Computational Analysis of Pressure and Wake Characteristics of an Aerofoil in Ground Effect

2004 ◽  
Vol 127 (2) ◽  
pp. 290-298 ◽  
Author(s):  
Stephen Mahon ◽  
Xin Zhang
Keyword(s):  
Flow Field ◽  
Surface Pressure ◽  
Stokes Equations ◽  
Turbulence Models ◽  
Ground Effect ◽  
Wake Flow ◽  
Suction Surface ◽  
Ride Height ◽  
Surface Pressure Distribution ◽  
Wake Characteristics

The pressure and wake of an inverted cambered aerofoil in ground effect was studied numerically by solving the Reynolds-averaged Navier-Stokes equations. Efforts were focused on the setting up of an accurate numerical model and assessing the abilities of various turbulence models in capturing major physical features associated with the flow, such as surface pressure distribution, separation, level of downforce, and wake. A number of ride heights were studied covering various force regions. Surface pressures, sectional forces, and wake characteristics were compared to experimental data. The k−ω SST and Realizable k−ε turbulence models were found to offer good overall simulations, with the k−ω SST performing better for the surface pressure and the Realizable k−ε better for the wake. The simulations at various ride heights correctly captured the trends in flow-field variations with ride height. The surface pressures, wake flow field, and region of separation on the suction surface of the aerofoil, at lower ride heights, were all modeled accurately.

Computational Analysis of a Inverted Double-Element Airfoil in Ground Effect

2006 ◽  
Vol 128 (6) ◽  
pp. 1172-1180 ◽  
Author(s):  
Stephen Mahon ◽  
Xin Zhang
Keyword(s):  
Flow Field ◽  
Stokes Equations ◽  
Near Field ◽  
Turbulence Models ◽  
Ground Effect ◽  
Wake Flow ◽  
Navier Stokes ◽  
Main Element ◽  
Ride Height ◽  
Navier Stokes Equations

The flow around an inverted double-element airfoil in ground effect was studied numerically, by solving the Reynolds averaged Navier-Stokes equations. The predictive capabilities of six turbulence models with regards to the surface pressures, wake flow field, and sectional forces were quantified. The realizable k−ε model was found to offer improved predictions of the surface pressures and wake flow field. A number of ride heights were investigated, covering various force regions. The surface pressures, sectional forces, and wake flow field were all modeled accurately and offered improvements over previous numerical investigations. The sectional forces indicated that the main element generated the majority of the downforce, whereas the flap generated the majority of the drag. The near field and far field wake development was investigated and suggestions concerning reduction of the wake thickness were offered. The main element wake was found to greatly contribute to the overall wake thickness with the contribution increasing as the ride height decreased.

Two-Dimensional Experimental Investigation on the Effects of a Fowler Flap Gap and Overlap Size on the Wake Flow Field

2016 ◽  
Vol 139 (2) ◽  
Author(s):  
David Demel ◽  
Mohsen Ferchichi ◽  
William D. E. Allan ◽  
Marouen Dghim
Keyword(s):  
Experimental Investigation ◽  
Flow Field ◽  
Angle Of Attack ◽  
Wake Flow ◽  
Two Dimensional ◽  
Edge Region ◽  
Suction Surface ◽  
Trailing Edge ◽  
Piv Measurements ◽  
Image Velocimetry

This work details an experimental investigation on the effects of the variation of flap gap and overlap sizes on the flow field in the wake of a wing-section equipped with a trailing edge Fowler flap. The airfoil was based on the NACA 0014-1.10 40/1.051 profile, and the flap was deployed with 40 deg deflection angle. Two-dimensional (2D) particle image velocimetry (PIV) measurements of the flow field in the vicinity of the main wing trailing edge and the flap region were performed for the optimal flap gap and overlap, as well as for flap gap and overlap increases of 2% and 4% chord beyond optimal, at angles of attack of 0 deg, 10 deg, and 12 deg. For all the configurations investigated, the flow over the flap was found to be fully stalled. At zero angle of attack, increasing the flap gap size was found to have minor effects on the flow field but increased flap overlap resulted in misalignment between the main wing boundary layer (BL) flow and the slot flow that forced the flow in the trailing edge region of the main wing to separate. When the angle of attack was increased to near stall conditions (at angle of attack of 12 deg), increasing the flap gap was found to energize and improve the flow in the trailing edge region of the main wing, whereas increased flap overlap further promoted flow separation on the main wing suction surface possibly steering the wing into stall.

Simulation Research on Aerodynamic Characteristics of Vehicle under Steady Crosswind Based on XFlow

2014 ◽  
Vol 494-495 ◽  
pp. 138-141
Author(s):  
Shan Ling Han ◽  
Zhi Yong Li ◽  
Jin Bin Li ◽  
Ru Xing Yu
Keyword(s):  
Flow Field ◽  
Surface Pressure ◽  
Body Surface ◽  
Crucial Role ◽  
Aerodynamic Characteristics ◽  
The Body ◽  
Wake Flow ◽  
Aerodynamic Coefficient ◽  
Simulation Research ◽  
The Asymmetry

The aerodynamic characteristics of vehicle play a crucial role in steering stability, comfort and safety of vehicle. The crosswind will affect the aerodynamic characteristics of vehicle. In this paper, the aerodynamic characteristics of ASMO model under steady crosswind is simulated by XFlow software, and the changes of aerodynamic characteristics under different steady crosswind are analyzed. It turned out that the asymmetry of wake flow field is enhanced with the increasing of crosswind, and the body surface pressure of windward is amplified, the six components of aerodynamic coefficient are also increased. It is found that the vehicle aerodynamic characteristics changed obviously under steady crosswind.

Effect of RANS Method on the Stall Onset Prediction by an Eigenvalue Approach

2018 ◽  
Vol 141 (3) ◽  
Author(s):  
Zhe Xie ◽  
Yangwei Liu ◽  
Xiaohua Liu ◽  
Lipeng Lu ◽  
Xiaofeng Sun
Keyword(s):  
Flow Field ◽  
Turbulence Model ◽  
Turbulence Models ◽  
Wake Flow ◽  
Spatial Discretization ◽  
Eigenvalue Approach ◽  
Trailing Edge ◽  
Transonic Compressor ◽  
Rans Simulation ◽  
Grid Independence

The eigenvalue approach is a recently developed compressor stability model used to predict stall onset. In this model, the flow field from a Reynolds-averaged Navier–Stokes (RANS) simulation provides the basic flow. This paper presents the effect of the RANS methods (including the computational grid, the turbulence model, and the spatial discretization scheme) on the eigenvalue and investigates the most influencing flow structures to the eigenvalue. The test compressor was the transonic compressor of NASA Rotor 37. Three individual meshes with different grid densities were used to validate the grid independence, and the results indicated that RANS simulation and eigenvalue calculation obtain grid independence at the same grid density. Then, the effect of four turbulence models (including Spalart–Allmaras (SA) turbulence model, two different k–ε models with the extended wall function model (EWFKE), and the Yang–Shih model (YSKE), and k–ω shear stress transport (SST) model), and three spatial discretization schemes (the central scheme, the flux difference splitting (FDS) scheme, and the symmetric total variation diminishing (STVD)) was also studied. Further investigation showed that the SA turbulence model combined with the STVD scheme provided the best stall point prediction, with a relative error of 0.05%. Detailed exploration of the three-dimensional flow field revealed that there were two flow patterns near the blade tip necessary for precisely predicting stall onset: the flow blockage generated by the shockwave-tip leakage vortex (TLV) interaction, and the trailing edge separation and corresponding wake flow. The effect of the blockage was greater than the effect of the trailing edge flow.

Numerical validation and back-pressure effect on internal compression flows of typical supersonic inlet

2015 ◽  
Vol 119 (1215) ◽  
pp. 631-645 ◽  
Author(s):  
F. Ding ◽  
C.-B. Shen ◽  
W. Huang ◽  
J. Liu
Keyword(s):  
Experimental Data ◽  
Flow Field ◽  
Stokes Equations ◽  
Numerical Study ◽  
Pressure Ratio ◽  
Turbulence Models ◽  
Wave Pattern ◽  
Back Pressure ◽  
Freestream Turbulence ◽  
Supersonic Inlet

AbstractA numerical study was conducted to analyse the performance of different turbulence models and different turbulence intensities and turbulence length scales specified for the boundary condition of the inflow to the internal compression flow field of a typical supersonic inlet. The effect of the back-pressure ratio on the properties of the flow field was also investigated. Computational results obtained by the commercial software FLUENT, which is used to solve the full two-dimensional Reynolds-averaged Navier-Stokes equations, were validated through both graphical and quantitative comparisons with previously published experimental data. The two-equation models that were considered in this study are the RNGk-ε, realisablek-ε, standardk-ε, and SSTk-ω turbulence models. The RNGk-ε model had the best performance among the four models and predicted good wall pressure distributions. The best agreement between the predicted results and experimental data was obtained when either the default values of the freestream turbulence intensity and length scale in the FLUENT solver were used, or the empirical formula was used to calculate the two parameters of the freestream turbulence properties. The shock wave pattern varied between the oblique mode and the fully developed normal mode with increasing back-pressure ratio, and the unstart phenomenon occurred when the back-pressure ratio was sufficiently high.

The Influence of Different Turbulence Models on the FlowField Characteristics of an Aerospike Nozzle

2011 ◽  
Vol 110-116 ◽  
pp. 437-443
Author(s):  
S. Noori ◽  
A. Shahrokhi
Keyword(s):  
Flow Field ◽  
Stokes Equations ◽  
Initial Conditions ◽  
Turbulence Models ◽  
State Density ◽  
Navier Stokes ◽  
Field Equations ◽  
Solution Convergence ◽  
Turbulent Models ◽  
Aerospike Nozzle

To improve the calculation of the flow properties of an aerospike nozzle, different turbulent models are studied in this research. The primary shape of the nozzle and the plug is determined through utilizing an approximate method. The flow field is then simulated using Navier-Stokes equations for compressible flow. The computational methodology utilizes steady state density-based formulation and a finite volume cell centered scheme to discretize the flow field equations. To accelerate the solution convergence, the flow field is divided into several zones. Each zone is facilitated with proper unstructured grid and appropriate initial conditions are implemented to each zone. The accuracy and the robustness of wall function based turbulence models i.e. standard and RNG k-ε models are compared with those of Spalart-Allmaras (S-A) and k-ω turbulence models.

Numerical analysis for wake flow field of Ahmed model based on a nonlinear-LRN/DES turbulence model

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Le Dian Zheng ◽  
Yi Yang ◽  
Guang Lin Qiang ◽  
Zhengqi Gu
Keyword(s):  
Experimental Data ◽  
Flow Field ◽  
Reynolds Stress ◽  
Turbulence Model ◽  
Turbulence Models ◽  
Aerodynamic Characteristics ◽  
Wake Flow ◽  
Field Analysis ◽  
Content Type ◽  
Des Model

Purpose This paper aims to propose a precise turbulence model for automobile aerodynamics simulation, which can predict flow separation and reattachment phenomena more accurately. Design/methodology/approach As the results of wake flow simulation with commonly used turbulence models are unsatisfactory, by introducing a nonlinear Reynolds stress term and combining the detached Eddy simulation (DES) model, this paper proposes a nonlinear-low-Reynolds number (LRN)/DES turbulence model. The turbulence model is verified in a backward-facing step case and applied in the flow field analysis of the Ahmed model. Several widely applied turbulence models are compared with the nonlinear-LRN/DES model and the experimental data of the above cases. Findings Compared with the experimental data and several turbulence models, the nonlinear-LRN/DES model gives better agreement with the experiment and can predict the automobile wake flow structures and aerodynamic characteristics more accurately. Research limitations/implications The nonlinear-LRN/DES model proposed in this paper suffers from separation delays when simulating the separation flows above the rear slant of the Ahmed body. Therefore, more factors need to be considered to further improve the accuracy of the model. Practical implications This paper proposes a turbulence model that can more accurately simulate the wake flow field structure of automobiles, which is valuable for improving the calculation accuracy of the aerodynamic characteristics of automobiles. Originality/value Based on the nonlinear eddy viscosity method and the scale resolved simulation, a nonlinear-LRN/DES turbulence model including the nonlinear Reynolds stress terms for separation and reattachment prediction, as well as the wake vortex structure prediction is first proposed.

Experimental Flow Field and Heat Transfer Study of a Slot Jet Reattaching Onto a Flat Plate

2001 ◽  
Author(s):  
V. Narayanan ◽  
J. Seyed-Yagoobi ◽  
R. H. Page
Keyword(s):  
Heat Transfer ◽  
Flow Field ◽  
Surface Pressure ◽  
Local Heat Transfer ◽  
Field Measurements ◽  
Local Heat ◽  
Surface Pressure Distribution ◽  
Mean Pressure ◽  
Transfer Study ◽  
Impingement Surface

Abstract Detailed heat transfer, impingement surface pressure and flow field measurements on a submerged slot jet reattachment nozzle are presented. The nozzle is comprised of a rectangular region of aspect ratio 20:1, with circular ends. The jet exits the nozzle parallel to an adjacent flat impingement surface and reattaches onto it. Contours of local heat transfer exhibit three-dimensionality within the recirculation and reattachment regions with increase in nozzle-to-surface spacing. Mean and time averaged fluctuating surface pressure distribution at the center plane of the nozzle along the minor indicate that the location of peak fluctuating pressure occurs upstream of the peak mean pressure. Flow field measurements are presented for a nozzle-to-surface spacing of 3.85 exit hydraulic diameters from the surface, at a turbulent exit Reynolds number of 10 500. Surface pressure and flow field observations are used to explain heat transfer results in the recirculation and reattachment regions.

Viscous Flow Field Computations for the VKI–1 Turbine Cascade Using Different Turbulence Models

1995 ◽  
Author(s):  
L. J. Lenke ◽  
A. W. Reichert ◽  
H. Simon
Keyword(s):  
Flow Field ◽  
Viscous Flow ◽  
Measurement Data ◽  
Turbulence Models ◽  
Algebraic Model ◽  
Turbulence Modelling ◽  
Wake Flow ◽  
Field Calculation ◽  
Wall Functions ◽  
Viscous Flow Field

The influence of the turbulence modelling on viscous flow field calculation results has often been discussed in the past. For a meaningful comparison of different turbulence models the access to reliable measurement data is necessary. The plane VKI–1 turbine profile has been investigated experimentally in many publications. Therefore this turbine profile is chosen for transonic 2D flow field calculations using three different turbulence models. The algebraic model of Baldwin and Lomax, the Standard k–ϵ model with wall functions and a low–Reynolds number model are considered in this investigation. The main differences between the models become apparent in the trailing edge region. The turbulence modelling influences the boundary layer thickness and the shape of the shear layers and the separation region in the wake flow. For the high Mach numbers appearing in this region, a strong influence on the flow field due to small shear layer changes has been found.

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