Can You Calculate Flow Rate from Pressure and Diameter
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Fluid Flow Rate Calculator
This calculator helps you estimate the flow rate of a fluid through a pipe given the pressure difference across the pipe and the pipe's inner diameter. This is based on a simplified application of the Hagen-Poiseuille equation, which describes laminar flow in a cylindrical pipe. It's important to note that this calculator assumes:
Laminar Flow: The fluid is flowing smoothly without turbulence. For turbulent flow, the calculations become more complex.
Incompressible Fluid: The density of the fluid does not change significantly with pressure.
Constant Viscosity: The fluid's viscosity remains constant throughout the pipe.
Long, Straight Pipe: The equation is most accurate for long pipes where entrance effects are negligible.
No Fittings or Obstructions: The pipe is assumed to be smooth with no bends, valves, or other elements that would impede flow.
The general principle is that a larger pressure difference will drive more fluid, and a wider pipe will allow more fluid to pass through with less resistance.
function calculateFlowRate() {
var pressureDifference = parseFloat(document.getElementById("pressureDifference").value);
var innerDiameter = parseFloat(document.getElementById("innerDiameter").value);
var fluidViscosity = parseFloat(document.getElementById("fluidViscosity").value);
var pipeLength = parseFloat(document.getElementById("pipeLength").value);
var resultDiv = document.getElementById("result");
resultDiv.innerHTML = ""; // Clear previous results
if (isNaN(pressureDifference) || isNaN(innerDiameter) || isNaN(fluidViscosity) || isNaN(pipeLength)) {
resultDiv.innerHTML = "Please enter valid numbers for all fields.";
return;
}
if (pressureDifference <= 0 || innerDiameter <= 0 || fluidViscosity <= 0 || pipeLength <= 0) {
resultDiv.innerHTML = "All input values must be positive.";
return;
}
// Calculate the radius
var radius = innerDiameter / 2;
// Calculate the flow rate (Q) using the Hagen-Poiseuille equation:
// Q = (π * ΔP * r^4) / (8 * η * L)
// Where:
// Q = volumetric flow rate
// ΔP = pressure difference
// r = inner radius of the pipe
// η = dynamic viscosity of the fluid
// L = length of the pipe
var flowRate = (Math.PI * pressureDifference * Math.pow(radius, 4)) / (8 * fluidViscosity * pipeLength);
// Display the result
resultDiv.innerHTML = "