What typically happens to pressure in an irrigation system when the pipe diameter is reduced?

• A. Pressure decreases
• B. Pressure increases
• C. Pressure remains the same
• D. Pressure fluctuates

Answer: (B)

When the diameter of a pipe in an irrigation system is reduced, the pressure typically increases due to the principles of fluid dynamics, specifically the Bernoulli effect and the continuity equation. As water flows through a narrower section of the pipe, the velocity of the water must increase to conserve mass. According to Bernoulli's principle, an increase in the velocity of a fluid results in a decrease in pressure. However, at the point of contraction where the diameter decreases, there is an initial increase in pressure due to the restriction of flow which causes the water to accelerate.

It's also important to consider the dynamics of an irrigation system as a whole. While pressure can increase momentarily at the point of reduced diameter, the system may ultimately experience a greater pressure loss over longer distances due to friction in the narrower pipe. This is particularly relevant for irrigation design, as it emphasizes the need for carefully calculating pipe sizes to maintain adequate pressure throughout the system.

In contrast, a decrease in pressure could occur if the system has many restrictions or if there are other factors at play like abrupt changes in elevation or extensive pipe runs, but those scenarios do not directly correlate with the immediate effect of a diameter reduction. Thus, the essence of fluid mechanics confirms that a reduction in pipe diameter