Field experiment on random wave forces acting on vertical cylinders

Abstract

The accuracy of the Morison equation for wave forces acting on cylinders was tested by conducting a field experiment at the Natural Ocean Engineering Laboratory (NOEL) using a database of about 69,000 individual wind waves. The test was conducted by comparing two stationary random forces as a function of time: Fa(t), the measured wave force, and Fc(t), the wave force calculated using the Morison equation. The particle velocity and acceleration components of the Morison equation were obtained using the linear theory of wind-generated waves from the directional wave spectrum obtained by measuring the wave elevation. The inertia coefficient Cin and drag coefficient Cdg are given as a function of the Keulegan–Carpenter number KE and Reynolds number RE for KE in (0, 20) and RE in (2⋅104,2⋅105). The trend of our data was compatible with the asymptotic values of Cin and Cdg suggested by Sarpkaya for large values of RE.