Types of Fluid Flow and Reynolds Number

5 TYPES OF FLUID FLOW AND REYNOLDS NUMBER 2.5A Introduction and Types of Fluid Flow 

The principles of the statics of fluids, treated in Section 2.2, are almost an exact science. On, the other hand, the principles of the motions of fluids are quite complex. The basic relations describing the motions of a fluid are the equations for the overall balances of mass, energy, and momentum, which will be covered in the following sections. 

These overall or macroscopic balances will be applied to a finite enclosure or control volume fixed in space. We use the term overall because we wish to describe these balances from outside the enclosure. The changes inside the enclosure are determined in terms of the properties of the streams entering and leaving and the exchanges of energy between the enclosure and its surroundings. 

When making overall balances on mass, energy, and momentum we are not interested in the details of what occurs inside the enclosure. For example, in an overall balance average inlet and outlet velocities are considered. However, in a differential balance the velocity distribution inside an enclosure can be obtained with the use of Newton s law of viscosity. 

In this section we first discuss the two types of fluid flow that can occur laminar and turbulent flow. Also, the Reynolds number used to characterize the regimes of flow is considered. Then in Sections 2.6, 2.7, and 2.8 the overall mass balance, energy balance, and momentum balance are covered together with a number of applications. Finally, a 

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