fluid flow

LEARNING OBJECTIVES

By the end of this topic, you are expected to;

• Understand the meaning of fluid flow
• Know the types of fluid flow
• Understand the elements of fluid flow

In engineering and physics, fluid dynamics is a branch of fluid mechanics that defines the flow of fluids. Fluids are liquids and gases. It has several subgroups such as aerodynamics (the study of air and other gases in motion) and hydrodynamics (the study of liquids in motion). Fluid dynamics has many applications like calculating moments and forces on aircraft, predicting weather patterns, modeling fission weapon detonation, understanding nebulae in interstellar space and determining the mass flow rate of petroleum through pipelines.

If you pour water from a mug, the velocity of the water will be very high over the lip, moderately high approaching the lip and very low at the mug’s bottom. The unbalanced force is gravity, and the flow continues provided water is available and the mug is tilted.

TYPES OF FLUID

• Ideal fluid. This refers to a fluid that cannot be compressed and whose viscosity doesn’t fall in the category of an ideal fluid. This fluid does not exist in reality; it is just an imaginary fluid.
• Real fluid. All the fluids are real since all the fluid has viscosity.
• Newtonian fluid. When a fluid obeys the Newtonian’s law of viscosity, it is known as a Newtonian fluid.
• Non-Newtonian fluid. When fluid doesn’t obey Newton’s law of viscosity it is called a Non-Newtonian fluid.
• Ideal plastic fluid. When the shear stress is proportional to the velocity gradient and shear stress is more than the yield value, it is called ideal plastic fluid.
• Incompressible fluid. When the density of the fluid does not change with the application of external force, it is called an incompressible fluid.
• Compressible fluid. When the density of the fluid changes with the application of external force, it is called a compressible fluid.

TYPES OF FLUID FLOW

Fluid flow has all aspects- steady or unsteady, viscous or non-viscous, rotational or irrotational and compressible or incompressible. Some of the characteristics reflect the properties of the liquid itself and others focus on how the fluid is moving.

STEADY OR UNSTEADY FLOW; Fluid flow may be steady or unsteady. This depends on the velocity of the fluid.

• Steady: In steady fluid flow, the velocity of the fluid is constant at any point.
• Unsteady: When the flow is unsteady, the velocity of the fluid can differ between any two points.

VISCOUS OR NON-VISCOUS FLOW: Fluid flow can be viscous or non-viscous.

• Viscosity: This is the measure of the thickness of a fluid. Gloppy fluids like shampoo or motor oil are called viscous fluids.

FLUID FLOW EQUATION

The volume of the replaced fluid in a given interval of time is known as the fluid flow equation.

Mass flow rate = ρ A V

Where,

ρ is density

V is velocity and

A is area.

Flow rate = Area x Velocity