Direct numerical simulation of turbulent flow in a sudden pipe expansion
Abstract
Direct numerical simulations (DNS) of fully developed turbulent pipe flow and sudden pipe expansion flow with an expansion ratio of ER = 1.2 have been performed. The former DNS provides inflow conditions for the latter. The upstream Reynolds number, based on friction velocity and pipe diameter is 360 or 6950 based on mean centerline velocity. This is too low a Reynolds number to obtain a universal logarithmic law of the wall. Moreover, transverse curvature effects are observed when the data are compared with DNS data of Kim, Moin, Moser in the plane channel. The reason for these effects is that the streak spacing is of the same order of magnitude as the pipe radius. Hence, the pipe expansion flow will also reflect transverse curvature effects. The mean reattachment length is 10.1 step heights. Instantaneous and statistical flow variables are presented. They give an impression of the complex flow dynamics in the free shear layer, the recirculation and reattachment regions.
 Publication:

In AGARD
 Pub Date:
 December 1994
 Bibcode:
 1994adle.agar.....W
 Keywords:

 Channel Flow;
 Computational Fluid Dynamics;
 Computerized Simulation;
 Expansion;
 Low Reynolds Number;
 Mixing Layers (Fluids);
 Pipe Flow;
 Shear Layers;
 Turbulence Models;
 Turbulent Flow;
 Wall Flow;
 Boundary Conditions;
 Computational Grids;
 Curvature;
 Flow Distribution;
 Flow Resistance;
 NavierStokes Equation;
 Shear Stress;
 Stress Tensors;
 Velocity Distribution;
 Fluid Mechanics and Heat Transfer