A sharp-edged entrance into a pipe has K = 0.5. If the pipe velocity is 0.8 m/s, compute the entrance head loss h_L.

• A. 0.008 m
• B. 0.016 m
• C. 0.032 m
• D. 0.064 m

Answer: (B)

When fluid flows into a pipe through a sharp edge, the loss of mechanical energy per unit weight (head loss) is modeled as h_L = K * (V^2)/(2g), where K is the loss coefficient and V is the pipe velocity just downstream of the entrance.

Here, K = 0.5 and V = 0.8 m/s. Compute the velocity head: V^2/(2g) = 0.8^2 / (2 * 9.81) = 0.64 / 19.62 ≈ 0.0326 m.

Multiply by the loss coefficient: h_L ≈ 0.5 * 0.0326 ≈ 0.0163 m.

So, the entrance head loss is about 0.016 m.