Detached-Eddy Simulation of Flow Around the NREL Phase-VI Blade

2002 ◽  
Author(s):  
J. Johansen ◽  
N. N. So̸rensen ◽  
J. A. Michelsen ◽  
S. Schreck
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Simulation Model ◽  
Three Dimensional ◽  
Turbulence Models ◽  
Navier Stokes ◽  
Detached Eddy Simulation ◽  
Eddy Simulation ◽  
Reynolds Averaged Navier Stokes ◽  
Nrel Phase Vi

The Detached-Eddy Simulation model implemented in the computational fluid dynamics code, EllipSys3D, is applied on the flow around the NREL Phase-VI wind turbine blade. Results are presented for flow around a parked blade at fixed angle of attack and a blade pitching along the blade axis. Computed blade characteristics are compared with experimental data from the NREL/NASA Ames Phase-VI unsteady experiment. The Detached-Eddy Simulation model is a method for predicting turbulence in computational fluid dynamics computations, which combines a Reynolds Averaged Navier-Stokes method in the boundary layer with a Large Eddy Simulation in the free shear flow. The present study focuses on static and dynamic stall regions highly relevant for stall regulated wind turbines. Computations do predict force coefficients and pressure distributions fairly good and results using Detached-Eddy Simulation show considerably more three-dimensional flow structures compared to conventional two-equation Reynolds Averaged Navier-Stokes turbulence models, but no particular improvements are seen on the global blade characteristics.

Aeroacoustics response of wind turbine blade profiles in normal and icing conditions

2018 ◽  
Vol 42 (3) ◽  
pp. 243-251 ◽  
Author(s):  
Edison H Caicedo ◽  
Muhammad S Virk
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Wind Turbine ◽  
Turbine Blade ◽  
Numerical Study ◽  
Turbulence Models ◽  
Wind Turbine Blade ◽  
Navier Stokes ◽  
Detached Eddy Simulation ◽  
Eddy Simulation

This article describes a multiphase computational fluid dynamics–based numerical study of the aeroacoustics response of symmetric and asymmetric wind turbine blade profiles in both normal and icing conditions. Three different turbulence models (Reynolds-averaged Navier–Stokes, detached eddy simulation, and large eddy simulation) have been used to make a comparison of numerical results with the experimental data, where a good agreement is found between numerical and experimental results. Detached eddy simulation turbulence model is found suitable for this study. Later, an extended computational fluid dynamics–based aeroacoustics parametric study is carried out for both normal (clean) and iced airfoils, where the results indicate a significant change in sound levels for iced profiles as compared to clean.

Turbulence modeling effects on the aerodynamic characterizations of a NASCAR Generation 6 racecar subject to yaw and pitch changes

2019 ◽  
Vol 233 (14) ◽  
pp. 3600-3620 ◽  
Author(s):  
Chen Fu ◽  
C Patrick Bounds ◽  
Christian Selent ◽  
Mesbah Uddin
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Shear Stress ◽  
Eddy Viscosity ◽  
Turbulence Models ◽  
Flow Region ◽  
Adverse Pressure Gradient ◽  
Navier Stokes ◽  
Shear Stress Transport ◽  
Reynolds Averaged Navier Stokes

The characterization of a racecar’s aerodynamic behavior at various yaw and pitch configurations has always been an integral part of its on-track performance evaluation in terms of lap time predictions. Although computational fluid dynamics has emerged as the ubiquitous tool in motorsports industry, a clarity is still lacking about the prediction veracity dependence on the choice of turbulence models, which is central to the prediction variability and unreliability for the Reynolds Averaged Navier–Stokes simulations, which is by far the most widely used computational fluid dynamics methodology in this industry. Subsequently, this paper presents a comprehensive assessment of three commonly used eddy viscosity turbulence models, namely, the realizable [Formula: see text] (RKE), Abe–Kondoh–Nagano [Formula: see text], and shear stress transport [Formula: see text], in predicting the aerodynamic characteristics of a full-scale NASCAR Monster Energy Cup racecar under various yaw and pitch configurations, which was never been explored before. The simulations are conducted using the steady Reynolds Averaged Navier–Stokes approach with unstructured trimmer cells. The tested yaw and pitch configurations were chosen in consultation with the race teams such that they reflect true representations of the racecar orientations during cornering, braking, and accelerating scenarios. The study reiterated that the prediction discrepancies between the turbulence models are mainly due to the differences in the predictions of flow recirculation and separation, caused by the individual model’s effectiveness in capturing the evolution of adverse pressure gradient flows, and predicting the onset of separation and subsequent reattachment (if there be any). This paper showed that the prediction discrepancies are linked to the computation of the turbulent eddy viscosity in the separated flow region, and using flow-visualizations identified the areas on the car body which are critical to this analysis. In terms of racecar aerodynamic performance parameter predictions, it can be reasonably argued that, excluding the prediction of the %Front prediction, shear stress transport is the best choice between the three tested models for stock-car type racecar Reynolds Averaged Navier–Stokes computational fluid dynamics simulations as it is the only model that predicted directionally correct changes of all aerodynamic parameters as the racecar is either yawed from the 0° to 3° or pitched from a high splitter-ground clearance to a low one. Furthermore, the magnitude of the shear stress transport predicted delta force coefficients also agreed reasonably well with test results.

Detached-Eddy Simulations and Reynolds-Averaged Navier-Stokes Simulations of Delta Wing Vortical Flowfields

2002 ◽  
Vol 124 (4) ◽  
pp. 924-932 ◽  
Author(s):  
Scott Morton ◽  
James Forsythe ◽  
Anthony Mitchell ◽  
David Hajek
Keyword(s):  
Vortex Breakdown ◽  
Delta Wing ◽  
Turbulence Models ◽  
Reynolds Numbers ◽  
Navier Stokes ◽  
Detached Eddy Simulation ◽  
Fighter Aircraft ◽  
Eddy Simulation ◽  
Reynolds Averaged Navier Stokes ◽  
High Reynolds

An understanding of vortical structures and vortex breakdown is essential for the development of highly maneuverable vehicles and high angle of attack flight. This is primarily due to the physical limits these phenomena impose on aircraft and missiles at extreme flight conditions. Demands for more maneuverable air vehicles have pushed the limits of current CFD methods in the high Reynolds number regime. Simulation methods must be able to accurately describe the unsteady, vortical flowfields associated with fighter aircraft at Reynolds numbers more representative of full-scale vehicles. It is the goal of this paper to demonstrate the ability of detached-eddy Simulation (DES), a hybrid Reynolds-averaged Navier-Stokes (RANS)/large-eddy Simulation (LES) method, to accurately predict vortex breakdown at Reynolds numbers above 1×106. Detailed experiments performed at Onera are used to compare simulations utilizing both RANS and DES turbulence models.

scholarly journals Comparative Study on CFD Turbulence Models for the Flow Field in Air Cooled Radiator

Processes ◽  
2020 ◽  
Vol 8 (12) ◽  
pp. 1687
Author(s):  
Chao Yu ◽  
Xiangyao Xue ◽  
Kui Shi ◽  
Mingzhen Shao ◽  
Yang Liu
Keyword(s):  
Flow Field ◽  
Transient Flow ◽  
Three Dimensional ◽  
Turbulence Models ◽  
Compartment Model ◽  
Navier Stokes ◽  
Engine Compartment ◽  
Detached Eddy Simulation ◽  
Eddy Simulation ◽  
Relevant Calculation

This paper compares the performances of three Computational Fluid Dynamics (CFD) turbulence models, Reynolds Average Navier-Stokes (RANS), Detached Eddy Simulation (DES), and Large Eddy Simulation (LES), for simulating the flow field of a wheel loader engine compartment. The distributions of pressure fields, velocity fields, and vortex structures in a hybrid-grided engine compartment model are analyzed. The result reveals that the LES and DES can capture the detachment and breakage of the trailing edge more abundantly and meticulously than RANS. Additionally, by comparing the relevant calculation time, the feasibility of the DES model is proved to simulate the three-dimensional unsteady flow of engine compartment efficiently and accurately. This paper aims to provide a guiding idea for simulating the transient flow field in the engine compartment, which could serve as a theoretical basis for optimizing and improving the layout of the components of the engine compartment.

On the Investigation of Flow around the Square Cylinder Based on Different LES Models

2012 ◽  
Vol 594-597 ◽  
pp. 2676-2679
Author(s):  
Zhe Liu
Keyword(s):  
Flow Characteristics ◽  
Turbulence Models ◽  
Navier Stokes ◽  
Detached Eddy Simulation ◽  
Square Cylinder ◽  
Rans Model ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Reynolds Averaged Navier Stokes ◽  
Les Model

Although the conventional Reynolds-averaged Navier–Stokes (RANS) model has been widely applied in the industrial and engineering field, it is worthwhile to study whether these models are suitable to investigate the flow filed varying with the time. With the development of turbulence models, the unsteady Reynolds-averaged Navier–Stokes (URANS) model, detached eddy simulation (DES) and large eddy simulation (LES) compensate the disadvantage of RANS model. This paper mainly presents the theory of standard LES model, LES dynamic model and wall-adapting local eddy-viscosity (WALE) LES model. And the square cylinder is selected as the research target to study the flow characteristics around it at Reynolds number 13,000. The influence of different LES models on the flow field around the square cylinder is compared.

scholarly journals A Hybrid RANS-LES Computational Fluid Dynamics Simulation of an FDA Medical device benchmark

Mechanika ◽  
2019 ◽  
Vol 25 (4) ◽  
pp. 291-298
Author(s):  
Primož Drešar ◽  
Jožef Duhovnik
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Turbulence Models ◽  
The United States ◽  
Dynamics Simulation ◽  
Sudden Expansion ◽  
Detached Eddy Simulation ◽  
Cfd Validation ◽  
Eddy Simulation ◽  
Advection Schemes

Computational fluid dynamics (CFD) is a valuable tool that complements experimental data in the development of medical devices. The reliability of CFD still presents an issue and for that reason, no standardized approaches are currently available. The United States Food and Drug Administration (FDA) has initiated the development of a program for CFD validation, and has presented an idealized nozzle benchmark model. In this study, a nozzle flow with sudden expansion has been simulated using advanced RANS-LES turbulence models. Such models partially resolve the flow and are cheaper in computer resources and time in comparison to the Large Eddy Simulation (LES). Furthermore, they are more accurate than standard Reynolds-averaged Navier-Stokes (RANS) models. A collection of hybrid turbulence models has been investigated: Detached Eddy Simulation (DES), Stress Blended Eddy Simulation (SBES), and Scale Adaptive Simulation (SAS), and compared to a standard RANS Shear Stress Transport (SST) model. Subsequently, all models were validated by experimental results already published by different research groups. Particle Image Velociometry (PIV) experiments were performed by inter-laboratory study, and the results are available online for numerical validation.  The flow conditions in this study are only restricted to a turbulence flow at a Reynolds number of Re =6500. Complementing the turbulence models investigation, two advection schemes were tested: high resolution (HR) and bounded central difference scheme (BCD). Among all advanced models the SBES model with BCD scheme has the best agreement with the experimental values.

Development and Validation of Computational Fluid Dynamics Models for Initial Stages of Cavitation

2014 ◽  
Vol 136 (8) ◽  
Author(s):  
Eduard Amromin
Keyword(s):  
Fluid Dynamics ◽  
Experimental Data ◽  
Computational Fluid Dynamics ◽  
Navier Stokes ◽  
Detached Eddy Simulation ◽  
Cavitating Flows ◽  
Cavitation Inception ◽  
Eddy Simulation ◽  
Cfd Models ◽  
Liquid Flows

Various computational fluid dynamics (CFD) models employed for cavitating flows are substantially based on semi-empirical assumptions about cavitation forms and liquid flows around cavitating bodies. Therefore, the model applicability must be validated with experimental data. The stages of validation of the models are analyzed here with data on cavitating hydrofoils and axisymmetric bodies in water. Results of Reynolds-averaged Navier–Stokes (RANS), large-eddy simulation (LES), detached-eddy simulation (DES), and viscous-inviscid interaction methods are compared. The necessity of simultaneous validation of several flow parameters (as cavitation inception number and location of the appearing cavity) is pointed out. Typical uncertainties in water tunnel model test data (water quality, simplified account of wall effect) and possibilities to take them into account are also discussed. The provided comparison with experimental data manifests the impossibility to describe initial stages of cavitating flows using any single model and importance of employment of a combination of models for both the cavitation zones and the flow outside of cavities.

Large eddy simulation of a homogeneously charged turbulent jet ignition system

2017 ◽  
Vol 20 (2) ◽  
pp. 181-193 ◽  
Author(s):  
Masumeh Gholamisheeri ◽  
Shawn Givler ◽  
Elisa Toulson
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Large Eddy Simulation ◽  
Peak Pressure ◽  
Turbulent Jet ◽  
Navier Stokes ◽  
Rapid Compression Machine ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Reynolds Averaged Navier Stokes

Transient jet ignition of a homogeneous methane air mixture in a turbulent jet ignition system is studied computationally using a large eddy simulation turbulence model. The jet discharges from a prechamber into a main combustion chamber via one or more orifice(s) and provides a distributed ignition source in turbulent jet ignition. The effect of orifice size and stoichiometry is studied numerically using the Converge computational fluid dynamics code. A reduced kinetic mechanism is used for combustion along with a Smagorinsky sub-model for turbulence modeling. The computed pressure traces are compared with experimental measurements through rapid compression machine tests. Computational fluid dynamics results are in acceptable agreement with the experimental data during compression and the early stage of combustion; however, an over-prediction of peak pressure was reported. Peak pressure error is in the range of 0.1%–4% for Reynolds-averaged Navier–Stokes simulation estimation compared to the experimental measurements. This error is a function of mixture stoichiometry and unburned gas temperature. The error calculation showed that with the large eddy simulation model, 1% and 12% improvements in peak pressure and burn rate estimations, respectively, were achieved compared to Reynolds-averaged Navier–Stokes results. The reduced large eddy simulation error relative to the Reynolds-averaged Navier–Stokes simulations were considered to be in the acceptable range; however, further improvements could be achieved through validation and testing of additional turbulence models. In addition, computational fluid dynamics temperature contours for various nozzle orifices and air–fuel ratios are compared to achieve deeper insight into the turbulent jet ignition combustion process in the rapid compression machine combustion cylinder. The numerical iso-surface temperature contours were obtained which enabled three-dimensional views of the flame propagation, the jet discharge, ignition and extinction events. The heat release process and regeneration of mid-range temperature iso-surfaces (1200 K) were not visible through the experimental images.

Comparison of Unsteady Reynolds Averaged Navier–Stokes and Large Eddy Simulation Computational Fluid Dynamics Methodologies for Air Swirl Fuel Injectors

2008 ◽  
Vol 131 (1) ◽  
Author(s):  
David Dunham ◽  
Adrian Spencer ◽  
James J. McGuirk ◽  
Mehriar Dianat
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Large Eddy Simulation ◽  
Temporal Dynamics ◽  
Navier Stokes ◽  
Fuel Injector ◽  
Fuel Injectors ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Reynolds Averaged Navier Stokes

It is well documented that various large-scale quasiperiodic flow structures, such as a precessing vortex core (PVC) and multiple vortex helical instabilities, are present in the swirling flows typical of air swirl fuel injectors. Prediction of these phenomena requires time-resolved computational methods. The focus of the present work was to compare the performance and cost implications of two computational fluid dynamics (CFD) methodologies—unsteady Reynolds averaged Navier–Stokes (URANS) using a k-ε model and large eddy simulation (LES) for such flows. The test case was a single stream radial swirler geometry, which has been the subject of extensive experimental investigation. Both approaches captured the gross (time-mean) features of strongly swirling confined flows in reasonable agreement with experiment. The temporal dynamics of the quadruple vortex pattern emanating from within the swirler and observed experimentally were successfully predicted by LES, but not by URANS. Spectral analysis of two flow configurations (with and without a central jet) revealed various coherent frequencies embedded within the broadband turbulent frequency range. LES reproduced these characteristics, in excellent agreement with experimental data, whereas URANS predicted the presence of coherent motions but at incorrect amplitudes and frequencies. For the no-jet case, LES-predicted spectral data indicated the occurrence of a PVC, which was also observed experimentally for this flow condition; the URANS solution failed to reproduce this measured trend. On the evidence of this study, although k-ε based URANS offers considerable computational savings, its inability to capture the temporal characteristics of the flows studied here sufficiently accurately suggests that only LES-based CFD, which captures the stochastic nature of the turbulence much more faithfully, is to be recommended for fuel injector flows.

scholarly journals Τυρβώδης ροή και διασπορά ρύπων στο αστικό περιβάλλον

2014 ◽  
Author(s):  
Νεκτάριος Κουτσουράκης
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Large Eddy Simulation ◽  
Navier Stokes ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Computational Fluid Dynamics Cfd ◽  
Reynolds Averaged Navier Stokes

Στην παρούσα διατριβή έγινε ανάπτυξη υπολογιστικής μεθοδολογίας μοντελοποίησης μεγάλων δινών και χρήση της σε προβλήματα μελέτης της ροής του ανέμου και της διασποράς αέριων ρύπων ανάμεσα σε κτίρια. Η μοντελοποίηση μεγάλων δινών (Large Eddy Simulation – LES) είναι μια μεθοδολογία υπολογιστικής ρευστομηχανικής (Computational Fluid Dynamics – CFD) με την οποία είναι δυνατή η λεπτομερής χρονική επίλυση της ροής και η ανάλυση των μεγάλων δινών της τύρβης. Έτσι η LES ενδείκνυται ιδιαίτερα για μελέτη των ασταθών τυρβωδών ροϊκών φαινομένων που συμβαίνουν σε αστικές γεωμετρίες. Η μεθοδολογία LES που αναπτύχθηκε ενσωματώθηκε σε προϋπάρχοντα κώδικα CFD, τον ADREA-HF. Η αναπτυχθείσα LES χρησιμοποιεί μεταξύ των άλλων και μια πρωτότυπη μέθοδο δημιουργίας τεχνητής ψευδοτύρβης για χρήση σε οριακές συνθήκες του υπολογιστικού χωρίου, η οποία βασίζεται σε μια γενικευμένη εξίσωση τύπου Langevin. Για πιστοποίηση του κώδικα έγιναν μοντελοποιήσεις πλήρως ανεπτυγμένης ροής σε κανάλι, αλλά και ροής και διασποράς ρύπων σε οδικές χαράδρες. Επίσης εξετάστηκαν και πιο σύνθετες περιπτώσεις, όπως έκλυση και διασπορά υδρογόνου σε κλειστούς χώρους, ροή και διασπορά ρύπων σε ασύμμετρες οδικές χαράδρες, ροή πάνω από πολύ μεγάλη τραχύτητα εδάφους και τέλος ροή και διασπορά ρύπων σε μια πρωτότυπη γεωμετρία ημι-εξιδανικευμένης πόλης. Στις εφαρμογές που μελετήθηκαν έγινε επιτυχής σύγκριση με πειραματικά δεδομένα, οπότε η μεθοδολογία που αναπτύχθηκε αποδείχθηκε αξιόπιστη. Εκτός από την LES, χρησιμοποιήθηκε και η απλούστερη μεθοδολογία RANS (Reynolds-Averaged Navier-Stokes), προσδιορίστηκε ο σχετικός ρόλος των δύο μεθοδολογιών και αναδείχθηκαν οι δυνατότητες συμπληρωματικής χρήσης τους στο ίδιο πρόβλημα. Σε κάθε πρακτική εφαρμογή που εξετάστηκε, μελετήθηκαν κυρίως θέματα στα οποία υπήρχε κενό στη βιβλιογραφία. Μεταξύ άλλων προσδιορίστηκαν οι μηχανισμοί απαγωγής των ρύπων σε ασύμμετρες οδικές χαράδρες και υπολογίστηκε για πρώτη φορά ο κρίσιμος λόγος υψών για δημιουργία δύο στροβίλων σε χαράδρες μείωσης αναβαθμού. Επίσης μελετήθηκαν λεπτομερώς ασταθή ροϊκά φαινόμενα και τυρβώδεις δομές στην ημι-εξιδανικευμένη πόλη, αποκαλύπτοντας φαινόμενα όπως ριπές ανέμου, εξωθήσεις ρύπου, μη-γκαουσιανές κατανομές ταχυτήτων, αλλά και μηχανισμούς δημιουργίας κάποιων συνεκτικών δομών της τύρβης (ιδίως πεταλοειδών στροβίλων). Με τη μεθοδολογία LES, ανοίγονται νέοι ορίζοντες στη μελέτη της τυρβώδους ροής και της διασποράς ρύπων στο αστικό περιβάλλον.

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