Influence of small-amplitude undulations on turbulent convection in an axisymmetric pipe flow - Experiments and numerical prediction

The influence of small-amplitude undulations on the turbulent flow in an axisymmetric pipe is studied experimentally and with a numerical model based on the concept of turbulent viscosity. Cross sectional variations, wall curvature, and reverse currents profoundly change the flow structure. The computational model has been extended to predict the thermal convection. The results obtained for the coefficients of local transfer and for the global properties show that the Reynolds analogy fails because of the complexity of the flow.