Stereo Particle Image Velocimetry Measurements of the Wake Fields Behind A Panamax Bulker Ship Model Under the Ballast Condition

Abstract

Particle image velocimetry is applied in this study to measure the wake flow field of a Panamax Bulker ship model under the ballast condition. This investigation revealed that the Froude number is 0.167. The time-averaged velocity, turbulent fluctuations, turbulent kinetic energy (TKE), Reynolds stresses, and vorticity information were measured to perform a comparison with the design condition. The time-averaged velocity contours indicated that the ballast and design conditions have distinct hook-like axial velocity contours; however, they appeared at different positions. The big difference under the ballast condition is that the top of the propeller disk area is near the free surface and a region with strong root mean square velocity fluctuation is formed near the free surface. The TKE, the Reynolds stresses, and the hub cap vortex (Hcv) are all affected by the turbulent velocity fluctuation region under the ballast condition. A strong bilge vortex (Bv) is produced when the water flows through the U-shaped stern for the design and ballast conditions.

Experimental Study on the Influence of Bulbous Bow Form on the Velocity Field around the Bow of a Trimaran Using Towed Underwater 2D-3C SPIV

“…The minimum spacing of the vector grid of one velocity vector in the time-averaged velocity map from 250 images per run was 2.45 × 2.45 mm 2 . In this study, the uncertainty and convergence analysis referred to by Falchi et al [9] and Bendat and Piersol [42,43] was basically the same as that in previous work [39][40][41], and the detailed uncertainty analysis method and convergence analysis process of the present SPIV are not described again. The distribution of the measurement errors was used to determine a 95% confidence interval that contained the true displacement.…”

“…The water was seeded with neutrally buoyant white polyamide tracer particles (PSP-50 Dantec Dynamics Inc., Skovlunde, Denmark) with an average diameter of 50 µm using a self-designed and manufactured particle-seeding device with customized rake-shaped pipes. The calibration and seeding processes have been described in detail in previous studies [12,[39][40][41].…”

“…The water was seeded with neutrally buoyant white polyamide tracer particles (PSP-50 Dantec Dynamics Inc., Skovlunde, Denmark) with an average diameter of 50 μm using a self-designed and manufactured particle-seeding device with customized rakeshaped pipes. The calibration and seeding processes have been described in detail in previous studies [12,[39][40][41]. The final sinkage and trim of the hull are related to the interaction between the bow and the water mass and the flow tendency of the water particles after flowing through the bow.…”

Numerical and Experimental Study of Flow Field between the Main Hull and Demi-Hull of a Trimaran

“…The size of the interrogation region is 2.45 × 2.45 mm. The 16 × 16-pixel interrogation window was employed to calculate the velocity vectors based on adaptive correlation method [30][31][32]. And the average number of particles in each interrogation region is about 22.…”