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.

A Four-Equation Eddy-Viscosity Approach for Modeling Bypass Transition

2014 ◽  
Vol 6 (4) ◽  
pp. 523-538
Author(s):  
Guoliang Xu ◽  
Song Fu
Keyword(s):  
Kinetic Energy ◽  
Transport Equation ◽  
Eddy Viscosity ◽  
Turbulent Viscosity ◽  
Transitional Region ◽  
Transition Model ◽  
Bypass Transition ◽  
Turbulence Transition ◽  
Sst Turbulence Model ◽  
Layer Flow

AbstractIt is very important to predict the bypass transition in the simulation of flows through turbomachinery. This paper presents a four-equation eddy-viscosity turbulence transition model for prediction of bypass transition. It is based on the SST turbulence model and the laminar kinetic energy concept. A transport equation for the non-turbulent viscosity is proposed to predict the development of the laminar kinetic energy in the pre-transitional boundary layer flow which has been observed in experiments. The turbulence breakdown process is then captured with an intermittency transport equation in the transitional region. The performance of this new transition model is validated through the experimental cases of T3AM, T3A and T3B. Results in this paper show that the new transition model can reach good agreement in predicting bypass transition, and is compatible with modern CFD software by using local variables.

scholarly journals Turbulent Kinetic Energy Production in the Vane of a Low-Pressure Linear Turbine Cascade with Incoming Wakes

2015 ◽  
Vol 2015 ◽  
pp. 1-15 ◽  
Author(s):  
V. Michelassi ◽  
J. G. Wissink
Keyword(s):  
Boundary Layer ◽  
Kinetic Energy ◽  
Large Eddy Simulation ◽  
Turbulent Kinetic Energy ◽  
Suction Side ◽  
Low Pressure ◽  
Eddy Simulation ◽  
Transition Mechanism ◽  
Principal Axes ◽  
Large Eddy

Incompressible large eddy simulation and direct numerical simulation of a low-pressure turbine atRe=5.18×104and1.48×105with discrete incoming wakes are analyzed to identify the turbulent kinetic energy generation mechanism outside of the blade boundary layer. The results highlight the growth of turbulent kinetic energy at the bow apex of the wake and correlate it to the stress-strain tensors relative orientation. The production rate is analytically split according to the principal axes, and then terms are computed by using the simulation results. The analysis of the turbulent kinetic energy is followed both along the discrete incoming wakes and in the stationary frame of reference. Both direct numerical and large eddy simulation concur in identifying the same production mechanism that is driven by both a growth of strain rate in the wake, first, followed by the growth of turbulent shear stress after. The peak of turbulent kinetic energy diffuses and can eventually reach the suction side boundary layer for the largest Reynolds number investigated here with higher incidence angle. As a consequence, the local turbulence intensity outside the boundary layer can grow significantly above the free-stream level with a potential impact on the suction side boundary layer transition mechanism.

scholarly journals IWC Analysis of Turbulent Plume Fires

2021 ◽  
Vol 65 (2-4) ◽  
pp. 196-200
Author(s):  
Francesco S. Ciani ◽  
Paolo Bonfiglio ◽  
Stefano Piva
Keyword(s):  
Spectral Analysis ◽  
Kinetic Energy ◽  
Turbulent Kinetic Energy ◽  
Power Law ◽  
Grid Size ◽  
Energy Spectra ◽  
Test Case ◽  
Wavenumber Domain ◽  
Taylor’S Hypothesis ◽  
Turbulent Plume

Plumes fires are characterized by a turbulent nature with a large number of different scales. LES is used to solve the largest structures and to model the smallest ones. Grid size and time steps become decisive to place a limit between solved and modelled turbulence. A spectral analysis, both in frequency and wavenumber domain of the specific turbulent kinetic energy is an instrument to check for the information investigated. Unfortunately, the spectra in the wavenumber domain can be difficult to achieve adequately, because the specific turbulent kinetic energy values should be available in many points. This issue can be overcome by identifying a correlation law between frequencies and wavenumbers. An approach to identify this correlation law can be to adopt the IWC method. Here, for a test case of a turbulent reacting plume of burning propane, specific turbulent kinetic energy is analysed both in frequency and wavenumber and a correlation law between them is identified by using the IWC method. A study has been performed to evaluate the grid dependency of the specific turbulent kinetic energy spectra, by assessing the extension of the Kolmogorov power law region. The correlation results are discussed and compared with the Taylor’s hypothesis.

scholarly journals On the influence of turbulent kinetic energy level on accuracy of k − ε and LRR turbulence models

2018 ◽  
Vol 45 (2) ◽  
pp. 139-149
Author(s):  
Djordje Novkovic ◽  
Jela Burazer ◽  
Aleksandar Cocic ◽  
Milan Lecic
Keyword(s):  
Kinetic Energy ◽  
Theoretical Analysis ◽  
Turbulent Kinetic Energy ◽  
Turbulent Flows ◽  
Cross Sections ◽  
Turbulence Models ◽  
Velocity Profiles ◽  
Navier Stokes ◽  
Test Case ◽  
Reynolds Stresses

This paper presents research regarding the influence of turbulent kinetic energy (TKE) level on accuracy of Reynolds averaged Navier?Stokes (RANS) based turbulence models. A theoretical analysis of influence TKE level on accuracy of the RANS turbulence models has been performed according to the Boussinesq hypothesis definition. After that, this theoretical analysis has been investigated by comparison of numerically and experimentally obtained results on the test case of a steady-state incompressible swirl-free flow in a straight conical diffuser named Azad diffuser. Numerical calculations have been performed using the OpenFOAM CFD software and first and secondorder closure turbulence models. TKE level, velocity profiles and Reynolds stresses have been calculated downstream in four different cross sections of the diffuser. Certain conclusions about modeling turbulent flows by ?? ??? and LRR turbulence models have been made by comparing the velocity profiles, TKE distribution and Reynolds stresses on the selected cross sections.

Improved Turbulence and Transition Prediction for Turbomachinery Flows

2014 ◽  
Author(s):  
Christoph Bode ◽  
Thorben Aufderheide ◽  
Jens Friedrichs ◽  
Dragan Kožulović
Keyword(s):  
Turbulence Model ◽  
Guide Vane ◽  
Cross Flow ◽  
Test Case ◽  
Transition Model ◽  
Additional Element ◽  
Flow Solver ◽  
Transition Prediction ◽  
Turbulence Decay ◽  
Improved Model

A correlation based approach for estimation of the turbulence length scale lT at the inflow boundary is proposed and presented. This estimation yields reasonable turbulence decay, supporting the transition model in accurately predicting the laminar-turbulent transition location and development. As an additional element of the approach, the sensitivity of the turbulence model to free stream values is suppressed by limiting the eddy viscosity in non-viscous regions. Therefore a criterion to detect those regions, based only on local variables, is derived. The method is implemented in DLR’s turbomachinery flow solver TRACE in the framework of the k–ω turbulence model by Wilcox 1988 [1] and the γ–Reθ transition model by Langtry and Menter [2] in combination with a cross flow (CF) induced transition criterion after Müller [3]. The improved model is tested to the T161 turbine test case [4], [5] and validated at the Durham turbine Cascade [6] and an outlet guide vane for low pressure turbine configurations [7].

A new model for the CBL growth based on the turbulent kinetic energy equation

2007 ◽  
Vol 7 (5) ◽  
pp. 409-419 ◽  
Author(s):  
Antonio G. Goulart ◽  
Davidson M. Moreira ◽  
Marco T. Vilhena ◽  
Gervásio A. Degrazia ◽  
Sergej S. Zilitinkevich
Keyword(s):  
Kinetic Energy ◽  
Turbulent Kinetic Energy ◽  
Energy Equation ◽  
New Model ◽  
Turbulent Kinetic Energy Equation

Probability law of turbulent kinetic energy in the atmospheric surface layer

2021 ◽  
Vol 6 (7) ◽  
Author(s):  
Mohammad Allouche ◽  
Gabriel G. Katul ◽  
Jose D. Fuentes ◽  
Elie Bou-Zeid
Keyword(s):  
Surface Layer ◽  
Kinetic Energy ◽  
Turbulent Kinetic Energy ◽  
Atmospheric Surface Layer
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