This book provides the intermittency equation that is derived a priori. Since the intermittency equation is mathematically obtained, the resulting gamma transition model no longer requires any extra parameters and terms to explicitly account for free-stream turbulence and pressure gradient like the previous transition models.
Instead, the present gamma transition model can naturally predict natural transition and effects of free-stream turbulence and pressure gradient on the transition process. Furthermore, the present gamma transition model requires much fewer model constants than the previous transition models.
The book is beneficial for CFD researchers in industry and academia who confront modern complex applications involving simultaneously laminar, transitional and turbulent flow regimes, and ideally relevant to graduate students in applied physics, applied mathematics and engineering who are interested in the world of laminar-to-turbulent transition modeling in CFD, or would like to further advance more realistic transition models in the future.
Author(s): Ekachai Juntasaro
Series: SpringerBriefs in Applied Sciences and Technology
Publisher: Springer
Year: 2022
Language: English
Pages: 90
City: Cham
Preface
Contents
1 Introduction
1.1 Transition Model
1.2 Two-Equation Transition Model
1.3 One-Equation Transition Model
1.4 Zero-Equation or Algebraic Transition Model
1.5 Transition Mechanisms in Transition Models
1.5.1 Sensing Parameter for Transition-Onset Detection
1.5.2 Mechanism for Transition-Process Regulation
1.6 Outline of This Book
References
2 Derivation of Intermittency Equation
2.1 Basic Definition
2.2 Decomposition of Variables
2.3 Conditions for Derivation
2.4 Derivation of Equation for γoverlineui uj
2.4.1 Rate of Change
2.4.2 Convection
2.4.3 Pressure Gradient
2.4.4 Diffusion
2.4.5 Equation for γoverlineui uj
2.5 Derivation of Equation for γ
References
3 Modeling Concept and Formulation
3.1 Closure Problem of Intermittency Equation
3.2 Lower-Bound and Upper-Bound Limits of εγ
3.3 Variation of εγ in Transition Zone
3.4 Onset Location and Length of Transition
3.5 Exchange of Source-Sink Roles
3.6 Functional Form of fONSET
3.7 Functional Form of fLENGTH
3.8 Functional Forms of γeff and γsep
3.9 Control of Base Turbulence Model
3.10 A Complete Set of Intermittency Equation
3.11 Boundary Conditions of Intermittency Equation
References
4 Model Constant Calibration
4.1 Experimental and DNS Data for Calibration
4.2 Calibration for Bypass and Natural Transition
4.2.1 Calibration of Ccrit
4.2.2 Calibration of B
4.3 Calibration of Separation-Induced Transition
4.3.1 Calibration of Ccrit,sep
4.3.2 Calibration of Bsep
4.3.3 Calibration of CRµ
4.3.4 Calibration of Csep
4.4 Mechanism of γsep
4.5 Summary
References
5 Model Validation
5.1 Effect of Free-Stream Turbulence
5.2 Effect of Pressure Gradient
5.3 Summary
References
6 Application Test Case
6.1 V103 Compressor Cascade
6.2 S809 Wind Turbine Airfoil
6.3 Summary
References
