# Introduction - Lesson 1

Did you ever notice the flow of water around an obstacle, say a flood gate? It is pretty straightforward to see that the flow is quite turbulent.

In fact, Leonardo da Vinci chronicled the turbulent nature of water flow as it passes an obstacle in the early 1500s!

But what, exactly, is turbulence? How can we define and characterize a turbulent flow? We will answer those questions in this course. Specifically, in this lesson, you will be introduced to the world of flow turbulence.

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