A Comparison of a Local Correlation-Based Transition Model Coupled with SA and SST Turbulence Models

2015 ◽  
Author(s):  
Jingyu Wang ◽  
Chunhua Sheng
Keyword(s):  
Turbulence Models ◽  
Transition Model ◽  
Local Correlation

Influence of Marine Propeller Geometry on Turbulence Model Selection for CFD Simulations

2021 ◽  
Vol 55 (2) ◽  
pp. 150-164
Author(s):  
Mohamed R. Shouman ◽  
Mohamed M. Helal
Keyword(s):  
Turbulent Flows ◽  
Small Diameter ◽  
Turbulence Models ◽  
Dynamics Simulation ◽  
Geometrical Parameters ◽  
Test Case ◽  
Transition Model ◽  
Transient Flows ◽  
Marine Propellers ◽  
Numerical Predictions

Abstract One of the big challenges yet to be addressed in the numerical simulation of wetted flow over marine propellers is the influence of propellers' geometry on the selection of turbulence models. Since the Reynolds number is a function of the geometrical parameters of the blades, the flow type is controlled by these parameters. The majority of previous studies employed turbulence models that are only appropriate for fully turbulent flows, and consequently, they mostly caused high discrepancy between numerical predictions and corresponding experimental measurements specifically at geometrical parameters generating laminar and transient flows. The present article proposes a complete procedure of computational fluid dynamics simulation for wetted flows over marine propellers using ANSYS FLUENT 16 and employing both transition-sensitive and fully turbulent models for comparison. The K-Kl-ω transition model and the fully turbulent standard K-ε model are suggested for this purpose. The investigation is carried out for two different propellers in geometrical features: the INSEAN E779a model and the Potsdam Propeller Test Case (PPTC) model. The results demonstrate the effectiveness of the K-Kl-ω transition model for the INSEAN E779a propeller rather than the PPTC propeller. This can be interpreted as the narrow-bladed and small-diameter propellers have more likely laminar and transient flows over its blades.

Local-Correlation Based Zero-Equation Transition Model for Turbomachinery

2019 ◽  
Author(s):  
Jatinder Pal Singh Sandhu
Keyword(s):  
Kinetic Energy ◽  
Turbulent Kinetic Energy ◽  
Gamma Transition ◽  
Test Case ◽  
Transition Model ◽  
Bypass Transition ◽  
Local Correlation ◽  
New Model ◽  
Transition Prediction ◽  
Transition Mechanism

Abstract In this paper, we present a new local-correlation based zero-equation transition model. The new model, which is derived from the local-correlation based one-equation gamma transition model (Menter, F. R., Smirnov, P. E., Liu, T., and Avancha, R., A One-Equation Local Correlation-Based Transition Model, Flow, Turbulence and Combustion, vol. 95, 2015, pp. 583619.), does not require any additional equation to be solved, by defining a new variable, which captures the turbulent kinetic energy and intermittency collectively. The new model only adds three more source terms to the existing transport equation of turbulent kinetic energy. Hence the new model is straightforward to implement in already existing RANS solvers and reduces the computational memory requirement as compared to the other transition models. The transition prediction capability of the new model is tested and compared against the one-equation gamma transition model, especially for turbomachinery applications, where bypass transition is the primary transition mechanism, using a standard flat plate test case, and S809 airfoil. Preliminary results show that the new zero-equation transition model produces satisfactory results in terms of transition-location prediction.

Influence of Roughness on the Transition Modeling in Compressor Flows

2021 ◽  
Author(s):  
Vera Tolksdorf ◽  
Anubhav Gokhale ◽  
Daniel Kessler ◽  
Leroy Benjamin ◽  
Christoph Bode ◽  
...  
Keyword(s):  
Dynamic Change ◽  
Operating Cost ◽  
Turbulence Models ◽  
Boundary Layer Transition ◽  
Transition To Turbulence ◽  
Transition Model ◽  
Model Combination ◽  
Roughness Effects ◽  
Layer Transition ◽  
Transition Modeling

Abstract Engine operating cost contributes a major share to an aircraft’s direct operating cost. Thus, the knowledge of the current and future state of their engines is a major concern to any airline operator. To be able to schedule shop visits, state-of-the-art diagnostic and prognostic tools including CFD methods are employed. These RANS-based turbulence and transition models are used to predict the overall efficiency and operational behavior of the engine components. Aerofoil surfaces undergo dynamic change during operation and surface roughness increases in complex non-homogeneous ways due to corrosion, erosion, and fouling processes; depending on the engine component and the environmental condition encountered. The influence of real fouling based roughness on the boundary layer transition is investigated experimentally and numerically within this study. For this purpose, the rotor midspan from the second HPC rotor of the CFM56 is used as the basis for experimental and numerical investigations. Realistic fouling based roughness is applied and investigated both in a cascade tunnel and a low speed compressor rig. The results shown here indicate that laminar boundary layers and their transition to turbulence must be included in the RANS model combination used. Furthermore, it is necessary to consider roughness effects in the respective turbulence and transition model. While the consideration of roughness for the turbulence models has already found wide acceptance, the results in this work motivate the additional extension of the transition model to include roughness effects.

Study on Numerical Methods for Conjugate Heat Transfer Simulation of an Air Cooling Turbine

2008 ◽  
Author(s):  
Qiang Wang ◽  
Chi Zhou ◽  
Zhaoyuan Guo ◽  
Peigang Yan ◽  
Guotai Feng ◽  
...  
Keyword(s):  
Numerical Methods ◽  
Thermal Conduction ◽  
Turbulence Models ◽  
Coupling Method ◽  
Experimental Result ◽  
Computational Grids ◽  
Air Cooling ◽  
Transition Model ◽  
Cooling Air ◽  
Near Wall

The effects of several numerical methods, including computational grids, coupling method, transition model and inner cooling air flow prediction, on the conjugate simulations were studied in the research. Firstly a finite difference conjugate solver was developed. Such solver included an N-S solver and a thermal conduction module for fluid flow and solid thermal conduction, respectively. Then conjugate simulations of an air cooling turbine were carried out. There were four kinds of conjugate simulations: the first one employs different types of computational grids, including H-type grids and O-type grids, for discretizing near-wall regions in fluid zone; the second one employs different coupling methods including indirect and direct ones; the third one employs different models including the B-L and q-ω turbulence models, and the AGS transition model; and the forth one employs different turbulence models for the prediction of flows in the cooling channels. All of the numerical results have been compared to the experimental result. Finally it concludes that to accurately predict thermal and aerodynamic load of the air cooled turbine, the conjugate simulation should employ O-type girds to discretize the near wall regions in the fluid zone, use the direct coupling method to transfer data between solid and fluid domains, and utilize the transition model to predict accurate flow details within the boundary layers, and also account for flows in the cooling air channels.

A One-Equation Local Correlation-Based Transition Model

2015 ◽  
Vol 95 (4) ◽  
pp. 583-619 ◽  
Author(s):  
Florian R. Menter ◽  
Pavel E. Smirnov ◽  
Tao Liu ◽  
Ravikanth Avancha
Keyword(s):  
Transition Model ◽  
Local Correlation

A Correlation-Based Transition Model Using Local Variables: Part I — Model Formulation

2004 ◽  
Author(s):  
F. R. Menter ◽  
R. B. Langtry ◽  
S. R. Likki ◽  
Y. B. Suzen ◽  
P. G. Huang ◽  
...  
Keyword(s):  
Mathematical Formulation ◽  
Turbulence Models ◽  
Transition Process ◽  
General Purpose ◽  
Transport Equations ◽  
Parallel Execution ◽  
Test Cases ◽  
Transition Model ◽  
Significant Step ◽  
Transition Modeling

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 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 form a framework for the implementation of correlation-based models into general-purpose CFD methods. Part I (this part) of this paper gives a detailed description of the mathematical formulation of the model and some of the basic test cases used for model validation, including a 2-D turbine blade. Part II of the paper details a significant number of test cases that have been used to validate the transition model for turbomachinery and aerodynamic applications. The authors believe that the current formulation is a significant step forward in engineering transition modeling, as it allows the combination of correlation-based transition models with general purpose CFD codes.

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