Evaluation of wave induced forces on tubular members of offshore structures is sensitive to the choice of hydrodynamic coefficients involved in the Morison's equation. The present study is based on experiments conducted in a wave flume to evaluate the coefficients of drag, inertia and lift for rough as well as inclined cylinders. Within the experimental range it was observed that the magnitude of the drag coefficient is more influenced by the degree of cylinder inclination along the ‘in-line’ direction than by its roughness. The 1nert1a and lift coefficients however are affected by the cylinder inclination as \0,7ell as by its roughness at high Reynolds numbers.
In practice, cylinder members of offshore structures have some inclination with respect to vertical. This would change the flow pattern around them and may consequently bring about a change in the values of the wave force coefficients. In addition, most members get covered by a marine growth in due course. The resulting roughness of their surfaces also changes the flow field around them causing further variations in the values of the wave force coefficients. Even though some experimental investigations on the wave force coefficients for either rough or inclined cylinders are reported in past(e.g. Sarpkaya et al (1977, 1982), Garrison (1980, 1985), Nath (1984), Chakrabarti (1982), Chakrabarti et al (1975, 1976a, 1976b) the wave flume studies on cylinders that are rough as well as inclined are very inconclusive. Present work is aimed in this direction.
The experimental evaluation of the wave force coefficients involves simultaneous measurements of wave as well as wave force profiles and their correlation by Morison's equation. The wave profile yields the wave height and wave period. These values together with that of the water depth give the water particle kinematics when a suitable wave theory is followed.
