Accurate predictions of turbulent flows occurring in many engineering and environmental applications remain a significant challenge. However, increasing computer power, particularly high performance parallel systems, is enabling more and more complex flows to be solved from first or nearly first principles through direct numerical and large eddy simulation. Such technologies can contribute greatly not only by enabling more accurate predictions but also by revealing details of physics that can contribute to a more complete understanding of turbulence. Several examples where large eddy simulations have provided new details including how rotation and buoyancy alter the structure of turbulence are described.