If the streamlines for a flow don't change with time, so that the flow is in a steady state, we say that the flow is laminarlaminar. As you might imagine, these are the easiest flows to understand and visualize. Unfortunately, nature usually provides us with turbulentturbulent flows, which constantly fluctuate in time with little or no apparent pattern. Turbulence is still not well understood, and is the subject of intense investigation by engineers and physicists alike. We'll postpone further discussion of turbulence for later, and stick with the more mundane laminar flows for right now.