Pressure along the pipe

It is easy to visualise that the forces acting upon the pipe flow are inertial, viscous force due to shear and the pressure forces. Let us ignore gravity, i.e., let the pipe be horizontal. When the flow is fully developed the pressure gradient and shear forces balance each other and the flow continues with a constant velocity profile. The pressure gradient remains constant.

In the entrance region the fluid is decelerating. A balance is achieved with inertia, pressure and shear forces. The pressure gradient is not constant in this part of the flow and in fact, it decreases as shown in Fig.7.5 .

Figure 7.5: Pressure distribution along the flow in a pipe.

(c) Aerospace, Mechanical & Mechatronic Engg. 2005
University of Sydney