Measurements of Fluid Friction Loss in 0.50 Caliber Rifled and Unrifled Gun Barrels

摘要

The High Speed Water Tunnel is operated by the CaliforniaudInstitute of Technology under Contract OEMsr-207 with the OSRD and is sponsored by Division 6, section 6.1 of the NDRC. The tests reported in this memorandum were made at the request of Division One of the NDRC of the OSRD.ududThe report covers measurements of the fluid friction lossudin two 0.50 caliber gun barrels, one rifled and the other unrifled, and compares the results with the friction loss through hydraulically smooth tubes. The conclusions may be summarized as follows:udud1. Within a margin of approximately 7% the loss in bothudgun barrels, for identical rates of flow, is the sameudas that for a hydraulically smooth tube of 0.500"uddiameter in the Reynolds number range of 0.5 x 10^5udto 1.5 x 10^5 covered by the tests (See Figure 4).udud2. The 7% margin represents the spread between the lossesudfor the two barrels as follows:udud(a) The loss in the unrifled barrel is 4% more thanudfor a hydraulically smooth tube due to itsudgreater roughness.udud( b ) The loss in the rifled barrel is 3% less thanudthe loss in a 0.500" diameter smooth tube dueudto its greater effective cross-section, andudconsequently lower average velocity of flow.udud3. An examination of typical trends of the friction factorudat higher Reynolds numbers indicates that values of "f"udcan probably be extrapolated parallel to the curve forudsmooth tubes shown in Figure 6.