Numerical Investigation of Flow Around a Multi-Element Airfoil with Hybrid RANS-LES Approaches Based on SST Model

AbstractAccurate prediction of the flow around multi-element airfoil is a prerequisite for improving aerodynamic performance, but its complex flow features impose high demands on turbulence modeling. In this work, delayed detached-eddy-simulation (DDES) and zonal detached-eddy-simulation (ZDES) was applied to simulate the flow past a three-element airfoil. To investigate the effects of numerical dissipation of spatial schemes, the third-order MUSCL and the fifth-order interpolation based on modified Roe scheme were implemented. From the comparisons between the calculations and the available experimental result, third-order MUSCL-Roe can provide satisfactory mean velocity profiles, but the excessive dissipation suppresses the velocity fluctuations level and eliminates the small-scale structures; DDES cannot reproduce the separation near the trailing edge of the flap which lead to the discrepancy in mean pressure coefficients, while ZDES result has better tally with the experiment.

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LES and Hybrid RANS/LES of a Fundamental Trailing Edge Slot

Volume 5B: Heat Transfer ◽

10.1115/gt2014-25906 ◽

2014 ◽

Cited By ~ 4

Author(s):

Elizaveta Ivanova ◽

Gregory M. Laskowski

Keyword(s):

Heat Transfer ◽

Experimental Data ◽

Numerical Study ◽

Mixing Layer ◽

Detached Eddy Simulation ◽

Trailing Edge ◽

Adiabatic Wall ◽

Mean Velocity ◽

Eddy Simulation ◽

Delayed Detached Eddy Simulation

This paper presents the results of a numerical study on the predictive capabilities of Large Eddy Simulation (LES) and hybrid RANS/LES methods for heat transfer, mean velocity, and turbulence in a fundamental trailing edge slot. The geometry represents a landless slot (two-dimensional wall jet) with adjustable slot lip thickness. The reference experimental data taken from the publications of Kacker and Whitelaw [1] [2] [3] [4] contains the adiabatic wall effectiveness together with the velocity and the Reynolds-stress profiles for various blowing ratios and slot lip thicknesses. The simulations were conducted at three different lip thickness and several blowing ratio values. The comparison with the experimental data shows a general advantage of LES and hybrid RANS/LES methods against unsteady RANS. The predictive capability of the tested LES models (dynamic ksgs-equation [5] and WALE [6]) was comparable. The Improved Delayed Detached Eddy Simulation (IDDES) hybrid method [7] also shows satisfactory agreement with the experimental data. In addition to the described baseline investigations, the influence of the inlet turbulence boundary conditions and their implication for the initial mixing layer and heat transfer development were studied for both LES and IDDES.

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A DDES study of the flow past a prolate spheroid using a high-order U-MUSCL scheme

International Journal of Modern Physics B ◽

10.1142/s0217979220400755 ◽

2020 ◽

Vol 34 (14n16) ◽

pp. 2040075

Author(s):

Yu-Chen Yang ◽

Zhen-Ming Wang ◽

Ning Zhao

Keyword(s):

Flow Separation ◽

Vortex Structure ◽

Prolate Spheroid ◽

High Order ◽

Detached Eddy Simulation ◽

Complex Flow ◽

Eddy Simulation ◽

Flow Past ◽

Delayed Detached Eddy Simulation ◽

Flow Phenomena

Flow past a prolate spheroid, which is a representative simplified configuration for vehicles such as maneuvering ships, submarines and missiles, comprises a series of complex flow phenomena including pressure-induced flow separation, which results in unsteady forces and movements that may be detrimental to vehicles’ performance. In this paper, a Delayed Detached Eddy Simulation (DDES) method combined with a new high-order U-MUSCL scheme is proposed to more precisely and accurately capture the flow separation and vortex structure. This method is applied to simulate the aerodynamic performance of the 6:1 prolate spheroid at an AOA of [Formula: see text] with the Reynolds number of [Formula: see text]. Axial pressure distribution of five individual chord wise sections and flow field structure of the aft body are analyzed. Numerical results agree well with the experimental data. It can be concluded that DDES combined with three-order U-MUSCL scheme demonstrates reliable performance since it captures the vortex structure of aft body distinctly and predicts the separation and reattachment points of the secondary vortex precisely.

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Flow in a Mechanical Bileaflet Heart Valve at Laminar and Near-Peak Systole Flow Rates: CFD Simulations and Experiments

Journal of Biomechanical Engineering ◽

10.1115/1.1993665 ◽

2005 ◽

Vol 127 (5) ◽

pp. 782-797 ◽

Cited By ~ 72

Author(s):

Liang Ge ◽

Hwa-Liang Leo ◽

Fotis Sotiropoulos ◽

Ajit P. Yoganathan

Keyword(s):

Heart Valve ◽

Turbulence Modeling ◽

Mechanical Heart Valve ◽

Reynolds Numbers ◽

Navier Stokes ◽

Detached Eddy Simulation ◽

Cfd Simulations ◽

Mean Velocity ◽

Eddy Simulation ◽

Flow Through

Time-accurate, fully 3D numerical simulations and particle image velocity laboratory experiments are carried out for flow through a fully open bileaflet mechanical heart valve under steady (nonpulsatile) inflow conditions. Flows at two different Reynolds numbers, one in the laminar regime and the other turbulent (near-peak systole flow rate), are investigated. A direct numerical simulation is carried out for the laminar flow case while the turbulent flow is investigated with two different unsteady statistical turbulence modeling approaches, unsteady Reynolds-averaged Navier-Stokes (URANS) and detached-eddy simulation (DES) approach. For both the laminar and turbulent cases the computed mean velocity profiles are in good overall agreement with the measurements. For the turbulent simulations, however, the comparisons with the measurements demonstrate clearly the superiority of the DES approach and underscore its potential as a powerful modeling tool of cardiovascular flows at physiological conditions. The study reveals numerous previously unknown features of the flow.

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Effects of inlet velocity profiles for thermal stripping phenomena in T-junctions

Journal of Physics Conference Series ◽

10.1088/1742-6596/2116/1/012026 ◽

2021 ◽

Vol 2116 (1) ◽

pp. 012026

Author(s):

Lisa Lampunio ◽

Yu Duan ◽

Raad Issa ◽

Matthew D. Eaton

Keyword(s):

Velocity Profiles ◽

Lower Sensitivity ◽

Detached Eddy Simulation ◽

Mean Velocity ◽

Inlet Velocity ◽

Eddy Simulation ◽

Delayed Detached Eddy Simulation ◽

Flow Domain ◽

The Mean ◽

Good Agreement

Abstract This paper investigates the effects of different inlet velocities on thermal stripping phenomena within a T-junction. The computational flow domain is modelled using the Improved Delayed Detached Eddy Simulation (IDDES) turbulence model implemented within the commercial CFD code STAR-CCM+ 12.04. The computational model is validated against the OECD-NEA-Vattenfall T-junction Benchmark data. The influence of flat and fully developed inlet velocity profiles is then assessed. The results are in good agreement with the experimental data. The different inlet velocity profiles have a non-negligible effect on the mean wall temperature. The mean velocity shows lower sensitivity to changes in inlet velocity profiles, whose influence is confined mainly to the recirculation zone near the T-junction.

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CFD Simulation of a Twin-Screw Ship Self-Propulsion Using DDES-Overset Method

Volume 7B: Ocean Engineering ◽

10.1115/omae2019-95527 ◽

2019 ◽

Author(s):

Jianhua Wang ◽

Decheng Wan

Keyword(s):

Cfd Simulation ◽

Ship Hull ◽

The Self ◽

Detached Eddy Simulation ◽

Complex Flow ◽

Ship Model ◽

Eddy Simulation ◽

Delayed Detached Eddy Simulation ◽

Twin Screw ◽

Cfd Method

Abstract Rotating propellers and moving rudders are necessary for the simulation of free running ship with the purpose of resolving detailed flow interaction. In the present work, CFD method is used to numerically investigate self-propulsion behavior for a twin-screw fully appended ship. The simulation conditions are following the experiment performed at IIHR. The benchmark ship model ONR Tumblehome is used for all the numerical computations. Overset grids are used to fully discretize the ship hull, twin propellers and rudders. Self-propulsion simulation is carried out using a PI controller to achieve target ship speed of Fr = 0.20 in calm water and the ship model is free to trim and sinkage. All the numerical calculations are carried out by the in-house CFD solver naoe-FOAM-SJTU. Unlike most previous studies based on RANS method, the present self-propulsion simulations adopt the Delayed Detached-Eddy-Simulation (DDES) approach to resolve the complex flow around ship hull, propeller and rudder. The main parameters of the self-propulsion as well as flow visualizations are presented. The predicted results are compared with previous RANS data and the available experimental data. The comparison with the experiment is satisfactory and the flow field shows that the present DDES-overset method can give more flow details for the self-propulsion condition.

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RANS and Hybrid RANS-LES Simulations of an H-Type Darrieus Vertical Axis Water Turbine

Energies ◽

10.3390/en11092348 ◽

2018 ◽

Vol 11 (9) ◽

pp. 2348 ◽

Cited By ~ 3

Author(s):

Omar Mejia ◽

Jhon Quiñones ◽

Santiago Laín

Keyword(s):

Turbulence Models ◽

Vertical Axis ◽

Navier Stokes ◽

Speed Ratio ◽

Small Scale ◽

Detached Eddy Simulation ◽

Eddy Simulation ◽

Delayed Detached Eddy Simulation ◽

Flow Phenomena ◽

Water Turbine

Nowadays, the global energy crisis has encouraged the use of alternative sources like the energy available in the water currents of seas and rivers. The vertical axis water turbine (VAWT) is an interesting option to harness this energy due to its advantages of facile installation, maintenance and operation. However, it is known that its efficiency is lower than that of other types of turbines due to the unsteady effects present in its flow physics. This work aims to analyse through Computational Fluid Dynamics (CFD) the turbulent flow dynamics around a small scale VAWT confined in a hydrodynamic tunnel. The simulations were developed using the Unsteady Reynolds Averaged Navier Stokes (URANS), Detached Eddy Simulation (DES) and Delayed Detached Eddy Simulation (DDES) turbulence models, all of them based on k-ω Shear Stress Transport (SST). The results and analysis of the simulations are presented, illustrating the influence of the tip speed ratio. The numerical results of the URANS model show a similar behaviour with respect to the experimental power curve of the turbine using a lower number of elements than those used in the DES and DDES models. Finally, with the help of both the Q-criterion and field contours it is observed that the refinements made in the mesh adaptation process for the DES and DDES models improve the identification of the scales of the vorticity structures and the flow phenomena present on the near and far wake of the turbine.

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Transition and Turbulence Modeling for the Prediction of Cavitating Tip Vortices

Journal of Fluids Engineering ◽

10.1115/1.4048133 ◽

2020 ◽

Vol 143 (1) ◽

Author(s):

Rens Liebrand ◽

Maarten Klapwijk ◽

Thomas Lloyd ◽

Guilherme Vaz

Keyword(s):

Boundary Layer ◽

Turbulence Modeling ◽

Tip Vortex ◽

Vapor Flow ◽

Cavity Size ◽

Detached Eddy Simulation ◽

Tip Vortices ◽

Eddy Simulation ◽

Numerical Predictions ◽

Delayed Detached Eddy Simulation

Abstract This study evaluates the influence of transition and turbulence modeling on the prediction of wetted and cavitating tip vortices for an elliptical wing, while investigating the numerical errors. Transition modeling increases the quality of numerical predictions since the assumption of a fully turbulent boundary layer, commonly found in literature, contributes to underprediction of the tip vortex cavity size. By applying the local correlation-based transition model (LCTM) and controlling the boundary layer thickness using different turbulent inflow conditions, the pressure in the vortex was found to reduce by 20% for an Angle of Attack (AoA) of 5 deg. The consequent increase in cavity size was found to be of a similar order of magnitude. At 9 deg AoA, transition always occurs just downstream of the leading edge, making this AoA more suitable to investigate the effect of different turbulence modeling approaches. Azimuthal and axial velocity fields are validated against stereographic-particle image velocimetry (S-PIV) measurements. The time-averaged velocity profiles predicted by delayed detached-eddy simulation (DDES) and improved delayed detached-eddy simulation (IDDES) are close to the experiments; however, no velocity fluctuations and vortex dynamics are observed around the vortex. A comparison of wetted and cavitating simulations shows that the cavity leads to a change in the balance between production and destruction of turbulence kinetic energy, which reduces the turbulent diffusion in and around the cavity compared to wetted flow conditions. Consequently, the vapor flow exhibits the characteristics of a potential flow. Whether this is physically plausible remains to be investigated.

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