Basic Definition Check – Coefficient of Discharge for an Orifice The coefficient of discharge Cd is defined as the ratio of the actual discharge to the theoretical discharge through an orifice under the same head.

Introduction:
Flow coefficients quantify how real flows deviate from ideal predictions. The coefficient of discharge is particularly important for calibrating orifices, nozzles, and weirs to obtain accurate flow rates from head measurements.

Given Data / Assumptions:

• Theoretical discharge Q_th is computed from ideal energy relations (no losses, perfect contraction).
• Actual discharge Q_act is measured experimentally.
• Same head across the orifice for both definitions.

Concept / Approach:

By standard definition, Cd = Q_act / Q_th. Since real flows experience contraction and viscous losses, Q_act < Q_th and Cd is typically less than 1. The statement in the stem reverses the ratio, so it is incorrect.

Step-by-Step Solution:

Verification / Alternative check:

Typical sharp-edged orifices show Cd ≈ 0.60 to 0.65, clearly less than 1, confirming the actual is a fraction of the theoretical, not vice versa.

Why Other Options Are Wrong:

Adding conditions such as “large heads” or “negligible viscosity” does not change the definition itself; Cd remains Q_act / Q_th.

Common Pitfalls:

Confusing Cd with coefficient of velocity Cv (V_act / V_th) and coefficient of contraction Cc (A_jet / A_orifice); note that Cd = Cc * Cv.

Final Answer:

False