This chapter is concerned with the computational modelling of turbulent flow around aerodynamic bodies such as planes and wind turbines. It examines the several key design and performance issues related to the idea of in situ processing at extreme scale on modern platforms. Unstructured grid approaches such as hexahedral-based spectral element methods and finite volume methods are also good choices when all of the grid length scales in every region are known a priori. Four main components have therefore been carefully combined in order to demonstrate covisualization capabilities. These are a massively parallel Computational fluid dynamics solver parallel hierarchic adaptive stabilized transient analysis, the visualization tool ParaView and its Co processing library, a fast I/O forwarding tool called GLEAN, and the full Argonne Leadership Computing Facility architecture. Numerical simulations provide a complementary and detailed view of the flow interactions and in turn give the insight required to understand and exploit the underlying physical mechanisms related to active flow control.