and trajectory with the static drift and dynamic pure yaw maneuvers. The present experiment is ongoing and the initial measurement results and analysis are discussed herein.