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DIFFRACTION OF PULSES BY ARBITRARY TWO DZMENSIONAL FREE SURFACES
COLUMBIA UNIV NEW YORK DEPT OF CIVIL ENGINEERING AND ENGINEERING MECHANICS
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The analysis of obstacles composed of free surfaces surfaces of constant potential and pressure corresponding to Dirichlet conditions are studied. The field variable of interest is the spatial derivative of the potential, i.e. the velocity. As in the rigid problem the effect of the discontinuity in the velocity at the wave front can be separated from the remaining surface effects and integrated directly. The remaining integrals are again approximated by assuming the surface velocity to have an averaged value over specified intervals in space and time. The integrations may then be replaced by summations which, because of the time-retarded effect, lead to successive non-simultaneous algebraic equations for the unknown surface velocities. The free surface configuration for which results are obtained is that formed by a boxshaped obstacle composed of free surfaces which is bisected by an infinite plane free surface the asymptotic velocity, field in the media is independent of time. The solution can be obtained from the case of the infinite media by the image principle, i.e. by an appropriate superposition of compression and expansion pulses of equal magnitude. Author
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