scholarly journals Testing the Accuracy of the Cell-Set Model Applied on Vane-Type Sub-Boundary Layer Vortex Generators

Processes ◽  
2021 ◽  
Vol 9 (3) ◽  
pp. 503
Author(s):  
Koldo Portal-Porras ◽  
Unai Fernandez-Gamiz ◽  
Iñigo Aramendia ◽  
Daniel Teso-Fz-Betoño ◽  
Ekaitz Zulueta
Keyword(s):  
Boundary Layer ◽  
Vortical Structure ◽  
Gradient Flow ◽  
Vortex Generators ◽  
Navier Stokes ◽  
Computational Time ◽  
Eddy Simulation ◽  
Mesh Model ◽  
Large Eddy ◽  
Modelling Techniques

Vortex Generators (VGs) are applied before the expected region of separation of the boundary layer in order to delay or remove the flow separation. Although their height is usually similar to that of the boundary layer, in some applications, lower VGs are used, Sub-Boundary Layer Vortex Generators (SBVGs), since this reduces the drag coefficient. Numerical simulations of sub-boundary layer vane-type vortex generators on a flat plate in a negligible pressure gradient flow were conducted using the fully resolved mesh model and the cell-set model, with the aim on assessing the accuracy of the cell-set model with Reynolds-Averaged Navier-Stokes (RANS) and Large Eddy Simulation (LES) turbulence modelling techniques. The implementation of the cell-set model has supposed savings of the 40% in terms of computational time. The vortexes generated on the wake behind the VG; vortical structure of the primary vortex; and its path, size, strength, and produced wall shear stress have been studied. The results show good agreements between meshing models in the higher VGs, but slight discrepancies on the lower ones. These disparities are more pronounced with LES. Further study of the cell-set model is proposed, since its implementation entails great computational time and resources savings.

Analysis of the Sutton Model for Aero-Optical Properties of Compressible Boundary Layers

2005 ◽  
Vol 128 (2) ◽  
pp. 239-246 ◽  
Author(s):  
Eric Tromeur ◽  
Eric Garnier ◽  
Pierre Sagaut
Keyword(s):  
Boundary Layer ◽  
Density Field ◽  
The Other ◽  
Navier Stokes ◽  
Eddy Simulation ◽  
Compressible Boundary Layers ◽  
Optical Effects ◽  
Large Eddy ◽  
The One ◽  
Reference Tool

In order to assess the capability of the Sutton model to evaluate aero-optical effects in a turbulent boundary layer, large-eddy simulation (LES) evolving spatially and Reynolds averaged Navier-Stokes (RANS) computations are carried out at Mach number equal to 0.9. First aerodynamic fields are proved to compare favorably with theoretical and experimental results. Once validated, the characteristics of the boundary layer allow us to obtain information concerning optical beam degradation. On the one hand, the density field is used to compute phase distortion directly and, on the other hand, by means of the Sutton model. Therefore, LES and RANS simulations allow us to study optical models and the validity of their assumptions. Finally, LES is proved to be considered as a reference tool to evaluate aero-optical effects.

Large Eddy Simulation of Turbulent Flow and Heat Transfer Characteristics in Rectangle Channel With Vortex Generators

2010 ◽  
Author(s):  
Juan Wen ◽  
Li Yang ◽  
Cheng Ying Qi
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Heat Transfer Enhancement ◽  
Coherent Structure ◽  
Vortex Generator ◽  
Vortex Generators ◽  
Transfer Enhancement ◽  
Heat Transfer Characteristics ◽  
Eddy Simulation ◽  
Large Eddy

The flow structures and heat transfer characteristics of rectangle channel with the new type of vortex generators are obtained using large eddy simulation (LES) and by the application of the hydromechanics software FLUENT6.3. The bevel-cut half-elliptical column vortex generators, which is one model of the passive heat transfer enhancement, are laid on the three-dimensional rectangle channel. The instantaneous characteristic and the variational law of various parameters, such as the velocity, the temperature, the pressure and the vorticity magnitude, is analyzed to find out the temperature stripe structure that is similar with the velocity stripe in the temperature field. A turbulent boundary layer interacting with the disturbance of the vortex generators, is investigated using a “coherent structure” type of approach. The coherent structure and the streak structure of turbulent boundary layer flow are showed and the characteristic of vortex induced by vortex generator and its influence on turbulent coherent structure are analyzed. The control of the coherent structure induced by vortex generator plays more important role in heat transfer enhancement and drag reduction. And this fow configuration is of interest in terms of both heat transfer and skin friction control. The result of simulation indicates that the turbulence coherent structure directly affects the temperature gradient at the wall and the heat transfer enhancement mechanism of vortex generator is explained. Then we can seek suitable form of vortex generator and structure parameters, in order to achieve enhanced heat transfer and flow of drag reduction.

Large eddy simulation of natural cavitating flows in Venturi-type sections

2010 ◽  
Vol 225 (2) ◽  
pp. 369-381 ◽  
Author(s):  
N M Nouri ◽  
S M H Mirsaeedi ◽  
M Moghimi
Keyword(s):  
Large Eddy Simulation ◽  
Preliminary Data ◽  
Cavitating Flow ◽  
Navier Stokes ◽  
Computational Time ◽  
Time Averaging ◽  
Cavitating Flows ◽  
Eddy Simulation ◽  
Wide Range ◽  
Large Eddy

Large eddy simulation (LES) is used here to model the cavitating flow at a Venturi-type section. Cavitating flows can occur in a wide range of applications. The flow is represented here by means of LES, which compared to Reynolds-averaged Navier—Stokes (RANS) has the advantage that in it the large, energy-containing structures are resolved directly, whereas most of these structures are modelled in RANS. This gives LES an improved fidelity over RANS, although, due to the time averaging, the required computational time is considerably lower for RANS than for LES. The conclusion of this work shows that the qualitative comparisons with earlier preliminary data and the simulated general cavitation behaviour correlate reasonably well with experimental observations and that the simulations have the ability to predict cavitation cycle in more detail.

Turbulence modelling techniques for aeroelastic problems: results and comments from the Second AIAA Aeroelastic Prediction Workshop

2017 ◽  
Vol 89 (5) ◽  
pp. 683-691 ◽  
Author(s):  
Marcello Righi
Keyword(s):  
Navier Stokes ◽  
Test Case ◽  
Detached Eddy Simulation ◽  
Special Flow ◽  
Content Type ◽  
Eddy Simulation ◽  
Delayed Detached Eddy Simulation ◽  
Large Eddy ◽  
Modelling Techniques

Purpose The quality of aeroelastic predictions strongly depends on the quality of aerodynamic predictions. At the boundary of a typical flight envelope, special flow conditions may arise, which challenge the conventional Reynolds-averaged Navier–Stokes (RANS) approach beyond reasonable limits. Design/methodology/approach Test Case 3 of the Second AIAA Aeroelastic Prediction Workshop is a representative test case, where the flow over a supercritical wing separates downstream of the shock waves and generates large turbulent lengthscales. Findings In this study, RANS predictions are compared to those obtained in this particular test case with the more sophisticated hybrid RANS–large eddy simulation (LES) approach, in particular with the Spalart–Allmaras–delayed detached eddy simulation model. Results are indeed closer to experimental data. Originality/value However, the costs associated with this approach are much higher. It is argued that adopting hybrid RANS–LES modelling is not a simple model switch.

A modified blending function for zonal hybrid Reynolds-averaged Navier—Stokes/large-eddy simulation methodology

2009 ◽  
Vol 223 (8) ◽  
pp. 1067-1081 ◽  
Author(s):  
M B Sun ◽  
J H Liang ◽  
Z G Wang
Keyword(s):  
Boundary Layer ◽  
Supersonic Flow ◽  
Large Eddy Simulation ◽  
Turbulent Flows ◽  
Navier Stokes ◽  
Empirical Constant ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Reynolds Averaged Navier Stokes ◽  
Blending Function

A modified blending function for zonal hybrid Reynolds averaged Navier—Stokes/large eddy simulation (RANS/LES) methodology was developed using an empirical analogy from Menter k—ω shear stress transport (SST) turbulent model (Menter, 1994) to predict complex turbulent flows. Tests of slot jet in supersonic flow and supersonic flow over compression—expansion ramp was conducted and prediction of separations was well improved when certain model constant was forced on the traditional blending function (Baurle et al., 2003). Analysis based on calculations of flat plate boundary layer demonstrated that an efficient empirical constant could be used in blending function and boundary layer could be well calculated without heavy contamination of RANS on wake region. Validation of the modified zonal hybrid RANS/LES approach for slot jet in supersonic flow, supersonic flow over compression—expansion ramp, supersonic flow over backward facing step, and supersonic cavity flow was conducted. The simulated results showed that the modified blending function performs well on complex turbulent flows. Deficiencies of traditional hybrid zonal RANS/LES method in over-prediction of separations associated with adverse pressure gradient flows were favourably improved.

Cost-effective hybrid RANS-LES type method for jet turbulence and noise prediction

2017 ◽  
Vol 16 (1-2) ◽  
pp. 97-111 ◽  
Author(s):  
M Mahak ◽  
IZ Naqavi ◽  
PG Tucker
Keyword(s):  
Boundary Layer ◽  
Large Eddy Simulation ◽  
Cost Effective ◽  
Wall Turbulence ◽  
Scale Model ◽  
Navier Stokes ◽  
High Concentration ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Layer Region

Jets at higher Reynolds numbers have a high concentration of energy in small scales in the nozzle vicinity. This is challenging for large-eddy simulation, potentially placing severe demands on grid density. To circumvent this, we propose a novel procedure based on well-known Reynolds number (Re) independent of jets. We reduce the jet Re while rescaling the boundary layer properties to maintain incoming boundary layer thickness consistent with high Re jet. The simulations are carried out using hybrid large-eddy simulation type of approach which is incorporated by using near-wall turbulence model with modified properties. No subgrid scale model is used in these simulations. Hence, they effectively become numerical large-eddy simulation with Reynolds-averaged Navier–Stokes covering the full boundary layer region. The noise post-processing is carried out using the Ffowcs-Williams-Hawking approach. The simulations are made for Mach numbers (M) of 0.75 and 0.875 (cold and hot). The results for the overall sound pressure level are observed to be within 2–3% of the measurements, and directivity of sound is also captured accurately for both the cases. Hence, the low Re simulations can be more beneficial in saving time and cost while providing reasonably accurate results.

Direct numerical simulation, large eddy simulation and unsteady Reynolds-averaged Navier—Stokes simulations of periodic unsteady flow in a low-pressure turbine cascade: A comparison

2003 ◽  
Vol 217 (4) ◽  
pp. 403-411 ◽  
Author(s):  
V Michelassi ◽  
J. G. Wissink ◽  
W Rodi
Keyword(s):  
Numerical Simulation ◽  
Boundary Layer ◽  
Large Eddy Simulation ◽  
Direct Numerical Simulation ◽  
Low Pressure ◽  
Navier Stokes ◽  
Stagnation Region ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Reynolds Averaged Navier Stokes

The unsteady periodic flow in a low-pressure (LP) prismatic turbine vane with incoming wakes is computed by direct numerical simulation (DNS), large eddy simulation (LES) and unsteady Reynolds-averaged Navier—Stokes simulations (URANSs). The results are compared with existing measurements at a Reynolds number Re = 5.18 × 104 which reveal the presence of a large unsteady stalled region on the suction side. Both DNS and LES suggest that the boundary layer separates while being still laminar, with subsequent turbulent reattachment. Several URANSs with and without a transition model and a constraint on the turbulence time-scale designed to prevent excessive production in the stagnation region are analysed and compared with the DNS and LES. The useful information provided by DNS and LES has made it possible to improve the results of the URANSs, which ensure a fair reproduction of the flow, especially in terms of blade load and losses, although they partly fail to detail the complex wake—boundary layer interaction in the separated flow region.

Cost-Effective Hybrid RANS-NLES Method for Jet Turbulence and Noise Prediction

2012 ◽  
Author(s):  
M. Mahak ◽  
Paul G. Tucker ◽  
Prasun K. Ray
Keyword(s):  
Boundary Layer ◽  
Cost Effective ◽  
Reynolds Numbers ◽  
Wall Turbulence ◽  
Navier Stokes ◽  
High Concentration ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Layer Region ◽  
Near Wall Turbulence

Jets at higher Reynolds numbers have a high concentration of energy in the small scales in the nozzle vicinity. This is challenging for LES, potentially placing severe demands on grid density. To circumvent this, we propose a novel procedure based on well known Reynolds number (Re) independence of jets. We reduce the jet Re whilst rescaling the boundary layer properties to maintain incoming boundary layer thickness consistent with high Re jet. The simulations are carried out using hybrid largeeddy simulation type of approach which is incorporated by using near wall turbulence model with modified properties. No Subgrid Scale (SGS) model is used in these simulations. Hence, they effectively become Numerical Large Eddy Simulation (NLES) with Reynolds-averaged Navier-Stokes (RANS) covering the full boundary layer region. The noise post processing is carried out using Ffowcs-Williams-Hawking (FWH) approach. The simulations are made for Mach numbers (M) of 0.75 and 0.875. The results for Overall Sound Pressure Level (OASPL) are observed to be within 2–3% accuracy range and directivity of sound is also captured accurately for both the cases. The low Re simulations hence, can be more beneficial in saving time and cost of the simulation while providing reasonably accurate results.

Large-Eddy Simulation of Supersonic Flat-Plate Boundary Layers Using the Monotonically Integrated Large-Eddy Simulation (MILES) Technique

2002 ◽  
Vol 124 (4) ◽  
pp. 868-875 ◽  
Author(s):  
H. Yan ◽  
D. Knight ◽  
A. A. Zheltovodov
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Heat Transfer Coefficient ◽  
Large Eddy Simulation ◽  
Flat Plate ◽  
Boundary Layers ◽  
Plate Boundary ◽  
Navier Stokes ◽  
Eddy Simulation ◽  
Large Eddy

A supersonic flat-plate boundary layer at a Reynolds number of 2×104 based on the inflow boundary layer thickness is investigated at different Mach numbers (M=2.88 and 4) using the monotonically integrated large-eddy simulation (MILES) technique. The inherent numerical dissipation is taken as an implicit subgrid scales (SGS) model to close the Favre-filtered compressible Navier-Stokes (NS) equations. A finite volume method with second-order accuracy in time and space is implemented for the solution of the Navier-Stokes equations on an unstructured grid of tetrahedra. The heat transfer coefficient is predicted by simulating both adiabatic and isothermal cases. The mean flowfield and turbulent stresses are in good agreement with experiment. The relationship between the predicted skin friction coefficient and heat transfer coefficient is in close agreement with the Reynolds analogy factor. The variation of turbulent Prandtl number cross the boundary layer falls within the experimental envelope. These are the first LES predictions of adiabatic and isothermal supersonic flat plate boundary layers using the MILES technique.

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