Direct numerical simulation of axisymmetric jets
Abstract
Results from numerical simulations of the evolution of the KelvinHelmholtz instability are presented for an unforced, subsonic, compressible, axisymmetric, spatiallyevolving shear layer. In addition, the effect of small, random pressure fluctuations at the nozzle orifice on the growth of the mixing layer is studied. These fluctuations model inflow perturbations in experimental flows arising from turbulence and boundary layers in the nozzle. The finitedifference numerical model used to perform the simulations solves the twodimensional timedependent conservation equations for an ideal fluid using the FluxCorrected Transport algorithm and timestepsplitting techniques. No subgrid turbulence model has been included. In the absence of perturbations, the calculations indicate that the large scale development of the unforced jet shear layer has an underlying degree of organization. This is the result of a feedback mechanism in which the shear layer ahead of the nozzle edge is modulated by the far field that is induced by the mergings downstream, near the end of the potential core of the jet. The studies with random high frequency perturbations on the inflow velocity show that they effectively tend to break the temporal correlations between the structures.
 Publication:

24th AIAA Aerospace Sciences Meeting
 Pub Date:
 January 1986
 Bibcode:
 1986aiaa.meetR....G
 Keywords:

 Axisymmetric Flow;
 Digital Simulation;
 Jet Flow;
 KelvinHelmholtz Instability;
 Shear Layers;
 Subsonic Flow;
 Compressible Flow;
 Conservation Equations;
 Finite Difference Theory;
 Flow Visualization;
 Free Flow;
 Mixing Layers (Fluids);
 Nozzle Flow;
 Time Dependence;
 Turbulence Models;
 Fluid Mechanics and Heat Transfer