RESEARCH ARTICLE Experimental study on hydrodynamic performance of a wave energy converter within multi-heaving-buoys Zhen Liu 1,3, * ,† , Na Qu 2 and Hongda Shi 1,3 1 Shandong Provincial Key Laboratory of Ocean Engineering, Ocean University of China, Qingdao, 266100, China 2 Department of Ocean Engineering, College of Engineering, Ocean University of China, Qingdao, 266100, China 3 Qingdao Municipal Key Laboratory of Ocean Renewable Energy, Ocean University of China, Qingdao, 266100, China SUMMARY A compact buoy-array-type wave energy converter called multi-heaving-buoys (MHB) is introduced in this study. The hydrodynamic performance of MHB under regular wave conditions was first investigated experimentally in a wave tank located in Ocean University of China. It was found that a limited number of heaving buoys had little effect on the wave fields around the device. The small period of the incident waves caused an intense interaction between the waves and the buoys. The phase difference between the buoys in different rows was determined by the distance between the buoys. It was found that the response amplitude operator of the buoys varied from 0.6 to 1.2. Correspondingly, the range of the averaged relative velocity of the heaving buoys was 0.6–1.3. The upper limit of the acceleration of the buoys’ motion was 0.2 times that of gravity. All of the experimental results provide valuable information for the future design of the hydraulic pressure power take-off systems. Copyright © 2017 John Wiley & Sons, Ltd. KEY WORDS wave energy conversion; multi-heaving-buoys; experimental study; wave field distribution; heaving performance Correspondence *Zhen Liu, Qingdao Municipal Key Laboratory of Ocean Renewable Energy, Ocean University of China, 266100 Qingdao, China. † E-mail: liuzhen@ouc.edu.cn Received 30 August 2016; Revised 29 December 2016; Accepted 7 January 2017 1. INTRODUCTION Marine energy is one of the renewable energy resources being rapidly developed in China. Since 2010, 200 million RMB per year has been allocated from the center budget to financially support the research and development activities for ocean energy through the State Oceanic Administra- tion. The key challenge for the utilization of ocean renew- able energy in China is the low energy density compared with the high demand for electricity from millions of residents living on offshore islands. Reliable devices with a high efficiency and stable output performance will be competitive in the electricity supply for offshore islands. The two-body-heaving (TBH)-type wave energy con- verter (WEC) is classified as a third-generation device, which is directly driven by ocean waves, and is expected to absorb more wave energy and have a better conversion efficiency. Because of its advantages, increasing efforts have recently been made to apply of the TBH-WEC to the exploration and capturing of ocean wave energy. The hydrodynamic characteristics of heaving buoys are one of the most important factors to consider in the design of a WEC, because they significantly affect the incident wave energy extraction and conversion [1]. The frequency domain model (FDM) is compatible with tuning the device to the frequencies representative of the typical wave spec- trum of the intended deployment site [2]. The computa- tional fluid dynamic software WAMIT, which uses the FDM, has also been used to simulate and optimize the heav- ing motion of a WEC [3,4]. Because the FDM is based on the linear wave theory, it is always used in the initial design stage. In addition, a time domain model, couples irregular waves, restrictions, and reactive controls could provide more information about the operating performance of a heaving type WEC [5,6]. In the previously mentioned stud- ies, the buoy was always simplified as an axisymmetric body (a cylinder or hemisphere). In order to deal with the viscous effects and nonlinear responses of heaving buoys more precisely, numerical models based on the Naiver- Stokes equations were proposed to analyze the heave of the floating bodies under the wave excitation [7–9]. It was also pointed out that the viscous model is more suitable for intense interactions between the waves and heaving bodies, especially for survivable conditions [10]. Because the size of the WEC cannot be expanded with- out limit, arrays of devices could be used as a wave farm to INTERNATIONAL JOURNAL OF ENERGY RESEARCH Int. J. Energy Res. (2017) Published online in Wiley Online Library (wileyonlinelibrary.com). DOI: 10.1002/er.3725 Copyright © 2017 John Wiley & Sons, Ltd.