# Category: Basic Principles

The factor of proportionality in the previous equations is called theĀ  Moody friction factor and is determined from the Moody resistance diagram shown in Figure 8-1. The friction factor is sometimes expressed in terms of the Fanning friction factor, which is one-fourth of the Moody friction factor. In some references the Moody friction factor is […]

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This equation, which is also sometimes called the Weisbach equation or the Darcy-Weisbach equation, states that the friction head loss between two points in a completely filled, circular cross section pipe is proportional to the velocity head and the length of pipe and inversely proportional to the pipe diameter. This can be written: Equations 8-5 […]

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It is customary to express the energy contained in a fluid in terms of the potential energy contained in an equivalent height or “head” of a column of the fluid. Using this convention, Bernoulli’s theorem breaks down the total energy at a point in terms of 1. The head due to its elevation above an […]

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Flow regimes describe the nature of fluid flow. There are two basic flow regimes for flow of a single-phase fluid: laminar flow and turbulent flow. Laminar flow is characterized by little mixing of the flowing fluid and a parabolic velocity profile. Turbulent flow involves complete mixing of the fluid and a more uniform velocity profile. […]

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The Reynolds number is a dimensionless parameter that relates the ratio of inertial forces to viscous forces. It can be expressed by the following general equation: The Reynolds number can be expressed in more convenient terms. For liquids, the equation becomes:

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