Smith effect

The Smith effect is the correction to wave-induced pressure that accounts for the decay of the dynamic (orbital) pressure with depth below the wave surface, named for W. E. Smith (1883). Linear wave pressure below the still-water line carries a factor exp of k z (z negative downward), so the pressure under a crest is less than the hydrostatic value implied by the surface elevation and under a trough is more. Including this depth attenuation in the Froude-Krylov pressure integration reduces the calculated wave bending moment relative to a naive surface-following column model. It is a standard component of buoyancy and wave-load calculations in hogging and sagging analysis.