A-to-Z Guide to Thermodynamics,
Heat & Mass Transfer, and Fluids Engineering

The dynamic (or velocity) pressure describes the kinetic energy per unit volume within a given streamtube. If u is the velocity and r the density, the dynamic pressure is given by ρu2/2. If the flow within a pipe, channel or duct is uniform throughout a given cross-section, this definition of the dynamic pressure applies to the entire cross-section. However, if the velocity is nonuniform, a correction factor (α) similar to that identified in the velocity head, must be applied to account for the variation in the kinetic energy from one streamtube to another. In this case, the dynamic pressure appropriate to the entire section is: where A is the cross-sectional area and ū is the mean velocity. If the Bernoulli Equation is described in terms of pressures rather than energy heads, the steady-flow solution yields: where the terms on the left are, respectively, the static pressure, the dynamic pressure and the potential or position pressure. The sum of these terms is usually referred to as the stagnation pressure.