A new correlation-based transition model has been developed, which is built strictly on local variables. As a result, the transition model is compatible with modern computational fluid dynamics techniques such as unstructured grids and massively parallel execution. The model is based on two transport equations, one for intermittency and one for a transition onset criterion in terms of momentum-thickness Reynolds number. A number of validation papers have been published on the basic formulation of the model. However, until now the full model correlations have not been published. The main goal of the present paper is to publish the full model and release it to the research community so that it can continue to be further validated and possibly extended or improved. Included in this paper are a number of test cases that can be used to validate the implementation of the model in a given computational fluid dynamics code. The authors believe that the current formulation is a significant step forward in engineering transition modeling, as it allows the combination of transition correlations with general-purpose computational fluid dynamics codes. There is a strong potential that the model will allow the first-order effects of transition to be included in everyday industrial computational fluid dynamics simulations.

Correlation-Based Transition Modeling for Unstructured Parallelized Computational Fluid Dynamics Codes

Comparative analysis of turbulence models for the aerodynamic simulation of H-Darrieus rotors

An intermittency model that is formulated in local variables is proposed for representing bypass transition in Reynolds-Averaged Navier-Stokes (RANS) computations. No external data correlation is used to fix transition. Transition is initiated by diffusion, and a source term carries it to completion. A sink term is created to predict the laminar region before transition, then it vanishes in the turbulent region. Both the source and sink are functions of a wall-distance Reynolds number and turbulence scale. A modification is introduced to predict transition in separated boundary layers. The transition model is incorporated with the k−ω RANS model. The present model is implemented into a general purpose, computational fluid dynamics (CFD) code. The model is validated with several test cases. Decent agreement with the available data is observed in a range of flows.

A Bypass Transition Model Based on the Intermittency Function

Currently available methods of computing the laminar–turbulent transition (LTT), including methods used in gas-dynamic software packages, are analyzed from the viewpoint of LTT simulation accuracy.

Engineering modeling of the laminar–turbulent transition: Achievements and problems (Review)

The correlation-based γ-Reθ transition model has been implemented into a hybrid Reynolds-averaged Navier-Stokes solver and evaluated on various test cases. The original model formulation and recently published approaches of different authors for relevant empirical model functions as well as different transition criteria are compared. The prediction of transition with the correlation-based model was applied to a zero pressure gradient flat plate test case and some well known one -element airfoil test cases. Comparison with the standard approach for transition prediction in the flow solver used based on the e N method was accomplished. Simulation results in terms of transition locations and skin friction coefficient distributions , performance and arising difficulties of both models for the various test cases are presented and discussed.

Evaluation of a Correlation-Based Transition Model and Comparison with the eN Method

A new correlation-based transition model has been developed, which is based strictly on local variables. As a result, the transition model is compatible with modern computational fluid dynamics (CFD) approaches, such as unstructured grids and massive parallel execution. The model is based on two transport equations, one for intermittency and one for the transition onset criteria in terms of momentum thickness Reynolds number. The proposed transport equations do not attempt to model the physics of the transition process (unlike, e.g., turbulence models) but from a framework for the implementation of correlation-based models into general-purpose CFD methods.

Robin Blair Langtry

Papers

A correlation-based transition model using local variables for unstructured parallelized CFD codes