Detached-Eddy Simulation of High Reynolds Number Beveled-Trailing-Edge Flows and Wakes

Near Wake ◽

Trailing Edge ◽

Eddy Simulation ◽

Instability Modes ◽

Trailing Edges ◽

Horseshoe Vortices ◽

Flow over three different trailing-edge geometries is studied using incompressible detached-eddy simulation and unsteady Reynolds-averaged Navier Stokes CFD methods. Of interest is the ability of DES, coupled with localized overset–grid refinement, to resolve the proper physics of separated flows from trailing edges—trailing-edge turbulence and vortex shedding, in particular. The DES model is shown to provide a good qualitative description of the trailing-edge flow. However, the modeled separations are overly energetic due to premature separation related to artificially low turbulence levels from upstream. The transition from RANS to DES is isolated as an issue. The simulated physics of the wake are shown to be in agreement with other LES studies: the model produces the “rib/roller” structures representing the first instability modes, horseshoe vortices are observed, and in regions of high resolution, small scales are formed, as expected. The turbulence statistics are qualitatively similar to benchmark data near the trailing edge and in the near wake, however, quantitative comparisons of urms show an over prediction in magnitude of 50–100%. Despite this, the results are promising, and future modeling efforts have been motivated and identified.

Detached-Eddy Simulation of High-Reynolds-Number Beveled-Trailing-Edge Boundary Layers and Wakes

10.1115/1.2012501 ◽

2005 ◽

Vol 127 (5) ◽

pp. 897-906 ◽

Cited By ~ 11

Author(s):

Eric G. Paterson ◽

Leonard J. Peltier

Keyword(s):

Qualitative Description ◽

Navier Stokes ◽

Near Wake ◽

Trailing Edge ◽

Eddy Simulation ◽

Instability Modes ◽

Trailing Edges ◽

Horseshoe Vortices ◽

Flow over three different trailing-edge geometries is studied using incompressible detached-eddy simulation and unsteady Reynolds-averaged Navier Stokes CFD methods. Of interest is the ability of DES, coupled, with localized overset-grid refinement, to resolve the proper physics of separated flows from trailing edges—trailing-edge turbulence and vortex shedding, in particular. The DES model is shown to provide a good qualitative description of the trailing-edge flow. However, the modeled separations are overly energetic due to premature separation related to artificially low turbulence levels from upstream. The transition from RANS to DES is isolated as an issue. The simulated physics of the wake are shown to be in agreement with other LES studies: the model produces the “rib/roller” structures representing the first instability modes, horseshoe vortices are observed, and in regions of high resolution, small scales are formed, as expected. The turbulence statistics are qualitatively similar to benchmark data near the trailing edge and in the near wake, however, quantitative comparisons of urms show an over prediction in magnitude of 50%–100%. Despite this, the results are promising, and future modeling efforts have been motivated and identified.

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

10.1115/1.1517570 ◽

2002 ◽

Vol 124 (4) ◽

pp. 924-932 ◽

Cited By ~ 46

Author(s):

Scott Morton ◽

James Forsythe ◽

Anthony Mitchell ◽

David Hajek

Keyword(s):

Vortex Breakdown ◽

Delta Wing ◽

Turbulence Models ◽

Reynolds Numbers ◽

Navier Stokes ◽

Fighter Aircraft ◽

Eddy Simulation ◽

Reynolds Averaged Navier Stokes ◽

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.

Partially Averaged Navier–Stokes (PANS) Method for Turbulence Simulations: Flow Past a Circular Cylinder

10.1115/1.4003154 ◽

2010 ◽

Vol 132 (12) ◽

Cited By ~ 46

Author(s):

Sunil Lakshmipathy ◽

Sharath S. Girimaji

Keyword(s):

Circular Cylinder ◽

Navier Stokes ◽

Length Scale ◽

Mean Flow ◽

Closure Model ◽

Variable Resolution ◽

Eddy Simulation ◽

Flow Past ◽

The objective of this study is to evaluate the capability of the partially averaged Navier–Stokes (PANS) method in a moderately high Reynolds number (ReD 1.4×105) turbulent flow past a circular cylinder. PANS is a bridging closure model purported for use at any level of resolution ranging from Reynolds-averaged Navier–Stokes to direct numerical simulations. The closure model is sensitive to the length-scale cut-off via the ratios of unresolved-to-total kinetic energy (fk) and unresolved-to-total dissipation (fε). Several simulations are performed to study the effect of the cut-off length-scale on computed closure model results. The results from various resolutions are compared against experimental data, large eddy simulation, and detached eddy simulation solutions. The quantities examined include coefficient of drag (Cd), Strouhal number (St), and coefficient of pressure distribution (Cp) along with the mean flow statistics and flow structures. Based on the computed results for flow past circular cylinder presented in this paper and analytical attributes of the closure model, it is reasonable to conclude that the PANS bridging method is a theoretically sound and computationally viable variable resolution approach for practical flow computations.

Volume 4: Terry Jones Pipeline Technology; Ocean Space Utilization; CFD and VIV Symposium ◽

Numerical Prediction of Bare and Straked Cylinder VIV

10.1115/omae2006-92334 ◽

2006 ◽

Cited By ~ 12

Author(s):

Yiannis Constantinides ◽

Owen H. Oakley

Keyword(s):

Turbulence Models ◽

Navier Stokes ◽

Eddy Simulation ◽

Numerical Studies ◽

Vortex Induced Vibrations ◽

Computational Fluid Dynamics Cfd ◽

Offshore Industry ◽

High Reynolds ◽

Cfd Method

The prediction of deepwater riser Vortex Induced Vibrations (VIV) is one of the most challenging areas in the offshore industry. Numerous experimental and numerical studies have been performed in an effort to improve the understanding and prediction of cylinder VIV behavior. This paper presents the numerical simulation of rigid circular sections, both bare and fitted with strakes, using a second order accurate finite element computational fluid dynamics (CFD) method. Two turbulence models are examined: the Spalart-Allmaras Reynolds Averaged Navier Stokes (RANS) and the Detached Eddy Simulation (DES). Pragmatic high Reynolds number simulations of fixed and moving cylinders are presented and compared with laboratory experiments. Flow visualization provides insights on how strakes mitigate VIV. Comparisons between RANS and DES results are also presented and discussed.

Aerodynamic and aeroacoustic behavior of span-wise wavy trailing edge modified SNL 100 m blade

Wind Engineering ◽

10.1177/0309524x18818646 ◽

2018 ◽

Vol 43 (1) ◽

pp. 4-25 ◽

Cited By ~ 1

Author(s):

Seung Joon Yang ◽

James D Baeder

Keyword(s):

Numerical Simulation ◽

Parametric Study ◽

Graphics Processing Unit ◽

Navier Stokes ◽

Processing Unit ◽

Trailing Edge ◽

Wind Speeds ◽

Eddy Simulation ◽

Edge Modification

The aerodynamic and aeroacoustic behaviors of wavy trailing edge modified flatback wind turbine blade have been investigated through numerical simulation. Previous studies have demonstrated aerodynamic and aeroacoustic benefits of the span-wise wavy trailing edge modification on the flatback trailing edge. The previous two-dimensional airfoil test cases have been extended to a complete set of design parametric study. Aerodynamic and aeroacoustic characteristics of the parametric study have been discussed, relying on the wave size, including recently added cases. Furthermore, in the current study, the wavy trailing edge modification has been applied to the Sandia flatback blade called “SNL100-03FB” and tested in rotating blade conditions. Several variations of the wavy trailing edge design have been tested for a range of wind speeds using an overset computation domain. The numerical simulation employs the in-house developed Navier–Stokes solver, OVERTURNS, as well as Graphics Processing Unit (GPU)-accelerated solver, GPURANS3D. Both are hybrid Reynolds Averaged Navier Stokes (RANS)/Large Eddy Simulation (LES) simulation; delayed detached eddy simulation has been used with the Spalart–Allmaras turbulent model and modified [Formula: see text] laminar–turbulent transition model.

Philosophical Transactions of The Royal Society A Mathematical Physical and Engineering Sciences ◽

Simulating flow separation from continuous surfaces: routes to overcoming the Reynolds number barrier

10.1098/rsta.2009.0002 ◽

2009 ◽

Vol 367 (1899) ◽

pp. 2885-2903 ◽

Cited By ~ 18

Author(s):

Michael Leschziner ◽

Ning Li ◽

Fabrizio Tessicini

Keyword(s):

Reynolds Number ◽

Turbulent Flows ◽

Major Elements ◽

Wall Layer ◽

Navier Stokes ◽

Eddy Simulation ◽

Large Eddy ◽

Rans Models ◽

High Reynolds ◽

Near Wall

This paper provides a discussion of several aspects of the construction of approaches that combine statistical (Reynolds-averaged Navier–Stokes, RANS) models with large eddy simulation (LES), with the objective of making LES an economically viable method for predicting complex, high Reynolds number turbulent flows. The first part provides a review of alternative approaches, highlighting their rationale and major elements. Next, two particular methods are introduced in greater detail: one based on coupling near-wall RANS models to the outer LES domain on a single contiguous mesh, and the other involving the application of the RANS and LES procedures on separate zones, the former confined to a thin near-wall layer. Examples for their performance are included for channel flow and, in the case of the zonal strategy, for three separated flows. Finally, a discussion of prospects is given, as viewed from the writer's perspective.

Proceedings of the Institution of Mechanical Engineers Part G Journal of Aerospace Engineering ◽

Numerical study of the flow over the modified simple frigate shape

10.1177/0954410020977752 ◽

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 ◽

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.

Detached Eddy Simulation of Transonic Rotor Stall Flutter Using a Fully Coupled Fluid-Structure Interaction

Volume 6: Structures and Dynamics, Parts A and B ◽

10.1115/gt2011-45437 ◽

2011 ◽

Cited By ~ 7

Author(s):

Hongsik Im ◽

Xiangying Chen ◽

Gecheng Zha

Keyword(s):

Stokes Equations ◽

Rotating Stall ◽

Rotor Blades ◽

Tip Clearance ◽

Weno Scheme ◽

Navier Stokes ◽

Eddy Simulation ◽

Stall Flutter ◽

Fully Coupled

Detached eddy simulation of an aeroelastic self-excited instability, flutter in NASA Rotor 67 is conducted using a fully coupled fluid/structre interaction. Time accurate compressible 3D Navier-Stokes equations are solved with a system of 5 decoupled modal equations in a fully coupled manner. The 5th order WENO scheme for the inviscid flux and the 4th order central differencing for the viscous flux are used to accurately capture interactions between the flow and vibrating blades with the DES (detached eddy simulation) of turbulence. A moving mesh concept that can improve mesh quality over the rotor tip clearance was implemented. Flutter simulations were first conducted from choke to stall using 4 blade passages. Stall flutter initiated at rotating stall onset, grows dramatically with resonance. The frequency analysis shows that resonance occurs at the first mode of the rotor blade. Before stall, the predicted responses of rotor blades decayed with time, resulting in no flutter. Full annulus simulation at peak point verifies that one can use the multi-passage approach with periodic boundary for the flutter prediction.

Detached-Eddy Simulations Over a Simplified Landing Gear

10.1115/1.1471532 ◽

2002 ◽

Vol 124 (2) ◽

pp. 413-423 ◽

Cited By ~ 113

Author(s):

L. S. Hedges ◽

A. K. Travin ◽

P. R. Spalart

Keyword(s):

Stokes Equations ◽

Separated Flow ◽

Flow Fields ◽

Equation Model ◽

Landing Gear ◽

Navier Stokes ◽

Navier Stokes Equations ◽

Instantaneous Flow ◽

Eddy Simulation

The flow around a generic airliner landing-gear truck is calculated using the methods of Detached-Eddy Simulation, and of Unsteady Reynolds-Averaged Navier-Stokes Equations, with the Spalart-Allmaras one-equation model. The two simulations have identical numerics, using a multi-block structured grid with about 2.5 million points. The Reynolds number is 6×105. Comparison to the experiment of Lazos shows that the simulations predict the pressure on the wheels accurately for such a massively separated flow with strong interference. DES performs somewhat better than URANS. Drag and lift are not predicted as well. The time-averaged and instantaneous flow fields are studied, particularly to determine their suitability for the physics-based prediction of noise. The two time-averaged flow fields are similar, though the DES shows more turbulence intensity overall. The instantaneous flow fields are very dissimilar. DES develops a much wider range of unsteady scales of motion and appears promising for noise prediction, up to some frequency limit.

Numerical Investigation of Energy Saving Device Effects on Ships With Propeller-Hull Interactions

Volume 7B: Ocean Engineering ◽

10.1115/omae2018-78600 ◽

2018 ◽

Author(s):

Ravi Chaithanya Mysa ◽

Le Quang Tuyen ◽

Ma Shengwei ◽

Vinh-Tan Nguyen

Keyword(s):

Energy Saving ◽

Full Scale ◽

Navier Stokes ◽

Propulsion Efficiency ◽

Operational Conditions ◽

Ship Resistance ◽

The Past ◽

Eddy Simulation ◽

Flow Features

Energy saving devices (ESD) such as propeller ducts, pre-swirl stators, pre-nozzles, etc have been explored as a more economic and reliable approach to reduce energy consumption for both in-operation and newly design ships over the past decades. Those energy saving devices work in the principle of reducing ship resistance and improving propulsion efficiency as well as hull-propeller interactions. Potential saving from various types of ESD have been reported in literature from the range of 3–9% [1] for propulsion efficiency dependent on different measures. Deployment of those devices on actual full-scale ships has been limited over the past years. One of the key obstacles in application of ESD is the lack of confidence in measuring its efficiency on full-scale ships in actual operational conditions. Advances in computational fluid dynamics (CFD) has provided an alternative approach from model scale test to better understand uncertainties in prediction of ESD efficiency in full-scale ship operations [Shin et al, 2013]. In this work a high fidelity CFD model is presented for investigation effects of pre-nozzles on propulsion efficiency and ship resistance. The model is based on the Reynolds Average Navier-Stokes (RANS) solver with different turbulent models including a hybrid detached eddy simulation (DES) approach for predictions of complex near body flow features as well as in the wake regions from hull and propeller. The model is validated with model test for both towing and self-propulsion conditions. Finally a study of pre-nozzle effects on propeller efficiency as well as hull-propeller interaction is presented and compared with available experimental data (Tokyo 2015 Workshop). The current work constitutes a fundamental approach towards designing more efficient ESD for a specific hull form and propeller.