Some properties of the large structure in a fully developed turbulent duct flow

Abstract

Some characteristic features of the large scale in a fully developed, two-dimensional, turbulent duct flow have been investigated with the use of a wall shear stress probe and a single hot wire, traversed across the duct. From space-time correlation measurements of wall shear stress and velocity fluctuations, the large scale structure is observed to be inclined at an angle of about 13° for y/d ≳ 0.15, where d is the duct half-width. The convection speed Uc of wall shear stress fluctuations is equal to 0.62 U0 for Rd ≳ 3.5×104, where U0 is the center-line velocity and Rd is the Reynolds number based on center-line velocity and duct half-width. The convection speed of velocity fluctuations is approximately constant over a wide range of Reynolds numbers. The integral length scale of wall shear stress fluctuations is nearly 0.38d. Joint probability density functions of velocity and wall shear stress fluctuations are presented and discussed.