Pitot Tube

A rapid way to measure gas velocity is to use a pitot tube inserted in flow. The pitot tube (also called a stagnation tube) consists of a thin tube held parallel to the flow and at the mouth of which fluid particles come to rest. This tube is typically of the size of a hypodermic needle and does not significantly alter the flow. In incompressible flow the pitot tube records the total pressure

A second probe with a tap whose axis is normal to the flow measures the static pressure . The difference between and is a measure of velocity. This arrangement is shown in Figure 2.2