Experimental study on the hydrodynamic characteristics of cylinder with rough surface
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ORIGINAL ARTICLE
Experimental study on the hydrodynamic characteristics of cylinder with rough surface Xiaojie Tian1,3 · Daoxi Li1 · Guijie Liu1,3 · Yingchun Xie1,3 · Wei Deng2 · Dashuai Xie1 Received: 7 April 2019 / Accepted: 3 October 2019 © The Japan Society of Naval Architects and Ocean Engineers (JASNAOE) 2019
Abstract The main purpose of this study is to establish a better understanding of the relationship between the hydrodynamic characteristic and cylinder with rough surface. Experiments were conducted to measure the force and the hydrodynamic efficient of a circular cylinder with different types of artificial rugged surface. The relative roughness coefficient ranged from k/D = 0.00005–0.02 (k is the roughness height, D is the outer diameter of cylinder) is used to evaluate the rough surface of experiment model. Wave and current experiments are conducted in the wave tank. Results show that relative roughness indeed plays an important role in affecting the hydrodynamic characteristic on the cylinder. For the drag coefficient (Cd) in current experiment, Cd enlarges a lot under the effect of rough surface compared with smooth cylinder and has a regular change with relative roughness. For the inertia coefficient (CM) in wave experiment, CM is greatly affected by the rough cylinders for small KC numbers. For the Cd in wave experiment, it is greatly affected by large rough cylinders. Keywords Hydrodynamic characteristic · Relative roughness · Rough cylinder · Drag coefficient · Inertia coefficient
1 Introduction Cylindrical structures are widely used in offshore and marine engineering, such as offshore platform, wind turbines, sea bridges, piers and jetties [1, 2]. In the offshore environment, these structures always suffer from waves and currents. It is necessary to accurately calculate the wave and current load on these structures. Research on the hydrodynamic forces of cylinders has been the subject of many investigations in the past several decades. In 1950, Morison et al. [3] put forward the Morison Equation, which can calculate the wave load for the small-scale cylinder structures. Currently, researchers mainly focus on the determination of hydrodynamic coefficient including the drag coefficient (Cd) and inertia * Guijie Liu [email protected]; [email protected] 1
Department of Mechanical and Electrical Engineering, Ocean University of China, Qingdao 266100, China
2
Institute of Oceanographic Instrumentation, Qilu University of Technology (Shandong Academy of Sciences), Qingdao 266061, China
3
Key Laboratory of Ocean Engineering of Shandong Province, Ocean University of China, Qingdao 266100, China
coefficient (CM), which is used in the Morison Equation. Usually, the smooth circular cylinders have been the subject of many investigations [4–6]. However, the rough cylinders are also common in the marine engineering, because of the rust, corrosion, or marine growth. Figure 1 is a jack-up platform leg attached by a large number of marine shells, resulting in uneven surface of the circu
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