Filtering analysis of a direct numerical simulation of the turbulent RayleighBenard problem
Abstract
A filtering analysis of a turbulent flow was developed which provides details of the path of the kinetic energy of the flow from its creation via thermal production to its dissipation. A lowpass spatial filter is used to split the velocity and the temperature field into a filtered component (composed mainly of scales larger than a specific size, nominally the filter width) and a fluctuation component (scales smaller than a specific size). Variables derived from these fields can fall into one of the above two ranges or be composed of a mixture of scales dominated by scales near the specific size. The filter is used to split the kinetic energy equation into three equations corresponding to the three scale ranges described above. The data from a direct simulation of the RayleighBenard problem for conditions where the flow is turbulent are used to calculate the individual terms in the three kinetic energy equations. This is done for a range of filter widths. These results are used to study the spatial location and the scale range of the thermal energy production, the cascading of kinetic energy, the diffusion of kinetic energy, and the energy dissipation. These results are used to evaluate two subgrid models typically used in largeeddy simulations of turbulence. Subgrid models attempt to model the energy below the filter width that is removed by a lowpass filter.
 Publication:

Final Interim Report Institute for Computer Applications in Science and Engineering
 Pub Date:
 December 1990
 Bibcode:
 1990icas.reptR....E
 Keywords:

 Computerized Simulation;
 Energy Dissipation;
 Kinetic Energy;
 Low Pass Filters;
 RayleighBenard Convection;
 Turbulence;
 Turbulent Flow;
 Vortices;
 Diffusion;
 Dissipation;
 Temperature Distribution;
 Thermal Energy;
 Velocity Distribution;
 Fluid Mechanics and Heat Transfer