Environmental Engineering Reference
In-Depth Information
Fig. 2.37 Hydrodynamic analysis of a monotower on a compact foundation [30]
considerably different from each other. Therefore, the loading equations should be
modified as follows (Figure 2.37):
- In order to obtain the pressure distribution over the entire structure for a subsequent
analysis in a finite element model, diffraction theory is applied to both the compact
foundation and also the monotower, but only as far as the still water level.
- At the same time, the Morison formula is applied to the monotower. The inertia
forces between the still water level and the top edge of the foundation are, however,
suppressed because these forces correspond to the distribution of the unsteady
pressure (p
inst
) determined from diffraction theory.
- In order to calculate the remaining drag forces appropriately, we apply not only the
potential of the incident wave (
F
0
) and the steady flow velocity (v
C
) but also the
F
diff
- “blockage effect”) ensuing from the foundation.
- However, the perturbation potential ensuing from the monotower must be sup-
pressed because it supplies diffraction effects that falsify the drag forces. (If we
require the drag forces on the foundation as well, the total perturbation potential
must be suppressed.)
- The drag forces below the still water level are distributed with a cosine form over the
circumference of the monotower. In doing so, a cylindrical or conical form is
assumed for the structure.
- The drag forces related to the axis of the structure must be assigned to the
hydrodynamic pressure acting on the surface. Corresponding bar elements and
partially loaded areas are therefore defined (Figure 2.38).
- Only the Morison formula is used above the still water level (Figure 2.37). The drag
and inertia forces acting in this area are determined because they can make an
appreciable contribution to the resulting forces and moments at foundation level.
The stability of the entire structure depends on these forces and moments.
perturbation potential (
