Computational Approaches

Abstract

The advent of the electronic computer opened new approaches to the turbulence problem. As early as in 1946 John von Neumann discerned turbulence as a challenge for the Electronic Computer Project at the Princeton Institute for Advanced Study (IAS). In the 1950s the IAS-computer became a role model of a first generation of digital high speed computers. The Cold War fuelled not only the development of computers but also the birth of computational sciences—first at Los Alamos and other facilities where research on atomic bombs and other weapons entailed a host of problems that could be solved by computational means only. Another area of rapid growth was numerical weather forecast, where atmospheric turbulence became a major problem. Concepts like Large Eddy Simulation (LES) were developed in order to compute flows on geophysical scales. The small unresolved scales required “sub-grid” modelling. Turbulence models based on the decomposition in mean and fluctuating quantities, however, had to address the “closure problem” because they resulted in more unknowns than equations. Until computers would be powerful enough for Direct Numerical Simulation (DNS), modelling of turbulent flows by one or another closure method remained the only viable computational approach.