Modeling of Turbulent Flows in Rectangular Ducts Using OpenFOAM

The present work aims to verify the applicability of Irwin probes and Preston tubes to turbulent incompressible flow in smooth rectangular ducts. For the experimental apparatus, an aspect ratio of 1:2 is considered and tests are conducted for Reynolds number values within the range of 104 to 9 × 104. Local friction coefficients are determined based on the pressure measurements obtained using pressure taps and a Preston tube. A linear relation is established between the local wall shear stress \( (\tau_{{w_{x} }} ) \) and the pressure difference \( {(\Delta }p_{I} ) \) measured with the Irwin probes. The numerical simulations implemented in the open source OpenFOAM® 2.4.0 CFD toolbox are benchmarked against ANSYS CFX results, and the two sets are compared against the experimental results. A viscous sub-layer formulation was used, with y+ ≈ 1 for the mesh. Although the focus of the present study is to investigate constant section ducts, some preliminary results for variable section ducts are also presented. Two representative cases—convergent with 1° slope (C1) and divergent with 1° slope (D1)—were selected. The Preston tube measurements are in good agreement with the numerical results and within the expected accuracy of the experimental results obtained under adverse pressure gradient conditions.