Action of the Fluid in the Air-Micrometer : 1st Report, Characteristics of Small-Diameter Nozzle and Orifice No.1,In the Case of Compressibility Being Ignored

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Using 5 types of rounded nozzles, 24 types of cylindrical nozzles (l/d=0.799〜16.520,l : length, d : diameter) and 5 types of knife-edged orifices of 0.3mm to 1.2mm diameter, the discharge characteristics were investigated for Reynolds number from 550 to 10000,using distilled water and low-pressure air. The results are summarized : 1. Discharge coefficients, which were calculated on the basis of experiments using distilled water and low-pressure air, fall on the same curves, if arranged by Reynolds number and l/d. 2. Discharge coefficients for each type of nozzle or orifice were collected and one experimental formula was worked out. 3. Downstream pressure of nozzle or orifice is reduced to a minimum at a position of about 1.2 times the pipe diameter and is recovered at about 5 times the pipe diameter. 4. Recovery rate of pressure is about 1.7 m (m : area ratio) for rounded nozzles and 1.2 m for others.