scholarly journals On the Navier-Stokes Calculation of Separation Bubbles With a New Transition Model

1996 ◽  
Author(s):  
Wolfgang Sanz ◽  
Max F. Platzer
Keyword(s):  
Navier Stokes ◽  
Transition Model ◽  
Compressor Cascade ◽  
Laminar Separation ◽  
Turbulent Transition ◽  
Separation Bubbles ◽  
Turbomachinery Blades ◽  
Naca 0012 ◽  
Onset Location ◽  
Laminar Separation Bubbles

Laminar separation bubbles are commonly observed on turbomachinery blades and therefore require effective methods for their prediction. Therefore, a newly developed transition model by Gostelow et al. (1995) is incorporated into an upwind-biased Navier-Stokes code to simulate laminar-turbulent transition in the boundary layer. A study of the influence of the two adjustable parameters of the model, the transition onset location and the spot generation rate, is conducted and it is found that it can predict laminar separation bubbles, measured on a NACA 0012 airfoil. Additional results are presented for separation bubbles in an annular compressor cascade.

On the Navier–Stokes Calculation of Separation Bubbles With a New Transition Model

1998 ◽  
Vol 120 (1) ◽  
pp. 36-42 ◽  
Author(s):  
W. Sanz ◽  
M. F. Platzer
Keyword(s):  
Navier Stokes ◽  
Transition Model ◽  
Compressor Cascade ◽  
Laminar Separation ◽  
Turbulent Transition ◽  
Separation Bubbles ◽  
Turbomachinery Blades ◽  
Naca 0012 ◽  
Onset Location ◽  
Laminar Separation Bubbles

Laminar separation bubbles are commonly observed on turbomachinery blades and therefore require effective methods for their prediction. Therefore, a newly developed transition model by Gostelow et al. (1996) is incorporated into an upwind-biased Navier–Stokes code to simulate laminar—turbulent transition in the boundary layer. A study of the influence of the two adjustable parameters of the model, the transition onset location and the spot generation rate, is conducted and it is found that it can predict laminar separation bubbles, measured on a NACA 0012 airfoil. Additional results are presented for separation bubbles in an annular compressor cascade.

scholarly journals On the Calculation of Laminar Separation Bubbles Using Different Transition Models

1997 ◽  
Author(s):  
Wolfgang Sanz ◽  
Max F. Platzer
Keyword(s):  
Transition Process ◽  
Navier Stokes ◽  
Laminar Separation ◽  
Controlled Diffusion ◽  
Laminar To Turbulent Transition ◽  
Turbulent Transition ◽  
Separation Bubbles ◽  
Turbomachinery Blades ◽  
Transition Models ◽  
Laminar Separation Bubbles

Laminar separation bubbles are commonly observed on turbomachinery blades and therefore require effective methods for their prediction. The location and size of the bubbles is critically dependent on the laminar-to-turbulent transition process. Therefore, in this paper the transition models of Solomon et al., Abu-Ghannam & Shaw, Mayle, Calvert, and Choi & Kang are incorporated into an upwind-biased Navier-Stokes solver and the computed results are compared with the measurements of Elazar & Shreeve in a cascade with controlled-diffusion blades. It is found that none of the models predicts the measured bubbles very well, although most of them give reasonable results as long as transition is predicted to occur within the bubble.

scholarly journals Characteristics and Effects of Laminar Separation Bubbles on NREL S809 Airfoil Using the γ - R e θ Transition Model

2020 ◽  
Vol 10 (17) ◽  
pp. 6095
Author(s):  
Jang-oh Mo ◽  
Beom-seok Rho
Keyword(s):  
Wind Tunnel ◽  
Wind Turbine ◽  
Leading Edge ◽  
Aerodynamic Performance ◽  
Transition Model ◽  
Clear Understanding ◽  
Airfoil Surface ◽  
Laminar Separation ◽  
Separation Bubbles ◽  
Laminar Separation Bubbles

Understanding the characteristics and effects of the laminar separation bubbles (LSBs) is important in the aerodynamic design of wind turbine airfoils for maximizing wind turbine efficiency. In the present study, numerical simulations using the γ-Reθ transition model were performed to analyze the flow structure of LSBs around a 21% thick NREL S809 airfoil. The simulation results obtained from the γ-Reθ transition model and the standard k-ε model for the aerodynamic coefficients at various angles of attack (AoAs) were compared with the wind tunnel data acquired from the Delft University 1.8 m × 1.25 m low-turbulence wind tunnel. When the AoA increased, the bubble on the suction airfoil surface was found to move closer to the leading edge owing to an earlier laminar separation (LS). Furthermore, the transition onset (TO) points were shown to occur right after separation, thus causing an abrupt increase in turbulence intensity (TI) and forming different bubble extents with increasing AoAs. Consequently, the transition model-based approaches can provide a clear understanding of the characteristics and effects of the LSB on airfoil aerodynamic performance. The findings of this study can provide important insights into redesigning an airfoil with a reduced bubble length causing the improved aerodynamic performance.

On the Numerical Difficulties in Calculating Laminar Separation Bubbles

2002 ◽  
Author(s):  
Wolfgang Sanz ◽  
Max F. Platzer
Keyword(s):  
Numerical Study ◽  
Separation Bubble ◽  
Turbine Blades ◽  
Turbulence Models ◽  
Separated Flow ◽  
Transition Model ◽  
Laminar Separation ◽  
Separation Bubbles ◽  
Transition Models ◽  
Laminar Separation Bubbles

Behaviour of laminar separation bubbles on the surfaces of compressor and turbine blades has increasingly attracted the attention of researchers and designers of turbomachinery in the last years. For the numerical investigation of laminar separation bubbles transition models are implemented into Navier-Stokes flow solvers to predict their location, extent and behaviour accurately. Several researchers conducted comparative studies to investigate the applicability of different transition models for separated-flow transition. In this work a comprehensive numerical study is carried out to investigate not only the influence of the transition model, but of the solution method in general on laminar separation bubble prediction. The flow around a NACA 0012 airfoil at different angles of attack where laminar separation bubbles were observed in experiments is chosen as test case. Different flow solvers (Osher and Roe scheme), different turbulence models as well as different solution procedures were applied together with transition models. The results show that besides the transition model other parameters like the discretisation scheme of the turbulence model or the flow solver have a comparably large influence on the computational result.

Transition mechanisms in laminar separation bubbles with and without incoming wakes and synthetic jet effects

2012 ◽  
Vol 53 (1) ◽  
pp. 173-186 ◽  
Author(s):  
Daniele Simoni ◽  
Marina Ubaldi ◽  
Pietro Zunino ◽  
Francesco Bertini
Keyword(s):  
Synthetic Jet ◽  
Laminar Separation ◽  
Separation Bubbles ◽  
Laminar Separation Bubbles
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