Calculate the volumetric and mass flow rate of a fluid through a Venturi meter.
Internal diameter of the main pipe in millimeters (mm).
Internal diameter of the constriction in millimeters (mm).
Density in kg/m³ (Water ≈ 998, Air ≈ 1.225).
Differential pressure between inlet and throat in Pascals (Pa).
Typically between 0.90 and 0.99 for Venturi tubes.
Volumetric Flow Rate (Q):0 m³/h
Volumetric Flow Rate (LPM):0 L/min
Mass Flow Rate (ṁ):0 kg/s
Throat Velocity (v2):0 m/s
Beta Ratio (β):0
Understanding the Venturi Flow Rate Calculator
This calculator determines the flow rate of a fluid passing through a Venturi meter based on the principle of differential pressure. By measuring the pressure drop created by a constriction (the throat) in the pipe, we can calculate the velocity and volume of the fluid utilizing Bernoulli's principle.
The Venturi Effect Formula
The calculation is based on the ISO 5167 standard formula for differential pressure flow meters. The relationship between the flow rate and pressure drop is given by:
Q = Cd × A2 × [ 1 / √(1 – β4) ] × √(2 × ΔP / ρ)
Where:
Q = Volumetric Flow Rate (m³/s)
Cd = Discharge Coefficient (accounts for friction and turbulence, typically ~0.98)
A2 = Cross-sectional area of the throat (m²)
β = Beta ratio (Diameter ratio = D2 / D1)
ΔP = Pressure difference between inlet and throat (Pa)
ρ = Fluid density (kg/m³)
Input Parameters Explained
Inlet Diameter (D1): The internal diameter of the piping system before the meter.
Throat Diameter (D2): The smallest diameter within the Venturi tube. This constriction increases fluid velocity and lowers pressure.
Fluid Density: The mass per unit volume of the fluid being measured. Temperature changes can affect density, so ensure this value is accurate for operating conditions.
Pressure Difference: Usually measured by a differential pressure transmitter connected to tapping points at the inlet and the throat.
Common Applications
Venturi meters are widely used in industrial applications due to their durability, low permanent pressure loss, and ability to measure dirty fluids. Common uses include:
Water and wastewater treatment plants.
Oil and gas pipelines (measuring crude oil or natural gas).
Carburetor airflow measurement in automotive engineering.
Medical devices measuring blood or oxygen flow.
Accuracy Factors
While Venturi tubes are accurate, errors can arise from incorrect density values (due to temperature measurement errors), pipe roughness, or installation too close to pipe bends or valves. Always ensure the Beta Ratio is between 0.3 and 0.75 for optimal accuracy.
function calculateFlow() {
// 1. Get DOM elements
var d1Input = document.getElementById('inletDiameter');
var d2Input = document.getElementById('throatDiameter');
var rhoInput = document.getElementById('fluidDensity');
var dpInput = document.getElementById('pressureDiff');
var cdInput = document.getElementById('dischargeCoeff');
var resultContainer = document.getElementById('resultContainer');
var errorDisplay = document.getElementById('errorDisplay');
// 2. Parse values
var d1_mm = parseFloat(d1Input.value);
var d2_mm = parseFloat(d2Input.value);
var rho = parseFloat(rhoInput.value);
var dp = parseFloat(dpInput.value);
var cd = parseFloat(cdInput.value);
// 3. Reset error and results
errorDisplay.style.display = 'none';
resultContainer.style.display = 'none';
errorDisplay.innerHTML = "";
// 4. Validation
if (isNaN(d1_mm) || isNaN(d2_mm) || isNaN(rho) || isNaN(dp) || isNaN(cd)) {
errorDisplay.innerHTML = "Please enter valid numbers in all fields.";
errorDisplay.style.display = 'block';
return;
}
if (d1_mm <= 0 || d2_mm <= 0 || rho <= 0 || dp = d1_mm) {
errorDisplay.innerHTML = "Throat diameter (D2) must be smaller than Inlet diameter (D1).";
errorDisplay.style.display = 'block';
return;
}
// 5. Calculation Logic
// Convert mm to meters
var d1_m = d1_mm / 1000;
var d2_m = d2_mm / 1000;
// Calculate Beta Ratio (beta)
var beta = d2_m / d1_m;
// Calculate Area of Throat (A2)
var A2 = Math.PI * Math.pow((d2_m / 2), 2);
// Calculate Velocity of Approach Factor (E) = 1 / sqrt(1 – beta^4)
var betaPow4 = Math.pow(beta, 4);
var approachFactor = 1 / Math.sqrt(1 – betaPow4);
// Calculate Flow Rate Q (m3/s)
// Formula: Q = Cd * A2 * (1 / sqrt(1-beta^4)) * sqrt(2 * dp / rho)
var sqrtTerm = Math.sqrt((2 * dp) / rho);
var Q_m3s = cd * A2 * approachFactor * sqrtTerm;
// Calculate Mass Flow Rate (kg/s)
var m_dot = Q_m3s * rho;
// Calculate Velocity at Throat (m/s)
var velocity_throat = Q_m3s / A2;
// 6. Unit Conversions for Display
var Q_m3h = Q_m3s * 3600; // cubic meters per hour
var Q_lpm = Q_m3s * 60000; // liters per minute
// 7. Display Results
document.getElementById('resQ_m3h').innerHTML = Q_m3h.toFixed(4) + " m³/h";
document.getElementById('resQ_lpm').innerHTML = Q_lpm.toFixed(2) + " L/min";
document.getElementById('resM_kgs').innerHTML = m_dot.toFixed(4) + " kg/s";
document.getElementById('resV_ms').innerHTML = velocity_throat.toFixed(2) + " m/s";
document.getElementById('resBeta').innerHTML = beta.toFixed(3);
resultContainer.style.display = 'block';
}