Free Flow Discharge under Head using Submerged Flow over Weir Formula

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Free Flow Discharge under Head H1 is the volumetric flow rate of water that is transported in a weir when there is insufficient backwater to reduce the discharge through the flume. Check FAQs
Q1=Qs(1-(H2H1)nhead)0.385
Q1 - Free Flow Discharge under Head H1?Qs - Submerged Discharge?H2 - Downstream Water Surface Elevation?H1 - Upstream Water Surface Elevation?nhead - Exponent of Head?

Free Flow Discharge under Head using Submerged Flow over Weir Example

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Here is how the Free Flow Discharge under Head using Submerged Flow over Weir equation looks like with Values.

Here is how the Free Flow Discharge under Head using Submerged Flow over Weir equation looks like with Units.

Here is how the Free Flow Discharge under Head using Submerged Flow over Weir equation looks like.

20.0067Edit=19Edit(1-(5Edit10.01Edit)2.99Edit)0.385
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Free Flow Discharge under Head using Submerged Flow over Weir Solution

Follow our step by step solution on how to calculate Free Flow Discharge under Head using Submerged Flow over Weir?

FIRST Step Consider the formula
Q1=Qs(1-(H2H1)nhead)0.385
Next Step Substitute values of Variables
Q1=19m³/s(1-(5m10.01m)2.99m)0.385
Next Step Prepare to Evaluate
Q1=19(1-(510.01)2.99)0.385
Next Step Evaluate
Q1=20.0066740000837m³/s
LAST Step Rounding Answer
Q1=20.0067m³/s

Free Flow Discharge under Head using Submerged Flow over Weir Formula Elements

Variables
Free Flow Discharge under Head H1
Free Flow Discharge under Head H1 is the volumetric flow rate of water that is transported in a weir when there is insufficient backwater to reduce the discharge through the flume.
Symbol: Q1
Measurement: Volumetric Flow RateUnit: m³/s
Note: Value can be positive or negative.
Submerged Discharge
Submerged Discharge for the flow over a weir is denoted by the symbol Qs.
Symbol: Qs
Measurement: Volumetric Flow RateUnit: m³/s
Note: Value can be positive or negative.
Downstream Water Surface Elevation
Downstream Water Surface Elevation measured above the Weir Crest.
Symbol: H2
Measurement: LengthUnit: m
Note: Value can be positive or negative.
Upstream Water Surface Elevation
Upstream Water Surface Elevation measured above the Weir Crest.
Symbol: H1
Measurement: LengthUnit: m
Note: Value can be positive or negative.
Exponent of Head
Exponent of Head in free flow head discharge relation is denoted by the symbol n.
Symbol: nhead
Measurement: LengthUnit: m
Note: Value should be greater than 0.

Other formulas in Flow Measuring Structures category

​Go Head over Weir given Discharge
H=(Qfk)1nsystem
​Go Discharge at Structure
Qf=k(Hnsystem)
​Go Submerged Flow over Weir using Villemonte Formula
Qs=Q1(1-(H2H1)nhead)0.385

How to Evaluate Free Flow Discharge under Head using Submerged Flow over Weir?

Free Flow Discharge under Head using Submerged Flow over Weir evaluator uses Free Flow Discharge under Head H1 = Submerged Discharge/(1-(Downstream Water Surface Elevation/Upstream Water Surface Elevation)^Exponent of Head)^0.385 to evaluate the Free Flow Discharge under Head H1, The Free Flow Discharge under Head using Submerged Flow over Weir formula is defined as the volumetric flow rate of water that is transported in a weir when there is insufficient backwater to reduce the discharge through the flume. Free Flow Discharge under Head H1 is denoted by Q1 symbol.

How to evaluate Free Flow Discharge under Head using Submerged Flow over Weir using this online evaluator? To use this online evaluator for Free Flow Discharge under Head using Submerged Flow over Weir, enter Submerged Discharge (Qs), Downstream Water Surface Elevation (H2), Upstream Water Surface Elevation (H1) & Exponent of Head (nhead) and hit the calculate button.

FAQs on Free Flow Discharge under Head using Submerged Flow over Weir

What is the formula to find Free Flow Discharge under Head using Submerged Flow over Weir?
The formula of Free Flow Discharge under Head using Submerged Flow over Weir is expressed as Free Flow Discharge under Head H1 = Submerged Discharge/(1-(Downstream Water Surface Elevation/Upstream Water Surface Elevation)^Exponent of Head)^0.385. Here is an example- 19.99903 = 19/(1-(5/10.01)^2.99)^0.385.
How to calculate Free Flow Discharge under Head using Submerged Flow over Weir?
With Submerged Discharge (Qs), Downstream Water Surface Elevation (H2), Upstream Water Surface Elevation (H1) & Exponent of Head (nhead) we can find Free Flow Discharge under Head using Submerged Flow over Weir using the formula - Free Flow Discharge under Head H1 = Submerged Discharge/(1-(Downstream Water Surface Elevation/Upstream Water Surface Elevation)^Exponent of Head)^0.385.
Can the Free Flow Discharge under Head using Submerged Flow over Weir be negative?
Yes, the Free Flow Discharge under Head using Submerged Flow over Weir, measured in Volumetric Flow Rate can be negative.
Which unit is used to measure Free Flow Discharge under Head using Submerged Flow over Weir?
Free Flow Discharge under Head using Submerged Flow over Weir is usually measured using the Cubic Meter per Second[m³/s] for Volumetric Flow Rate. Cubic Meter per Day[m³/s], Cubic Meter per Hour[m³/s], Cubic Meter per Minute[m³/s] are the few other units in which Free Flow Discharge under Head using Submerged Flow over Weir can be measured.
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