STOCHASTIC ESTIMATION OF MULTIPOINT CONDITIONAL AVERAGES AND THEIR SPATIOTEMPORAL EVOLUTION

A novel application of the stochastic estimation procedure is used to examine the three-dimensional structure of the turbulent wake of a cyl inder at x/d = 100 and Re(D) = 5000. The basis for this method is the measurements of the full 3-D correlation tensor for all components acr oss the width of the wake. Using this large data base, events contribu ting most to the Reynolds stress are identified and the most likely en semble-averaged structures corresponding to these events are reconstru cted using the stochastic estimation procedure. This powerful techniqu e offers the distinct advantage that multi-point conditional averages can readily be estimated. An extension of this multi-point conditional average estimation is presented in this paper in the form of a pseudo -dynamic reconstruction of the flow field. To that effect, measured ti me sequences of ''conditions'' at several points in the wake are used to estimate the three-dimensional structures most likely associated wi th these events, hence providing a useful tool to reconstruct the evol ution of the large-scale flow structures.