The lid-driven cavity flow involves a fluid in a square box driven by constant "blow" near the lid. Depending on the physical conditions, a stable eddy can form within the box (as shown by the streamlines). You may notice that when a stable eddy occupies the entire box, its center is actually cooler than the edge, indicating the faster heat transfer rate through forced convection than through conduction. The lid-driven cavity problem is one of the most important benchmarks for computational fluid dynamics.