Numerical study of transonic cavity flows using large-eddy and detached-eddy simulation

2007 ◽  
Vol 111 (1117) ◽  
pp. 153-164 ◽  
Author(s):  
P. Nayyar ◽  
G. N. Barakos ◽  
K. J. Badcock
Keyword(s):  
Energy Content ◽  
Numerical Study ◽  
Flow Characteristics ◽  
Navier Stokes ◽  
Detached Eddy Simulation ◽  
Complex Flow ◽  
Promising Alternative ◽  
Eddy Simulation ◽  
Massively Separated Flows ◽  
Large Eddy

Numerical analysis of the flow in weapon bays modelled as open rectangular cavities of length-to-depth (L/D) ratio of 5 and width-to-depth (W/D) ratio of 1 with doors-on and doors-off is presented. Flow conditions correspond to Mach and Reynolds numbers (based on cavity length) of 0·85 and 6·783m respectively. Results from unsteady Reynolds-averaged Navier-Stokes (URANS), large-eddy simulation (LES) and detached-eddy simulation (DES) are compared with the simulation methods demonstrating the best prediction of this complex flow. It was found that URANS was not able to predict the change of flow characteristics between the doors-on and doors-off configurations. In addition, the energy content of the cavity flow modes was much better resolved with DES and LES. Further, the DES was found to be quite capable for this problem giving accurate results (within 3dB of) experiments and appears to be a promising alternative to LES for modelling massively separated flows.

Current Capabilities of DES and LES for Submarines at Straight Course

2010 ◽  
Vol 54 (03) ◽  
pp. 184-196 ◽  
Author(s):  
N. Alin ◽  
R.E. Bensow ◽  
C. Fureby ◽  
T. Huuva ◽  
U. Svennberg
Keyword(s):  
Statistical Moments ◽  
Navier Stokes ◽  
Detached Eddy Simulation ◽  
Complex Flow ◽  
First Order ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Actuator Disc ◽  
Rans Models ◽  
Coarse Grids

The flow around an axisymmetric hull, with and without appendages, is investigated using large eddy simulation (LES), detached eddy simulation (DES), and Reynolds averaged Navier Stokes (RANS) models. The main objectives of the study is to investigate the effect of the different simulation methods and to demonstrate the feasibility of using DES and LES on relatively coarse grids for submarine flows, but also to discuss some generic features of submarine hydrodynamics. For this purpose the DARPA Suboff configurations AFF1 (bare hull) and AFF8 (fully appended model) are used. The AFF1 case is interesting because it is highly demanding, in particular for LES and DES, due to the long midship section on which the boundary layer is developed. The AFF8 case represents the complex flow around a fully appended submarine with sail and aft rudders. An actuator disc model is used to emulate some of the effects of the propulsor for one of the AFF8 cases studied. Results for the AFF8 model are thus presented for both "towed" and "self-propelled" conditions, where as for the bare hull, only a "towed" condition is considered. For the AFF1 and the "towed" AFF8 cases experimental data are available for comparison, and the results from both configurations show that all methods give good results for first-order statistical moments although LES gives a better representation of structures and second-order statistical moments in the complex flow in the AFF8 case.

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 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.

NUMERICAL STUDY OF DETONATION PROPAGATION IN VISCOUS TURBULENT FLOW IN A DUCT

2020 ◽  
Author(s):  
V. A. SABELNIKOV ◽  
◽  
V. V. VLASENKO ◽  
S. BAKHNE ◽  
S. S. MOLEV ◽  
...  
Keyword(s):  
Complex Geometry ◽  
Numerical Study ◽  
Navier Stokes ◽  
Detonation Waves ◽  
Detonation Propagation ◽  
Eddy Simulation ◽  
Detonation Structure ◽  
Classical Studies ◽  
Large Eddy ◽  
Physical Effects

Gasdynamics of detonation waves was widely studied within last hundred years - analytically, experimentally, and numerically. The majority of classical studies of the XX century were concentrated on inviscid aspects of detonation structure and propagation. There was a widespread opinion that detonation is such a fast phenomenon that viscous e¨ects should have insigni¦cant in§uence on its propagation. When the era of calculations based on the Reynolds-averaged Navier- Stokes (RANS) and large eddy simulation approaches came into effect, researchers pounced on practical problems with complex geometry and with the interaction of many physical effects. There is only a limited number of works studying the in§uence of viscosity on detonation propagation in supersonic §ows in ducts (i. e., in the presence of boundary layers).

Numerical study of the flow over the modified simple frigate shape

2020 ◽  
pp. 095441002097775
Author(s):  
Tong Li ◽  
Yibin Wang ◽  
Ning Zhao
Keyword(s):  
Bluff Body ◽  
Recirculation Zone ◽  
Numerical Study ◽  
Reference Value ◽  
Flow Fields ◽  
Navier Stokes ◽  
Detached Eddy Simulation ◽  
Eddy Simulation ◽  
Delayed Detached Eddy Simulation ◽  
Simulation Results

The simple frigate shape (SFS) as defined by The Technical Co-operative Program (TTCP), is a simplified model of the frigate, which helps to investigate the basic flow fields of a frigate. In this paper, the flow fields of the different modified SFS models, consisting of a bluff body superstructure and the deck, were numerically studied. A parametric study was conducted by varying both the superstructure length L and width B to investigate the recirculation zone behind the hangar. The size and the position of the recirculation zones were compared between different models. The numerical simulation results show that the size and the location of the recirculation zone are significantly affected by the superstructure length and width. The results obtained by Reynolds-averaged Navier-Stokes method were also compared well with both the time averaged Improved Delayed Detached-Eddy Simulation results and the experimental data. In addition, by varying the model size and inflow velocity, various flow fields were numerically studied, which indicated that the changing of Reynolds number has tiny effect on the variation of the dimensionless size of the recirculation zone. The results in this study have certain reference value for the design of the frigate superstructure.

On LES Methods Applied to Seal Geometries

2012 ◽  
Author(s):  
James Tyacke ◽  
Richard Jefferson-Loveday ◽  
Paul Tucker
Keyword(s):  
Maximum Error ◽  
Labyrinth Seal ◽  
Navier Stokes ◽  
Final Solution ◽  
Complex Flow ◽  
Eddy Simulation ◽  
Wide Range ◽  
Large Eddy ◽  
Rans Models ◽  
Flow Through

Nine Large Eddy Simulation (LES) methods are used to simulate flow through two labyrinth seal geometries and are compared with a wide range of Reynolds-Averaged Navier-Stokes (RANS) solutions. These involve one-equation, two-equation and Reynolds Stress RANS models. Also applied are linear and nonlinear pure LES models, hybrid RANS-Numerical-LES (RANS-NLES) and Numerical-LES (NLES). RANS is found to have a maximum error and a scatter of 20%. A similar level of scatter is also found among the same turbulence model implemented in different codes. In a design context, this makes RANS unusable as a final solution. Results show that LES and RANS-NLES is capable of accurately predicting flow behaviour of two seals with a scatter of less than 5%. The complex flow physics gives rise to both laminar and turbulent zones making most LES models inappropriate. Nonetheless, this is found to have minimal tangible results impact. In accord with experimental observations, the ability of LES to find multiple solutions due to solution non-uniqueness is also observed.

Large Eddy Simulation of Cross Flow in Pipe Junction

2018 ◽  
Author(s):  
Jiajun Chen ◽  
Yue Sun ◽  
Hang Zhang ◽  
Dakui Feng ◽  
Zhiguo Zhang
Keyword(s):  
Large Eddy Simulation ◽  
Stokes Equations ◽  
Numerical Study ◽  
Three Dimensional ◽  
Cross Flow ◽  
Exciting Force ◽  
Navier Stokes ◽  
Pipe Network ◽  
Eddy Simulation ◽  
Large Eddy

Mixing in pipe junctions can play an important role in exciting force and distribution of flow in pipe network. This paper investigated the cross pipe junction and proposed an improved plan, Y-shaped pipe junction. The numerical study of a three-dimensional pipe junction was performed for calculation and improved understanding of flow feature in pipe. The filtered Navier–Stokes equations were used to perform the large-eddy simulation of the unsteady incompressible flow in pipe. From the analysis of these results, it clearly appears that the vortex strength and velocity non-uniformity of centerline, can be reduced by Y-shaped junction. The Y-shaped junction not only has better flow characteristic, but also reduces head loss and exciting force. The results of the three-dimensional improvement analysis of junction can be used in the design of pipe network for industry.

scholarly journals 3D Numerical Study of the Flow Properties in a Double-Spur Dikes Field during a Flood Process

Water ◽  
2018 ◽  
Vol 10 (11) ◽  
pp. 1574 ◽  
Author(s):  
Xun Han ◽  
Pengzhi Lin
Keyword(s):  
Water Surface ◽  
Numerical Study ◽  
Flow Characteristics ◽  
Field Measurements ◽  
Navier Stokes ◽  
Eddy Simulation ◽  
River Bed ◽  
Hydrodynamic Evolution ◽  
Spur Dikes ◽  
Potential Damage

A 3D numerical model is developed to study the flow characteristics of a double-spur dikes field on Yangtze River during a flood process, which was presented by the variation of the flow condition. The model is based on Navier–Stokes (NS) equations, the porous medium method (PMM) is employed to treat the solid structures including the river bed surface, the volume of fluid (VOF) method is applied to track the motion of the water surface during the flood process, and large eddy simulation (LES) is adopted to capture the turbulence transport and dissipation. Using this model, the target reach’s flow field before the construction of double-spur dikes is simulated first, while the numerical results are compared to the field measurements on flow velocity and water surface level, and fairly good agreements are shown. Then, the model is applied to reproduce the hydrodynamic evolution during a flood process after double-spur dikes’ constructions, while the detailed 3D flow fields are obtained under some certain states with different submergence rates of the spur dikes; finally, the potential damage positions around these spur dikes are analyzed accordingly.

Flow Characteristics in a Three-Dimensional Rectangular Channel With a Pair of Ribs Placed Symmetrically at the Channel Walls

2000 ◽  
Author(s):  
M. Singh ◽  
P. K. Panigrahi ◽  
G. Biswas
Keyword(s):  
Heat Transfer ◽  
Large Scale ◽  
Numerical Study ◽  
Rectangular Channel ◽  
Turbine Blades ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Navier Stokes ◽  
Complex Flow ◽  
Energy Equations

Abstract A numerical study of rib augmented cooling of turbine blades is reported in this paper. The time-dependent velocity field around a pair of symmetrically placed ribs on the walls of a three-dimensional rectangular channel was studied by use of a modified version of Marker-And-Cell algorithm to solve the unsteady incompressible Navier-Stokes and energy equations. The flow structures are presented with the help of instantaneous velocity vector and vorticity fields, FFT and time averaged and rms values of components of velocity. The spanwise averaged Nusselt number is found to increase at the locations of reattachment. The numerical results are compared with available numerical and experimental results. The presence of ribs leads to complex flow fields with regions of flow separation before and after the ribs. Each interruption in the flow field due to the surface mounted rib enables the velocity distribution to be more homogeneous and a new boundary layer starts developing downstream of the rib. The heat transfer is primarily enhanced due to the decrease in the thermal resistance owing to the thinner boundary layers on the interrupted surfaces. Another reason for heat transfer enhancement can be attributed to the mixing induced by large-scale structures present downstream of the separation point.

Sign in / Sign up

Export Citation Format

Share Document