scholarly journals Large Eddy Simulation and RANS Analysis of the End-Wall Flow in a Linear Low-Pressure-Turbine Cascade—Part II: Loss Generation

2019 ◽  
Vol 141 (5) ◽  
Author(s):  
Michele Marconcini ◽  
Roberto Pacciani ◽  
Andrea Arnone ◽  
Vittorio Michelassi ◽  
Richard Pichler ◽  
...  
Keyword(s):  
Large Eddy Simulation ◽  
Flow Characteristics ◽  
Turbulence Models ◽  
Low Pressure ◽  
Companion Paper ◽  
Turbine Cascade ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Wall Flow ◽  
End Wall

In low-pressure turbines (LPT) at design point, around 60–70% of losses are generated in the blade boundary layers far from end walls, while the remaining 30–40% is controlled by the interaction of the blade profile with the end-wall boundary layer. Increasing attention is devoted to these flow regions in industrial design processes. This paper discusses the end-wall flow characteristics of the T106 profile with parallel end walls at realistic LPT conditions, as described in the experimental setup of Duden, A., and Fottner, L., 1997, “Influence of Taper, Reynolds Number and Mach Number on the Secondary Flow Field of a Highly Loaded Turbine Cascade,” Proc. Inst. Mech. Eng., Part A, 211(4), pp.309–320. Calculations are carried out by both Reynolds-averaged Navier–Stokes (RANS), due to its continuing role as the design verification workhorse, and highly resolved large eddy simulation (LES). Part II of this paper focuses on the loss generation associated with the secondary end-wall vortices. Entropy generation and the consequent stagnation pressure losses are analyzed following the aerodynamic investigation carried out in the companion paper (GT2018-76233). The ability of classical turbulence models generally used in RANS to discern the loss contributions of the different vortical structures is discussed in detail and the attainable degree of accuracy is scrutinized with the help of LES and the available test data. The purpose is to identify the flow features that require further modeling efforts in order to improve RANS/unsteady RANS (URANS) approaches and make them able to support the design of the next generation of LPTs.

scholarly journals Large-Eddy Simulation and RANS Analysis of the End-Wall Flow in a Linear Low-Pressure Turbine Cascade, Part I: Flow and Secondary Vorticity Fields Under Varying Inlet Condition

2019 ◽  
Vol 141 (12) ◽  
Author(s):  
Richard Pichler ◽  
Yaomin Zhao ◽  
Richard Sandberg ◽  
Vittorio Michelassi ◽  
Roberto Pacciani ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Large Eddy Simulation ◽  
Secondary Flow ◽  
Low Pressure ◽  
Eddy Simulation ◽  
Wall Boundary Layer ◽  
Wall Boundary ◽  
Large Eddy ◽  
Wall Flow ◽  
End Wall

Abstract In low-pressure turbines (LPTs), around 60–70% of losses are generated away from end-walls, while the remaining 30–40% is controlled by the interaction of the blade profile with the end-wall boundary layer. Experimental and numerical studies have shown how the strength and penetration of the secondary flow depends on the characteristics of the incoming end-wall boundary layer. Experimental techniques did shed light on the mechanism that controls the growth of the secondary vortices, and scale-resolving computational fluid dynamics (CFD) allowed to dive deep into the details of the vorticity generation. Along these lines, this paper discusses the end-wall flow characteristics of the T106 LPT profile at Re = 120 K and M = 0.59 by benchmarking with experiments and investigating the impact of the incoming boundary layer state. The simulations are carried out with proven Reynolds-averaged Navier–Stokes (RANS) and large-eddy simulation (LES) solvers to determine if Reynolds-averaged models can capture the relevant flow details with enough accuracy to drive the design of this flow region. Part I of the paper focuses on the critical grid needs to ensure accurate LES and on the analysis of the overall time-averaged flow field and comparison between RANS, LES, and measurements when available. In particular, the growth of secondary flow features, the trace and strength of the secondary vortex system, and its impact on the blade load variation along the span and end-wall flow visualizations are analyzed. The ability of LES and RANS to accurately predict the secondary flows is discussed together with the implications this has on design.

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

scholarly journals LES and RANS Analysis of the End-Wall Flow in a Linear LPT Cascade With Variable Inlet Conditions: Part II — Loss Generation

2018 ◽  
Author(s):  
Michele Marconcini ◽  
Roberto Pacciani ◽  
Andrea Arnone ◽  
Vittorio Michelassi ◽  
Richard Pichler ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Boundary Layers ◽  
Flow Characteristics ◽  
Turbulence Models ◽  
Companion Paper ◽  
Wall Boundary Layer ◽  
Wall Flow ◽  
Inlet Conditions ◽  
End Wall ◽  
The Impact

In low-pressure-turbines (LPT) at design point around 60–70% of losses are generated in the blade boundary layers far from end-walls, while the remaining 30%–40% is controlled by the interaction of the blade profile with the end-wall boundary layer. Increasing attention is devoted to these flow regions in industrial design processes. Experimental techniques have shed light on the mechanism that controls the growth of the secondary vortices, and scale-resolving CFD have provided a detailed insight into the vorticity generation. Along these lines, this paper discusses the end-wall flow characteristics of the T106 profile with parallel end-walls at realistic LPT conditions, as described in the experimental setup of Duden and Fottner (1997) “Influence of Taper, Reynolds Number and Mach Number on the Secondary Flow Field of a Highly Loaded Turbine Cascade”, P. I. Mech. Eng. A-J. Pow., 211 (4), pp.309–320. The simulations target first the same inlet conditions as documented in the experiments, and determines the impact of the incoming boundary layer thickness by running additional cases with modified incoming boundary layers. Calculations are carried out by both RANS, due to its continuing role as the design verification workhorse, and highly-resolved LES. Part II of the paper focuses on the loss generation associated with the secondary end-wall vortices. Entropy generation and the consequent stagnation pressure losses are analyzed following the aerodynamic investigation carried out in the companion paper. The ability of classical turbulence models generally used in RANS to discern the loss contributions of the different vortical structures is discussed in detail and the attainable degree of accuracy is scrutinized with the help of LES and the available test data. The purpose is to identify the flow features that require further modelling efforts in order to improve RANS/URANS approaches and make them able to support the design of the next generation of LPTs.

Large Eddy Simulation of Secondary Flows in an Ultra-High Lift Low Pressure Turbine Cascade at Various Inlet Incidences

2020 ◽  
Vol 37 (2) ◽  
pp. 195-207
Author(s):  
Site Hu ◽  
Chao Zhou ◽  
Shiyi Chen
Keyword(s):  
Large Eddy Simulation ◽  
Engine Performance ◽  
Low Pressure ◽  
Secondary Flows ◽  
Turbine Cascade ◽  
High Lift ◽  
Blade Loading ◽  
Low Pressure Turbine ◽  
Eddy Simulation ◽  
Large Eddy

AbstractIncreasing the blade loading of a low pressure turbine blade decreases the number of blades, thus improving the aero-engine performance in terms of the weight and manufacture cost. Many studies focused on the blade-to-blade flow field of ultra-high lift low pressure turbines. The secondary flows of ultra-high lift low pressure turbines received much less attention. This paper investigates the secondary flows in an ultra-high lift low pressure turbine cascade T106C by large eddy simulation at a Reynolds number of 100,000. Both time-averaged and instantaneous flow fields of this ultra-high lift low pressure turbine are presented. To understand the effects of the inlet angle, five incidences of ‒10°, ‒5°, 0, +5° and +10° are investigated. The case at the design incidence is analyzed first. Detailed data is used to illustrate the how the fluids in boundary layers develops into secondary flows. Then, the cases with different inlet incidences are discussed. The aerodynamic performances are compared. The effect of blade loading on the vortex structures is investigated. The horseshoe vortex, passage vortex and the suction side corner vortex are very sensitive to the loading of the front part of the blade.

scholarly journals Large Eddy Simulation of Film Cooling Involving Compound Angle Holes: Comparative Study of LES and RANS

Processes ◽  
2021 ◽  
Vol 9 (2) ◽  
pp. 198
Author(s):  
Seung Il Baek ◽  
Joon Ahn
Keyword(s):  
Large Eddy Simulation ◽  
Film Cooling ◽  
Orientation Angle ◽  
Turbulence Models ◽  
Film Cooling Effectiveness ◽  
Injection Angle ◽  
Blowing Ratio ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Compound Angle

A large eddy simulation (LES) was performed for film cooling in the gas turbine blade involving spanwise injection angles (orientation angles). For a streamwise coolant injection angle (inclination angle) of 35°, the effects of the orientation angle were compared considering a simple angle of 0° and 30°. Two ratios of the coolant to main flow mass flux (blowing ratio) of 0.5 and 1.0 were considered and the experimental conditions of Jung and Lee (2000) were adopted for the geometry and flow conditions. Moreover, a Reynolds averaged Navier–Stokes simulation (RANS) was performed to understand the characteristics of the turbulence models compared to those in the LES and experiments. In the RANS, three turbulence models were compared, namely, the realizable k-ε, k-ω shear stress transport, and Reynolds stress models. The temperature field and flow fields predicted through the RANS were similar to those obtained through the experiment and LES. Nevertheless, at a simple angle, the point at which the counter-rotating vortex pair (CRVP) collided on the wall and rose was different from that in the experiment and LES. Under the compound angle, the point at which the CRVP changed to a single vortex was different from that in the LES. The adiabatic film cooling effectiveness could not be accurately determined through the RANS but was well reflected by the LES, even under the compound angle. The reattachment of the injectant at a blowing ratio of 1.0 was better predicted by the RANS at the compound angle than at the simple angle. The temperature fluctuation was predicted to decrease slightly when the injectant was supplied at a compound angle.

scholarly journals Modeling of Breaching-Generated Turbidity Currents Using Large Eddy Simulation

2020 ◽  
Vol 8 (9) ◽  
pp. 728
Author(s):  
Said Alhaddad ◽  
Lynyrd de Wit ◽  
Robert Jan Labeur ◽  
Wim Uijttewaal
Keyword(s):  
Experimental Data ◽  
Numerical Model ◽  
Large Eddy Simulation ◽  
Flow Characteristics ◽  
Turbidity Current ◽  
Turbidity Currents ◽  
Eddy Simulation ◽  
Failure Evolution ◽  
Large Eddy ◽  
Flow Slides

Breaching flow slides result in a turbidity current running over and directly interacting with the eroding, submarine slope surface, thereby promoting further sediment erosion. The investigation and understanding of this current are crucial, as it is the main parameter influencing the failure evolution and fate of sediment during the breaching phenomenon. In contrast to previous numerical studies dealing with this specific type of turbidity currents, we present a 3D numerical model that simulates the flow structure and hydrodynamics of breaching-generated turbidity currents. The turbulent behavior in the model is captured by large eddy simulation (LES). We present a set of numerical simulations that reproduce particular, previously published experimental results. Through these simulations, we show the validity, applicability, and advantage of the proposed numerical model for the investigation of the flow characteristics. The principal characteristics of the turbidity current are reproduced well, apart from the layer thickness. We also propose a breaching erosion model and validate it using the same series of experimental data. Quite good agreement is observed between the experimental data and the computed erosion rates. The numerical results confirm that breaching-generated turbidity currents are self-accelerating and indicate that they evolve in a self-similar manner.

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