Orifices
Fluid Mechanics · FE Reference Handbook section
Handbook notes for this section
Definitions and conditions exactly as the handbook states them.
- The cross-sectional area at the vena contracta A2 is characterized by a coefficient of contraction Cc and given by Cc A0.
- where C, the coefficient of the meter (orifice coefficient), is given by
- Bober, W., and R.A. Kenyon, Fluid Mechanics, Wiley, 1980. Diagrams reprinted by permission of William Bober and Richard A. Kenyon.
- For incompressible flow through a horizontal orifice meter installation
Core formulas for this FE topic
Definitions, applicability, units, assumptions and worked examples for each relation.
Worked exam-style examples
The four ways this section is written on the real exam — thoughts first, then equations, then substitution.
A 75 mm sharp-edged orifice in the side of a tank discharges freely to the atmosphere under a head of 2.7 m. With a discharge coefficient of 0.60, compute the theoretical velocity, the actual discharge and the jet's volume delivered in one minute.
Given
Find
V_theoretical, Q and the one-minute volume
Start with the thinking
- Torricelli's result comes straight from Bernoulli with atmospheric pressure on both ends.
- The discharge coefficient bundles the vena-contracta area reduction with velocity losses.
Step-by-step solution
Formula
Substituting
Orifice area
Formula
Substituting
Volume in 60 s
Why the other options are there
- 0.0322 m³/s (C_d ignored)
- 0.1404 m³/s (square root omitted)
Reference: FE Reference Handbook — Fluid Mechanics → Orifices
A 75 mm sharp-edged orifice in the side of a tank discharges freely to the atmosphere under a head of 4.5 m. With a discharge coefficient of 0.59, compute the theoretical velocity, the actual discharge and the jet's volume delivered in one minute.
Given
Find
V_theoretical, Q and the one-minute volume
Start with the thinking
- Torricelli's result comes straight from Bernoulli with atmospheric pressure on both ends.
- The discharge coefficient bundles the vena-contracta area reduction with velocity losses.
Step-by-step solution
Formula
Substituting
Orifice area
Formula
Substituting
Volume in 60 s
Why the other options are there
- 0.0415 m³/s (C_d ignored)
- 0.2301 m³/s (square root omitted)
Reference: FE Reference Handbook — Fluid Mechanics → Orifices
A 35 mm sharp-edged orifice in the side of a tank discharges freely to the atmosphere under a head of 1.6 m. With a discharge coefficient of 0.61, compute the theoretical velocity, the actual discharge and the jet's volume delivered in one minute.
Given
Find
V_theoretical, Q and the one-minute volume
Start with the thinking
- Torricelli's result comes straight from Bernoulli with atmospheric pressure on both ends.
- The discharge coefficient bundles the vena-contracta area reduction with velocity losses.
Step-by-step solution
Formula
Substituting
Orifice area
Formula
Substituting
Volume in 60 s
Why the other options are there
- 0.0054 m³/s (C_d ignored)
- 0.0184 m³/s (square root omitted)
Reference: FE Reference Handbook — Fluid Mechanics → Orifices
A 35 mm sharp-edged orifice in the side of a tank discharges freely to the atmosphere under a head of 4.9 m. With a discharge coefficient of 0.62, compute the theoretical velocity, the actual discharge and the jet's volume delivered in one minute.
Given
Find
V_theoretical, Q and the one-minute volume
Start with the thinking
- Torricelli's result comes straight from Bernoulli with atmospheric pressure on both ends.
- The discharge coefficient bundles the vena-contracta area reduction with velocity losses.
Step-by-step solution
Formula
Substituting
Orifice area
Formula
Substituting
Volume in 60 s
Why the other options are there
- 0.0094 m³/s (C_d ignored)
- 0.0573 m³/s (square root omitted)
Reference: FE Reference Handbook — Fluid Mechanics → Orifices
A 70 mm sharp-edged orifice in the side of a tank discharges freely to the atmosphere under a head of 6.2 m. With a discharge coefficient of 0.59, compute the theoretical velocity, the actual discharge and the jet's volume delivered in one minute.
Given
Find
V_theoretical, Q and the one-minute volume
Start with the thinking
- Torricelli's result comes straight from Bernoulli with atmospheric pressure on both ends.
- The discharge coefficient bundles the vena-contracta area reduction with velocity losses.
Step-by-step solution
Formula
Substituting
Orifice area
Formula
Substituting
Volume in 60 s
Why the other options are there
- 0.0424 m³/s (C_d ignored)
- 0.2762 m³/s (square root omitted)
Reference: FE Reference Handbook — Fluid Mechanics → Orifices
A 30 mm sharp-edged orifice in the side of a tank discharges freely to the atmosphere under a head of 4.0 m. With a discharge coefficient of 0.65, compute the theoretical velocity, the actual discharge and the jet's volume delivered in one minute.
Given
Find
V_theoretical, Q and the one-minute volume
Start with the thinking
- Torricelli's result comes straight from Bernoulli with atmospheric pressure on both ends.
- The discharge coefficient bundles the vena-contracta area reduction with velocity losses.
Step-by-step solution
Formula
Substituting
Orifice area
Formula
Substituting
Volume in 60 s
Why the other options are there
- 0.0063 m³/s (C_d ignored)
- 0.0361 m³/s (square root omitted)
Reference: FE Reference Handbook — Fluid Mechanics → Orifices
A 25 mm sharp-edged orifice in the side of a tank discharges freely to the atmosphere under a head of 3.8 m. With a discharge coefficient of 0.65, compute the theoretical velocity, the actual discharge and the jet's volume delivered in one minute.
Given
Find
V_theoretical, Q and the one-minute volume
Start with the thinking
- Torricelli's result comes straight from Bernoulli with atmospheric pressure on both ends.
- The discharge coefficient bundles the vena-contracta area reduction with velocity losses.
Step-by-step solution
Formula
Substituting
Orifice area
Formula
Substituting
Volume in 60 s
Why the other options are there
- 0.0042 m³/s (C_d ignored)
- 0.0238 m³/s (square root omitted)
Reference: FE Reference Handbook — Fluid Mechanics → Orifices
A 95 mm sharp-edged orifice in the side of a tank discharges freely to the atmosphere under a head of 8.3 m. With a discharge coefficient of 0.64, compute the theoretical velocity, the actual discharge and the jet's volume delivered in one minute.
Given
Find
V_theoretical, Q and the one-minute volume
Start with the thinking
- Torricelli's result comes straight from Bernoulli with atmospheric pressure on both ends.
- The discharge coefficient bundles the vena-contracta area reduction with velocity losses.
Step-by-step solution
Formula
Substituting
Orifice area
Formula
Substituting
Volume in 60 s
Why the other options are there
- 0.0905 m³/s (C_d ignored)
- 0.7387 m³/s (square root omitted)
Reference: FE Reference Handbook — Fluid Mechanics → Orifices
A 60 mm sharp-edged orifice in the side of a tank discharges freely to the atmosphere under a head of 4.1 m. With a discharge coefficient of 0.64, compute the theoretical velocity, the actual discharge and the jet's volume delivered in one minute.
Given
Find
V_theoretical, Q and the one-minute volume
Start with the thinking
- Torricelli's result comes straight from Bernoulli with atmospheric pressure on both ends.
- The discharge coefficient bundles the vena-contracta area reduction with velocity losses.
Step-by-step solution
Formula
Substituting
Orifice area
Formula
Substituting
Volume in 60 s
Why the other options are there
- 0.0254 m³/s (C_d ignored)
- 0.1456 m³/s (square root omitted)
Reference: FE Reference Handbook — Fluid Mechanics → Orifices
A 95 mm sharp-edged orifice in the side of a tank discharges freely to the atmosphere under a head of 4.0 m. With a discharge coefficient of 0.65, compute the theoretical velocity, the actual discharge and the jet's volume delivered in one minute.
Given
Find
V_theoretical, Q and the one-minute volume
Start with the thinking
- Torricelli's result comes straight from Bernoulli with atmospheric pressure on both ends.
- The discharge coefficient bundles the vena-contracta area reduction with velocity losses.
Step-by-step solution
Formula
Substituting
Orifice area
Formula
Substituting
Volume in 60 s
Why the other options are there
- 0.0628 m³/s (C_d ignored)
- 0.3616 m³/s (square root omitted)
Reference: FE Reference Handbook — Fluid Mechanics → Orifices