On the capability of transition models to predict relaminarization

Authors

Pascal Bader - Institute for Thermal Turbomachinery and Machine Dynamics, Graz University of Technology
Paul Pieringer - Springer und Pieringer EDV Dienstleistungen OG
Wolfgang Sanz - Institute for Thermal Turbomachinery and Machine Dynamics, Graz University of Technology

Abstract

In flows along solid body surfaces the boundary layer represents the narrow zone between the wall and the free stream where viscous effects are important. Its state of flow (laminar or turbulent) may have strong impact on transport processes like wall friction and heat transfer. These processes influence the efficiency as well as the thermal stress, for example of a turbine blade, and may affect other flow characteristics in a machine as well. Under certain flow conditions (like strong acceleration), a reverse transition or relaminarization from turbulent to laminar can also occur. In this work, this type of process is numerically analyzed in order to see the capability of the the well-known γ-Re_θ; transition model in predicting relaminarization. The model is used together with the Menter SST turbulence model which are both incorporated in the in-house code LINARS. First, the behavior of the flow during acceleration is analyzed. The results of the present case are compared qualitatively to DNS and measurement results. It is shown, that the transition model successfully predicts relaminarization. Secondly it is found out, which processes inside the boundary layer are triggered by the model allowing us a better understanding how relaminarization is modeled. The objective of this work reaching a better understanding of the model parameters influencing the relaminarization prediction by the γ-Re_θ transition model will enable an effective future parameter modification in order to enhance the accuracy of the model.