UTAT - Unsteady transitional flows in axial turbomachines
Overview
Background & policy context:
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The main goal of this project was to contribute to the improvement of global performance in turbomachinery by the means of developing new unsteady design methods. One particular key issue is the unsteady transition from laminar to turbulent flow. Laminar to turbulent transition typically occurs in LP turbines at Reynolds numbers lying between 80 000 and 300 000. It can be due to natural boundary layer development (natural transition), to turbulence diffusion from the main flow into the boundary layer (bypass transition), to unsteady effects such as wake passing along the suction side (wake induced transition) or downstream potential blade row interaction, or may be tripped by dedicated blade surface roughness elements.
Objectives:
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The original research objectives resulted from the need to improve physical understanding as well as analytical and numerical modeling capacities of this phenomenon in axial turbomachines with a special emphasis on wake or potential interaction induced transition in LP turbines.
Methodology:
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To address these issues, the project was divided into 4 main areas of interest (Work Packages) : Assessment and development of RANS-based transition models and CFD methodologies The objective is the investigation of advanced RANS/URANS and hybrid URANS/LES models to study boundary layer transition caused by wake-blade interactions, potential interactions and blade surface roughness. The outcoming developed transition-models have been distributed to the industrial partners in order to test and validate industrial CFD codes against selected test cases. Experimental investigations of the different effects causing transition.
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