Application of Delayed Detached Eddy Simulation and RANS to Compressor Cascade Flow

2008 ◽  
Author(s):  
Chunwei Gu ◽  
Meilan Chen ◽  
Xuesong Li ◽  
Fan Feng
Keyword(s):  
Experimental Data ◽  
Flow Field ◽  
Mixing Process ◽  
Detached Eddy Simulation ◽  
Compressor Cascade ◽  
Eddy Simulation ◽  
Cascade Flow ◽  
Delayed Detached Eddy Simulation ◽  
Comparison Results ◽  
Instantaneous Flow Field

Spalart-Allmaras (S-A) model based Delayed Detached Eddy Simulation (DDES) is performed to investigate the flow field in a compressor cascade (NACA64A-905) with experimental data for calibration. The value of the modeling coefficient CDES in DDES is open for revision and depends heavily on the numerical schemes. The effects of CDES on the DDES results are studied and an optimal CDES value is estimated for the specific case, with MUSCL reconstructed Roe scheme incorporated in in-house CFD codes. CDES value of 0.2 is turned out reliable concerning both accuracy and convergence. S-A model is also performed for comparison. Results from different methods indicate that the time-averaged results by DDES with CDES of 0.2 are more consistent with the experimental results than those by S-A model. The instantaneous flow field predictions show that DDES is well capable of capturing the unsteady features of the cascade flow, especially the wake mixing process.

Numerical Investigation of Intermittent Corner Separation in a Linear Compressor Cascade

2016 ◽  
Author(s):  
Wei Ma ◽  
Feng Gao ◽  
Xavier Ottavy ◽  
Lipeng Lu ◽  
A. J. Wang
Keyword(s):  
Flow Field ◽  
Large Scale ◽  
Leading Edge ◽  
Suction Side ◽  
Detached Eddy Simulation ◽  
Compressor Cascade ◽  
Linear Compressor ◽  
Corner Separation ◽  
Eddy Simulation ◽  
Linear Compressor Cascade

Recently bimodal phenomenon in corner separation has been found by Ma et al. (Experiments in Fluids, 2013, doi:10.1007/s00348-013-1546-y). Through detailed and accurate experimental results of the velocity flow field in a linear compressor cascade, they discovered two aperiodic modes exist in the corner separation of the compressor cascade. This phenomenon reflects the flow in corner separation is high intermittent, and large-scale coherent structures corresponding to two modes exist in the flow field of corner separation. However the generation mechanism of the bimodal phenomenon in corner separation is still unclear and thus needs to be studied further. In order to obtain instantaneous flow field with different unsteadiness and thus to analyse the mechanisms of bimodal phenomenon in corner separation, in this paper detached-eddy simulation (DES) is used to simulate the flow field in the linear compressor cascade where bimodal phenomenon has been found in previous experiment. DES in this paper successfully captures the bimodal phenomenon in the linear compressor cascade found in experiment, including the locations of bimodal points and the development of bimodal points along a line that normal to the blade suction side. We infer that the bimodal phenomenon in the corner separation is induced by the strong interaction between the following two facts. The first is the unsteady upstream flow nearby the leading edge whose angle and magnitude fluctuate simultaneously and significantly. The second is the high unsteady separation in the corner region.

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

2014 ◽  
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.

scholarly journals Numerical Investigation of Fluid Flow and Performance Prediction in a Fluid Coupling Using Large Eddy Simulation

2017 ◽  
Vol 2017 ◽  
pp. 1-11
Author(s):  
Wei Cai ◽  
Yuan Li ◽  
Xingzhong Li ◽  
Chunbao Liu
Keyword(s):  
Experimental Data ◽  
Flow Field ◽  
Large Eddy Simulation ◽  
Performance Prediction ◽  
Subgrid Scale ◽  
Eddy Simulation ◽  
Comparison Results ◽  
Large Eddy ◽  
Hydraulic Coupling ◽  
And Performance

Large eddy simulation (LES) with various subgrid-scale (SGS) models was introduced to numerically calculate the transient flow of the hydraulic coupling. By using LES, the study aimed to advance description ability of internal flow and performance prediction. The CFD results were verified by experimental data. For the purpose of the description of the flow field, six subgrid-scale models for LES were employed to depict the flow field; the distribution structure of flow field was legible. Moreover, the flow mechanism was analyzed using 3D vortex structures, and those showed that DSL and KET captured abundant vortex structures and provided a relatively moderate eddy viscosity in the chamber. The predicted values of the braking torque for hydraulic coupling were compared with experimental data. The comparison results were compared with several simulation models, such as SAS and RKE, and SSTKW models. Those comparison results showed that the SGS models, especially DSL and KET, were applicable to obtain the more accurate predicted results than SAS and RKE, and SSTKW models. Clearly, the predicted results of LES with DSL and KET were far more accurate than the previous studies. The performance prediction was significantly improved.

Detached Eddy Simulation of Transition in Turbomachinery: Linear Compressor Cascade

2021 ◽  
pp. 1-10
Author(s):  
Zifei Yin ◽  
Paul Durbin
Keyword(s):  
Boundary Layer ◽  
Large Scale ◽  
Separated Flow ◽  
Adaptive Model ◽  
Detached Eddy Simulation ◽  
Compressor Cascade ◽  
Linear Compressor ◽  
Eddy Simulation ◽  
Delayed Detached Eddy Simulation ◽  
Linear Compressor Cascade

Abstract The adaptive, l2-omega delayed detached eddy simulation model was selected to simulate the flow in the V103 linear compressor cascade. The Reynolds number based on axial chord length is 138,500. Varies inflow turbulent intensities from 0% to 10% were tested to evaluate the performance of the adaptive model. The adaptive model is capable of capturing the laminar boundary layer and the large scale perturbations inside it. The instability of large scale disturbances signals the switch to a hybrid simulation of turbulent boundary layer -- the transition front is thus predicted. In the case of separation-induced transition, the adaptive model, which uses eddy simulation in separated flow, can predict the separation bubble size accurately. Generally, the adaptive, delayed detached eddy simulation model can simulate the transitional separated flow in a linear compressor cascade, with a correct response to varying turbulent intensities.

Comparisons of Shear Stress Transport and Detached Eddy Simulations of the Flow Around Trains

2018 ◽  
Vol 140 (11) ◽  
Author(s):  
Tian Li ◽  
Hassan Hemida ◽  
Jiye Zhang ◽  
Mohammad Rashidi ◽  
Dominic Flynn
Keyword(s):  
Experimental Data ◽  
Shear Stress ◽  
Flow Field ◽  
Surface Pressure ◽  
Experimental Uncertainty ◽  
Detached Eddy Simulation ◽  
Aerodynamic Forces ◽  
Force Coefficients ◽  
Eddy Simulation ◽  
Shear Stress Transport

Shear stress transport (SST) k–ω model and detached eddy simulation (DES) have been widely applied in crosswind stability simulations for trains in the literature. In the previous research, the influence of the SST and DES approaches on the flow field around trains, which affects the surface pressure and consequently the aerodynamic forces of the train, was not properly investigated in terms of their influence flow field. The SST and improved delayed detached eddy simulation (IDDES) turbulence models have been tested in this study for their ability to predict the flow field around, surface pressure, and aerodynamic forces on a 1/25th scale Class 390 train subjected to crosswinds. Numerical simulation results were validated with experimental data. Results show that both SST and IDDES predict similar trends in the mean flow field around the train. However, there were some slight differences observed in the size of vortices, the position of separation points, and consequently, the separation and attachment lines. The SST results compared more closely to the experimental data than IDDES for pressure coefficient on the leeward surface and roof at certain loops. Slight differences were observed in force coefficients for SST and DES. The side force coefficients calculated using computational fluid dynamics (CFD) sit within the experimental uncertainty, whereas the lift force coefficients deviated greatly due to the omission of some underbody geometrical features. Both SST and IDDES approaches used the linear-upwind stabilized transport (LUST) scheme and were able to predict accurately the time-averaged surface pressure within the margin of the experimental uncertainty.

Investigation of Corner Separation in a Linear Compressor Cascade Using DDES

2015 ◽  
Author(s):  
Yangwei Liu ◽  
Hao Yan ◽  
Lipeng Lu
Keyword(s):  
Flow Field ◽  
Eddy Viscosity ◽  
Three Dimension ◽  
Separation Region ◽  
Detached Eddy Simulation ◽  
Compressor Cascade ◽  
Suction Surface ◽  
Simple Modification ◽  
Corner Separation ◽  
Eddy Simulation

Delayed Detached Eddy Simulation (DDES) method, compared with the RANS method, can more accurately predict the complexity and unsteadiness naturally associated with the compressor flow. DDES method, which incorporates a simple modification into the initial detached eddy simulation (DES) introduces kinematic eddy viscosity into turbulence model to take both effects of grid spacing and eddy-viscosity field into considerations. An attempt is made in the present paper to apply DDES for investigating the flow field in a compressor cascade. Three-dimension (3D) corner separation, which is also referred as corner separation, have been identified as an inherent flow feature of the corner formed by the blade suction surface and endwall of axial compressors. The flow visualization and the quantification of passage blockage expose that corner separation contribute most to the total passage blockage. In order to accurately predict 3D corner separation by employing CFD and increase the performance in compressor routine design by controlling such phenomenon, this paper tries to figure out its mechanism and investigate the turbulence flow field by using DDES method. Numerical simulations are conducted under different incidences in a linear PVD compressor cascade. The results show passage vortex starting at mid-chord position in cascade develops into dominant secondary vortex and obviously enhances corner separation in the PVD cascade. DDES method, which can capture intensive vortex flow and predict complicated flow at the separation region, also illustrates the corner vortex breaks into small stripe vortices which mix with the mainstream flow at the blade trailing edge. The total pressure loss is high in the corner separation region.

Effect of solidity on aeroacoustic performance of a vertical axis wind turbine using improved delayed detached eddy simulation

2021 ◽  
pp. 1475472X2110032
Author(s):  
Sepehr Rasekh ◽  
Saeed Karimian
Keyword(s):  
Flow Field ◽  
Noise Level ◽  
Angle Of Attack ◽  
Vertical Axis ◽  
Speed Ratio ◽  
Detached Eddy Simulation ◽  
Urban Regions ◽  
Eddy Simulation ◽  
Delayed Detached Eddy Simulation ◽  
Effective Angle

Vertical axis wind turbines (VAWTs) can be suitably installed in urban regions. Although the power performance is essential, the noise generated by a VAWT may influence the living environment. An accurate prediction of power and noise performance is therefore necessary. In the present study, a precise aerodynamic and aeroacoustic performance assessment of a Darrieus VAWT is accomplished with the aim of exploring the effect of solidity parameter using a high-fidelity method. The improved delayed detached eddy simulation (IDDES) and the Ffowcs Williams and Hawkings (FW-H) acoustic analogy approaches have been utilized for predicting flow field and noise level. The simulations were performed in three different solidities at a specific tip speed ratio (TSR). It is shown that changing the solidity parameter affects both power and noise level remarkably. Change in the aerodynamic performance mostly occurs due to variation in instantaneous effective angle of attack which comprises many detailed discussions. The lower the solidity the higher the value of effective angle of attack. The noise level also affects by changing solidity as consequence of flow field variation. It is discussed here how the noise level would alter in terms of solidity, TSR, distance and azimuth angle. As the solidity increases, the sound pressure level (SPL) at blade pass frequency increases. Since design of quieter VAWT with application in urban regions recently is of the most interest and importance therefore such deep studies could appropriately address hybrid criteria and be helpful in future investigations.

Sign in / Sign up

Export Citation Format

Share Document