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.
Highlights
Bulk carriers, oil tankers, and container ships are three main types of ships and they occupy a very important position in the international shipping industry
By having detailed measurements combined with an accurate knowledge and an insight into the flow characteristics of ships, this forms the basis for the theory and numerical simulations verification of the hull optimization and the propeller design
Our previous paper [2] described in detail the measurement of the wake fields based on the particle image velocimetry (PIV) under the design-loading condition, and most of the literature focuses on the flow characteristics around the hulls under the design conditions [5,6,7,8,9,10,11,12,13]
Summary
Oil tankers, and container ships are three main types of ships and they occupy a very important position in the international shipping industry. The experimental and numerical results show that the draft and inclination angle of the ships are different under the different loading conditions, which leads to a different inflow velocity and flow direction in the stern region, and different wake field distribution characteristics. The vorticity information was analyzed based on the parameters of vorticity, lambda 2-criterion, planar 2nd invariant Q, the swirling strength, and the evolution of the bilge vortex (Bv) and the propeller hub cap vortex (Hcv) These characteristics are compared to our previous study of the wake field under the design condition, which reveals the loading condition influence on the flow field distribution.
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