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*

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The drag coefficients for cylinders normal to the flow have been determined experimentally at Mach ∼2, Mach ∼4, and Mach ∼6 with Knudsen numbers extending from continuum conditions to free-molecule-flow conditions. The results indicate a smooth transition from inviscid values at low Knudsen numbers to free-molecule-flow predictions for diffuse reflection at high Knudsen number. Small departure theories which are applicable to the ``near free molecule flow'' regime are compared to the experimental data.

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