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.

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 Evaluation of Shear Stress Transport, Large Eddy Simulation and Detached Eddy Simulation for the Flow around a Statically Loaded Tire

Symmetry ◽  
2021 ◽  
Vol 13 (8) ◽  
pp. 1319
Author(s):  
Haichao Zhou ◽  
Huiyun Li ◽  
Qingyun Chen ◽  
Lingxin Zhang
Keyword(s):  
Shear Stress ◽  
Wind Tunnel ◽  
Large Eddy Simulation ◽  
Surface Pressure ◽  
Pressure Coefficient ◽  
Wind Tunnel Test ◽  
Tire Model ◽  
Detached Eddy Simulation ◽  
Eddy Simulation ◽  
Large Eddy

To select a more suitable turbulence model to study tire aerodynamics, the characteristics of a deformed profile of a 185/65 R14 passenger tire were reproduced using 3D printing technology. Based on the distance from automobile chassis to the ground, a partially loaded tire model with a height of 150 mm was selected in this paper, and the surface pressure coefficient of the tire model was determined using a wind tunnel test. A computational fluid dynamics (CFD) model was established according to the tire wind tunnel test. The surface pressure coefficient results of three turbulence models, shear stress transport (SST) k-ω, large eddy simulation (LES), and detached eddy simulation (DES) were obtained. Compared with the wind tunnel test results, the mean relative errors of the surface pressure coefficients predicted using SST, LES, and DES in the longitudinal section were 22.4%, 20.9%, and 14.8%, respectively. The LES and DES can capture details of the unsteady flow field that were not predicted by SST. By synthetically analyzing the results of the surface pressure coefficient and flow fields, the DES model is more advantageous than the other two models in predicting the flow characteristics around a statically loaded tire. This study can help designers in the tire industry to apply these cost-effective tools for minimizing the aerodynamic drag of a new tire design.

scholarly journals Assessing IDDES-Based Wall-Modeled Large-Eddy Simulation (WMLES) for Separated Flows with Heat Transfer

Fluids ◽  
2021 ◽  
Vol 6 (7) ◽  
pp. 246
Author(s):  
Rozie Zangeneh
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Large Eddy Simulation ◽  
Skin Friction ◽  
Heat Fluxes ◽  
Separated Flows ◽  
Detached Eddy Simulation ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Isothermal Wall

The Wall-modeled Large-eddy Simulation (WMLES) methods are commonly accompanied with an underprediction of the skin friction and a deviation of the velocity profile. The widely-used Improved Delayed Detached Eddy Simulation (IDDES) method is suggested to improve the prediction of the mean skin friction when it acts as WMLES, as claimed by the original authors. However, the model tested only on flow configurations with no heat transfer. This study takes a systematic approach to assess the performance of the IDDES model for separated flows with heat transfer. Separated flows on an isothermal wall and walls with mild and intense heat fluxes are considered. For the case of the wall with heat flux, the skin friction and Stanton number are underpredicted by the IDDES model however, the underprediction is less significant for the isothermal wall case. The simulations of the cases with intense wall heat transfer reveal an interesting dependence on the heat flux level supplied; as the heat flux increases, the IDDES model declines to predict the accurate skin friction.

scholarly journals Unsteady Simulation of Transonic Buffet of a Supercritical Airfoil with Shock Control Bump

Aerospace ◽  
2021 ◽  
Vol 8 (8) ◽  
pp. 203
Author(s):  
Yufei Zhang ◽  
Pu Yang ◽  
Runze Li ◽  
Haixin Chen
Keyword(s):  
Lift Coefficient ◽  
Pressure Coefficient ◽  
Flow Characteristics ◽  
Control Effect ◽  
Shock Control Bump ◽  
Shock Control ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Unsteady Simulation ◽  
Drag Ratio

The unsteady flow characteristics of a supercritical OAT15A airfoil with a shock control bump were numerically studied by a wall-modeled large eddy simulation. The numerical method was first validated by the buffet and nonbuffet cases of the baseline OAT15A airfoil. Both the pressure coefficient and velocity fluctuation coincided well with the experimental data. Then, four different shock control bumps were numerically tested. A bump of height h/c = 0.008 and location xB/c = 0.55 demonstrated a good buffet control effect. The lift-to-drag ratio of the buffet case was increased by 5.9%, and the root mean square of the lift coefficient fluctuation was decreased by 67.6%. Detailed time-averaged flow quantities and instantaneous flow fields were analyzed to demonstrate the flow phenomenon of the shock control bumps. The results demonstrate that an appropriate “λ” shockwave pattern caused by the bump is important for the flow control effect.

Large eddy simulation study of turbulent flow around smooth and rough domes

2013 ◽  
Vol 227 (12) ◽  
pp. 2686-2700 ◽  
Author(s):  
N Kharoua ◽  
L Khezzar
Keyword(s):  
Large Eddy Simulation ◽  
Turbulent Flow ◽  
Flow Behavior ◽  
Pressure Coefficient ◽  
Horseshoe Vortex ◽  
Scale Model ◽  
Stream Velocity ◽  
Mean Velocity ◽  
Eddy Simulation ◽  
Large Eddy

Large eddy simulation of turbulent flow around smooth and rough hemispherical domes was conducted. The roughness of the rough dome was generated by a special approach using quadrilateral solid blocks placed alternately on the dome surface. It was shown that this approach is capable of generating the roughness effect with a relative success. The subgrid-scale model based on the transport of the subgrid turbulent kinetic energy was used to account for the small scales effect not resolved by large eddy simulation. The turbulent flow was simulated at a subcritical Reynolds number based on the approach free stream velocity, air properties, and dome diameter of 1.4 × 105. Profiles of mean pressure coefficient, mean velocity, and its root mean square were predicted with good accuracy. The comparison between the two domes showed different flow behavior around them. A flattened horseshoe vortex was observed to develop around the rough dome at larger distance compared with the smooth dome. The separation phenomenon occurs before the apex of the rough dome while for the smooth dome it is shifted forward. The turbulence-affected region in the wake was larger for the rough dome.

Investigation of Aerator Flow Pressure Fluctuation Using Detached Eddy Simulation with VOF Method

2022 ◽  
Vol 148 (1) ◽  
Author(s):  
Zhengwen Li ◽  
Zhaowei Liu ◽  
Haoran Wang ◽  
Yongcan Chen ◽  
Ling Li ◽  
...  
Keyword(s):  
Pressure Fluctuation ◽  
Vof Method ◽  
Detached Eddy Simulation ◽  
Eddy Simulation ◽  
Flow Pressure

scholarly journals Large-Eddy Simulation of Internal Flow through Human Vocal Folds

2018 ◽  
Vol 180 ◽  
pp. 02054
Author(s):  
Martin Lasota ◽  
Petr Šidlof
Keyword(s):  
Large Eddy Simulation ◽  
Stokes Equations ◽  
Turbulent Viscosity ◽  
Internal Flow ◽  
Vocal Folds ◽  
Computational Domain ◽  
Subgrid Scale ◽  
Eddy Simulation ◽  
Scale Models ◽  
Large Eddy

The phonatory process occurs when air is expelled from the lungs through the glottis and the pressure drop causes flow-induced oscillations of the vocal folds. The flow fields created in phonation are highly unsteady and the coherent vortex structures are also generated. For accuracy it is essential to compute on humanlike computational domain and appropriate mathematical model. The work deals with numerical simulation of air flow within the space between plicae vocales and plicae vestibulares. In addition to the dynamic width of the rima glottidis, where the sound is generated, there are lateral ventriculus laryngis and sacculus laryngis included in the computational domain as well. The paper presents the results from OpenFOAM which are obtained with a large-eddy simulation using second-order finite volume discretization of incompressible Navier-Stokes equations. Large-eddy simulations with different subgrid scale models are executed on structured mesh. In these cases are used only the subgrid scale models which model turbulence via turbulent viscosity and Boussinesq approximation in subglottal and supraglottal area in larynx.

scholarly journals Numerical Investigation on Fluid Flow in a 90-Degree Curved Pipe with Large Curvature Ratio

2015 ◽  
Vol 2015 ◽  
pp. 1-12 ◽  
Author(s):  
Yan Wang ◽  
Quanlin Dong ◽  
Pengfei Wang
Keyword(s):  
Fluid Flow ◽  
Internal Flow ◽  
Fluid Flows ◽  
Detached Eddy Simulation ◽  
Number Range ◽  
Curvature Ratio ◽  
Large Curvature ◽  
Curved Pipe ◽  
Eddy Simulation ◽  
Curved Pipes

In order to understand the mechanism of fluid flows in curved pipes, a large number of theoretical and experimental researches have been performed. As a critical parameter of curved pipe, the curvature ratioδhas received much attention, but most of the values ofδare very small (δ<0.1) or relatively small (δ≤0.5). As a preliminary study and simulation this research studied the fluid flow in a 90-degree curved pipe of large curvature ratio. The Detached Eddy Simulation (DES) turbulence model was employed to investigate the fluid flows at the Reynolds number range from 5000 to 20000. After validation of the numerical strategy, the pressure and velocity distribution, pressure drop, fluid flow, and secondary flow along the curved pipe were illustrated. The results show that the fluid flow in a curved pipe with large curvature ratio seems to be unlike that in a curved pipe with small curvature ratio. Large curvature ratio makes the internal flow more complicated; thus, the flow patterns, the separation region, and the oscillatory flow are different.

Detailed Investigation of Detached-Eddy Simulation for the Flow Past a Circular Cylinder at Re=3900

2012 ◽  
Vol 232 ◽  
pp. 471-476 ◽  
Author(s):  
Rui Zhao ◽  
Chao Yan
Keyword(s):  
Reynolds Number ◽  
Circular Cylinder ◽  
Flow Structures ◽  
Detached Eddy Simulation ◽  
Eddy Simulation ◽  
Flow Past ◽  
Large Eddy ◽  
Mesh Resolution ◽  
Physical Phenomena

The flow past a circular cylinder at a subcritical Reynolds number 3900 was simulated by the method of detached-eddy simulation (DES). The objective of this present work is not to investigate the physical phenomena of the flow but to study modeling as well as numerical aspects which influence the quality of DES solutions in detail. Firstly, four typical spanwise lengths are chosen and the results are systematically compared. The trend of DES results along the span increment is different from previous large-eddy simulation (LES) investigation. A wider spanwise length does not necessary improve the results. Then, the influence of mesh resolution is studied and found that both too coarse and over refined grids will deteriorate the performance of DES. Finally, different orders of numerical schemes are applied in the inviscid fluxes and the viscous terms. The discrepancies among different schemes are found tiny. However, the instantaneous flow structures produced by 5th order WENO with 4th order central differencing scheme are more abundant than the others. That is, for the time-averaged quantities, the second-order accurate schemes are effective enough, whereas the higher-order accurate methods are needed to resolve the transient characteristics of the flow.

Sign in / Sign up

Export Citation Format

Share Document