Friction Factor Calculator

Head loss occurs when fluids lose energy while traveling through a pipe or duct, resulting in a reduction in pressure and velocity. Surface roughness and friction are the main causes of these losses. In addition, modest losses are caused by changes in pipe cross-section such as enlargement or contraction, bends, and branching. 

The Darcy-Weisbach equation uses the friction head loss to calculate the pressure drop Δp for a fluid flowing at a velocity V in a pipe with length L and pipe diameter D and friction factor f, is Δp = fLV^2/(2gD),

• Where, g = acceleration due to gravity
• f = friction factor
• L= length of pipe
• D = diameter of the pipe

The Colebrook equation can be used to calculate the term friction factor, for a pipe with a surface roughness of k: 1/√f = -2 * log(k / (3.7 * D) + 2.51/(Re * √f)),

Where Re = Reynold's number of the pipe

Only numerical approximations can be used to solve the Colebrook-White problem. Lewis Moody, often known as Moody chart or Moody diagram, provided one of the most widely used approximations. The Darcy friction factor is calculated using Moody's approximation in this calculator. The following is Moody's approximation, sometimes known as the Moody equation: f = 0.0055 ( 1 + (2 * 10^4 * k/D + 10^6/Re)^(1/3)

This approximation is appropriate for flow regimes with Reynold's numbers ranging from 4,000 to 5*108, as well as pipes with a k/D ratio of less than 0.01. This Moody diagram calculator also uses this approximation.

Factors influence on friction factor:

1. Pipe diameter;
2. Reynolds number,
3. Surface roughness

Factors influence on Reynold’s Number:

1. Flow velocity,
2. Fluid density and viscosity,
3. Pipe length.

To calculate the Darcy friction factor using the Moody equation, follow the steps below.

• Step 1: Enter the pipe or conduit's hydraulic diameter.
• Step 2: Enter the pipe's surface roughness. The equation is only applicable when the k/D ratio is smaller than 0.01.
• Step 3: Enter the flow regime's Reynold's number. It's worth noting that the equation only applies to pipe flows with Reynold's numbers in the range 4000< Re< 5*10^8.
• Step 4: To estimate Reynold's number, utilize the advanced mode of the calculator. To find Reynold's number, use the fluid parameters of density, viscosity, and flow velocity. You can also directly input a value for the relative roughness k/D in advanced mode.
• Step 4: The Darcy friction factor will be calculated using the Moody diagram calculator.

• Step 1: Calculate the flow's Reynold's number (using the formula ρVD/μ).
• Step 2: Make sure the relative roughness (k/D) is less than 0.01.
• Step 3: In the Moody formula, use the Reynold's number, roughness - f = 0.0055 (1 + (2 x 10^4 k/D + 10^6/Re)^(1/3)

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1. What does the term "friction factor" mean?

Friction factor definition: The friction factor is a measurement of how much pressure a fluid loses in a pipe as a result of interactions between the fluid and the pipe.

2. What is the procedure for calculating the friction factor using the Reynolds number?

Divide 64 by Reynold's number to get the friction factor for laminar flow.

3. What is the friction factor formula for laminar flow?

The friction factor has a direct relationship with the Reynolds number when the fluid flow is laminar (Re < 2000), such as f m = 64 / Re or f f = 16 / Re.

4. When the Reynolds number rises, why does the friction factor decrease?

It's worth noting that for very large Reynolds numbers, the friction factor is completely independent of the Reynolds number. This is due to the fact that when the Reynolds number rises, the thickness of the laminar (viscous) sublayer decreases.

5. What is meant by pipe roughness and friction factor?

The relative roughness of a pipe is calculated by dividing its roughness by its internal diameter (e/D), and this number is used to compute the pipe friction factor, which is then utilized in the Darcy-Weisbach equation to determine the friction loss in a pipe for moving fluid.