A variety of concepts of deep draft semi-submersibles (DDS) have been developed in order to improve the vertical motions. However, the DDS may experience critical vortex-induced motions (VIMs) stemming from the fluctuating forces on the columns. Aiming to investigate the excitation loads and the fluid mechanism of VIM, this paper presents experimental and numerical studies of the three-dimensional (3-D) flow around four circular section cylinders in a square configuration at subcritical Reynolds numbers (Re). The experimental measurements were carried out by using the piezoelectric load cells in a wind tunnel, while the numerical simulations were conducted by employing the Large Eddy Simulation (LES) method. The effects of three spacing ratios (L/D) and four array attack angles (α) ranging from 0° to 45° in 15° increments were investigated. The results show that the vortex structures are the key to understand the behaviours of the forces and the Strouhal number (St). Consequently, the downstream cylinders are normally subjected to smaller mean drags but more serious fluctuating forces than the upstream cylinders, due to the influence of unsteady wake vortices. Furthermore, at the present range of L/D ratios, the effect of spacing ratio on the excitation forces is not significant.


    Access

    Access via TIB

    Check availability in my library

    Order at Subito €


    Export, share and cite



    Title :

    Experimental and numerical studies on the excitation loads and vortex structures of four circular section cylinders in a square configuration



    Published in:

    Publication date :

    2016




    Type of media :

    Article (Journal)


    Type of material :

    Print


    Language :

    English



    Classification :

    BKL:    50.92 / 50.92 Meerestechnik / 55.40 / 55.40 Schiffstechnik, Schiffbau




    A Numerical Study of Oscillatory Flow Around Circular and Square Cylinders

    Okajima, A. / Yasuda, T. | British Library Online Contents | 1997


    Numerical Investigation of High Reynolds Number Flows over Square and Circular Cylinders

    Shih-Chieh Lo / Klaus Hoffmann / Jean-Francois Dietiker | AIAA | 2005


    Numerical Investigation of Different Flow Regimes for Square Cylinders in Staggered Configuration

    Islam, Shams Ul / Nazeer, Ghazala / Shigri, Sehrish Hassan | Online Contents | 2019