doi:10.3850/978-981-08-7619-7_P012

ABSTRACT

The paper shows some results of a small-scale-field experiment on wave forces on a vertical truncated cylinder. The experiment was performed off the city of Reggio Calabria where often there are wind waves with Hs within 1m . We measured wave pressures on the cylinder, and free surface displacements at the point x_o,y_o where the ideal axis of the cylinder pierces the free surface, and at a point close to x_o,y_o. We took 500 records of pure wind waves (no swell superimposed on wind waves) with H_s ranging between 0.3m and 1.1m, with three diameters of the cylinder: 0.07m, 0.14m, and 0.22m. Our data enable us to get a picture of the relationship between C_in, C_dg and K_E, R_E, for K_E in (0,20) and R_E in (2.10⁴, 2.10⁵). C_in vs R_E for some fixed values of K_E is a monotonically increasing function. C_dg vs R_E for some fixed values of K_E is a decreasing function. This is like what emerges from the data of Sarpkaya, from laboratory experiments with a periodic flow in a conduct. However, our values of C_in and C_dg prove to be somewhat smaller than Sarpkaya's. This difference from the data of Sarpkaya, gets smaller as K_E grows. The trend of our data is compatible with the asympotic values of C_in and C_dg suggested by Sarpkaya for large values of R_E.

Keywords: Morison equation, Small scale field experiment, Drag coefficient, Inertia coefficient.

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