t Experimental data for the foroe distribution on three model oylind-rioal piles for three nave conditions.are presented. These results are compared to the previously published theory.**' Introduetiom The purpoao of this report is to present experimental data on the foroe distribution exerted by surfaoe waves on piles* From these data the ooeffioients of drag and mass that appear in the equation**' for the foroe were obtained* The experimental results were compared to the calculated foroe distribution* In order to simplify the presentation, the foroe (lbs) was divided by the projected area (ft 2) of a segment of the pile to give a foroe intensity (lbe/ft 2). The measurement of foroe was made on a one-inoh'high segment of several model piles of various diameters* The results of these studies are that the experimentally determined coefficient of mass shows good agreement with the theoretical value of 2*oC 7 » 8), and relatively good agreement with the values in previously presented experiments(1#2,3,4,5,467. The results also show that the experimentally determined ooeffioient of drag is in relatively good agreement with the value 1*6 as found in previous experiments(^» 2 » 5 »*»* 6 '' The measurements of the foroe intensity distribution showed good agreement with the oaloulated distribution using the previously mentioned values of the ooeffioi-ents in the equation for the foroe*

The results of an experimental investigation on the damping action of submerged rectangular breakwaters are presented. The experimental data also are compared with published theories. A new theory is presented which compares more favorably with the experiments than the previous theories. Also given is a summary of all available published theoretical and experimental information on the damping action of trapezoidal and triangular breakwaters, reefs of various configurations, and plane barriers of various orientations.

In the design of a pile structure exposed to surface waves of a given height and period, some of the factors involved in the problem and studied herein are the size, shape and spacing of the piles and the moment distribution on uniform and non-uniform piles. Theoretical and experimental investigations have shown that the force exerted by surface waves on a pile consists of two components — a drag force and an inertia force. The drag force is proportional to the fluid density, the projected area and the square of the fluid particle velocity. The inertia force, including the virtual mass, is proportional to the fluid density, the volume of the object and the fluid particle acceleration. The virtual mass is the apparent increase of the displaced mass of fluid necessary to account for the increase in force resulting from the acceleration of the fluid relative to the object. This factor is included in the coefficient of mass term in the force calculations.

t Experimental data for the foroe distribution on three model oylindrioal piles for three nave conditions.are presented. These results are compared to the previously published theory.**' Introduetiom The purpoao of this report is to present experimental data on the foroe distribution exerted by surfaoe waves on piles* From these data the ooeffioients of drag and mass that appear in the equation**' for the foroe were obtained* The experimental results were compared to the calculated foroe distribution* In order to simplify the presentation, the foroe (lbs) was divided by the projected area ( Figure 1)* The displacement of the pile segment was converted to a foroe by means of a oonversion faotor obtained by calibration. In order to obtain a flow pattern similar to a continuous pile and to reduce the tare on the pendulum rod, a cylindrical shroud representing a pile was plaoed between the one-inoh segment and the pivot (whioh was always above the wave surfaoe)* By the use of a frame, a dummy pile seotion was held below the one-inoh segment to represent the lower portion of a oontinuous pile* The tare of the system without the segment was a very small peroentage of the foroe on the segment* The natural frequency of the system was relatively near the frequency of the uniform, periodio wave trains* This oaused considerable, unavoidable trouble whioh the one-inoh segment was near the surfaoe of the waves; ©specially when the waves were very steep and when the waves were in relatively shallow water* "lumbers in ( ) are reference numbers.

No abstract