Accession Number : AD0803982

Title :   THE EFFECT OF AIR COMPRESSIBILITY IN THE IMPACT OF A FLAT BODY UPON A FREE SURFACE.

Descriptive Note : Technical rept.,

Corporate Author : CALIFORNIA UNIV BERKELEY COLL OF ENGINEERING

Personal Author(s) : Johnson, Robert S.

Report Date : SEP 1966

Pagination or Media Count : 168

Abstract : It has been suggested that the high pressures exerted on the bottom of a ship's hull during slamming are developed in the air trapped between the hull and the water's surface. To test this hypothesis, the two-dimensional, unsteady problem of the flow of air, where compressibility is accounted for, between a rigid, flat-bottomed block falling towards a rigid plane, is solved using a numerical method. The computed pressures exceeded those found experimentally by Maclean (Lewison and Maclean, 1966), and it is concluded that the deformation of the water's free surface must be accounted for in order to obtain agreement with the experiment. To the author's knowledge, the numerical method, a modified version of Sauer's method of Near Characteristics, is applied here for the first time and a maximum allowable time step, for this problem, is found by digital computer experimentation. (Author)

Descriptors :   (*FREE FALL MODELS, IMPACT SHOCK), SHIP HULLS, HYDRODYNAMICS, FLAT PLATE MODELS, AIR, COMPRESSIVE PROPERTIES, COMPRESSIBLE FLOW, PRESSURE, WATER IMPINGEMENT, DEFORMATION, MATHEMATICAL MODELS, PARTIAL DIFFERENTIAL EQUATIONS, NUMERICAL METHODS AND PROCEDURES.

Subject Categories : Marine Engineering
      Fluid Mechanics

Distribution Statement : APPROVED FOR PUBLIC RELEASE