In the second part we shall use a pitot static tube to determine the behavior of air flow.
The basic principle of both the pitot, static and pitot static tube is that the pressure of a flowing fluid will increase if it is brought to rest at a point of stagnation of the probe. If an assumption is made that if the flow in the fluid is similar to that of a gas, the velocity of the fluid will be much smaller as compared to the speed of sound such that the changes in the density may be overlooked (Bertin, 2002). Therefore, the fluid basically behaves like an incompressible fluid. The point of stagnation can be located on the system and the streamlines can be bent past the body of the aircraft. The pressure experienced at the point of stagnation is referred to as the stagnation pressure. If the viscous effects experienced by the body are negligible, the difference between the stagnation pressure and the static pressure is usually related to the dynamic pressure which is then related to the square of the velocity (Panton, 2005). Therefore, the velocity information is then converted to a pressure difference which can e measured by a measuring device for pressure such as the manometer (von Kármán, 2000).
The static tube is composed of a cross section surface with tubes and a manometer. The air flows across the cross section into the manometer where the density of air can be determined. The manometer allows for the determination of the static pressure, the dynamic pressure and the stagnation pressure of the fluid.
The pitot static tube is a combination of the static and pitot tube. In this tube, the flow in the tube is axi-symmetric and within the vicinity of the nose. The pitot tube is then connected to one limb of a U tube manometer while the other limb of the manometer is connected to a tap made on the tube wall. Both the tap and the nose of the tube approximately on the same planes.