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Orifice Discharging Freely into Atmosphere

Fluid Mechanics · FE Reference Handbook section

Fluid Mechanics
5 formulas
10 exam-style examples
~55 min
All Fluid Mechanics lectures

Handbook notes for this section

Definitions and conditions exactly as the handbook states them.

  • in which h is measured from the liquid surface to the centroid of the orifice opening.

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.

Example 1
Discharge from a sharp-edged orifice venting to atmosphere — Orifice Discharging Freely into Atmosphere

A 35 mm sharp-edged orifice in the side of a tank discharges freely to the atmosphere under a head of 5.1 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

  • d=35mmd = 35 mm
  • H=5.1mH = 5.1 m
  • Cd=0.61C_d = 0.61

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

  1. Formula

    V=2gHV = \sqrt{2gH}
  2. Substituting

    V=(2×9.81×5.1)=10.00m/sV = \sqrt(2\times9.81\times5.1) = 10.00 m/s
  3. Orifice area

    A=π(0.035)2/4=0.00096m2A = \pi(0.035)^{2}/4 = 0.00096 m^{2}
  4. Formula

    Q=CdA2gHQ = C_d A\sqrt{2gH}
  5. Substituting

    Q=0.61(0.00096)(10.00)=0.0059m3/sQ = 0.61(0.00096)(10.00) = 0.0059 m^{3}/s
  6. Volume in 60 s

    ∀=0.0059(60)=0.35m3\forall = 0.0059(60) = 0.35 m^{3}
Answer:
V=10.00m/s,Q=0.0059m3/s(5.9L/s)V = 10.00 m/s, Q = 0.0059 m^{3}/s (5.9 L/s)

Why the other options are there

  • 0.0096 m³/s (C_d ignored)
  • 0.0587 m³/s (square root omitted)

Reference: FE Reference Handbook — Fluid Mechanics → Orifice Discharging Freely into Atmosphere

Example 2
Discharge from a sharp-edged orifice venting to atmosphere — Orifice Discharging Freely into Atmosphere (2)

A 95 mm sharp-edged orifice in the side of a tank discharges freely to the atmosphere under a head of 1.7 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

  • d=95mmd = 95 mm
  • H=1.7mH = 1.7 m
  • Cd=0.60C_d = 0.60

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

  1. Formula

    V=2gHV = \sqrt{2gH}
  2. Substituting

    V=(2×9.81×1.7)=5.78m/sV = \sqrt(2\times9.81\times1.7) = 5.78 m/s
  3. Orifice area

    A=π(0.095)2/4=0.00709m2A = \pi(0.095)^{2}/4 = 0.00709 m^{2}
  4. Formula

    Q=CdA2gHQ = C_d A\sqrt{2gH}
  5. Substituting

    Q=0.60(0.00709)(5.78)=0.0246m3/sQ = 0.60(0.00709)(5.78) = 0.0246 m^{3}/s
  6. Volume in 60 s

    ∀=0.0246(60)=1.47m3\forall = 0.0246(60) = 1.47 m^{3}
Answer:
V=5.78m/s,Q=0.0246m3/s(24.6L/s)V = 5.78 m/s, Q = 0.0246 m^{3}/s (24.6 L/s)

Why the other options are there

  • 0.0409 m³/s (C_d ignored)
  • 0.1419 m³/s (square root omitted)

Reference: FE Reference Handbook — Fluid Mechanics → Orifice Discharging Freely into Atmosphere

Example 3
Discharge from a sharp-edged orifice venting to atmosphere — Orifice Discharging Freely into Atmosphere (3)

A 55 mm sharp-edged orifice in the side of a tank discharges freely to the atmosphere under a head of 7.9 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

  • d=55mmd = 55 mm
  • H=7.9mH = 7.9 m
  • Cd=0.61C_d = 0.61

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

  1. Formula

    V=2gHV = \sqrt{2gH}
  2. Substituting

    V=(2×9.81×7.9)=12.45m/sV = \sqrt(2\times9.81\times7.9) = 12.45 m/s
  3. Orifice area

    A=π(0.055)2/4=0.00238m2A = \pi(0.055)^{2}/4 = 0.00238 m^{2}
  4. Formula

    Q=CdA2gHQ = C_d A\sqrt{2gH}
  5. Substituting

    Q=0.61(0.00238)(12.45)=0.0180m3/sQ = 0.61(0.00238)(12.45) = 0.0180 m^{3}/s
  6. Volume in 60 s

    ∀=0.0180(60)=1.08m3\forall = 0.0180(60) = 1.08 m^{3}
Answer:
V=12.45m/s,Q=0.0180m3/s(18.0L/s)V = 12.45 m/s, Q = 0.0180 m^{3}/s (18.0 L/s)

Why the other options are there

  • 0.0296 m³/s (C_d ignored)
  • 0.2246 m³/s (square root omitted)

Reference: FE Reference Handbook — Fluid Mechanics → Orifice Discharging Freely into Atmosphere

Example 4
Discharge from a sharp-edged orifice venting to atmosphere — Orifice Discharging Freely into Atmosphere (4)

A 90 mm sharp-edged orifice in the side of a tank discharges freely to the atmosphere under a head of 8.0 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

  • d=90mmd = 90 mm
  • H=8.0mH = 8.0 m
  • Cd=0.64C_d = 0.64

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

  1. Formula

    V=2gHV = \sqrt{2gH}
  2. Substituting

    V=(2×9.81×8.0)=12.53m/sV = \sqrt(2\times9.81\times8.0) = 12.53 m/s
  3. Orifice area

    A=π(0.090)2/4=0.00636m2A = \pi(0.090)^{2}/4 = 0.00636 m^{2}
  4. Formula

    Q=CdA2gHQ = C_d A\sqrt{2gH}
  5. Substituting

    Q=0.64(0.00636)(12.53)=0.0510m3/sQ = 0.64(0.00636)(12.53) = 0.0510 m^{3}/s
  6. Volume in 60 s

    ∀=0.0510(60)=3.06m3\forall = 0.0510(60) = 3.06 m^{3}
Answer:
V=12.53m/s,Q=0.0510m3/s(51.0L/s)V = 12.53 m/s, Q = 0.0510 m^{3}/s (51.0 L/s)

Why the other options are there

  • 0.0797 m³/s (C_d ignored)
  • 0.6391 m³/s (square root omitted)

Reference: FE Reference Handbook — Fluid Mechanics → Orifice Discharging Freely into Atmosphere

Example 5
Discharge from a sharp-edged orifice venting to atmosphere — Orifice Discharging Freely into Atmosphere (5)

A 80 mm sharp-edged orifice in the side of a tank discharges freely to the atmosphere under a head of 2.3 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

  • d=80mmd = 80 mm
  • H=2.3mH = 2.3 m
  • Cd=0.61C_d = 0.61

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

  1. Formula

    V=2gHV = \sqrt{2gH}
  2. Substituting

    V=(2×9.81×2.3)=6.72m/sV = \sqrt(2\times9.81\times2.3) = 6.72 m/s
  3. Orifice area

    A=π(0.080)2/4=0.00503m2A = \pi(0.080)^{2}/4 = 0.00503 m^{2}
  4. Formula

    Q=CdA2gHQ = C_d A\sqrt{2gH}
  5. Substituting

    Q=0.61(0.00503)(6.72)=0.0206m3/sQ = 0.61(0.00503)(6.72) = 0.0206 m^{3}/s
  6. Volume in 60 s

    ∀=0.0206(60)=1.24m3\forall = 0.0206(60) = 1.24 m^{3}
Answer:
V=6.72m/s,Q=0.0206m3/s(20.6L/s)V = 6.72 m/s, Q = 0.0206 m^{3}/s (20.6 L/s)

Why the other options are there

  • 0.0338 m³/s (C_d ignored)
  • 0.1384 m³/s (square root omitted)

Reference: FE Reference Handbook — Fluid Mechanics → Orifice Discharging Freely into Atmosphere

Example 6
Discharge from a sharp-edged orifice venting to atmosphere — Orifice Discharging Freely into Atmosphere (6)

A 40 mm sharp-edged orifice in the side of a tank discharges freely to the atmosphere under a head of 7.4 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

  • d=40mmd = 40 mm
  • H=7.4mH = 7.4 m
  • Cd=0.60C_d = 0.60

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

  1. Formula

    V=2gHV = \sqrt{2gH}
  2. Substituting

    V=(2×9.81×7.4)=12.05m/sV = \sqrt(2\times9.81\times7.4) = 12.05 m/s
  3. Orifice area

    A=π(0.040)2/4=0.00126m2A = \pi(0.040)^{2}/4 = 0.00126 m^{2}
  4. Formula

    Q=CdA2gHQ = C_d A\sqrt{2gH}
  5. Substituting

    Q=0.60(0.00126)(12.05)=0.0091m3/sQ = 0.60(0.00126)(12.05) = 0.0091 m^{3}/s
  6. Volume in 60 s

    ∀=0.0091(60)=0.55m3\forall = 0.0091(60) = 0.55 m^{3}
Answer:
V=12.05m/s,Q=0.0091m3/s(9.1L/s)V = 12.05 m/s, Q = 0.0091 m^{3}/s (9.1 L/s)

Why the other options are there

  • 0.0151 m³/s (C_d ignored)
  • 0.1095 m³/s (square root omitted)

Reference: FE Reference Handbook — Fluid Mechanics → Orifice Discharging Freely into Atmosphere

Example 7
Discharge from a sharp-edged orifice venting to atmosphere — Orifice Discharging Freely into Atmosphere (7)

A 50 mm sharp-edged orifice in the side of a tank discharges freely to the atmosphere under a head of 4.2 m. With a discharge coefficient of 0.63, compute the theoretical velocity, the actual discharge and the jet's volume delivered in one minute.

Given

  • d=50mmd = 50 mm
  • H=4.2mH = 4.2 m
  • Cd=0.63C_d = 0.63

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

  1. Formula

    V=2gHV = \sqrt{2gH}
  2. Substituting

    V=(2×9.81×4.2)=9.08m/sV = \sqrt(2\times9.81\times4.2) = 9.08 m/s
  3. Orifice area

    A=π(0.050)2/4=0.00196m2A = \pi(0.050)^{2}/4 = 0.00196 m^{2}
  4. Formula

    Q=CdA2gHQ = C_d A\sqrt{2gH}
  5. Substituting

    Q=0.63(0.00196)(9.08)=0.0112m3/sQ = 0.63(0.00196)(9.08) = 0.0112 m^{3}/s
  6. Volume in 60 s

    ∀=0.0112(60)=0.67m3\forall = 0.0112(60) = 0.67 m^{3}
Answer:
V=9.08m/s,Q=0.0112m3/s(11.2L/s)V = 9.08 m/s, Q = 0.0112 m^{3}/s (11.2 L/s)

Why the other options are there

  • 0.0178 m³/s (C_d ignored)
  • 0.1019 m³/s (square root omitted)

Reference: FE Reference Handbook — Fluid Mechanics → Orifice Discharging Freely into Atmosphere

Example 8
Discharge from a sharp-edged orifice venting to atmosphere — Orifice Discharging Freely into Atmosphere (8)

A 25 mm sharp-edged orifice in the side of a tank discharges freely to the atmosphere under a head of 7.4 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

  • d=25mmd = 25 mm
  • H=7.4mH = 7.4 m
  • Cd=0.62C_d = 0.62

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

  1. Formula

    V=2gHV = \sqrt{2gH}
  2. Substituting

    V=(2×9.81×7.4)=12.05m/sV = \sqrt(2\times9.81\times7.4) = 12.05 m/s
  3. Orifice area

    A=π(0.025)2/4=0.00049m2A = \pi(0.025)^{2}/4 = 0.00049 m^{2}
  4. Formula

    Q=CdA2gHQ = C_d A\sqrt{2gH}
  5. Substituting

    Q=0.62(0.00049)(12.05)=0.0037m3/sQ = 0.62(0.00049)(12.05) = 0.0037 m^{3}/s
  6. Volume in 60 s

    ∀=0.0037(60)=0.22m3\forall = 0.0037(60) = 0.22 m^{3}
Answer:
V=12.05m/s,Q=0.0037m3/s(3.7L/s)V = 12.05 m/s, Q = 0.0037 m^{3}/s (3.7 L/s)

Why the other options are there

  • 0.0059 m³/s (C_d ignored)
  • 0.0442 m³/s (square root omitted)

Reference: FE Reference Handbook — Fluid Mechanics → Orifice Discharging Freely into Atmosphere

Example 9
Discharge from a sharp-edged orifice venting to atmosphere — Orifice Discharging Freely into Atmosphere (9)

A 110.0 mm sharp-edged orifice in the side of a tank discharges freely to the atmosphere under a head of 8.4 m. With a discharge coefficient of 0.63, compute the theoretical velocity, the actual discharge and the jet's volume delivered in one minute.

Given

  • d=110.0mmd = 110.0 mm
  • H=8.4mH = 8.4 m
  • Cd=0.63C_d = 0.63

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

  1. Formula

    V=2gHV = \sqrt{2gH}
  2. Substituting

    V=(2×9.81×8.4)=12.84m/sV = \sqrt(2\times9.81\times8.4) = 12.84 m/s
  3. Orifice area

    A=π(0.110)2/4=0.00950m2A = \pi(0.110)^{2}/4 = 0.00950 m^{2}
  4. Formula

    Q=CdA2gHQ = C_d A\sqrt{2gH}
  5. Substituting

    Q=0.63(0.00950)(12.84)=0.0769m3/sQ = 0.63(0.00950)(12.84) = 0.0769 m^{3}/s
  6. Volume in 60 s

    ∀=0.0769(60)=4.61m3\forall = 0.0769(60) = 4.61 m^{3}
Answer:
V=12.84m/s,Q=0.0769m3/s(76.9L/s)V = 12.84 m/s, Q = 0.0769 m^{3}/s (76.9 L/s)

Why the other options are there

  • 0.1220 m³/s (C_d ignored)
  • 0.9867 m³/s (square root omitted)

Reference: FE Reference Handbook — Fluid Mechanics → Orifice Discharging Freely into Atmosphere

Example 10
Discharge from a sharp-edged orifice venting to atmosphere — Orifice Discharging Freely into Atmosphere (10)

A 105.0 mm sharp-edged orifice in the side of a tank discharges freely to the atmosphere under a head of 8.2 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

  • d=105.0mmd = 105.0 mm
  • H=8.2mH = 8.2 m
  • Cd=0.64C_d = 0.64

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

  1. Formula

    V=2gHV = \sqrt{2gH}
  2. Substituting

    V=(2×9.81×8.2)=12.68m/sV = \sqrt(2\times9.81\times8.2) = 12.68 m/s
  3. Orifice area

    A=π(0.105)2/4=0.00866m2A = \pi(0.105)^{2}/4 = 0.00866 m^{2}
  4. Formula

    Q=CdA2gHQ = C_d A\sqrt{2gH}
  5. Substituting

    Q=0.64(0.00866)(12.68)=0.0703m3/sQ = 0.64(0.00866)(12.68) = 0.0703 m^{3}/s
  6. Volume in 60 s

    ∀=0.0703(60)=4.22m3\forall = 0.0703(60) = 4.22 m^{3}
Answer:
V=12.68m/s,Q=0.0703m3/s(70.3L/s)V = 12.68 m/s, Q = 0.0703 m^{3}/s (70.3 L/s)

Why the other options are there

  • 0.1098 m³/s (C_d ignored)
  • 0.8916 m³/s (square root omitted)

Reference: FE Reference Handbook — Fluid Mechanics → Orifice Discharging Freely into Atmosphere

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