The performance characteristics of four different axisymmetric contraction shapes with the same contraction ratio are experimentally investigated for incompressible flow. The pre- and postcontraction mean and turbulent velocity profiles and spectra, and the variation of the mean and turbulent velocities along the axis as a function of local contraction ratio and axial length are presented in this paper. The results show that all the nozzles are of essentially equal effectiveness as far as the core flow in the exit plane is concerned. But the mean and turbulence characteristics of the exit boundary layer, the upstream influence of the contraction, and the departure from equipartition within the nozzle vary significantly with the contraction shape. The data demonstrate the inadequacy of the Batchelor-Proudman-Ribner-Tucker theory in predicting the effect of a contraction on the turbulence structure. These data are of interest in wind tunnel and nozzle design, and in boundary layer prediction.
Experiments on reverse transition were conducted in two-dimensional accelerated incompressible turbulent boundary layers. Mean velocity profiles, longitudinal velocity fluctuations $\tilde{u}^{\prime}(=(\overline{u^{\prime 2}})^{\frac{1}{2}})$ and the wall-shearing stress (TW) were measured. The mean velocity profiles show that the wall region adjusts itself to laminar conditions earlier than the outer region. During the reverse transition process, increases in the shape parameter (H) are accompanied by a decrease in the skin friction coefficient (Cf). Profiles of turbulent intensity (u’2) exhibit near similarity in the turbulence decay region. The breakdown of the law of the wall is characterized by the parameter
\[
\Delta_p (=\nu[dP/dx]/\rho U^{*3}) = - 0.02,
\]
where U* is the friction velocity. Downstream of this region the decay of $\tilde{u}^{\prime}$ fluctuations occurred when the momentum thickness Reynolds number (R) decreased roughly below 400.
In the wake of a rectangular cylinder measurements of mean velocity and some turbulent stresses are carried out in a straight duct and in a curved duct. The difference in turbulent quantities in the wake of the body, in the straight duct an in the curved duct is significant especially in the downstream side of the wake. The shear stresses are more sensitive to curvature than the normal stresses.
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