FUSION RULES IN NAVIER-STOKES TURBULENCE - FIRST EXPERIMENTAL TESTS

We present the first experimental tests of the recently derived fusion rules for Navier-Stokes turbulence. The fusion rules address the asym ptotic properties of many-point correlation functions as some of the c oordinates coalesce. and form an important ingredient of the nonpertur bative statistical theory of turbulence. Here we test the fusion rules when the spatial separations lie within the inertial range, and find good agreement between experiment and theory. For inertial-range separ ations and for velocity increments which are not too large, a simple l inear relation appears to exist for the Laplacian of the velocity fluc tuation conditioned on velocity increments. [S0031-9007(97)04425-6].