Orifices — Typical Average Value of Coefficient of Velocity (Cv) For a sharp-edged orifice under ordinary laboratory conditions, what is a commonly accepted average value of the coefficient of velocity Cv?

Introduction:
Three principal coefficients describe orifice discharge: coefficient of contraction Cc, coefficient of velocity Cv, and coefficient of discharge Cd = Cc * Cv. Recognizing typical magnitudes helps in quick estimates and cross-checks of experimental data.

Given Data / Assumptions:

• Sharp-edged thin-plate orifice.
• Clean approach flow, moderate heads.
• Water at room temperature.

Concept / Approach:
Coefficient of velocity Cv accounts for the difference between theoretical and actual jet velocities at the vena contracta. With small energy losses, Cv is close to unity, typically around 0.97–0.99 for sharp-edged orifices.

Step-by-Step Solution:
Recall Cd ≈ 0.61 for sharp edges and Cc ≈ 0.62.Compute a check: Cv ≈ Cd / Cc ≈ 0.61 / 0.62 ≈ 0.98.Thus a representative average is Cv ≈ 0.97.

Verification / Alternative check:
Laboratory measurements of jet trajectory (using horizontal range) yield velocities very close to theoretical, confirming Cv near 1.

Why Other Options Are Wrong:
0.62 is typical of Cc, not Cv; 0.76 and 0.84 are too low for velocity coefficient under normal conditions.

Common Pitfalls:
Confusing Cv with Cd or Cc; using atypical values from rough-edged or partially blocked orifices.

Final Answer:
0.97