Large-Eddy Simulation of a High-Pressure Turbine Vane With Inlet Turbulence

2016 ◽  
Author(s):  
Solkeun Jee ◽  
Jongwook Joo ◽  
Gorazd Medic
Keyword(s):  
Boundary Layer ◽  
High Pressure ◽  
Large Eddy Simulation ◽  
Turbulence Intensity ◽  
The State ◽  
High Pressure Turbine ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Turbine Vane ◽  
The Impact

It is important to be able to predict the state of the boundary layer on a high-pressure turbine vane with incoming turbulence. The laminar-to-turbulent transition significantly changes the heat transfer on the blade, which impacts the turbine performance and durability assessment. In this study, an experimental cascade with a high-pressure turbine vane was simulated with large-eddy simulation (LES). To incorporate the impact of turbulence from the freestream on the boundary layer, appropriate turbulence data sets were generated in separate direct-numerical simulation and fed into the LES inlet. The state of the boundary layer is reasonably well predicted for the test condition of the turbulence intensity of Tu=4%. Streamwise vortical structures and spanwise two-dimensional waves are observed in the transitional boundary layer. Discrepancy for the case with the higher turbulence intensity Tu=6% is discussed with the focus on the need for more detailed information about the freestream disturbances.

Compressible large eddy simulation of the unsteady evolution process in a LPT Cascade with incoming wakes

2020 ◽  
pp. 095441002096753
Author(s):  
Yunfei Wang ◽  
Huanlong Chen ◽  
Huaping Liu ◽  
Yanping Song ◽  
Fu Chen
Keyword(s):  
Boundary Layer ◽  
Large Eddy Simulation ◽  
Boundary Layer Separation ◽  
Main Flow ◽  
Reynolds Stresses ◽  
Flow Area ◽  
Eddy Simulation ◽  
Reduced Frequency ◽  
Large Eddy ◽  
The Impact

An in-house large eddy simulation (LES) code based on three-dimensional compressible N-S equations is used to research the impact of incoming wakes on unsteady evolution characteristic in a low-pressure turbine (LPT) cascade. The Mach number is 0.4 and Reynolds number is 0.6 × 105 (based on the axial chord and outlet velocity). The reduced frequency of incoming wakes is Fred = 0 (without wakes), 0.37 and 0.74. A detailed analysis of Reynolds stresses and turbulent kinetic energy inside the boundary layer has been carried out. Particular consideration is devoted to the transport process of incoming wakes and the intermittent property of the unsteady boundary layer. With the increase of reduced frequency, the inhibiting effect of wakes on boundary layer separation gradually enhances. The separation at the rear part of the suction side is weakened and the separation point moves downstream. However, incoming wakes lead to an increase in dissipation and aerodynamic losses in the main flow area. Excessive reduced frequency ( Fred = 0.74) causes the main flow area to become one of the main source areas of loss. An optimal reduced frequency exists to minimize the aerodynamic loss of the linear cascade.

Large Eddy Simulation of Combustor and Complete Single-Stage High-Pressure Turbine of the FACTOR Test Rig

2019 ◽  
Author(s):  
Martin Thomas ◽  
Jerome Dombard ◽  
Florent Duchaine ◽  
Laurent Gicquel ◽  
Charlie Koupper
Keyword(s):  
High Pressure ◽  
Large Eddy Simulation ◽  
Combustion Chamber ◽  
Measurement Data ◽  
Single Stage ◽  
High Pressure Turbine ◽  
Lean Burn ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Compact Design

Abstract Development goals for next generation aircraft engines are mainly determined by the need to reduce fuel consumption and environmental impact. To reduce NOx emissions lean combustion technologies will be applied in future development projects. The more compact design and the absence of dilution holes in this type of engines shortens residence times in the combustion chamber and reduces mixing which results in higher levels of swirl, turbulence and temperature distortions at the exit of the combustion chamber. For these engines interactions between components are more important, so that the traditional engine design approach of component-wise optimization will have to be adapted. To study new lean burn architectures the European FACTOR project investigates the transport of hot streaks produced by a non-reactive combustor simulator through a single stage high-pressure turbine. In this work high-fidelity Large Eddy Simulation (LES) of combustor and complete high-pressure turbine are discussed and validated against experimental data. Measurement data is available on P40 (exit of the combustion chamber), P41 (exit of the stator) and P42 (exit of the rotor) and generally shows a good agreement to LES data.

scholarly journals Strongly sheared stratocumulus convection: an observationally based large-eddy simulation study

2012 ◽  
Vol 12 (11) ◽  
pp. 5223-5235 ◽  
Author(s):  
S. Wang ◽  
X. Zheng ◽  
Q. Jiang
Keyword(s):  
Large Eddy Simulation ◽  
Turbulence Intensity ◽  
Wind Shear ◽  
Richardson Number ◽  
Marine Boundary Layer ◽  
Turbulence Structure ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Wind Shears ◽  
The Impact

Abstract. Unusually large wind shears across the inversion in the stratocumulus-topped marine boundary layer (MBL) were frequently observed during VOCALS-REx. To investigate the impact of wind shear on the MBL turbulence structure, a large-eddy simulation (LES) model is used to simulate the strongly sheared MBL observed from Twin-Otter RF 18 on 13 November 2008. The LES simulated turbulence statistics agree in general with those derived from the measurements, with the MBL exhibiting a decoupled structure characterized by an enhanced entrainment and a turbulence intensity minimum just below the clouds. Sensitivity simulations show that the shear forcing tends to reduce the dynamic stability of the inversion, characterized by the bulk (or gradient) Richardson number. This decrease enhances the entrainment mixing, leading to reduced cloud water. Consequently, the turbulence intensity in the MBL is significantly weakened by the intense wind shear. The inversion thickens considerably and the MBL top separates from the cloud top, creating a finite cloud-free sublayer of 10–50 m thickness within the inversion, depending on the Richardson number. The weakened inversion tends to enhance the turbulence buoyant consumption and simultaneously lead to a reduced buoyant production in the cloud layer due to less radiative cooling. These effects may result in a decoupling process that creates the different heating/moistening rates between the cloud and subcloud layer, leading to a two-layered structure in the strongly sheared stratocumulus-topped MBL.

scholarly journals Strongly sheared stratocumulus convection: an observationally based large-eddy simulation study

2012 ◽  
Vol 12 (2) ◽  
pp. 4941-4977
Author(s):  
S. Wang ◽  
X. Zheng ◽  
Q. Jiang
Keyword(s):  
Large Eddy Simulation ◽  
Turbulence Intensity ◽  
Wind Shear ◽  
Marine Boundary Layer ◽  
Turbulence Structure ◽  
Heating Rates ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Wind Shears ◽  
The Impact

Abstract. Unusually large wind shears across the inversion in the stratocumulus-topped marine boundary layer (MBL) were frequently observed during VOCALS-REx. To investigate the impact of wind shear on the MBL turbulence structure, a large-eddy simulation (LES) model is used to simulate the strongly sheared MBL observed from Twin-Otter RF 18 on 13 November 2008. The LES simulated turbulence statistics agree in general with those derived from the measurements, with the MBL exhibiting a decoupled structure characterized by an enhanced entrainment and a turbulence intensity minimum just below the clouds. Sensitivity simulations show that the shear tends to reduce the dynamic stability of the inversion, enhance the entrainment mixing, and decrease the cloud water. Consequently, the turbulence intensity in the MBL is significantly weakened by the intense wind shear. The inversion thickens considerably and the MBL top separates from the cloud top, creating a finite cloud-free sublayer of 10–50 m thickness within the inversion, depending on the shear intensity. The wind shear enhances the turbulence buoyant consumption within the inversion, and simultaneously weakens the buoyant production in the cloud layer. These effects may result in different heating rates between the cloud and subcloud layer, leading to a process that tends to decouple the cloud from the subcloud layer. The decoupling process occurs even without solar radiation in the case of an intense wind shear similar to the observations.

scholarly journals Nocturnal Boundary Layer Erosion Analysis in the Amazon Using Large-Eddy Simulation during GoAmazon Project 2014/5

Atmosphere ◽  
2021 ◽  
Vol 12 (2) ◽  
pp. 240
Author(s):  
Rayonil Carneiro ◽  
Gilberto Fisch ◽  
Theomar Neves ◽  
Rosa Santos ◽  
Carlos Santos ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Large Eddy Simulation ◽  
Rainy Season ◽  
Nocturnal Boundary Layer ◽  
Enso Event ◽  
Dry Season ◽  
Dry Period ◽  
Additional Energy ◽  
Eddy Simulation ◽  
Large Eddy

This study investigated the erosion of the nocturnal boundary layer (NBL) over the central Amazon using a high-resolution model of large-eddy simulation (LES) named PArallel Les Model (PALM) and observational data from Green Ocean Amazon (GoAmazon) project 2014/5. This data set was collected during four intense observation periods (IOPs) in the dry and rainy seasons in the years 2014 (considered a typical year) and 2015, during which an El Niño–Southern Oscillation (ENSO) event predominated and provoked an intense dry season. The outputs from the PALM simulations represented reasonably well the NBL erosion, and the results showed that it has different characteristics between the seasons. During the rainy season, the IOPs exhibited slow surface heating and less intense convection, which resulted in a longer erosion period, typically about 3 h after sunrise (that occurs at 06:00 local time). In contrast, dry IOPs showed more intensive surface warming with stronger convection, resulting in faster NBL erosion, about 2 h after sunrise. A conceptual model was derived to investigate the complete erosion during sunrise hours when there is a very shallow mixed layer formed close to the surface and a stable layer above. The kinematic heat flux for heating this layer during the erosion period showed that for the rainy season, the energy emitted from the surface and the entrainment was not enough to fully heat the NBL layer and erode it. Approximately 30% of additional energy was used in the system, which could come from the release of energy from biomass. The dry period of 2014 showed stronger heating, but it was also not enough, requiring approximately 6% of additional energy. However, for the 2015 dry period, which was under the influence of the ENSO event, it was shown that the released surface fluxes were sufficient to fully heat the layer. The erosion time of the NBL probably influenced the development of the convective boundary layer (CBL), wherein greater vertical development was observed in the dry season IOPs (~1500 m), while the rainy season IOPs had a shallower layer (~1200 m).

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