XSEDE12

Science: Massively parallel direct numerical simulations of forced compressible turbulence: a hybrid MPI/OpenMP approach

Abstract: A highly scalable simulation code for turbulent flowswhich solves the fully compressible Navier-Stokesequations is presented. The code, which supports one, twoand three dimensional domain decompositionsis shown to scale well on up to 262,144cores. Introducing multiple levels of parallelism based ondistributed message passing and shared-memory paradigms results in areductionof up to 33\% of communication time at large core counts.The code has been used to generate a large database ofhomogeneous isotropic turbulence in a stationary state created by forcingthe largest scales in the flow.The scaling of spectra of velocity and density fluctuationsare presented. While the former follow classical theories strictly validfor incompressible flows, the latter presents a more complicated behavior.Fluctuations in velocity gradients and derived quantitiesexhibit extreme though rare fluctuations, a phenomenon known as intermittency.The simulations presented provide data to disentangle Reynolds andMach number effects.