AbstractThe vortex-induced vibration behind an isolated cylinder under the wake interference of an oscillating airfoil at different oscillating frequencies and amplitudes have been studied numerically. Our previous research [11] mainly focused on the two degree of freedom vibration problem, several types of the phase portraits of the displacement have been newly found, including the "half -8″ and "cone-net" types as reduced velocity increases. At present, we have continued the research to the single degree of freedom vibration, the corresponding results had been found that under the wake of the free steady flow, as the reduced velocity increases, the phase portraits displacements of the single degree of freedom vibrating cylinder will begin to rotate counterclockwise from the first and third quadrants to the second and fourth quadrants in a Cartesian coordinate system. Under the wake of the oscillating airfoil, the single bending curve and the single closed orbit (double “8-shape” like) of the displacements are newly found in the drag and thrust producing cases respectively. Except this, the two triplets of vortices have also been newly found in the pair and single plus pair wakes at each cycle. The vorticity dynamics behind the vibrating cylinder together with the corresponding force variations have also been obtained computationally and analyzed in details.

    HighlightsPhase portraits (1-DOF) will rotate counterclockwise in Cartesian coordinate.Single bending and double “8-shape” are newly found in displacement curves.The “2T” vortices mode have been newly found in 2P and 2P+2S vortex wakes.


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    Title :

    Vortex-induced vibration for an isolated circular cylinder under the wake interference of an oscillating airfoil: Part II. Single degree of freedom


    Contributors:
    Zhang, G.Q. (author) / Ji, L.C. (author) / Hu, X. (author)

    Published in:

    Acta Astronautica ; 133 ; 311-323


    Publication date :

    2017-01-14


    Size :

    13 pages




    Type of media :

    Article (Journal)


    Type of material :

    Electronic Resource


    Language :

    English


    Keywords :

    <italic>A</italic> , Oscillating amplitude (<italic>m</italic>) , <italic>A</italic><inf><italic>D</italic></inf> , dimensionless amplitude of airfoil (<italic>A</italic><inf><italic>D</italic></inf>=2<italic>A/L</italic>) , <italic>c</italic> , damping of the system (N·s/m) , <italic>C</italic><inf><italic>D</italic></inf> , Drag coefficient , <italic>D</italic> , Diameter of cylinder (m) , <italic>C</italic><inf><italic>L</italic></inf> , Lift coefficient , <italic>F</italic> , vortex-induced coupling force (<italic>N</italic>) , <italic>Re</italic> , Reynold number (Re=<italic>LU</italic>/<italic>v</italic>) , <italic>k</italic> , stiffness of the spring (N/m) , <italic>St</italic><inf><italic>D</italic></inf> , width-based Strouhal number (<italic>St</italic><inf><italic>D</italic></inf>=<italic>fL</italic>/<italic>U</italic>) , <italic>L</italic> , width of airfoil (m) , <italic>Vr</italic> , Reduced velocity (<italic>Vr=U/(f</italic><inf><italic>N</italic></inf><italic>D</italic>) , <italic>m</italic> , mass of the cylinder (kg) , <italic>υ</italic> , kinematic viscosity of the fluid (cm<sup>2</sup><hsp></hsp>s<sup>−1</sup>) , <italic>P</italic> , static pressure (Pa) , <italic>ξ</italic> , non-dimensional damping coefficient , <italic>Q</italic> , center position of the cylinder (m) , <italic>"P"</italic> , a pair of vortices , <italic>t</italic> , flow time (s) , <italic>"S"</italic> , single vortex , <italic>U</italic> , free stream velocity (m/s) , <italic>VIV</italic> , vortex induced vibration , <italic>f</italic> , oscillating frequency of airfoil (s<sup>−1</sup>) , <italic>DOF</italic> , degree of freedom , <italic>f</italic><inf><italic>so</italic></inf> , vortex-shedding frequency (cylinder) , <italic>X ,</italic>Y , nodes in the streamwise/ transverse direction , <italic>f</italic><inf><italic>N</italic></inf> , natural frequency (cylinder) , <italic>i, j</italic> , nodes on the whole edge of airfoil /cylinder , Vortex shedding , Vortex-induced-vibration , Cylinder , Airfoil , Oscillating