Investigation of Flow Over an Airfoil Using a Hybrid Detached Eddy Simulation–Algebraic Stress Turbulence Model

2017 ◽  
Vol 139 (5) ◽  
Author(s):  
Saman Beyhaghi ◽  
Ryoichi S. Amano
Keyword(s):  
Pressure Coefficient ◽  
Turbulence Models ◽  
Published Data ◽  
Detached Eddy Simulation ◽  
Airfoil Surface ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Wall Flow ◽  
Turbulent Air Flow ◽  
Near Wall

Turbulent air flow over an NACA 4412 airfoil is investigated computationally. To overcome the near-wall inaccuracies of higher order turbulence models such as large Eddy simulation (LES) and detached Eddy simulation (DES), it is proposed to couple DES with algebraic stress model (ASM). Angles of attack (AoA) of 0 and 14 deg are studied for an airfoil subjected to flow with Re = 1.6 × 106. Distribution of the pressure coefficient at airfoil surface and the chordwise velocity component at four locations near the trailing edge are determined. Results of the baseline DES and hybrid DES–ASM models are compared against published data. It is demonstrated that the proposed hybrid model can slightly improve the flow predictions made by the DES model. Findings of this research can be used for the improvement of the near-wall flow predictions for wind turbine applications.

Adaptive Detached-Eddy Simulation of Three-Dimensional Diffusers

2016 ◽  
Vol 138 (10) ◽  
Author(s):  
Paul Durbin ◽  
Zifei Yin ◽  
Elbert Jeyapaul
Keyword(s):  
Pressure Coefficient ◽  
Three Dimensional ◽  
Side Wall ◽  
Turbulence Models ◽  
Adaptive Method ◽  
Detached Eddy Simulation ◽  
Mean Velocity ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Default Data

An adaptive method for detached-eddy simulation (DES) is tested by simulations of flow in a family of three-dimensional (3D) diffusers. The adaptive method either adjusts the model constant or defaults to a bound if the grid is too coarse. On the present grids, the adaptive method adjusts the model constant over most of the flow, without resorting to the default. Data for the diffuser family were created by wall-resolved, large-eddy simulation (LES), using the dynamic Smagorinsky model, for the purpose of testing turbulence models. The family is a parameterized set of geometries that allows one to test whether the pattern of separation is moving correctly from the top to the side wall as the parameter increases. The adaptive DES model is quite accurate in this regard. It is found to predict the mean velocity accurately, but the pressure coefficient is underpredicted. The latter is due to the onset of separation being slightly earlier in the DES than in the LES.

scholarly journals Prediction of flow and dispersion in cross–ventilated buildings

2019 ◽  
Vol 128 ◽  
pp. 05002
Author(s):  
Ali Cemal Benim ◽  
Michael Diederich ◽  
Ali Nahavandi
Keyword(s):  
Computational Analysis ◽  
Turbulence Models ◽  
Reynolds Stress Model ◽  
Turbulence Structure ◽  
Detached Eddy Simulation ◽  
Mean Velocity ◽  
Eddy Simulation ◽  
Large Eddy ◽  
The Mean ◽  
Grid Independence

The present paper presents a detailed computational analysis of flow and dispersion in a generic isolated single–zone buildings. First, a grid generation strategy is discussed, that is inspired by a previous computational analysis and a grid independence study. Different turbulence models are appliedincluding two-equation turbulence models, the differential Reynolds Stress Model, Detached Eddy Simulation and Zonal Large Eddy Simulation. The mean velocity and concentration fields are calculated and compared with the measurements. A satisfactory agreement with the experiments is not observed by any of the modelling approaches, indicating the highly demanding flow and turbulence structure of the problem.

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.

Large Eddy Simulation of Flow Over a Hemispherical Obstacle Within a Cylindrical Tube

2020 ◽  
Author(s):  
Amit Sharma ◽  
Urmila Ghia ◽  
Leonid A. Turkevich
Keyword(s):  
Cylindrical Tube ◽  
Front Surface ◽  
Horseshoe Vortex ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Strong Shear ◽  
Horseshoe Vortices ◽  
Wall Flow ◽  
Upstream Flow ◽  
Near Wall

Abstract Motivated by recent experiments on the dustiness of nanoscale powders, this research addresses the modeling of powder aerosolization within the Venturi Dustiness Test (VDT) apparatus. As a first step in such modeling, we investigate the flow over a hemispherical (powder) hill, at the operating Reynolds number Re ∼ 20,000, in the powder holding tube attached to the VDT. The powder holding tube is idealized as a cylindrical tube, obstructed by a hemispherical (powder) hill. The upstream flow field is characterized by the presence of a horse-shoe vortex, formed due to the separation of the boundary layer from the wall of the tube. A stagnation point occurs at the lower front surface of the bump. Strong near-wall vorticity is generated midway up the bump, and the flow is separated near the top of the bump. Kelvin-Helmholtz vortices are produced due to the strong shear-layer vorticity, and these then travel downstream with the flow. The upstream near-wall flow is dominated by a horseshoe vortex forming a necklace pushed out into the wake area. The flow detaches from the bump at the separation line, leading to vortex ‘roll-up’. These rolled-up vortices merge with the horseshoe vortices to form a large entangled hairpin vortex. The arch-type vortices shed with a frequency consistent with the Strouhal estimate fSt ∼ 6700 Hz.

Adaptive Detached Eddy Simulation of End-Wall Flow in a Linear Compressor Cascade

2020 ◽  
Author(s):  
Zifei Yin
Keyword(s):  
Pressure Coefficient ◽  
Detached Eddy Simulation ◽  
Compressor Cascade ◽  
Local Flow ◽  
Linear Compressor ◽  
Eddy Simulation ◽  
Wall Flow ◽  
Linear Compressor Cascade ◽  
End Wall ◽  
Des Model

Abstract Delayed detached eddy simulations and wall-modeled eddy simulations using the adaptive DES model were performed to simulate corner separation in the Ecole Centrale de Lyon linear compressor cascade. The adaptive DES model directly uses length scale to define eddy viscosity, which makes it nature to compute the model constant CDES dynamically. The dynamic procedure adapts viscosity to local flow and grid. Delayed detached eddy simulations, with and without the dynamic procedure, were performed to demonstrate the benefit of adapting viscosity to local flow. Recycling method was adopted to generate inflow unsteady turbulent boundary layer for wall-modeled eddy simulations. The wall-modeled eddy simulation showed improvement over delayed-DES, in terms of static pressure coefficient around the blade and total pressure loss at downstream locations.

scholarly journals Research and Application of Filtering Grid Scale in Detached Eddy Simulation Model

Symmetry ◽  
2020 ◽  
Vol 12 (8) ◽  
pp. 1252
Author(s):  
Liang Dong ◽  
Chao Guo ◽  
Ying Wang ◽  
Houlin Liu ◽  
Cui Dai
Keyword(s):  
Geometric Mean ◽  
Pressure Coefficient ◽  
Polar Angle ◽  
Internal Flow ◽  
Experimental Result ◽  
Detached Eddy Simulation ◽  
Quadratic Mean ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Flow Pressure

The existing definition method of filter grid scale in a Detached Eddy Simulation (DES) hybrid model is unreasonable, which will lead to the unreasonable trigger of a boundary layer large eddy simulation and reduce computational efficiency. In view of this problem, the filter grid scale is discussed in this paper. The 90° square curved elbow is selected as the research object. The effects of three grid definition methods: geometric mean (ΔGM), arithmetic mean (ΔAM) and quadratic mean (ΔQM) on the simulation results of the DES model are compared, and the velocity distribution of the flow cross section and the distribution of the flow pressure coefficient on the outer arc surface are compared with the experimental results of Taylor. The results show that the order of the three definition methods is ΔGM≤ΔAM≤ΔQM. Meanwhile, within 30° < polar angle(θ) < 75°, the results are closer to the experiment, and the development trends and numerical values of ΔAM and ΔQM are closer to the experiment in general. However, when θ > 60°, the value of ΔQM is slightly closer to the experimental result than ΔAM. ΔQM is more suitable for calculating the internal flow in a curved elbow than the other two methods.

Assessment of Eddy-Viscosity Turbulence Models on Flow in a Wheelhouse

2019 ◽  
Author(s):  
Kaloki L. Nabutola ◽  
Sandra K. S. Boetcher
Keyword(s):  
Experimental Data ◽  
Eddy Viscosity ◽  
Turbulence Models ◽  
Grid Size ◽  
Detached Eddy Simulation ◽  
Wind Tunnel Experiments ◽  
Time Step ◽  
Turbulent Eddies ◽  
Eddy Simulation ◽  
Large Eddy

Abstract Six different turbulence models were used to simulate the flow within the wheelhouse of a simplified body. The performance of each model was evaluated by comparing the results to data collected from wind tunnel experiments. The performance of large eddy simulation (LES) and detached eddy simulation (DES) is largely dependent on the time step and grid size to accurately resolve turbulent eddies. The standard k–ω and k–ω SST models deviated the most from the experimental data. The standard k–ε model was found to produce the most consistent results which matched experimental data for the simplified body and wheel.

scholarly journals Effect of Local Grid Refinement on Performance of Scale-Resolving Models for Simulation of Complex External Flows

Aerospace ◽  
2019 ◽  
Vol 6 (8) ◽  
pp. 86 ◽  
Author(s):  
Amne ElCheikh ◽  
Michel ElKhoury
Keyword(s):  
Computational Cost ◽  
Flow Characteristics ◽  
Turbulence Models ◽  
Pollutant Dispersion ◽  
Uniform Grid ◽  
Grid Refinement ◽  
Detached Eddy Simulation ◽  
Eddy Simulation ◽  
Uniform Grids ◽  
Large Eddy

Numerical simulations are crucial for fast and accurate estimations of the flow characteristics in many engineering applications such as atmospheric boundary layers around buildings, external aerodynamics around vehicles, and pollutant dispersion. In the simulation of flow over urban-like obstacles, it is crucial to accurately resolve the flow characteristics with reasonable computational cost. Therefore, Large Eddy Simulations on non-uniform grids are usually employed. However, an undesirable accumulation of energy at grid-refinement interfaces was observed in previous studies using non-uniform grids. This phenomenon induced oscillations in the spanwise velocity component, mainly on fine-to-coarse grid interfaces. In this study, the two challenging test cases of flow over urban-like cubes and flow over a 3-D circular cylinder were simulated using three different scale-resolving turbulence models. Simulations were performed on uniform coarse and fine grids on one hand, and a non-uniform grid on the other, to assess the effect of mesh density and mesh interfaces on the models’ performance. Overall, the proposed One-Equation Scale-Adaptive Simulation (One-Equation SAS) showed the least deviation from the experimental results in both tested cases and on all grid sizes and types when compared to the Shear Stress Transport-Improved Delayed Detached Eddy Simulation (IDDES) and the Algebraic Wall-Modeled Large Eddy Simulation (WMLES).

scholarly journals Large Eddy Simulation and RANS Analysis of the End-Wall Flow in a Linear Low-Pressure-Turbine Cascade—Part II: Loss Generation

2019 ◽  
Vol 141 (5) ◽  
Author(s):  
Michele Marconcini ◽  
Roberto Pacciani ◽  
Andrea Arnone ◽  
Vittorio Michelassi ◽  
Richard Pichler ◽  
...  
Keyword(s):  
Large Eddy Simulation ◽  
Flow Characteristics ◽  
Turbulence Models ◽  
Low Pressure ◽  
Companion Paper ◽  
Turbine Cascade ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Wall Flow ◽  
End Wall

In low-pressure turbines (LPT) at design point, around 60–70% of losses are generated in the blade boundary layers far from end walls, while the remaining 30–40% is controlled by the interaction of the blade profile with the end-wall boundary layer. Increasing attention is devoted to these flow regions in industrial design processes. This paper discusses the end-wall flow characteristics of the T106 profile with parallel end walls at realistic LPT conditions, as described in the experimental setup of Duden, A., and Fottner, L., 1997, “Influence of Taper, Reynolds Number and Mach Number on the Secondary Flow Field of a Highly Loaded Turbine Cascade,” Proc. Inst. Mech. Eng., Part A, 211(4), pp.309–320. Calculations are carried out by both Reynolds-averaged Navier–Stokes (RANS), due to its continuing role as the design verification workhorse, and highly resolved large eddy simulation (LES). Part II of this paper focuses on the loss generation associated with the secondary end-wall vortices. Entropy generation and the consequent stagnation pressure losses are analyzed following the aerodynamic investigation carried out in the companion paper (GT2018-76233). The ability of classical turbulence models generally used in RANS to discern the loss contributions of the different vortical structures is discussed in detail and the attainable degree of accuracy is scrutinized with the help of LES and the available test data. The purpose is to identify the flow features that require further modeling efforts in order to improve RANS/unsteady RANS (URANS) approaches and make them able to support the design of the next generation of LPTs.

scholarly journals Turbulence Models for Simulation of the Flow in a Rotor-Stator Cavity

2019 ◽  
Vol 213 ◽  
pp. 02104
Author(s):  
Lucie Zemanová ◽  
Pavel Rudolf
Keyword(s):  
Turbulence Models ◽  
Reynolds Stress Model ◽  
Operating Conditions ◽  
Narrow Gap ◽  
Detached Eddy Simulation ◽  
Axial Thrust ◽  
Eddy Simulation ◽  
Adaptive Simulation ◽  
Large Eddy

Modelling of the flow in the cavities between rotor and stator in turbomachines (e.g. pumps or turbines) is a task of great interest. Correctly evaluated pressure and velocity fields enable calculation of the disk losses and therefore assessment of efficiency. It is also crucial for determination of axial thrust and thus design of the bearings. The study demonstrates abilities of various turbulence models to describe the flow in a narrow gap between rotating and stationary disks. Numerical simulations were performed in order to find out the ability of particular models to capture unstable structures appearing during specific operating conditions as well as to calculate the velocity profiles precisely. Large Eddy Simulation (LES), Scale Adaptive Simulation (SAS), Detached Eddy Simulation (DES), Reynolds stress model (RSM) and SST k – ω model were used. Obtained results were also compared with experimental measurement published by Viazzo et al. [1]

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