Computational Evaluation of the Periodic Performance of a NACA 0012 Fitted With a Gurney Flap

2001 ◽  
Vol 124 (1) ◽  
pp. 227-234 ◽  
Author(s):  
James C. Date ◽  
Stephen R. Turnock
Keyword(s):  
Vortex Shedding ◽  
Navier Stokes ◽  
Two Dimensional ◽  
Time Step ◽  
Computational Evaluation ◽  
Gurney Flap ◽  
Section Design ◽  
Computationally Intensive ◽  
Lift And Drag ◽  
Naca 0012

A detailed computational investigation into the periodic two-dimensional performance of a NACA 0012 section fitted with 2 and 4 percent h/c Gurney flaps operating at a Reynolds number of 0.85×106 is presented. The aim of the work was to determine the suitability of the incompressible Reynolds-averaged Navier-Stokes (RANS) formulation in modeling the vortex shedding experienced by lifting sections with blunt, sharp edged features. In particular, whether under-converged steady state calculations could be used for section design performance evaluation in place of the computationally intensive time accurate flow simulations. Steady, periodic, and time-averaged two-dimensional lift and drag coefficients, as well as vortex shedding frequency, were predicted and compared with the available experimental data. Reasonable agreement was found, once sufficiently fine grids had been generated, and the correct time step determined for the time accurate simulations.

Unsteady RANS Computations of the Flow Past an Airfoil in the Wake of a Rod

2002 ◽  
Author(s):  
Je´roˆme Boudet ◽  
Damiano Casalino ◽  
Marc C. Jacob ◽  
Pascal Ferrand
Keyword(s):  
Vortex Shedding ◽  
Turbulence Models ◽  
Leading Edge ◽  
Navier Stokes ◽  
Two Dimensional ◽  
Vorticity Field ◽  
Unsteady Rans ◽  
Variable Configuration ◽  
Naca 0012 ◽  
Insight Into

Two-dimensional Reynolds Averaged Navier-Stokes (RANS) equations are solved in order to simulate the interaction between a Ka´rma´n vortex street shed from a rod and a NACA-0012 airfoil in the wake of the rod. Two closure turbulence models are tested, a linear and a nonlinear k-ω model, for a chord based Reynolds number Rec ∼ 4.8105. These models provide consistent results in terms of both mean and fluctuating flow quantities. Insight into the instantaneous vorticity field shows that the vortex shedding pattern near the wall is quite well predicted, despite an over-estimated frequency. Downstream, computations always exhibit head-on interactions of the vortices with the airfoil leading edge whereas the experiments show a more variable configuration.

The turning couples on an elliptic particle settling in a vertical channel

1994 ◽  
Vol 271 ◽  
pp. 1-16 ◽  
Author(s):  
Peter Y. Huang ◽  
Jimmy Feng ◽  
Daniel D. Joseph
Keyword(s):  
Shear Stress ◽  
Vortex Shedding ◽  
Stokes Equations ◽  
Vertical Channel ◽  
Navier Stokes ◽  
Front Face ◽  
Two Dimensional ◽  
Navier Stokes Equations ◽  
Back Face ◽  
The One

We do a direct two-dimensional finite-elment simulation of the Navier–Stokes equations and compute the forces which turn an ellipse settling in a vertical channel of viscous fluid in a regime in which the ellipse oscillates under the action of vortex shedding. Turning this way and that is induced by large and unequal values of negative pressure at the rear separation points which are here identified with the two points on the back face where the shear stress vanishes. The main restoring mechanism which turns the broadside of the ellipse perpendicular to the fall is the high pressure at the ‘stagnation point’ on the front face, as in potential flow, which is here identified with the one point on the front face where the shear stress vanishes.

scholarly journals Prediction of Turbulent Flow Around a Square Cylinder With Rounded Corners

2017 ◽  
Vol 139 (3) ◽  
Author(s):  
S. S. Dai ◽  
B. A. Younis ◽  
H. Y. Zhang
Keyword(s):  
Turbulent Flow ◽  
Vortex Shedding ◽  
Turbulence Closure ◽  
Navier Stokes ◽  
Square Cylinder ◽  
Mean Flow ◽  
Drag Forces ◽  
Turbulence Closures ◽  
High Reynolds ◽  
Lift And Drag

Predictions are reported of the two-dimensional turbulent flow around a square cylinder with rounded corners at high Reynolds numbers. The effects of rounded corners have proved difficult to predict with conventional turbulence closures, and hence, the adoption in this study of a two-equation closure that has been specifically adapted to account for the interactions between the organized mean-flow motions due to vortex shedding and the random motions due to turbulence. The computations were performed using openfoam and were validated against the data from flows past cylinders with sharp corners. For the case of rounded corners, only the modified turbulence closure succeeded in capturing the consequences of the delayed flow separation manifested mainly in the reduction of the magnitude of the lift and drag forces relative to the sharp-edged case. These and other results presented here argue in favor of the use of the computationally more efficient unsteady Reynolds-averaged Navier-Stokes approach to this important class of flows provided that the effects of vortex shedding are properly accounted for in the turbulence closure.

scholarly journals Effect of Reynolds Number on Aerodynamics of Airfoil with Gurney Flap

2015 ◽  
Vol 2015 ◽  
pp. 1-10 ◽  
Author(s):  
Shubham Jain ◽  
Nekkanti Sitaram ◽  
Sriram Krishnaswamy
Keyword(s):  
Reynolds Number ◽  
Lift Coefficient ◽  
Angle Of Attack ◽  
Reynolds Numbers ◽  
Low Reynolds Numbers ◽  
Critical Range ◽  
Gurney Flap ◽  
Stall Angle ◽  
Lift And Drag ◽  
Naca 0012

Steady state, two-dimensional computational investigations performed on NACA 0012 airfoil to analyze the effect of variation in Reynolds number on the aerodynamics of the airfoil without and with a Gurney flap of height of 3% chord are presented in this paper. RANS based one-equation Spalart-Allmaras model is used for the computations. Both lift and drag coefficients increase with Gurney flap compared to those without Gurney flap at all Reynolds numbers at all angles of attack. The zero lift angle of attack seems to become more negative as Reynolds number increases due to effective increase of the airfoil camber. However the stall angle of attack decreased by 2° for the airfoil with Gurney flap. Lift coefficient decreases rapidly and drag coefficient increases rapidly when Reynolds number is decreased below critical range. This occurs due to change in flow pattern near Gurney flap at low Reynolds numbers.

Coupled Multibody-Fluid Dynamics Simulation of Flapping Wings

2013 ◽  
Author(s):  
Mattia Alioli ◽  
Marco Morandini ◽  
Pierangelo Masarati
Keyword(s):  
Fluid Dynamics ◽  
Differential Equations ◽  
General Purpose ◽  
Free Software ◽  
Dynamics Simulation ◽  
Flapping Wings ◽  
Navier Stokes ◽  
Element Approximation ◽  
Time Step ◽  
Naca 0012

This paper deals with the coupled structural and fluid-dynamics analysis of flexible flapping wings using multibody dynamics. A general-purpose multidisciplinary multibody solver is coupled with a computational fluid dynamics code by means of a general-purpose, meshless boundary interfacing approach based on Moving Least Squares with Radial Basis Functions. The general-purpose, free software multibody solver MBDyn is used. A nonlinear 4-node shell element has been used for the structural model. The fluid dynamics code is based on a stabilized finite element approximation of the unsteady Navier-Stokes equations. The method (often referred to in the literature as G2 method) has been implemented within the programming environment provided by the free software project FEniCS, a collection of libraries specifically designed for the automated and efficient solution of differential equations. FEniCS provides extensive scripting capabilities, with a domain-specific language for the specification of variational formulations of Partial Differential Equations that is embedded within the programming language Python. This approach makes it possible to easily and quickly build complex simulation codes that are, at the same time, extremely efficient and easily adapted to run in parallel. The coupling of the multibody and Navier-Stokes codes is strictly enforced at each time step. The fluid dynamics discretization is automatically refined to keep the error on the overall lift and drag coefficients below a user-defined tolerance. The method is first tested by computing the drag force of a non-oscillating NACA 0012 airfoil traveling in air. Subsequently, the drag and lift forces on a rigid and flexible oscillating NACA 0012 wing are compared with experimental data. Encouraging results obtained from the modeling and analysis of the dynamics and aeroelasticity of flexible oscillating wing models confirm the ability of the structural and fluid dynamics models to capture the physics of the problem.

scholarly journals A TIME ACCURATE PSEUDO-WAVELET SCHEME FOR TWO-DIMENSIONAL TURBULENCE

2005 ◽  
Vol 03 (04) ◽  
pp. 587-599 ◽  
Author(s):  
B. V. RATHISH KUMAR ◽  
MANI MEHRA
Keyword(s):  
Galerkin Method ◽  
Taylor Series ◽  
Stokes Equations ◽  
Taylor Series Expansion ◽  
Navier Stokes ◽  
Two Dimensional ◽  
Time Step ◽  
Navier Stokes Equations ◽  
Time Stepping ◽  
Taylor Galerkin Method

In this paper, we propose a wavelet-Taylor–Galerkin method for solving the two-dimensional Navier–Stokes equations. The discretization in time is performed before the spatial discretization by introducing second-order generalization of the standard time stepping schemes with the help of Taylor series expansion in time step. Wavelet-Taylor–Galerkin schemes taking advantage of the wavelet bases capabilities to compress both functions and operators are presented. Results for two-dimensional turbulence are shown.

Dissipative, forced turbulence in two-dimensional magnetohydrodynamics

1977 ◽  
Vol 17 (3) ◽  
pp. 369-398 ◽  
Author(s):  
David Fyfe ◽  
David Montgomery ◽  
Glenn Joyce
Keyword(s):  
Vector Potential ◽  
Spectral Power ◽  
Equations Of Motion ◽  
Power Laws ◽  
Navier Stokes ◽  
Two Dimensional ◽  
Dynamo Action ◽  
Time Step ◽  
Forced Turbulence ◽  
External Forces

The equations of motion for turbulent two-dimensional magnetohydrodynamic flows are solved in the presence of finite viscosity and resistivity, for the case in which external forces (mechanical and/or magnetic) act on the fluid. The goal is to verify the existence of a magnetohydrodynamic dynamo effect which is represented mathematically by a substantial back-transfer of mean square vector potential to the longest allowed Fourier wavelengths. External forces consisting of a random part plus a fraction of the value at the previous time step are employed, after the manner of Lilly for the Navier–Stokes case. The regime explored is that for which the mechanical and magnetic Reynolds numbers are in the region of 100 to 1000. The conclusions are that mechanical forcing terms alone cannot lead to dynamo action, but that dynamo action can result from either magnetic forcing terms or from both mechanical and magnetic forcing terms simultaneously. Most real physical cases seem most accurately modelled by the third situation. The spatial resolution of the 32 × 32 calculation is not adequate to test accurately the predictions of the spectral power laws previously arrived at on the basis of the assumption of simultaneous cascades of energy and vector potential. Some speculations are offered concerning possible relations between turbulent cascades and the ‘disruptive instability’.

Two-Dimensional Numerical Simulation of Vortex Shedding of Multiple Stranded Ropes

2019 ◽  
Author(s):  
Xinxin Wang ◽  
Liuyi Huang ◽  
Yanli Tang ◽  
Fenfang Zhao ◽  
Peng Sun
Keyword(s):  
Numerical Simulation ◽  
Reynolds Number ◽  
Vortex Shedding ◽  
Stokes Equations ◽  
Flow Distribution ◽  
Hydrodynamic Performance ◽  
Navier Stokes ◽  
Hydrodynamic Characteristics ◽  
Two Dimensional ◽  
Navier Stokes Equation

Abstract The stranded rope is one of the important components of the fishery aquaculture equipment. We investigate the fluid flow through two-dimensional stranded rope by direct simulation of the Navier-Stokes equations. We show that for different kinds of stranded rope structures, there are significant differences in hydrodynamic performance. This paper established a numerical model of unsteady flow past the stranded rope based on the Navier-Stokes equation and Morison formulas to study the hydrodynamic characteristics of three-stranded rope, four-stranded rope, and seven-stranded rope, respectively. The turbulence flow was simulated using Standard k-ε model and Shear-Stress Transport k-ω (SST) model. The flow distribution strongly depends on the Reynolds number, a range of 3,900 and 30,000. With increasing Reynolds number, the alternate eddy formation and shedding were repeated behind the stranded ropes. Such parameters of hydrodynamic characteristics of multiple stranded ropes were calculated as the lift and drag coefficients, and vortex shedding frequencies. The numerical simulation results presented flow performances of different cross sections (a, b, c, d) at different Reynolds numbers. However, Reynolds number has no significant impact on the Strouhal number for the same attack angle of the stranded rope.

Numerical investigation of the unsteady aerodynamics of NACA 0012 with suction surface protrusion

2019 ◽  
Vol 92 (2) ◽  
pp. 186-200
Author(s):  
Aslesha Bodavula ◽  
Rajesh Yadav ◽  
Ugur Guven
Keyword(s):  
Vortex Shedding ◽  
Stokes Equations ◽  
Lift Coefficient ◽  
Unsteady Aerodynamics ◽  
Leading Edge ◽  
Navier Stokes ◽  
Suction Surface ◽  
Content Type ◽  
Energy Harvesters ◽  
Naca 0012

Purpose The purpose of this paper is to investigate the effect of surface protrusions on the flow unsteadiness of NACA 0012 at a Reynolds number of 100,000. Design/methodology/approach Effect of protrusions is investigated through numerical simulation of two-dimensional Navier–Stokes equations using a finite volume solver. Turbulent stresses are resolved through the transition Shear stress transport (four-equation) turbulence model. Findings The small protrusion located at 0.05c and 0.1c significantly improve the lift coefficient by up to 36% in the post-stall regime. It also alleviates the leading edge stall. The larger protrusions increase the drag significantly along with significant degradation of lift characteristics in the pre-stall regime as well. The smaller protrusions also increase the frequency of the vortex shedding. Originality/value The effect of macroscopic protrusions or deposits in rarely investigated. The delay in stall shown by smaller protrusions can be beneficial to micro aerial vehicles. The smaller protrusions increase the frequency of the vortex shedding, and hence, can be used as a tool to enhance energy production for energy harvesters based on vortex-induced vibrations and oscillating wing philosophy.

In-flight icing simulation for two-dimensional configurations

2020 ◽  
Vol 34 (14n16) ◽  
pp. 2040068
Author(s):  
Tong Liu ◽  
Jin-Sheng Cai ◽  
Kun Qu ◽  
Shu-Cheng Pan
Keyword(s):  
Navier Stokes ◽  
Simulation Tool ◽  
Two Dimensional ◽  
Ice Accretion ◽  
Aircraft Icing ◽  
Droplet Impingement ◽  
Droplet Flow ◽  
Accretion Model ◽  
Median Volume ◽  
Naca 0012

This paper presents a comprehensive aircraft icing simulation tool implemented in an in-house Navier–Stokes parallel multi-block solver. In detail, the droplet flow field is solved by Eulerian approach, and a Partial Differential Equation (PDE)-based ice accretion model is adopted to determine the runback water flow and icing rate. Numerical validations are performed on the two-dimensional (2D) NACA 0012 airfoil, where good agreements with the literature are observed. Additionally, the paper investigates the influence of droplet size on the final ice shape. Results show that droplets with greater Median Volume Diameter (MVD) are more likely to impact on the wall, which results in larger droplet impingement limit and icing limit.

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