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MS Thesis R. Hager - Hawaii National Marine Renewable Energy ...

MS Thesis R. Hager - Hawaii National Marine Renewable Energy ...

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XiAgCgi 2 (58)3.4 Equations of MotionThe equations of motion for a freely-floating, stable body are derived from equating Eq. (34)with Newton’s second law of physics,FT i m ijj . The mass matrix, m ij , for a twodimensionalbody is:m ijm000m00 0I 22where, m denotes the mass of the body and I 22 denotes the mass moment of inertia withrespect to the z-axis. Rewrite Eq. (34) as:FTi m k X eijjijjitj M B ijjijjwhere, k ij is the hydrostatic stiffness matrix. Thus, the time-dependent equations of motionper unit wave amplitude assuming harmonic oscillation is:X eiti ( m M ) B k (59) for j=1, 3, 5ijijjijjijj0The amplitude of the motion is written in terms of the complex amplitude of motion, :jj 0jite The equation of motion in the frequency domain per unit wave amplitude is:0Xi(60) for j=1, 3, 5j2 ( m M ) iB ( k ) ijijijij3.5 Wave <strong>Energy</strong>The total energy per unit area depth-averaged is:49

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