Simulation of Multistage Compressor at Off-Design Conditions

2017 ◽  
Vol 140 (2) ◽  
Author(s):  
Feng Wang ◽  
Mauro Carnevale ◽  
Luca di Mare ◽  
Simon Gallimore
Keyword(s):  
Mass Flow ◽  
High Speed ◽  
Eddy Viscosity ◽  
Turbulence Models ◽  
Viscosity Model ◽  
Eddy Viscosity Model ◽  
Pressure Profiles ◽  
Multistage Compressor ◽  
Stage Matching ◽  
The Right

Computational fluid dynamics (CFD) has been widely used for compressor design, yet the prediction of performance and stage matching for multistage, high-speed machines remains challenging. This paper presents the authors' effort to improve the reliability of CFD in multistage compressor simulations. The endwall features (e.g., blade filet and shape of the platform edge) are meshed with minimal approximations. Turbulence models with linear and nonlinear eddy viscosity models are assessed. The nonlinear eddy viscosity model predicts a higher production of turbulent kinetic energy in the passages, especially close to the endwall region. This results in a more accurate prediction of the choked mass flow and the shape of total pressure profiles close to the hub. The nonlinear viscosity model generally shows an improvement on its linear counterparts based on the comparisons with the rig data. For geometrical details, truncated filet leads to thicker boundary layer on the filet and reduced mass flow and efficiency. Shroud cavities are found to be essential to predict the right blockage and the flow details close to the hub. At the part speed, the computations without the shroud cavities fail to predict the major flow features in the passage, and this leads to inaccurate predictions of mass flow and shapes of the compressor characteristic. The paper demonstrates that an accurate representation of the endwall geometry and an effective turbulence model, together with a good quality and sufficiently refined grid, result in a credible prediction of compressor matching and performance with steady-state mixing planes.

Simulation of Multi-Stage Compressor at Off-Design Conditions

2017 ◽  
Author(s):  
Feng Wang ◽  
Mauro Carnevale ◽  
Luca di Mare ◽  
Simon Gallimore
Keyword(s):  
Mass Flow ◽  
High Speed ◽  
Eddy Viscosity ◽  
Turbulence Models ◽  
Viscosity Model ◽  
Eddy Viscosity Model ◽  
Multi Stage ◽  
Pressure Profiles ◽  
Non Linear ◽  
The Right

Computational Fluid Dynamics (CFD) has been widely used for compressor design, yet the prediction of performance and stage matching for multi-stage, high-speed machines remain challenging. This paper presents the authors’ effort to improve the reliability of CFD in multistage compressor simulations. The endwall features (e.g. blade fillet and shape of the platform edge) are meshed with minimal approximations. Turbulence models with linear and non-linear eddy viscosity models are assessed. The non-linear eddy viscosity model predicts a higher production of turbulent kinetic energy in the passages, especially close to the endwall region. This results in a more accurate prediction of the choked mass flow and the shape of total pressure profiles close to the hub. The non-linear viscosity model generally shows an improvement on its linear counterparts based on the comparisons with the rig data. For geometrical details, truncated fillet leads to thicker boundary layer on the fillet and reduced mass flow and efficiency. Shroud cavities are found to be essential to predict the right blockage and the flow details close to the hub. At the part speed the computations without the shroud cavities fail to predict the major flow features in the passage and this leads to inaccurate predictions of massflow and shapes of the compressor characteristic. The paper demonstrates that an accurate representation of the endwall geometry and an effective turbulence model, together with a good quality and sufficiently refined grid result in a credible prediction of compressor matching and performance with steady state mixing planes.

Modeling Separation-Induced Transition Using a Non-Linear Three Equation Turbulence Model and a Reynolds Stress Turbulence Model

2010 ◽  
Author(s):  
Zinon Vlahostergios ◽  
Kyros Yakinthos
Keyword(s):  
Transport Equation ◽  
Reynolds Stress ◽  
Turbulence Model ◽  
Eddy Viscosity ◽  
Turbulence Models ◽  
Viscosity Model ◽  
Transitional Flows ◽  
Eddy Viscosity Model ◽  
Non Linear ◽  
Stress Models

This paper presents an effort to model separation-induced transition on a flat plate with a semi-circular leading edge, by using two advanced turbulence models, the three equation non-linear model k-ε-A2 of Craft et al. [16] and the Reynolds-stress model of Craft [13]. The mechanism of the transition is governed by the different inlet velocity and turbulence intensity conditions, which lead to different recirculation bubbles and different transition onset points for each case. The use of advanced turbulence models in predicting the development of transitional flows has shown, in past studies, good perspectives. The k-ε-A2 model uses an additional transport equation for the A2 Reynolds stress invariant and it is an improvement of Craft et al. [12] non-linear eddy viscosity model. The use of the third transport equation gives improved results in the prediction of the longitudinal Reynolds stress distributions and especially, in flows where transitional phenomena may occur. Although this model is a pure eddy-viscosity model, it borrows many aspects from the more complex Reynolds-stress models. On the other hand, the use of an advanced Reynolds-stress turbulence model, such as the one of Craft [13], can predict many complex flows and there are indications that it can be applied to transitional flows also, since the crucial terms of Reynolds stress generation are computed exactly and normal stress anisotropy is resolved. The model of Craft [13], overcomes the drawbacks of the common used Reynolds-stress models regarding the computation of wall-normal distances and vectors in order to account for wall proximity effects. Instead of these quantities, it employs “normalized turbulence lengthscale gradients” which give the ability to identify the presence of strong inhomogeneity in a flow development, in an easier way. The final results of both turbulence models showed acceptable agreement with the experimental data. In this work it is shown that there is a good potential to model separation-induced transitional flows, with advanced turbulence modeling without any additional use of ad-hoc modifications or additional equations, based on various transition models.

Full Field Algebraic Anisotropic Eddy Viscosity Model for the Film Cooling Flows

2012 ◽  
Author(s):  
Xueying Li ◽  
Jing Ren ◽  
Hongde Jiang
Keyword(s):  
Flow Field ◽  
Film Cooling ◽  
Eddy Viscosity ◽  
Turbulence Models ◽  
Viscosity Model ◽  
Wall Region ◽  
Mean Flow ◽  
Experiment Data ◽  
Anisotropic Models ◽  
Eddy Viscosity Model

The algebraic anisotropic eddy viscosity model proposed by the authors is further developed to make it suitable to the full flow field in order to focus not only in the near wall region but also in the main flow field. The three anisotropic eddy viscosity ratios for u′v′, u′w′, v′w′ are determined from the eddy viscosity hypothesis and algebraic Reynolds stress transport equations and expressed in Cartesian coordinate system. This model is applied to four isotropic two-equation turbulence models to make them anisotropic. These anisotropic models are validated with the experiment data from Sinha et al.[1]. Thorough tests are performed with all these isotropic and anisotropic turbulence models for film cooling on a flatplate with different blowing ratios. Detailed analyses of computational simulations are presented. The predicted adiabatic film cooling effectiveness and mean flow field show that the algebraic anisotropic eddy-viscosity turbulence models agree better with the experiment data. Among the four anisotropic models, the anisotropic models based on the realizable k-ε and RNG k-ε models stand out as the most promising models for flatplate film cooling predictions. It’s a big advantage of this model that it deals with the whole flow field and can be combined with different turbulence models.

Sensitization of a Transition-Sensitive Linear Eddy-Viscosity Model to Rotation and Curvature Effects

2015 ◽  
Vol 137 (3) ◽  
Author(s):  
Varun Chitta ◽  
Tej P. Dhakal ◽  
D. Keith Walters
Keyword(s):  
Transport Equation ◽  
Eddy Viscosity ◽  
Computational Cost ◽  
Turbulence Models ◽  
Viscosity Model ◽  
Flow Transition ◽  
New Model ◽  
Streamline Curvature ◽  
Curvature Effects ◽  
Eddy Viscosity Model

A new scalar eddy-viscosity turbulence model is proposed, designed to exhibit physically correct responses to flow transition, streamline curvature, and system rotation effects. The eddy-viscosity model (EVM) developed herein is based on the k–ω framework and employs four transport equations. The transport equation for a structural variable (v2) from a curvature-sensitive Shear Stress Transport (SST) k–ω–v2 model, analogous to the transverse turbulent velocity scale, is added to the three-equation transition-sensitive k–kL–ω model. The physical effects of rotation and curvature (RC) enter the model through the added transport equation. The new model is implemented into a commercial computational fluid dynamics (CFD) solver and is tested on a number of flow problems involving flow transition and streamline curvature effects. The results obtained from the test cases presented here are compared with available experimental data and several other Reynolds-Averaged Navier-Stokes (RANS) based turbulence models. For the cases tested, the new model successfully resolves both flow transition and streamline curvature effects with reasonable engineering accuracy, for only a small increase in computational cost. The results suggest that the model has potential as a practical tool for the prediction of flow transition and curvature effects over blunt bodies.

scholarly journals On the extension of the eddy viscosity model to compressible flows

2014 ◽  
Vol 26 (4) ◽  
pp. 041702 ◽  
Author(s):  
M. Germano ◽  
A. Abbà ◽  
R. Arina ◽  
L. Bonaventura
Keyword(s):  
Compressible Flows ◽  
Eddy Viscosity ◽  
Viscosity Model ◽  
Eddy Viscosity Model

Improved compressor corner separation prediction using the quadratic constitutive relation

2017 ◽  
Vol 231 (7) ◽  
pp. 618-630 ◽  
Author(s):  
Xinrong Su ◽  
Xin Yuan
Keyword(s):  
Constitutive Relation ◽  
Eddy Viscosity ◽  
Pressure Coefficient ◽  
Momentum Equation ◽  
Viscosity Model ◽  
Corner Separation ◽  
Pressure Loss Coefficient ◽  
Eddy Viscosity Model ◽  
Relation Model ◽  
Separation Size

This work presents the implementation and study of the quadratic constitutive relation nonlinear eddy-viscosity model with representative compressor application, for which the corner separation has been poorly predicted with the widely used linear Boussinesq eddy-viscosity model. With the introduction of the Reynolds stress anisotropy, the secondary flow of the second kind and its effect on the corner flow can be well captured and this results in greatly improved prediction of pressure coefficient, total pressure loss coefficient and the corner separation size. Without the quadratic constitutive relation model, the separation size and loss are generally over-estimated. The mechanism of the improvement is studied using both the vortex dynamics and the momentum equation. It is proved that quadratic constitutive relation model consumes low CPU time and provides much improved compressor corner separation prediction without worsening the convergence property.

Sign in / Sign up

Export Citation Format

Share Document