Numerical Investigation of Compound Angle Effusion Cooling Using Differential Reynolds Stress Model and Zonal Detached Eddy Simulation Approaches

2016 ◽  
Vol 138 (10) ◽  
Author(s):  
G. Arroyo-Callejo ◽  
E. Laroche ◽  
P. Millan ◽  
F. Leglaye ◽  
F. Chedevergne
Keyword(s):  
Reynolds Stress ◽  
Flow Behavior ◽  
Reynolds Stress Model ◽  
Formation Mechanisms ◽  
Stress Model ◽  
Detached Eddy Simulation ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Eddy Simulation ◽  
Depth Analysis

Effusion cooling is one of the most effective and widespread techniques to prevent combustor liner from being damaged. However, most recent developments in combustion techniques, resulting from increasingly stricter air pollution regulations, have highlighted the necessity of reducing the amount of air available for effusion cooling while keeping an adequate level of protection. Adoption of compound angles in effusion cooling is increasingly recognized by jet engine manufacturers as a powerful solution to meet new combustor requirements. Therefore, understanding the flow behavior and developing methods able to provide accurate estimates of wall temperatures is of a major importance. This study assesses the capability of a high-level Reynolds-averaged Navier–Stokes (RANS) method, differential Reynolds stress model (DRSM), in conjunction with a generalized gradient diffusion hypothesis (GGDH), and of a hybrid RANS–large eddy simulations (LES) method, zonal detached eddy simulation (ZDES), to predict overall film effectiveness. Both approaches are compared with the experimental data from Zhang et al. (2009, “Cooling Effectiveness of Effusion Walls With Deflection Hole Angles Measured by Infrared Imaging,” Appl. Therm. Eng., 29(5), pp. 966–972) and with a classical well-known RANS model (k–ω shear-stress transport (SST) model). Despite the fact that some discrepancies are found, both approaches have proved suitable and reliable for predicting wall temperatures (relative errors of about 5%). Moreover, a new method to deal with ZDES length scales for unstructured grids is proposed. ZDES applicability and its general advantages and drawbacks are also discussed. Finally, an in-depth analysis of the film structure is carried out on the basis of the ZDES simulations. The principal structures are identified (an asymmetric main vortex (AMV) and a counter rotating vortex pair, CRVP), and the film formation mechanisms are presented. Significant spanwise-homogeneous distributions of surface overall film cooling effectiveness are observed.

A Reynolds Stress Model for Turbulent Corner Flows—Part I: Development of the Model

1976 ◽  
Vol 98 (2) ◽  
pp. 261-268 ◽  
Author(s):  
F. B. Gessner ◽  
A. F. Emery
Keyword(s):  
Reynolds Stress ◽  
Flow Behavior ◽  
Reynolds Stress Model ◽  
Turbulence Structure ◽  
Stress Model ◽  
Mixing Length ◽  
Corner Flow ◽  
Global Representation ◽  
Corner Flows ◽  
Algebraic Reynolds Stress Model

A Reynolds stress model is proposed for modeling the local turbulence structure in flow along a streamwise corner. Initial discussion centers on present methods of predicting internal and extenal corner flow behavior. An algebraic Reynolds stress model is then developed by operating on a modified form of the Reynolds stress transport equations. Application of the model involves specification of two empirical constants and a global representation for the mixing length. The paper concludes with a discussion of the features and limitations of the model.

Numerical Simulation of Flow Around a Generic Pickup With ISIS-CFD

2010 ◽  
Author(s):  
Emmanuel Guilmineau
Keyword(s):  
Reynolds Stress Model ◽  
Stress Model ◽  
Detached Eddy Simulation ◽  
Cfd Simulations ◽  
Flow Solver ◽  
Pickup Truck ◽  
Eddy Simulation ◽  
Computational Fluid Dynamics Cfd ◽  
Simulation Results ◽  
Algebraic Reynolds Stress Model

Computational Fluid Dynamics (CFD) is used to simulate the flow over a pickup truck. The flow solver used is ISIS-CFD developed by the CFD Department of the Fluid Mechanics Laboratory of Ecole Centrale de Nantes. CFD simulations are carried out with the Explicit Algebraic Reynolds Stress Model (EARSM) turbulence model and the Detached Eddy Simulation (DES). The focus of the simulation is to assess the capabilities of ISIS-CFD for vehicle aerodynamic development for pickup trucks. Detailed comparisons are made between the CFD simulations and the existing experiments for a generic pickup truck. The comparisons between the simulation results and the time-averaged measurements reveals that the CFD calculations are able to track the flow trends.

scholarly journals Kajian Numerik Efektifitas Film Cooling pada Sudu Turbin Gas

ROTASI ◽  
2019 ◽  
Vol 21 (1) ◽  
pp. 10
Author(s):  
Agus Jamaldi ◽  
Marwan Effendy
Keyword(s):  
Film Cooling ◽  
Discharge Coefficient ◽  
Detached Eddy Simulation ◽  
Trailing Edge ◽  
Adiabatic Wall ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Pin Fin ◽  
Eddy Simulation ◽  
Shedding Frequency

Penelitian ini bertujuan untuk mengevaluasi penggunaan model turbulensi Detached Eddy Simulation Spallart-Almaras (DES-SA) pada studi numerik tentang sistem pendinginan trailing edge (TE) pada sudu turbin gas. Sebuah desain TE cutback cooling dengan susunan staggered pin-fin dipilih sebagai spesimen pengujian berbasis simulasi. Tiga parameter penting seperti discharge coefficient (CD), adiabatic film cooling effectiveness (ηaw), dan shedding frequency (fs) menjadi fokus utama dalam penyelidikan kinerja sistem pendinginan TE sudu turbin gas. Penelitian dilakukan pada variasi tiga blowing ratios (M) yaitu 0,5; 0,8; dan 1,1. Hasil riset menunjukkan bahwa nilai CD yang diperoleh dari hasil simulasi memiliki kesesuaian trend jika dibandingkan dengan data peneliti terdahulu, dimana nilai CD sedikit meningkat seiring dengan M yang semakin besar. Penyelidikan terkait ηaw yang terjadi pada permukaan adiabatic wall menunjukkan bahwa nilainya konsisten dengan data penelitian yang terdahulu, baik secara eksperimen maupun simulasi. Frekuensi aliran vorteks (fs) berturut-turut 2043, 2323, dan 1976 Hz untuk masing-masing blowing ratios  0,5; 0,8; dan 1,1.

Very Large Eddy Simulation of Film Cooling Effectiveness on Trailing Edge Cutback

2020 ◽  
Author(s):  
Xin Yan
Keyword(s):  
Gas Turbine ◽  
Vortex Shedding ◽  
Film Cooling ◽  
Cooling Effect ◽  
Detached Eddy Simulation ◽  
Trailing Edge ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Eddy Simulation ◽  
Large Eddy

Abstract The trailing edge of high pressure gas turbine blade in aeroengine is usually designed as thin as possible to achieve higher aerodynamic efficiency. However, as the inlet temperature of modern gas turbine is continuously increasing, thermal stress in a thin trailing edge will become much significant, resulting in possibilities of erosion and creep problems. To find a balance between these two conflicting goals, one method is the use of pressure-side cutback, which extends into the coolant slot to get film cooling and also achieves a thin trailing edge. Due to the interactions between mainstream and coolant flow, film cooling effect on trailing edge cutback is significantly affected by the vortex shedding downstream the cooling slot. To resolve the coherent flow structures and understand their role on film cooling effect on trailing-edge cutback, this paper implemented a Very Large Eddy Simulation (VLES) model into the solver ANSYS Fluent with user defined functions. By introducing a resolution control factor, the turbulence viscosity predicted by transient SST k-ω model was corrected and the VLES computations were realized in the whole computational region. With the VLES method, film cooling effectiveness distributions on trailing-edge cutback at three blowing ratios were computed and compared against the experimental data. The coherent unsteadiness in cutback region was visualized to reveal the mixing process between mainstream and coolant flow. The numerical accuracies between different unsteady prediction methods, i.e. URANS (Unsteady Reynolds Averaged Navier-Stokes), SAS (Scale-Adaptive Simulation), DES (Detached Eddy Simulation), DDES (Delayed-Detached Eddy Simulation), SBES (Stress-Blended Eddy Simulation), and VLES were compared with respect to the resolutions of cooling effect and vortex shedding. The results show that the periodic vortex shedding induced by the interactions between mainstream and coolant is the main factor that affecting the cooling performance on cutback. VLES method has a comparable accuracy in predicting the film cooling effect on trailing edge cutback with DDES and SBES approaching. In the detached shear layer, VLES method exhibits a good ability to resolve coherent unsteadiness caused by vortex shedding. Compared with URANS and SAS methods, the VLES method has a higher accuracy in resolving the periodic vortex shedding and film cooling effectiveness distributions, especially in low blowing ratio cases.

Comparison of RANS and Detached Eddy Simulation Modeling Against Measurements of Leading Edge Film Cooling on a First-Stage Vane

2017 ◽  
Vol 139 (5) ◽  
Author(s):  
S. Ravelli ◽  
G. Barigozzi
Keyword(s):  
Film Cooling ◽  
Leading Edge ◽  
Intensity Level ◽  
Edge Region ◽  
Detached Eddy Simulation ◽  
Cooling Effectiveness ◽  
Stagnation Line ◽  
Film Cooling Effectiveness ◽  
Eddy Simulation ◽  
Adiabatic Effectiveness

The performance of a showerhead arrangement of film cooling in the leading edge region of a first-stage nozzle guide vane was experimentally and numerically evaluated. A six-vane linear cascade was tested at an isentropic exit Mach number of Ma2s = 0.42, with a high inlet turbulence intensity level of 9%. The showerhead cooling scheme consists of four staggered rows of cylindrical holes evenly distributed around the stagnation line, angled at 45 deg toward the tip. The blowing ratios tested are BR = 2.0, 3.0, and 4.0. Adiabatic film cooling effectiveness distributions on the vane surface around the leading edge region were measured by means of thermochromic liquid crystals (TLC) technique. Since the experimental contours of adiabatic effectiveness showed that there is no periodicity across the span, the computational fluid dynamics (CFD) calculations were conducted by simulating the whole vane. Within the Reynolds-averaged Navier–Stokes (RANS) framework, the very widely used realizable k–ε (Rke) and the shear stress transport k–ω (SST) turbulence models were chosen for simulating the effect of the BR on the surface distribution of adiabatic effectiveness. The turbulence model which provided the most accurate steady prediction, i.e., Rke, was selected for running detached eddy simulation (DES) at the intermediate value of BR = 3. Fluctuations of the local temperature were computed by DES, due to the vortex structures within the shear layers between the main flow and the coolant jets. Moreover, mixing was enhanced both in the wall-normal and spanwise directions, compared to RANS modeling. DES roughly halved the prediction error of laterally averaged film cooling effectiveness on the suction side of the leading edge. However, neither DES nor RANS provided the expected decay of effectiveness progressing downstream along the pressure side, with 15% overestimation of ηav at s/C = 0.2.

Prediction of strongly curved turbulent duct flows with Reynolds stress model

AIAA Journal ◽  
1997 ◽  
Vol 35 ◽  
pp. 91-98
Author(s):  
Jiang Luo ◽  
Budugur Lakshminarayana
Keyword(s):  
Reynolds Stress ◽  
Reynolds Stress Model ◽  
Stress Model
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