SPATIAL AND TEMPORAL FILTERING OF EXPERIMENTAL-DATA FOR A-PRIORI STUDIES OF SUBGRID-SCALE STRESSES

The viability of utilizing experimental time series for the investigat ion of SGS physics is investigated by filtering temporal and spatial d ata from a DNS of fully developed turbulent channel flow. It is found that temporal filtering of single-point data corresponds to filtering in the streamwise direction, if an appropriate convection velocity is introduced. One-dimensional filtering, however, is not effective at se parating the large and small scales in the near-wall region due to the strong flow anisotropy. Two-dimensional filtering in planes parallel to the wall is equivalent to three-dimensional filtering above y(+) si milar or equal to 10. Away from the wall, for y(+) greater than or sim ilar to 50, where the turbulent eddies tend towards isotropy, streamwi se (or temporal) filtering, is adequate. (C) 1996 American Institute o f Physics.