scholarly journals Assessing IDDES-Based Wall-Modeled Large-Eddy Simulation (WMLES) for Separated Flows with Heat Transfer

Fluids ◽  
2021 ◽  
Vol 6 (7) ◽  
pp. 246
Author(s):  
Rozie Zangeneh
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Large Eddy Simulation ◽  
Skin Friction ◽  
Heat Fluxes ◽  
Separated Flows ◽  
Detached Eddy Simulation ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Isothermal Wall

The Wall-modeled Large-eddy Simulation (WMLES) methods are commonly accompanied with an underprediction of the skin friction and a deviation of the velocity profile. The widely-used Improved Delayed Detached Eddy Simulation (IDDES) method is suggested to improve the prediction of the mean skin friction when it acts as WMLES, as claimed by the original authors. However, the model tested only on flow configurations with no heat transfer. This study takes a systematic approach to assess the performance of the IDDES model for separated flows with heat transfer. Separated flows on an isothermal wall and walls with mild and intense heat fluxes are considered. For the case of the wall with heat flux, the skin friction and Stanton number are underpredicted by the IDDES model however, the underprediction is less significant for the isothermal wall case. The simulations of the cases with intense wall heat transfer reveal an interesting dependence on the heat flux level supplied; as the heat flux increases, the IDDES model declines to predict the accurate skin friction.

scholarly journals Investigation of the Turbulent Near Wall Flame Behavior for a Sidewall Quenching Burner by Means of a Large Eddy Simulation and Tabulated Chemistry

Fluids ◽  
2018 ◽  
Vol 3 (3) ◽  
pp. 65 ◽  
Author(s):  
Arne Heinrich ◽  
Guido Kuenne ◽  
Sebastian Ganter ◽  
Christian Hasse ◽  
Johannes Janicka
Keyword(s):  
Heat Flux ◽  
Large Eddy Simulation ◽  
Gas Turbines ◽  
Internal Combustion Engines ◽  
Heat Fluxes ◽  
Maximum Heat ◽  
Eddy Simulation ◽  
Tabulated Chemistry ◽  
Large Eddy ◽  
Near Wall

Combustion will play a major part in fulfilling the world’s energy demand in the next 20 years. Therefore, it is necessary to understand the fundamentals of the flame–wall interaction (FWI), which takes place in internal combustion engines or gas turbines. The FWI can increase heat losses, increase pollutant formations and lowers efficiencies. In this work, a Large Eddy Simulation combined with a tabulated chemistry approach is used to investigate the transient near wall behavior of a turbulent premixed stoichiometric methane flame. This sidewall quenching configuration is based on an experimental burner with non-homogeneous turbulence and an actively cooled wall. The burner was used in a previous study for validation purposes. The transient behavior of the movement of the flame tip is analyzed by categorizing it into three different scenarios: an upstream, a downstream and a jump-like upstream movement. The distributions of the wall heat flux, the quenching distance or the detachment of the maximum heat flux and the quenching point are strongly dependent on this movement. The highest heat fluxes appear mostly at the jump-like movement because the flame behaves locally like a head-on quenching flame.

Large Eddy Simulation of Conjugate Heat Transfer Around a Multi-Perforated Plate With Deviation

2016 ◽  
Author(s):  
Dorian Lahbib ◽  
Antoine Dauptain ◽  
Florent Duchaine ◽  
Franck Nicoud
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Large Eddy Simulation ◽  
Conjugate Heat Transfer ◽  
Pressure Ratio ◽  
Perforated Plate ◽  
Inlet Temperature ◽  
Plate Temperature ◽  
Eddy Simulation ◽  
Large Eddy

To improve gas turbine efficiency, engine manufacturers increase both the overall compressor pressure ratio and the turbine inlet temperature, resulting into a higher thermal load of the combustion chamber walls. Cooling systems such as multi-perforated plates are in this context good candidates to lower the thermal constraints on the liners. Such technological devices consist in introducing, through submillimetric holes, a cold air flow into the boundary layer of the chamber wall. Though commonly used in industrial applications, perforations with an angle of deviation, i.e. not aligned with the main flow, have not been studied in most experimental and numerical studies. The deviation angle impacts the liner temperature by modifying the flow structure around the plate. Conjugate heat transfer computations coupling Large Eddy Simulation and heat conduction are performed on streamwise and 45 angled configurations composed of 12 rows at an operating point representative of helicopter combustors to analyze the effect of the deviation. The flow organization around the plate is modified, yielding different heat flux distribution and plate temperature. The major differences are observed within the perforations where the heat flux coefficient increases up to 54% in the configuration with deviation.

Constrained large-eddy simulation of turbulent flow and heat transfer in a stationary ribbed duct

2016 ◽  
Vol 26 (3/4) ◽  
pp. 1069-1091 ◽  
Author(s):  
Zhou Jiang ◽  
Zuoli Xiao ◽  
Yipeng Shi ◽  
Shiyi Chen
Keyword(s):  
Heat Transfer ◽  
Large Eddy Simulation ◽  
Turbulent Flow ◽  
Thermodynamic Quantities ◽  
Detached Eddy Simulation ◽  
Square Duct ◽  
Content Type ◽  
Eddy Simulation ◽  
Flow And Heat Transfer ◽  
Large Eddy

Purpose – The knowledge about the heat transfer and flow field in the ribbed internal passage is particularly important in industrial and engineering applications. The purpose of this paper is to identify and analyze the performance of the constrained large-eddy simulation (CLES) method in predicting the fully developed turbulent flow and heat transfer in a stationary periodic square duct with two-side ribbed walls. Design/methodology/approach – The rib height-to-duct hydraulic diameter ratio is 0.1 and the rib pitch-to-height ratio is 9. The bulk Reynolds number is set to 30,000, and the bulk Mach number of the flow is chosen as 0.1 in order to keep the flow almost incompressible. The CLES calculated results are thoroughly assessed in comparison with the detached-eddy simulation (DES) and traditional large-eddy simulation (LES) methods in the light of the experimentally measured data. Findings – It is manifested that the CLES approach can predict both aerodynamic and thermodynamic quantities more accurately than the DES and traditional LES methods. Originality/value – This is the first time for the CLES method to be applied to simulation of heat and fluid flow in this widely used geometry.

Aerothermal Prediction of an Aeronautical Combustion Chamber Based on the Coupling of Large Eddy Simulation, Solid Conduction and Radiation Solvers

2015 ◽  
Author(s):  
Sandrine Berger ◽  
Stéphane Richard ◽  
Gabriel Staffelbach ◽  
Florent Duchaine ◽  
Laurent Gicquel
Keyword(s):  
Heat Transfer ◽  
Large Eddy Simulation ◽  
Combustion Chamber ◽  
Gas Turbines ◽  
Thermal Environment ◽  
Heat Fluxes ◽  
High Fidelity ◽  
Eddy Simulation ◽  
Precise Knowledge ◽  
Large Eddy

A precise knowledge of the thermal environment is essential for gas turbines design. Combustion chamber walls in particular are subject to strong thermal constraints. It is thus essential for designers to characterize accurately the local thermal state of such devices. Today, the determination of wall temperatures is performed experimentally by complex thermocolor tests. To limit such expensive experiments and integrate the knowledge of the thermal environment earlier in the design process, efforts are currently performed to provide high fidelity numerical tools able to predict the combustion chamber walls temperature. Many coupled physical phenomena are involved: turbulent combustion, convection and mixing of hot products and cold flows, conduction in the solid parts as well as gas to gas, gas to wall and wall to wall radiative transfers. The resolution of such a multiphysics problem jointly in the fluid and the solid domains can be done numerically through the use of several dedicated numerical and algorithmic approaches. In this paper, a partitioned coupling methodology is used to investigate the solid steady state wall temperature of a helicopter combustor in take-off conditions. The methodology relies on a high fidelity Large Eddy Simulation reacting flow solver coupled to conduction and radiative solvers. Different computations are presented in order to assess the role of each heat transfer process in the temperature field. A conjugate heat transfer simulation is first proposed and compared with experimental thermocolor tests. The effect of radiation is then investigated comparing relative importance of convective and radiative heat fluxes.

scholarly journals Large-Eddy Simulation and Conjugate Heat Transfer in a Round Impinging Jet

2014 ◽  
Author(s):  
Francis Shum-Kivan ◽  
Florent Duchaine ◽  
Laurent Gicquel
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Large Eddy Simulation ◽  
Unsteady Flow ◽  
Conjugate Heat Transfer ◽  
Wall Jet ◽  
Hybrid Strategy ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Flow Features

This study addresses and evaluates the use of high fidelity Large Eddy Simulation (LES) for the prediction of Conjugate Heat Transfer (CHT) of an impinging jet at a Reynolds number of 23 000, a Mach number of 0.1 and for a nozzle to plate distance of H/D = 2. For such simulations mesh point localization as well as the turbulent model and the numerical scheme are known to be of primary importance. In this context, a compressible unstructured third order in time and space LES solver is assessed through the use of WALE sub-grid scale model in a wall-resolved methodology. All simulations discussed in this document well recover main unsteady flow features (the jet core development, the impinging region, the deviation of the flow and the wall jet region) as well as the mean statistics of velocity. Convergence of the wall mesh resolution is investigated by use of 3 meshes and predictions are assessed in terms of wall friction and heat flux. The meshes are based either on full tetrahedral cells or on a hybrid strategy with prism layers at the wall and tetrahedral elsewhere. The hybrid strategy allows reaching good discretization of the boundary layers with a reasonable number of cells. Unsteady flow features retrieved in the jet core, shear layer, impinging region and wall jet region are analyzed and linked to the unsteady and mean heat flux measured at the wall. To finish, a LES based CHT computation relying on the finer grid is used to access the plate temperature distribution. Nusselt number profiles along the plate for the isothermal and the coupled cases are also provided and compared.

scholarly journals Computational analysis of transitional and massively separated flows with application to wind turbines

2019 ◽  
Author(s):  
Κωνσταντίνος Διακάκης
Keyword(s):  
Large Eddy Simulation ◽  
Wind Turbines ◽  
Computational Analysis ◽  
Separated Flows ◽  
Navier Stokes ◽  
Detached Eddy Simulation ◽  
Eddy Simulation ◽  
Massively Separated Flows ◽  
Large Eddy ◽  
Unsteady Rans

Στην παρούσα διατριβή μελετήθηκε η μετάβαση της ροής από στρωτή σε τυρβώδη καθώς και η συμπεριφορά ροών μεγάλων αριθμών Reynolds στα πλαίσια προσομοίωσης τους με μεθόδους υψηλής πιστότητας.Για την προσομοίωση ροών με μετάβαση εξετάστηκαν μέθοδοι με υπολογισμό οριακού στρώματος και μέθοδοι με εξισώσεις μεταφοράς. Αυτές περιλαμβάνουν την μέθοδο e N καθώς και τα μοντέλα γ-Re θ , γ και AFT. Όλες οι μέθοδοι δοκιμάστηκαν σε αεροτομές, πτέρυγες και άτρακτο γενικής μορφής, σε εφαρμογές οι οποίες προέρχονταν από τους τομείς της αεροναυτικής και της αιολικής ενέργειας. Οι συγκρίσεις αφορούσαν κατά κύριο λόγο σε αεροδυναμικά φορτία και θέσεις μετάβασης. Στα πλαίσια διδιάστατων προσομοιώσεων, η μέθοδος e N με υπολογισμό οριακού στρώματος και το μοντέλο AFT έδωσαν πιο ακριβή αποτελέσματα από τις υπόλοιπες μεθόδους. Το μοντέλο γ-Re θ είναι μια καλή εναλλακτική, αρκεί ο αριθμός Reynolds να μην υπερβαίνει τα 6 εκατομμύρια. Πέραν αυτού του ορίου, η ακρίβεια των αποτελεσμάτων του μοντέλου μειώνεται σημαντικά. Ωστόσο, η μέθοδος e N και το μοντέλο AFT δεν δύνανται να χρησιμοποιηθούν για την μοντελοποίηση τρισδιάστατης μετάβασης στο πλαίσιο τρισδιάστατων προσομοιώσεων. Σε αυτές τις περιπτώσεις, το μοντέλο γ-Re θ εμπλουτισμένο με όρους εγκάρσιας ροής μπορεί να δώσει καλά αποτελέσματα, αρκεί ο αριθμός Reynolds να είναι στα αποδεκτά για το μοντέλο όρια. Όσον αφορά στις μεθόδους προσομοίωσης τύρβης υψηλής πιστότητας, εξετάστηκαν οι μέθοδοι Large Eddy Simulation (LES) και Detached Eddy Simulation (DES). Για τις προσομοιώσεις LES χρησιμοποιήθηκε το μοντέλο μικρών κλιμάκων του Smagorinsky. Η εφαρμογή του DES περιελάμβανε τις μεθόδους Delayed DES (DDES) και Improved Delayed DES (IDDES). Το ενδιαφέρον εστιάστηκε στην μοντελοποίηση ροών με μεγάλη αποκόλληση. Τόσο το LES όσο και το DES ήταν σε θέση να δώσουν πιο ακριβή αποτελέσματα από τους απλούς, μη-μόνιμους Reynolds Averaged Navier Stokes υπολογισμούς (Unsteady RANS) σε σύγκριση με πειράματα και υπολογιστικά αποτελέσματα από τη βιβλιογραφία. Το μοντέλο DES θεωρείται λιγότερο απαιτητικό σε υπολογιστικούς πόρους λόγω της μοντελοποίησης του οριακού στρώματος η οποία οδηγεί σε μικρότερες απαιτήσεις πλέγματος κοντά στην στερεή επιφάνεια. Ωστόσο, το DES δεν αναμένεται να μπορεί να δώσει αξιόπιστα αποτελέσματα σε ροές όπου η παρουσία και η εξέλιξη μικρών κλιμάκων τύρβης στο οριακό στρώμα είναι σημαντική, και που το μοντέλο LES πλεονεκτεί εκ κατασκευής. Σχετικά σημειώνεται ότι οι LES προσομοιώσεις δεν έφτασαν στα υπολογιστικά τους όρια όσον αφορά στο πλέγμα. Για να παραχθούν αξιόπιστα αποτελέσματα σε αυτές τις περιπτώσεις πρέπει να χρησιμοποιηθεί LES με πυκνό υπολογιστικό πλέγμα.

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