What's a turbulent flow?

What pop-ups in your mind when someone says the phrase "turbulent flow"? Well, engineers working in fluid simulation know a lot about the concept.

Still, many of these engineers are only interested in setting the turbulent flow boundary conditions required by the simulation software they use and do not even have a good physical understanding of what the turbulent flow is.

Well absolutely, the one who does not work or know flow simulation, most likely does not even recognize the term at all.

Turbulent currents are all around us and that they affect our way of life. The airflow around a moving vehicle, be it a car, a train, or a plane, is turbulent. Even as people walk, the airflow around them is turbulent. The airflow from an air conditioner is turbulent, as is due to the rotating blades of the electric fans.

Additionally, water flowing from a faucet is turbulent. we say that we are surrounded by turbulent currents.

This series of articles will discuss the positive and negative aspects of turbulent flows and their mechanisms. they will also discuss why flow calculations are so difficult.

What is a turbulent flow?

As mentioned before this section, turbulent flows are all around us. It can be identified everywhere. But what can be the defining quality of turbulent flow? The term "turbulent flow" literally means a stream in a turbulent state.

Since it is not useful to define an expression with an equivalent expression, what does turbulence mean? Since most streams are invisible, this makes it super difficult to identify a true turbulent stream. However, some turbulent flows are visible.

Imagine standing by a river. If leaves float along the river, they can be identified to see the flow behavior of the water. The water in the river flows from upstream to downstream.

Looking closely at the leaves that flow along the river, there is likely to be at least one leaf that rotates in a circular path as part of the current that swirls from upstream to downstream. In other words, there are separate motions besides the most current, and motions like it are a turbulence flow.

Then imagine the smoke flow rising from a candle in a room where there is no airflow. Smoke rises from candlelight thanks to buoyancy. The smoke rises upward as a straight line, but its pattern changes at a certain point when the flow interrupts turbulently.

If the movement of the plum at this transition point is closely monitored, some vertebrae (regions where the plum recirculates over itself) will be observed where the flow becomes turbulent.

Like the river, movements that break away the most current occur within the foam. The movements are called turbulent. These movements occur because the momentum (inertia force) of flow has been greater than the force acting against the flow (viscosity).

Most types of fluid flow are turbulent, except for laminar flow at the leading edge of solids moving relative to liquids or extremely close to solid surfaces, such as the inside of a tube, or in the case of high viscosity fluids. (relatively large inertia) slowly flows through small channels.

Common examples of turbulent flow are blood flow in arteries, oil transport in pipelines, lava flow, atmosphere and ocean currents, the flow through pumps and turbines, and the flow in boat wakes and around flight tips.