scholarly journals LES and RANS Investigations Into Buoyancy-Affected Convection in a Rotating Cavity With a Central Axial Throughflow

2006 ◽  
Vol 129 (2) ◽  
pp. 318-325 ◽  
Author(s):  
Zixiang Sun ◽  
Klas Lindblad ◽  
John W. Chew ◽  
Colin Young
Keyword(s):  
Tangential Velocity ◽  
Rotating Disk ◽  
Navier Stokes ◽  
Test Cases ◽  
Eddy Simulation ◽  
Rotating Cavity ◽  
Large Eddy ◽  
Rans Modeling ◽  
Les Model ◽  
Compressor Disk

The buoyancy-affected flow in rotating disk cavities, such as occurs in compressor disk stacks, is known to be complex and difficult to predict. In the present work, large eddy simulation (LES) and unsteady Reynolds-averaged Navier-Stokes (RANS) solutions are compared to other workers’ measurements from an engine representative test rig. The Smagorinsky-Lilly model was employed in the LES simulations, and the RNG k-ε turbulence model was used in the RANS modeling. Three test cases were investigated in a range of Grashof number Gr=1.87 to 7.41×108 and buoyancy number Bo=1.65 to 11.5. Consistent with experimental observation, strong unsteadiness was clearly observed in the results of both models; however, the LES results exhibited a finer flow structure than the RANS solution. The LES model also achieved significantly better agreement with velocity and heat transfer measurements than the RANS model. Also, temperature contours obtained from the LES results have a finer structure than the tangential velocity contours. Based on the results obtained in this work, further application of LES to flows of industrial complexity is recommended.

scholarly journals LES and RANS Investigations Into Buoyancy-Affected Convection in a Rotating Cavity With a Central Axial Throughflow

2006 ◽  
Author(s):  
Zixiang Sun ◽  
Klas Lindblad ◽  
John W. Chew ◽  
Colin Young
Keyword(s):  
Heat Transfer ◽  
Tangential Velocity ◽  
Navier Stokes ◽  
Test Cases ◽  
Test Rig ◽  
Rotating Disc ◽  
Eddy Simulation ◽  
Rotating Cavity ◽  
Large Eddy ◽  
Les Model

The buoyancy-affected flow in rotating disc cavities, such as occurs in compressor disc stacks, is known to be complex and difficult to predict. In the present work large eddy simulation (LES) and unsteady Reynolds-averaged Navier-Stokes (RANS) solutions are compared with other workers’ measurements from an engine representative test rig. The Smagorinsky-Lilly model was employed in the LES simulations, and the RNG k-ε turbulence model was used in the RANS modelling. Three test cases were investigated in a range of Grashof number Gr = 1.87 to 7.41×108 and buoyancy number Bo = 1.65 to 11.5. Consistent with experimental observation, strong unsteadiness was clearly observed in the results of both models, however the LES results exhibited a finer flow structure than the RANS solution. The LES model also achieved significantly better agreement with velocity and heat transfer measurements than the RANS model. Also, temperature contours obtained from the LES results have a finer structure than the tangential velocity contours. Based on the results obtained in this work, further application of LES to flows of industrial complexity is recommended.

Wind-Driven Natural Ventilation in an Areaway-Attached Basement with a Single-Sided Opening for Residential Purposes

2011 ◽  
Vol 383-390 ◽  
pp. 5344-5349
Author(s):  
Zhen Bu
Keyword(s):  
Natural Ventilation ◽  
Ventilation Rate ◽  
Navier Stokes ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Effective Ventilation ◽  
The Mean ◽  
Ventilation Rates ◽  
Les Model ◽  
Good Agreement

This paper discusses the sustainability of the areaway-attached basement concept with the attentions focused on wind-driven single-sided natural ventilation. First, numerical simulations were performed on an areaway-attached basement with a single-sided opening. Two CFD approaches: Reynolds averaged Navier-Stokes (RANS) and large-eddy simulation (LES) were used and compared with the previous experimental results of effective ventilation rate. A good agreement between the measurement and LES model was found and RANS model tends to underestimate the ventilation rates. Furthermore, Based on LES with the inflow turbulent fluctuations, the mean airflow patterns within and around the areaway-attached basement was investigated for different wind incidence angles to examine the influences of wind direction on ventilation performances.

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.

scholarly journals Implementing Large-Eddy Simulation Capability in a Compressible Mesoscale Model

2014 ◽  
Vol 142 (8) ◽  
pp. 2733-2750 ◽  
Author(s):  
Nicolas Gasset ◽  
Robert Benoit ◽  
Christian Masson
Keyword(s):  
Large Eddy Simulation ◽  
Mesoscale Model ◽  
Wind Farms ◽  
Test Cases ◽  
Eddy Simulation ◽  
Large Size ◽  
Large Eddy ◽  
Vertical Turbulence ◽  
Les Model ◽  
Future Work

Abstract The large size of modern wind turbines and wind farms triggers processes above the surface layer, which extend to the junction between microscales and mesoscales, and pushes the limits of existing approaches to predict the wind. The main objectives of this study are thus to introduce and evaluate an approach that will better account for physical processes within the atmospheric boundary layer (ABL), and allow for both microscale and mesoscale modeling. The proposed method, in which mathematical model and main numerical aspects are presented, combines a mesoscale approach with a large-eddy simulation (LES) model based on the Compressible Community Mesoscale Model (MC2). It is evaluated relying on a shear-driven ABL case allowing the authors to assess the model behavior at very high resolution as well as more specific numerical aspects such as the vertical discretization and time and space splitting of turbulence-related terms. The proposed LES-capable mesoscale model is shown to perform on par with other similar reference LES models, while being slightly more dissipative. A new vertical discretization of the turbulent processes eliminates a spurious numerical mode in the solution. Finally, the splitting of horizontal and vertical turbulence-related terms is shown to have no impact on the results of the test cases. It is thus demonstrated that the revised MC2 is suitable at both microscales and mesoscales, thus setting a strong foundation for future work.

Some Observations on the Computational Sensitivity of Rotating Cavity Flows

2021 ◽  
Vol 143 (4) ◽  
Author(s):  
Tom Hickling ◽  
Li He
Keyword(s):  
Heat Transfer ◽  
Eddy Viscosity ◽  
Systematic Investigation ◽  
Navier Stokes ◽  
Cavity Flows ◽  
Detached Eddy Simulation ◽  
Bulk Fluid ◽  
Eddy Simulation ◽  
Rotating Cavity ◽  
Large Eddy

Abstract Across the open literature, there is no clear consensus on what the most suitable modeling fidelity is for rotating cavity flows. Although it is a widely held opinion that unsteady Reynolds-averaged-Navier–Stokes (URANS) approaches are unsuitable, many authors have succeeded in getting reasonable heat transfer results with them. There is also a lack of research into the validity of hybrid URANS/large eddy simulation (LES) type approaches such as detached eddy simulation (DES). This paper addresses these research challenges with a systematic investigation of a rotating cavity with axial throughflow at Grashof numbers of 3.03×109 and 3.03×1011. The disk near-wall layers remained laminar at both conditions, meaning that a turbulence model should not be active in these regions. The disk heat transfer was observed to affect the near-disk aerodynamics, which in turn affect the disk heat transfer: this feedback loop implies that conjugate heat transfer computations of rotating cavities may be worth investigating. On the shroud, additional eddy viscosity in URANS and DES was found to interfere with the formation of heat transfer enhancing streaks, whilst these were always captured by LES. DES exhibited a concerning behavior at the higher Grashof number. Locally generated eddy viscosity from the shroud was injected into the bulk fluid by the radial inflow. This contaminated the entire cavity with nonphysical modeled turbulence. As the radial inflow is a characteristic feature of rotating cavity flows, these results show that caution is necessary when applying hybrid URANS/LES approaches to this type of flow.

Hybrid LES Approach for Practical Turbomachinery Flows—Part II: Further Applications

2011 ◽  
Vol 134 (2) ◽  
Author(s):  
Paul Tucker ◽  
Simon Eastwood ◽  
Christian Klostermeier ◽  
Hao Xia ◽  
Prasun Ray ◽  
...  
Keyword(s):  
Navier Stokes ◽  
Jet Flows ◽  
Hybrid Strategy ◽  
Eddy Simulation ◽  
Wall Flows ◽  
Large Eddy ◽  
Blade Section ◽  
Transition Modeling ◽  
Fan Blade ◽  
Les Model

A hybrid large eddy simulation (LES) related technique is used to explore some key turbomachinery relevant flows. Near wall Reynolds-averaged Navier-Stokes (RANS) modeling is used to cover over especially small scales, the LES resolution of which is generally intractable with current computational power. Away from walls, large eddy type simulation is used but with no LES model (numerical LES (NLES)). Linking of the two model zones through a Hamilton–Jacobi equation is explored. The hybrid strategy is used to predict turbine and compressor end wall flows, flow around a fan blade section, jet flows, and a cutback trailing edge. Also, application of NLES to the flow in an idealized high pressure compressor drum cavity is considered. Generally, encouraging results are found. However, challenges remain, especially for flows where transition modeling is important.

Large Eddy Simulation of Aerodynamic Forces on a Bridge Pylon

2011 ◽  
Vol 243-249 ◽  
pp. 1578-1582
Author(s):  
Xu Yong Ying ◽  
Fu You Xu ◽  
Zhe Zhang ◽  
Yong Gang Tan
Keyword(s):  
Large Eddy Simulation ◽  
Bluff Body ◽  
Stokes Equations ◽  
Three Dimensional ◽  
Wind Tunnel Test ◽  
Navier Stokes ◽  
Aerodynamic Forces ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Les Model

In this study, aerodynamic forces on a bridge pylon are investigated by three-dimensional computational fluid dynamics using Large eddy simulation (LES) technology. The main objective is to identify the wind load parameters of the pylon and examine the accuracy of LES model applied to the bluff-body flows. The numerical results were compared with the available wind tunnel test results. Also, a comparison between using LES and Reynolds averaged Navier-Stokes equations with the RNG model have been made. It is found that the LES model competes the RNG model in accuracy for predictions of aerodynamic forces on the pylon.

LES Validation for a Rotating Cylindrical Cavity With Radial Inflow

2016 ◽  
Author(s):  
Michel Onori ◽  
Dario Amirante ◽  
Nicholas J. Hills ◽  
John W. Chew
Keyword(s):  
Boundary Layers ◽  
Source Region ◽  
Tangential Velocity ◽  
Large Eddy Simulations ◽  
Navier Stokes ◽  
Subgrid Scale ◽  
Rotating Cavity ◽  
Scale Models ◽  
Large Eddy ◽  
Type Boundary

This paper describes Large-Eddy Simulations (LES) of the flow in a rotating cavity with narrow inter-disc spacing and a radial inflow introduced from the shroud. Simulations have been conducted using a compressible, unstructured, finite-volume solver, and testing different subgrid scale models. These include the standard Smagorinsky model with Van Driest damping function near the wall, the WALE model and the implicit LES procedure. Reynolds averaged Navier-Stokes (RANS) results, based on the Spalart-Allmaras and SST k-ω models, are also presented. LES solutions reveal a turbulent source region, a laminar oscillating core with almost zero axial and radial velocity and turbulent Ekman type boundary layers along the discs. Validations are carried out against the experimental data available from the study of Firouzian et al. [1]. It is shown that the tangential velocity and the pressure drop across the cavity are very well predicted by both RANS and LES, although significant differences are observed in the velocity profiles within the boundary layers.

scholarly journals Heat Transfer Prediction From Large Eddy Simulation of a Rotating Cavity With Radial Inflow

2019 ◽  
Vol 141 (12) ◽  
Author(s):  
Michel Onori ◽  
Dario Amirante ◽  
Nicholas J. Hills ◽  
John W. Chew
Keyword(s):  
Nusselt Number ◽  
Large Eddy Simulation ◽  
Source Region ◽  
Outer Region ◽  
Outer Radius ◽  
Heated Wall ◽  
Navier Stokes ◽  
Eddy Simulation ◽  
Rotating Cavity ◽  
Large Eddy

Abstract This paper describes a large eddy simulation (LES) conducted for a nonadiabatic rotating cavity with a radial inflow introduced from the shroud. The dimensionless mass flowrate of the radial inflow is Cw = 3500 and the rotational Reynolds number, based on the cavity outer radius, is equal to Reθ=1.2×106. The time-averaged local Nusselt number on the heated wall is compared with the experimental data available from the literature, and with those derived from the solution of two unsteady Reynolds-averaged Navier–Stokes (URANS) eddy viscosity models, namely, the Spalart–Allmaras and the k−ω shear stress transport (SST) model. It is shown that the Nusselt number is underpredicted in the lower part of the disk and overpredicted in the outer region by both URANS models, whereas the LES provides a much better agreement with the measurements. The behavior results primarily from a different flow structure in the source region, which, in the LES, is found to be considerably more extended and show localized buoyancy phenomena that the URANS models investigated do not capture.

A Novel Fix to Reduce the Log-Layer Mismatch in Wall-Modeled Large-Eddy Simulations of Turbulent Channel Flow

2016 ◽  
Author(s):  
Rey DeLeon ◽  
Inanc Senocak
Keyword(s):  
Pressure Gradient ◽  
Channel Flow ◽  
Friction Velocity ◽  
Turbulent Channel Flow ◽  
Navier Stokes ◽  
Gradient Term ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Mean Pressure ◽  
Les Model

The log-layer mismatch arises when a Reynolds-averaged Navier-Stokes (RANS) model is blended with a large-eddy simulation (LES) model in a hybrid fashion. Numerous researchers have tackled this problem by simulating a turbulent channel flow. We show that the log-layer mismatch in hybrid RANS-LES can be reduced substantially by splitting the mean pressure gradient term in the wall-normal direction in a manner that keeps the mass flow rate constant. Additionally, an analysis of the wall-normal variation of the friction velocity shows a constant value is recovered in the resolved LES region different than the value at the wall. Second-order turbulence statistics agree very well with direct numerical simulation (DNS) benchmarks when scaled with the friction velocity extracted from the resolved LES region. In light of our findings, we suggest that the current convention to drive a turbulent periodic channel flow with a uniform mean pressure gradient be revisited in testing eddy-viscosity-based hybrid RANS-LES models as it appears to be the culprit behind the log-layer mismatch.

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