Large Eddy Simulation of a Free Circular Jet

Abstract

A large eddy simulation (LES) of an incompressible spatially developing circular jet at a Reynolds number of 10,000 is performed. The shearimproved Smagorinsky model (Lأ©vأھque et al., 2007, “A ShearImproved Smagorinsky Model for the LargeEddy Simulation of WallBounded Turbulent Flows,â€‌ J. Fluid Mech., 570, pp. 491–502) is used for the resolution of the subgrid stress tensor within the filtered threedimensional unsteady Navier–Stokes equations. Higherorder spatial and temporal discretization schemes are used for capturing the details of the turbulent flow field. With the help of instantaneous and timeaveraged flow data, the spatial transition from the laminar state to the turbulent is analyzed. Flow structures are visualized using isosurfaces of the Qcriterion. Instantaneous flow patterns show single tearing and multiple pairing processes. Tracing individual vortex rings over a longer time period, a detailed understanding of the vortex interaction is revealed. The observed trends and the length of the potential core are in conformity with the findings of earlier experiments. The timeaveraged axial velocity profile shows that the jet attains selfsimilarity and the computed profile matches well with the experimental results of Hussein et al. (1994, “Velocity Measurements in a HighReynoldsNumber, MomentumConserving, Axisymmetric, Turbulent Jet,â€‌ J. Fluid Mech., 258, pp. 31–75). The centerline decay of the velocity and entrainment rate are in agreement with published experiments. The Reynolds stress components u'u'آ¯, v'v'آ¯, and u'v'آ¯ and the thirdorder velocity moment are in good agreement with thr experimental results, thus confirming the validity of the present simulation.