SCALE EFFECT ON THE LINEAR HYDRODYNAMIC COEFFICIENTS OF DARPA SUBOFF

Abstract

As well known, forces and moments acting on a ship are functions of Froude and Reynolds numbers. As a ship gets larger in size, these two numbers grow, which leads to different flow regimes around the hull. However, the state-of-the-art in maneuvering calculations is to consider the hydrodynamic coefficients as constants for model and full ship scales. For submerged bodies, the Froude number is insignificant due to the distant free water surface; therefore, these forces only depend on the Reynolds number. In this study, we consider the benchmark ‘DARPA’ Suboff form, which is extensively studied in the literature, and investigated the scale effects on the hydrodynamic coefficients with respect to the Reynolds number. Numerical studies are carried out on the bare hull form of the submarine. Captive motions of static drift and pure yaw motions are conducted utilizing the oblique towing and rotating arm tests via RANS-based CFD. Linear hydrodynamic coefficients are expressed with logarithmic equations as functions of the Reynolds number, explicitly showing the dependency on the ship’s model scale.

Keywords

• CFD
• DARPA
• maneuvering derivatives
• pure yaw
• static drift

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