Browsing by Author "Balachandran, Balakumar"
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- Energy transfer from wind to wavesBalachandran, Balakumar (Virginia Polytechnic Institute and State University, 1986)The growth rate function is necessary to determine the energy transfer from wind to waves. Analytically, the growth rate function is determined from the Phillips model, for which the mean velocity profile over water surface is important. The analytical model of Phillips using logarithmic form of the mean velocity profile has not been successful. In the present study, two different mean velocity profile models have been used. One of them, based on a mixing length formulation, is found to be appropriate. This profile is related to the sea state, through two approaches, thus enabling the growth rate function from the analytical model to be linked to the sea state. The growth rate function obtained from the analytical model, using this profile, is found to be comparable to that obtained from empirical relations based on pressure measurements when a correction is made to one of the Phillips coefficients.
- A theoretical and experimental study of modal interactions in resonantly forced structuresBalachandran, Balakumar (Virginia Tech, 1990-10-06)The influence of modal interactions on the response of harmonically excited flexible L-shaped metallic and composite structures has been investigated analytically and experimentally. Each metallic structure possesses a two-to-one internal resonance, while each composite structure possesses a three-to-one internal resonance and either a two-to-one or a one-to-·one internal resonance. For the metallic structures, a weakly nonlinear analysis is used to derive the autonomous system of equations which describe the evolution of the amplitudes and phases of the internally resonant modes. These equations are obtained for primary- and secondary-resonant excitations. The excitation frequency or amplitude is used as a control parameter and the resulting bifurcations (saddle-node, pitchfork, and Hopf bifurcations) are studied. Theoretical analyses for internally resonant systems are used to predict and explain the responses of the composite structures.