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Water 2019, 11(1), 118; https://doi.org/10.3390/w11010118
2. Experimental Apparatus
3. Results of the Orifice Outflow Study
3.1. Inclination of the Circular Orifice Outflow
3.2. Cross-Sectional Area and Velocity of the Circular Orifice Outflow
3.3. Discharge Coefficient of the Circular Orifice
3.4. Effect of the Shape of the Orifice
4. Results of the Orifice Inflow Study
- The main pipe flow velocity influenced the orifice outflow. When the pressure difference across the orifice was constant, with the increase of the main pipe flow velocity, the outflow velocity increased, but the contraction area of the jet and the outflow discharge coefficient (as calculated using the conventional orifice equation) decreased.
- For the orifice outflow, three types of orifices were considered: a circular orifice to simulate a pinhole leak, a rectangular orifice to simulate a longitudinal crack in a pipe wall, and a rectangular orifice to simulate a circumferential crack. When the orifice pressures and the orifice opening areas were the same, the discharge of the circumferential orifice was the most sensitive to the main pipe flow velocity, and the discharge of the longitudinal orifice was the least sensitive.
- The main pipe flow velocity promoted the orifice inflow. When the pressure difference across the orifice was constant, with the increase of the main pipe flow velocity, the inflow discharge coefficient increased, which the opposite pattern to that of the orifice outflow. For the same pressure difference and the main pipe velocity, the inflow discharge coefficient was larger than the outflow counterpart.
- For both the orifice inflow and outflow, the impact of the main pipe flow velocity was more significant for the lower pressure head difference across the orifice.
Conflicts of Interest
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