Nose Cavitation Ogives and Sphereogives

This report covers the progress made to date on an investigation of cavitation on various projectile nose shapes. It is closely allied with and supplements the report by Dr. R. T. Knapp, entitled "Entrance and Cavitation Bubbles " No 6.1-sr207-i900, dated December 27, 1944. All work reported herein was conducted at the Hydraulic Machinery Laboratory of the California Institute of Technology and was authorized by a letter dated January 17, 1944 from Dr. E. H. Colpitts, Chief of Section 61, National Defense Research Committee. As this investigation has developed, it is apparent that a very extensive series of tests will have to be made in order to cover the ground in a satisfactory manner. It was, therefore, thought best to prepare this progress report without further delay so that the results so far obtained might be made available. Other progress reports will be issued from time to time as additional tests are completed. In this report only the tests of ogive and spherogive noses will be described. A total of about 50 models of these two types of nose shape have been tested, and, it is believed some interesting and valuable information has been obtained. However, all data in this report must be considered as preliminary only and subject to corrections based on future tests. The work so far done has furnished a fairly comprehensive overall picture of the performance of these two types of nose even though the test data are rather meager. In order to obtain consistent results it has been found necessary to make the models to very close tolerances. All linear dimensions are held within + or - 0.001". Especial care is exercised to be certain that the curves forming the nose are truly tangent and match within 0.0001" or less. The angle of the spherical segment forming the tip of a spherogive nose must be held to within a quarter of a degree as in some cases a variation of 1° will cause a change of 15% in the value of the cavitation parameter