Question

If the coefficient of discharge and coefficient of velocity for an orifice are 0.63 and 0.75 respectively, then the coefficient of contraction is

• A. 0.47
• B. 0.75
• C. 0.84
• D. 1.19

Hint:

Remember the physical meaning and relationship of the orifice coefficients:
- $C_v = \frac{\text{Actual Velocity}}{\text{Theoretical Velocity}}$ (accounts for friction loss)
- $C_c = \frac{\text{Area of Vena Contracta}}{\text{Area of Orifice}}$ (accounts for streamline contraction)
- $C_d = \frac{\text{Actual Discharge}}{\text{Theoretical Discharge}} = C_c \times C_v$

Answer 1

The Correct Option is C

Step 1: Understanding the Question:
C_d=0.63, C_v=0.75. Find C_c.

Step 2: Key Relationship (Alternate):
C_d = C_c × C_v. C_c = C_d/C_v.

Step 3: Detailed Explanation:
C_c = 0.63/0.75 = 63/75 = 21/25 = 0.84. C_d accounts for both contraction and velocity losses. C_c < 1 due to vena contracta.

Step 4: Final Answer:
0.84.