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The maximum force and its phase is determined for laboratory wave forces on smooth vertical cylinders. The maximum force coefficient, and the normalized phase angle, of the force with respect to the wave particle velocity, can be related to the force transfer coefficients, C subscript d and c subscript m, for the Morison equation. This method enables the data to be plotted in a way that immediately shows the drag or inertia dependency for the wave/cylinder conditions. In addition, the C subscript d and C subscript m so derived are more likely to properly predict the maximum value of the force, although they may also increase the rms error between the measured force and the predicted force in the time domain.

A 12.75-inch diameter vertical cylinder was subjected to large laboratory waves with Keulegan-Carpenter number up to 17 at the local force transducer (20 at the still water surface) and Reynolds number up to 270,000(320,000 at the still water surface). Local force, local pressures, total force, and the elements for determining the overturning moments were measured. The purpose was to produce a high quality data set in the wave regime where both the velocity and the acceleration-dependent components of the wave forces are important. It was found that the forces were more acceleration-dependent than originally anticipated. The local forces were predicted quite well with the two-term Morison equation using the kinematics from the measurements, the linear, and the stream function wave theories. The best predictions used the measured kinematics. Keywords: Wave forces; Experiments; Large scale; Morison equations; High Reynolds; Cylinders; In-line forces; Transverse forces.

Contents: Executive Summary: Coastal and Ocean Hazards, A Technology Deficit, Hazard Mitigation Efforts and Research Needs, General Conclusions and Recommendations; Benefits from Coastal and Ocean Engineering Research: Miami Beach Nourishment Project, Fixed Platforms in the Gulf of Mexico; Natural Hazards: Overview and Recommendations: Winter Storms and Hurricanes, Long-Term Sea Level Rise, Tsunamis, Ice and Other Cold Region Hazards, Other Marine Environment Problems; Research Needs: Hazard Reduction through University Engineering Research, Coastal and Ocean Engineering Education, Social and Economic Studies, Programs Abroad.

The report presents an experimental and analytic study of wind drag within simulated forest canopy fields. The drag coefficients, aerodynamic roughness and wind velocity profiles are studied for various types of forest canopies. Furthermore, a brushy canopy field was studied which simulated the leafy portion of a forest without the tree trunks present. The wind drag force on a single experimental tree was also studied. This information is useful to those who are concerned with diffusion within a canopy in an atmospheric boundary layer. In the course of the study a shear plate was developed which reliably measures a drag force from 0.1 gram to 2000 grams. The function of this plate was successfully validated by testing it in a turbulent flow over a smooth surface. The drag coefficient of a single model tree, which was the same as those used in the simulated forest canopy fields, was compared with prototype conifers. The work found that a plastic model tree has drag coefficients between those for spruce and Douglas fir trees. The variation of the tree drag coefficient among trees of the same type is concluded by a statistical study on a number of plastic trees which have the same amount of foliage but which are different in the arrangement of the tree branches and the tree leaves. (Author)