Steady and Unsteady Flows in Fluid Mechanics

Fluid mechanics is a very important area for mechanical engineering and also for other engineering areas. So, fluid flows are a very important part of the fluid mechanics field. And also, they design lots of devices with fluid have fluid flow inside them. Fluid flows are classified in different ways in fluid mechanics and steady and unsteady flow classifications are two important examples of them. 

Difference between Steady and Unsteady Flow

The difference between the steady and unsteady flows in Fluid Mechanics may appear pretty obvious. But the exact definition of steady and unsteady conditions in most fluid mechanics devices is not easy stuff. 

So, in the steady operation conditions of a device, the volume and the mass of the fluid and the total energy content of the fluid do not change with time. We calculate all the properties as time-averaged. If we made a steady flow definition for a device that has fluid flow, we can suppose all the values as time-averaged values. 

Which Devices are Working in Steady Flow Conditions?

There are lots of kinds of engineering systems and devices where we make all the fluid flow analyses under steady conditions. The most important examples are pumps, boilers, heat exchangers, and power plant systems. In these systems, we use incompressible flows and incompressible fluids. And also, in the steady working conditions of these devices, the mass, volume, and total energy content does not change. We make all the engineering analyses according to steady-flow conditions for these devices. 

Devices with Unsteady Flow Conditions

The most important devices that have unsteady fluid flow conditions are the reciprocating engine pistons and compressors. For reciprocating engine pistons, the fluid flow inside the pistons and outside of the pistons is not in steady conditions. The fluid which is fuel burns inside the pistons and exhaust fumes are thrown outside of the pistons. 

For compressors, the fluid is compressible and fluid flow is compressible. So, there is a great change in the density of the flowing fluid which prevents the occurrence of the steady flow conditions. 

Conclusion

Finally, we can summarize the general difference between the steady flow and unsteady flow in fluid mechanics as above. 

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