Experiment
Towing-tank experiments are performed for a surface combatant as it undergoes static and dynamic planar motion mechanism maneuvers in calm water. The data includes global forces/moment/motions and phase-averaged local flow-fields, and uncertainty assessment. The geometry is DTMB model 5512, a 1:46.6 scale, 3.048 m long, fiber reinforced Plexiglas hull. Model 5512 is a geosim of DTMB model 5415, a 1:24.8 scale 5.72 m model. The model is unappended except for bilge keels, i.e., not equipped with shafts, struts, propellers, or rudders. The experiments are performed in a 3.048 × 3.048 × 100 m towing tank. The measurement system features a custom designed planar motion mechanism, a towed stereoscopic particle image velocimetry system, a Krypton contactless motion tracker, and a 6-component loadcell. The forces/moment and UA are conducted in collaboration with two international facilities (FORCE and INSEAN), including test matrix and overlapping tests using the same model geometry but with different scales. Quality of the data is assessed by monitoring the statistical convergence, including tests for randomness, stationarity, and normality. Uncertainty is assessed following the ASME Standards (1998 and 2005). Hydrodynamic derivatives are determined from the forces/moment data by using the Abkowitz (1966) mathematical model, with two different ‘Multiple-Run (MR)’ and ‘Single-Run (SR)’ methods. The results for reconstructions of the forces/moment indicate that usually the MR method is more accurate than the SR. Comparisons are made of the hydrodynamic derivatives across different facilities. The scale effect is small for sway derivatives, whereas considerable for yaw derivatives. Heave, pitch, and roll motions exhibit cross-coupling between the motions and forces and moment data, as expect based on ship motions theory. Hydrodynamic derivatives are compared between different mount conditions. Linear derivative values are less sensitive to the mounting conditions, whereas the non-linear derivatives are considerably different. Phase-averaged flowfield results indicate maneuvering-induced vortices and their interactions with the turbulent boundary layer. The tests are sufficiently documented and detailed so as to be useful as benchmark EFD data for CFD validation.
Data, Equipment, and Conditions
| Data | Equipment | Fr | Maneuver |
| Ship motions/forces and moments | Krypton motion tracker/loadcell, respectively | 0.138, 0.28, 0.41 | Static drift:Pure Sway:Pure Yaw:Yaw and drift: |
| Phase-averaged velocity field | 3D PIV | 0.28 | Pure yaw |
Sample Image
This photo shows model 5512 mounted to the PMM carriage with the towed, 3DPIV system in the foreground supported by the PMM carriage strongback. The underwater camera enclosures and lasersheet generator (all submerged) are visible in the image.
Sample Data
The figure below shows the pure yaw, phase-averaged axial velocity field at six stations for Fr=0.28. PMM conditions are ymax=10.2 deg, rmax=0.30, ymax/L=0.107.
References:
Yoon, H.S., (2009), “Phase-Averaged Stereo-PIV Flow Field and Force/Moment/Motion Measurements for Surface Combatant in PMM Maneuvers,” Department of Mechanical Engineering, The University of Iowa. (pdf)
Longo, J., Yoon, H-S, Toda, Y., and Stern, F., “Phase-Averaged 3DPIV/Wave Elevations and Force/Moment Measurements for Surface Compatant in PMM Maneuvers,” Proc. 26th ONR Symposium on Naval Hydrodynamics, Rome, Italy, 2006. (pdf)
Yoon, H.; Simonsen, C. D.; Benedetti, L.; Longo, J.; Toda, Y.; and Stern, F., “Benchmark CFD validation data for surface combatant 5415 in PMM maneuvers – Part I: Force/moment/motion measurements,” Ocean Engineering, 109, pp.Pages 705-734, November 2015.
Yoon, H.; Longo, J.; Toda, Y.; and Stern, F., “Benchmark CFD validation data for surface combatant 5415 in PMM maneuvers – Part II: Phase-averaged stereoscopic PIV flow field measurements,” Ocean Engineering, 109, pp. 735-750, November 2015.