The figure shows experimental data for the roll decay wave field. The test conditions are Fr=0.138 and f0=-10 deg. The upper left frame is the steady wave field. The next seven frames from right to left and downward are sequences of the wave field in the first roll cycle.
Experiment
Towing-tank experiments are performed for an advancing surface combatant in free roll decay motions. Results are presented for motions (surge, sway, heave, roll, pitch and yaw), forces (resistance, sway and heave), moments (pitch and yaw), phase-averaged velocities (U, V and W) for a measurement region near the bilge keel and free surface elevations. The geometry of interest 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 3x3x100m towing tank equipped with a plunger-type wavemaker. The measurement systems include Krypton contactless motion tracker, 4-component load cell, towed 2-D particle image velocimetry (PIV) system, and servo wave probes with 2-D traverse. Uncertainty assessment following standard procedures is used to evaluate the quality of the data.
Data, Equipment, and Conditions
| Data | Equipment | Fr | f0 (º) |
| Ship motions | Krypton motion tracker | 0.069, 0.096, 0.138, 0.19, 0.28, 0.34, 0.41 | 0, -2.5, -3.0, -4.0, -5.0, -7.5, -10.0, -12.5, -15.0, -20.0 |
| Forces and moments | Loadcell | 0.069, 0.096, 0.138, 0.19, 0.28, 0.34, 0.41 | 0, -2.5, -3.0, -4.0, -5.0, -7.5, -10.0, -12.5, -15.0, -20.0 |
| Phase-averaged wave field | Servo wave gages (4) | 0.138 | -10.0 |
| Phase-averaged velocity field | 2DPIV | 0.138 | -10.0 |
Sample Image
The photo below shows model 5512 suspended in air from the IIHR towing tank carriage. The models mass properties are set with ballast weights to achieve the correct center of gravity and roll gyradius.
Download 5415 Geometry
Click on the image below to download an .igs file of the appended model 5415 (all dimensions are given in inches).
Sample Data
The figure below shows experimental data for the roll decay wave field. The test conditions are Fr=0.138 and f0=-10 deg. The upper left frame is the steady wave field. The next seven frames from right to left and downward are sequences of the wave field in the first roll cycle.
Reference: Irvine, M., Longo, J., Stern, F., “Towing Tank Tests for Surface Combatant for Free Roll Decay and Coupled Pitch and Heave Motions,” Proc. 25th ONR Symposium on Naval Hydrodynamics, St Johns, Canada, 2004.