Numerical experiments on turbulent mixing
Abstract
Mixing in simple turbulent flows has been investigating using 64 cubed and 128 cubed Direct Numerical Simulations. In turbulent combustion, mixing by molecular transport is an essential process that is not well understood. Because mixing occurs on the smallest length and time scales it is difficult to study experimentally. Instead, we have employed direct numerical simulation of turbulence, initially for a conserved passive scalar in homogeneous isotropic turbulence. The Eulerian velocity and scalar fields are calculated from the exact evolution equations, and both Eulerian and Lagrangian statistics are deduced from the computed fields. A particletracking scheme, needed to extract Lagrangian information, has been implemented. The testing of a number of such particle tracking schemes has been completed with good results: accurate Lagrangian information can be extracted at a modest computational cost. In order to study processes in stationary turbulence, a forcing algorithm has been implemented. Tests on this scheme are complete, again with good results: the small scales are unaffected by the details of the forcing. Studies have been performed of: the mixing of a passive scalar; Lagrangian velocity, Acceleration and dissipation statistics; and mixing and combustion problems viewed in terms of surfaces.
 Publication:

Cornell Univ. Final Report
 Pub Date:
 February 1988
 Bibcode:
 1988cuni.rept.....P
 Keywords:

 Computation;
 Mathematical Models;
 Numerical Analysis;
 Simulation;
 Turbulent Flow;
 Turbulent Mixing;
 Acceleration (Physics);
 Algorithms;
 Combustion;
 Dissipation;
 Lagrange Multipliers;
 Molecular Structure;
 Particles;
 Scalars;
 Time;
 Tracking (Position);
 Transport Properties;
 Velocity;
 Fluid Mechanics and Heat Transfer