ABSTRACT
Consider the flow of a fluid (recall that the word fluid includes liquids, gases, and vapors) in a constant-area, rigid-walled conduit as in Fig. 4-9. The variables of primary interest are the average fluid pressure p (1b1 /in2, or pascal) and the volume flow rate q (inch3 /sec, or m3 /sec). The average flow velocity v (inch/sec or mjsec) is defined as qj A, where A is the conduit cross-sectional area (in2 or m2). Note that the product of p and q has the dimensions (inch-lb1 )/sec and is in fact the fluid power, just as (f x v) is mechanical power and (e x i) electrical power. While the actual fluid pressure and velocity vary from point to point over the flow cross section in a real fluid flow, we will assume a so-called one-dimensional flow model in which the velocity and pressure are uniform over the area. Thus, the average velocity and average pressure correspond numerically with the values at any point in the cross
