Implicit Large Eddy Simulation of a Stalled Low-Pressure Turbine Airfoil

2016 ◽  
Vol 138 (7) ◽  
Author(s):  
C. L. Memory ◽  
J. P. Chen ◽  
J. P. Bons
Keyword(s):  
Flow Field ◽  
Large Eddy Simulation ◽  
Separation Zone ◽  
Low Pressure ◽  
Numerical Code ◽  
Flow Measurements ◽  
Low Pressure Turbine ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Implicit Large Eddy Simulation

Time-accurate numerical simulations were conducted on the aft-loaded L1A low-pressure turbine airfoil at a Reynolds number of 22,000 (based on inlet velocity magnitude and axial chord length). This flow condition produces a nonreattaching laminar separation zone on the airfoil suction surface. The numerical code TURBO is used to simulate this flow field as an implicit large eddy simulation (ILES). Generally, good agreement was found when compared to experimental time-averaged and instantaneous flow measurements. The numerical separation zone is slightly larger than that in the experiments, though integrated wake loss values improved from Reynolds-averaged Navier–Stokes (RANS)-based simulations. Instantaneous snapshots of the numerical flow field showed the Kelvin Helmholtz instability forming in the separated shear layer and a large-scale vortex shedding pattern at the airfoil trailing edge. These features were observed in the experiments with similar sizes and vorticity levels. Power spectral density analyses revealed a global passage oscillation in the numerics that was not observed experimentally. This oscillation was most likely a primary resonant frequency of the numerical domain.

Implicit Large Eddy Simulation of a Stalled Low Pressure Turbine Airfoil

2015 ◽  
Author(s):  
C. L. Memory ◽  
J. P. Chen ◽  
J. P. Bons
Keyword(s):  
Flow Field ◽  
Large Eddy Simulation ◽  
Separation Zone ◽  
Low Pressure ◽  
Numerical Code ◽  
Flow Measurements ◽  
Low Pressure Turbine ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Implicit Large Eddy Simulation

Time-accurate numerical simulations were conducted on the aft-loaded L1A low pressure turbine airfoil at a Reynolds number of 22,000 (based on inlet velocity magnitude and axial chord length). This flow condition produces a non-reattaching laminar separation zone on the airfoil suction surface. The numerical code TURBO is used to simulate this flow field as an Implicit Large Eddy Simulation. Generally good agreement was found when compared to experimental time-averaged and instantaneous flow measurements. The numerical separation zone is slightly larger than that in the experiments, though integrated wake loss values improved from RANS-based simulations. Instantaneous snapshots of the numerical flow field showed the Kelvin Helmholtz instability forming in the separated shear layer and a large-scale vortex shedding pattern at the airfoil trailing edge. These features were observed in the experiments with similar sizes and vorticity levels. Power spectral density analyses revealed a global passage oscillation in the numerics that was not observed experimentally. This oscillation was most likely a primary resonant frequency of the numerical domain.

Large Eddy Simulation of a Low Pressure Turbine Cascade

2003 ◽  
Author(s):  
Yoshinori Ooba ◽  
Hidekazu Kodama ◽  
Chuichi Arakawa ◽  
Yuichi Matsuo ◽  
Hitoshi Fujiwara ◽  
...  
Keyword(s):  
Large Eddy Simulation ◽  
Low Pressure ◽  
Turbine Cascade ◽  
Low Pressure Turbine ◽  
Eddy Simulation ◽  
Large Eddy

Large Eddy Simulation and CDNS Investigation of T106C Low-Pressure Turbine

2017 ◽  
Vol 140 (1) ◽  
Author(s):  
Site Hu ◽  
Chao Zhou ◽  
Zhenhua Xia ◽  
Shiyi Chen
Keyword(s):  
Large Eddy Simulation ◽  
Flow Separation ◽  
Separated Flow ◽  
Low Pressure ◽  
Secondary Flows ◽  
Computational Domain ◽  
Suction Surface ◽  
Low Pressure Turbine ◽  
Eddy Simulation ◽  
Large Eddy

This study investigates the aerodynamic performance of a low-pressure turbine, namely the T106C, by large eddy simulation (LES) and coarse grid direct numerical simulation (CDNS) at a Reynolds number of 100,000. Existing experimental data were used to validate the computational fluid dynamics (CFD) tool. The effects of subgrid scale (SGS) models, mesh densities, computational domains and boundary conditions on the CFD predictions are studied. On the blade suction surface, a separation zone starts at a location of about 55% along the suction surface. The prediction of flow separation on the turbine blade is always found to be difficult and is one of the focuses of this work. The ability of Smagorinsky and wall-adapting local eddy viscosity (WALE) model in predicting the flow separation is compared. WALE model produces better predictions than the Smagorinsky model. CDNS produces very similar predictions to WALE model. With a finer mesh, the difference due to SGS models becomes smaller. The size of the computational domain is also important. At blade midspan, three-dimensional (3D) features of the separated flow have an effect on the downstream flows, especially for the area near the reattachment. By further considering the effects of endwall secondary flows, a better prediction of the flow separation near the blade midspan can be achieved. The effect of the endwall secondary flow on the blade suction surface separation at the midspan is explained with the analytical method based on the Biot–Savart Law.

The Effects of Periodic Wakes on Boundary Layer Separation of Low-Pressure Turbine Using Large Eddy Simulation

2016 ◽  
Author(s):  
Xiaodi Wu ◽  
Fu Chen ◽  
Yunfei Wang
Keyword(s):  
Boundary Layer ◽  
Flow Field ◽  
Boundary Layer Separation ◽  
Low Pressure ◽  
Layer Separation ◽  
Low Pressure Turbine ◽  
Eddy Simulation ◽  
Instantaneous Flow Field ◽  
Large Eddy ◽  
Scale Structures

For low-pressure turbine, the unsteady disturbances are dominated by relative motions between rotors and stators and the unsteady flow is closely associated with aerodynamic efficiency of low-pressure turbine and engine performance. One of its most important manifestations is the boundary layer separation on the turbine blades by the passing wakes produced by upstream rows of blades. Hence, accurate prediction of the flow physics at low Reynolds number conditions is required to effectively implement flow control techniques which can help mitigate separation induced losses. The present paper concentrates on simulations for boundary layer separation of low-pressure turbine cascade under periodic wakes. In this paper, a multiblock computational fluid dynamics (CFD) code of compressible N-S equations is developed for predicting the phenomenon of boundary layer separation, transition and reattachment using large eddy simulation (LES) in the field of turbomachinery. The large-scale structures can be directly obtained from the solution of the filtered Naiver-Strokes equations and the small-scale structures are modeled by dynamic subgrid-scale model of turbulence. Firstly, unsteady boundary layer separation on a flat plate with adverse pressure gradient is simulated under periodic inflow. The time-averaged field, the phase-averaged field and the instantaneous flow field are presented and analyzed. The separation bubble becomes unstable and the location of transition moves back and forth due to vortex shedding. Secondly, a stator of turbomachinery which is influenced by wakes periodically passing is simulated. The results of the numerical simulations are discussed and compared with experimental data. For the instantaneous flow field, it seems that the spanwise vortices induced by upstream wakes are the primary reason of the initial roll-up of the shear layer and the Kelvin-Helmholtz instability plays an important role in the transition to turbulence which is observed in the separated flow.

Large-Eddy Simulation of Transitional Flow Through a Low-Pressure Turbine Cascade

2006 ◽  
Author(s):  
Shirdish Poondru ◽  
Urmila Ghia ◽  
Karman Ghia
Keyword(s):  
Large Eddy Simulation ◽  
Air Force ◽  
Time Integration ◽  
Low Pressure ◽  
Transitional Flow ◽  
Low Pressure Turbine ◽  
Compact Difference ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Flow Through

Subsonic, transitional flow through a low-pressure turbine (LPT) cascade is investigated using high-order compact difference scheme in conjunction with large-eddy simulation (LES). Three-dimensional simulations are performed at chord inlet Reynolds numbers (Re) of 25,000 and 50,000. The inlet Mach number is approximately 0.06. An MPI-based higher-order accurate, Chimera version of the FDL3DI flow solver developed by the Air Force Research Laboratory at Wright Patterson Air Force base, is extended for the present turbomachinery application. The implicit solver is based on an approximate factored time-integration method of Beam and Warming. Fourth-order compact-difference formulations are used for discretizing spatial derivatives in conjunction with sixth-order non-dispersive filtering. Solutions are obtained both with and without a sub-grid scale (SGS) model. A dual topology, 16-block, structured grid generated using GridPro is utilized for all simulations. The flow features are examined, and the results for both LES approaches are compared to each other, and with experimental data.

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