Calculate the flow rate threshold for turbulence transition (Reynolds Number).
Unit: Millimeters (mm)
Unit: kg/m³
Unit: Pascal-seconds (Pa·s)
Transition point (Laminar to Turbulent)
Calculation Results
Critical Velocity (v):–
Critical Flow Rate (m³/h):–
Critical Flow Rate (L/min):–
Critical Flow Rate (L/s):–
Understanding Critical Flow Rate
The Critical Flow Rate in fluid dynamics typically refers to the velocity or volumetric flow rate at which the behavior of a fluid flowing through a pipe changes from a smooth, orderly laminar flow to a chaotic, fluctuating turbulent flow. This transition is governed by a dimensionless quantity known as the Reynolds Number (Re).
Why is this calculation important?
Pressure Drop: Turbulent flow creates significantly higher friction and pressure drop compared to laminar flow. Engineers must predict this to size pumps correctly.
Heat Transfer: Turbulent flow enhances heat transfer efficiency, which is desirable in heat exchangers.
Mixing: In chemical processing, turbulence ensures proper mixing of reactants, whereas laminar flow might result in poor separation.
Formulas Used
To find the critical flow rate, we first determine the critical velocity required to reach the critical Reynolds Number (typically assumed to be 2300 for circular pipes).
Converting to Liters per minute: $0.0000903 \times 60,000 \approx \mathbf{5.42 \text{ L/min}}$.
Any flow rate above 5.42 L/min in this pipe will likely begin to transition to turbulence.
function calculateCriticalFlow() {
// 1. Get Input Values
var diameterMM = document.getElementById("pipeDiameter").value;
var density = document.getElementById("fluidDensity").value;
var viscosity = document.getElementById("fluidViscosity").value;
var reCrit = document.getElementById("criticalRe").value;
// 2. Validate Inputs
if (diameterMM === "" || density === "" || viscosity === "" || reCrit === "") {
alert("Please fill in all fields correctly.");
return;
}
var d_mm = parseFloat(diameterMM);
var rho = parseFloat(density);
var mu = parseFloat(viscosity);
var re = parseFloat(reCrit);
if (d_mm <= 0 || rho <= 0 || mu <= 0 || re m/s
var velocity = (re * mu) / (rho * d_m);
// Calculate Pipe Area (A = pi * r^2)
var radius_m = d_m / 2;
var area = Math.PI * Math.pow(radius_m, 2);
// Calculate Flow Rate in m³/s
var flowM3S = velocity * area;
// Convert Flow Rates
var flowM3H = flowM3S * 3600; // Cubic meters per hour
var flowLMin = flowM3S * 60000; // Liters per minute
var flowLS = flowM3S * 1000; // Liters per second
// 4. Update UI
document.getElementById("resVelocity").innerText = velocity.toFixed(4) + " m/s";
document.getElementById("resFlowM3H").innerText = flowM3H.toFixed(4) + " m³/h";
document.getElementById("resFlowLMin").innerText = flowLMin.toFixed(2) + " L/min";
document.getElementById("resFlowLS").innerText = flowLS.toFixed(4) + " L/s";
// Show result container
document.getElementById("resultContainer").style.display = "block";
}