scholarly journals Effect of Leading-Edge Bulges on Aerodynamic Characteristics of Bionic Wingsail

2021 ◽  
Author(s):  
Chen Li ◽  
Peiting Sun ◽  
Hongming Wang
Keyword(s):  
Stokes Equations ◽  
Lift Coefficient ◽  
Leading Edge ◽  
Aerodynamic Characteristics ◽  
Navier Stokes ◽  
Suction Surface ◽  
Ansys Fluent ◽  
Navier Stokes Equations ◽  
Extension Direction ◽  
Lift And Drag

The leading-edge bulges along the extension direction are designed on the marine wingsail. The height and the spanwise wavelength of the protuberances are 0.1c and 0.25c, respectively. At Reynolds number Re=5×105, the Reynolds Averaged Navier-Stokes equations are applied to the simulation of the wingsail with the bulges thanks to ANSYS Fluent finite-volume solver based on the SST K-ω models. The grid independence analysis is carried out with the lift and drag coefficients of the wingsail at AOA = 8° and AOA=20°. The results show that while the efficiency of the wingsail is reduced by devising the leading-edge bulges before stall, the bulges help to improve the lift coefficient of the wingsail when stalling. At AOA=22° under the action of the leading-edge tubercles, a convective vortex is formed on the suction surface of the modified wingsail, which reduces the flow loss. So the bulges of the wingsail can delay the stall.

scholarly journals Investigating the Effect of Roughness and Stiffness in 2D Aeroelastic Around Oscillatory Airfoil

2020 ◽  
Vol 15 ◽  
Keyword(s):  
Rough Surface ◽  
Smooth Surface ◽  
Stokes Equations ◽  
Lift Coefficient ◽  
Leading Edge ◽  
Simulation Method ◽  
Navier Stokes ◽  
Time Step ◽  
Navier Stokes Equations ◽  
Lift And Drag

In this research, a software has been developed to investigate the effect of roughness and stiffness in twodimensional aeroelastic in unsteady viscous flow around oscillatory airfoil. In this simulation to solve the Navier-Stokes equations, finite volume method has been used in the code with a high resolution scheme for fluid and structure simulation in transonic flows. For this purpose, fluid and structural behavior is solved separately at each time step and the effect of each one on the other is considered. For computing convection term in transonic unsteady compressible flow, high order SBIC (Second and Blending Interpolation Combined) scheme based on discretization of Normalized Variables Diagram (NVD) is used. Here the technique of inlet velocity vector oscillation which is a simpler method in comparison with rather complicated methods such as dynamic mesh is applied. The two-dimensional motion equations are obtained from the Lagrangian equations which are combined with the aerodynamic equations. The results of validation show that the extracted data has a desirable accuracy and had good agreement to experimental data. The FSI results show that, 1: Lift coefficient in smooth surface is more than the rough surface and also the drag coefficient in rough surface is more than the smooth surface, 2: Shock strength is weaker in the rough surface, 3: The shock’s place has moved to leading edge in the rough surface, 4: The number of oscillations in rough surface is reduced, 5:The structural stability of the airfoil when the surface of the airfoil is rough is much greater than smooth surface, 6: Because the density of the air and the amplitude of the oscillations are small and also small effect on the lift and drag coefficients, can be ignored the added mass in this simulation method

Numerical Simulation of Clocking Effect on Wake Transportation and Interaction in a 1.5-Stage Axial Turbine

2010 ◽  
Author(s):  
Wei Li ◽  
Hua Ouyang ◽  
Zhao-hui Du
Keyword(s):  
Stokes Equations ◽  
Three Dimensional ◽  
Leading Edge ◽  
Navier Stokes ◽  
Maximum Efficiency ◽  
Suction Surface ◽  
Navier Stokes Equations ◽  
Pressure Surface ◽  
Turbine Efficiency ◽  
Small Influence

To give insight into the clocking effect and its influence on the wake transportation and its interaction, the unsteady three-dimensional flow through a 1.5-stage axial low pressure turbine is simulated numerically using a density-correction based, Reynolds-Averaged Navier-Stokes equations commercial CFD code. The 2nd stator clocking is applied over ten equal tangential positions. The results show that the harmonic blade number ratio is an important factor affecting the clocking effect. The clocking effect has a very small influence on the turbine efficiency in this investigation. The efficiency difference between the maximum and minimum configuration is nearly 0.1%. The maximum efficiency can be achieved when the 1st stator wake enters the 2nd stator passage near blade suction surface and its adjacent wake passes through the 2nd stator passage close to blade pressure surface. The minimum efficiency appears if the 1st stator wake impinges upon the leading edge of the 2nd stator and its adjacent wake of the 1st stator passed through the mid-channel in the 2nd stator.

An analysis of aerodynamic forces on a delta wing

1996 ◽  
Vol 316 ◽  
pp. 173-196 ◽  
Author(s):  
Chien-Cheng Chang ◽  
Sheng-Yuan Lei
Keyword(s):  
Mach Number ◽  
Stokes Equations ◽  
Delta Wing ◽  
Leading Edge ◽  
Navier Stokes ◽  
Flow Structures ◽  
Aerodynamic Forces ◽  
Navier Stokes Equations ◽  
Lift And Drag ◽  
Secondary Vortices

The present study aims at relating lift and drag to flow structures around a delta wing of elliptic section. Aerodynamic forces are analysed in terms of fluid elements of non-zero vorticity and density gradient. The flow regime considered is Mα = 0.6 ∼ 1.8 and α = 5° ∼ 19°, where Mα denotes the free-stream Mach number and α the angle of attack. Let ρ denote the density, u velocity, and ω vorticity. It is found that there are two major source elements Re(x) and Ve(x) which contribute about 95% or even more to the aerodynamic forces for all the cases under consideration, \[R_e({\bm x})=-\frac{1}{2} {\bm u}^2 \nabla\rho \cdot \nabla\phi\quad {\rm and}\quad V_e ({\bm x}) = -\rho{\bm u}\times {\bm \omega}\cdot \nabla\phi,\] where θ is an acyclic potential, generated by the delta wing moving with unit velocity in the negative direction of the force (lift or drag). All the physical quantities are non-dimensionalized. Detailed force contributions are analysed in terms of the flow structures and the elements Re(x) and Ve(x). The source elements Re(x) and Ve(x) are concentrated in the following regions: the boundary layer in front of (below) the delta wing, the primary and secondary vortices over the delta wing, and a region of expansion around the leading edge. It is shown that Ve(x) due to vorticity prevails as the source of forces at relatively low Mach number, Mα < 0.7. Above about Mα = 0.75, Re(x) due to compressibility generally becomes the dominating contributor to the lift, while the overall contribution from Ve(x) decreases with increasing Mα, and even becomes negative at Mα = 1.2 for the lift, and at a higher Mα for the drag. The analysis is carried out with the aid of detailed numerical results by solving the Reynolds-averaged Navier–Stokes equations, which are in close agreement with experiments in comparisons of the surface pressure distributions.

Investigation on Propeller Slipstream by Using an Unstructured Rans Solver Based on Overlapping Grids

2017 ◽  
Vol 34 (2) ◽  
pp. 89-101 ◽  
Author(s):  
X. Q. Gong ◽  
M. S. Ma ◽  
J. Zhang ◽  
J. Tang
Keyword(s):  
Pressure Distribution ◽  
Stokes Equations ◽  
Lift Coefficient ◽  
Linear Interpolation ◽  
Aerodynamic Characteristics ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Overlapping Grids ◽  
Moment Coefficient ◽  
Grid Technique

AbstractBased on unstructured hybrid grid and dynamic overlapping grid technique, numerical simulations of Unsteady Reynolds Averaged Navier-Stokes equations were performed and investigation on isolated propeller aerodynamic characteristics and effects of propeller slipstream on turboprops were undertaken. The computational grid consisted of rotational subzone of propeller and stationary major-zone of aircraft, and walls criterion was used in the automatic hole-cutting procedure. Distance weight interpolation and tri-linear interpolation were developed to transfer information between the rotational and stationary subzones. The boundaries of overlapping grids were optimized for fixed axis rotation. The governing equations were solved by dual-time method and Lower Upper-Symmetric Gauss-Seidel method. The method and grid technique were verified by isolated propeller configuration and the computational results were in well agreement with the experimental data. The grid independence was studied to establish the numerical results. Finally, the flow around a turboprop case was simulated and the influence of propeller slipstream was presented by analyzing the surface pressure contours, profile pressure distribution, vorticity contours and profile streamline. It's indicated that the slipstream accelerates and rotates the free stream flow, changing the local angle of attack, enhancing the downwash effects, affecting the pressure distribution on wing and horizontal tail, as well as increasing the drag coefficient, pitching moment coefficient and the slope of lift coefficient.

Spectral Difference Solution of Incompressible Flow Over an Inline Tube Bundle With Oscillating Cylinder

2012 ◽  
Author(s):  
Christopher Cox ◽  
Chunlei Liang ◽  
Michael Plesniak
Keyword(s):  
Forced Oscillation ◽  
Stokes Equations ◽  
Tube Bundle ◽  
Lift Coefficient ◽  
Flow Simulation ◽  
Navier Stokes ◽  
Spectral Difference ◽  
Navier Stokes Equations ◽  
Incompressible Viscous Flow ◽  
Lift And Drag

A high-order spectral difference (SD) method for solving the Navier-Stokes equations on moving, deformable unstructured grids has been developed [1]. In this paper, the SD method and the artificial compressibility method (ACM) are integrated with a dual time-stepping scheme to model unsteady incompressible viscous flow past an inline tube bundle of cylinders equally sized (diameter = d) and spaced (spacing = 2.1*d) over an unstructured grid. Flow simulation results are obtained using a fourth-order space accurate SD method. Two forced oscillation cases are considered; (1) 1st cylinder oscillation and (2) 2nd cylinder oscillation. The Reynolds number used for both cases is 100 and the flow is laminar. Forced oscillation is performed in the tranverse direction, and the subsequent altering of the flow physics of the system is studied. The frequency of vortex shedding behind each cylinder is the same. Root mean square results show that the lift coefficient is greatest for the 4th inline cylinder in both cases. Furthermore, a reduction in both lift and drag coefficients is seen from case (1) to case (2).

scholarly journals A Numerical Investigation of Co-flow Jet Effects on Airfoil Aerodynamic Characteristics

2021 ◽  
Author(s):  
Shima Yazdani ◽  
Erfan Salimipour ◽  
Ayoob Salimipour
Keyword(s):  
Reynolds Number ◽  
Stokes Equations ◽  
Active Flow Control ◽  
Lift Coefficient ◽  
Reynolds Numbers ◽  
Aerodynamic Characteristics ◽  
Dynamic Stall ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Momentum Coefficient

Abstract The present paper numerically investigates the performance of a Co-Flow Jet (CFJ) on the static and dynamic stall control of the NACA 0024 airfoil at Reynolds number 1.5 × 105. The two-dimensional Reynolds-averaged Navier-Stokes equations are solved using the SST k-ω turbulence model. The results show that the lift coefficients at the low angles of attack (up to α = 15̊) are significantly increased at Cµ = 0.06, however for the higher momentum coefficients, it is not seen an improvement in the aerodynamic characteristics. Also, the dynamic stall for a range of α between 0̊ and 20̊ at the mentioned Reynolds number and with the reduced frequency of 0.15 for two CFJ cases with Cµ = 0.05 and 0.07 are investigated. For the case with Cµ = 0.07, the lift coefficient curve did not present a noticeable stall feature compared to Cµ = 0.05. The effect of this active flow control by increasing the Reynolds numbers from 0.5 × 105 to 3 × 105 is also investigated. At all studied Reynolds numbers, the lift coefficient enhances as the momentum coefficient increases where its best performance is obtained at the angle of attack α = 15̊.

Numerical Simulation on the Aerodynamic Characteristics Effect of Ribs Acting on the Cooling Tower

2017 ◽  
Vol 259 ◽  
pp. 227-231
Author(s):  
Petr Harazim ◽  
Lukáš Vráblík
Keyword(s):  
Cooling Tower ◽  
Stokes Equations ◽  
Meridional Wind ◽  
Aerodynamic Characteristics ◽  
Navier Stokes ◽  
Infinite Cylinder ◽  
Turbulent Model ◽  
Ansys Fluent ◽  
Navier Stokes Equations ◽  
Critical Flow Regime

The experimental work deals with the modelling of flow around a two-dimensional model of an infinite cylinder in a trans-critical flow regime. Herein, there was used ANSYS Fluent and the turbulent model k-ε realizable for the calculation of the pressure distribution around the cylinder. This turbulence model belongs to Reynolds Averaged Navier-Stokes equations (RANS). The simulated numerical domain considered half of the cylinder with the diameter of 70 m, wind flow was set to 35 m.s-1, which resulting in the Reynolds number of Re = 1,68.108. In this study, meridional wind ribs were modelled physically. A parametric study was modelled with the different shape of ribs, ribs spacing and height. Simulated results were compared with experimentally ascertained data and guidelines.

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.

scholarly journals Effects of leading-edge rod on dynamic stall performance of a wind turbine airfoil

2017 ◽  
Vol 231 (8) ◽  
pp. 753-769 ◽  
Author(s):  
Junwei Zhong ◽  
Jingyin Li ◽  
Penghua Guo
Keyword(s):  
Stokes Equations ◽  
Leading Edge ◽  
Aerodynamic Characteristics ◽  
Dynamic Stall ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Moment Coefficient ◽  
Wind Turbine Airfoil ◽  
Stall Angle ◽  
The Moment

A cylindrical rod placed at the leading edge of the S809 airfoil is used as an alternative for the conventional vortex generators. In this paper, extensive numerical investigations have been conducted on the effects of the rod on the static and dynamic stall performance of the S809 airfoil. The flows around the stationary and sinusoidally oscillating S809 airfoils at Re = 106 are simulated by solving the unsteady two-dimensional Reynolds-averaged Navier–Stokes equations with the Shear Stress Transport k–ω model. For the stationary airfoil, the leading edge rod can effectively enhance the aerodynamic characteristics of the airfoil and delay the stall angle, with the maximum lift–drag ratio increased by 30.7%. For the airfoil undergoing deep dynamic stall, the rod shows the capacity of eliminating the dynamic stall vortex at the leading edge and suppressing the flow separation at the tailing edge. It also reduces the peak of the negative pitching moment and the hysteresis effects substantially, and eliminates the negative damping sub-loop of the moment coefficient. Moreover, the distance between the rod and the airfoil has a strong influence on the lift forces but little effect on drag and moment coefficients of airfoil under deep dynamic stall.

scholarly journals Numerical study of airfoil with wavy leading edge at high Reynolds number regime

2020 ◽  
Author(s):  
William Denner Pires Fonseca ◽  
Rafael Rosario Da Silva ◽  
Reinaldo Marcondes Orselli ◽  
Adson Agrico De Paula ◽  
Ricardo Galdino da Silva
Keyword(s):  
Reynolds Number ◽  
Turbulence Modeling ◽  
Stokes Equations ◽  
Numerical Study ◽  
Lift Coefficient ◽  
Leading Edge ◽  
Numerical Data ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
High Reynolds

In this work, a numerical study of flow around an airfoil with wavy leading edge is presented at a Reynolds number of 3X106. The flow is resolved by considering the RANS (Reynolds Average Navier-Stokes)equations. The baseline geometry is based on the NACA 0021 profile. The wavy leading edge has an amplitude of 3% and wavelength of 11%, both with respect to the airfoil chord. Cases without and with wavy leadingedges are simulated and compared. Initially, studies of the numerical sensitivity with respect to the obtained results, considering aspects such as turbulence modeling and mesh refinement, are carried out as well as bycomparison with corresponding results in the literature. Numerical data such as pressure distribution, shear stress lines on the wing surface, and aerodynamics coefficients are used to describe and investigate the flowfeatures around the wavy leading airfoil. Comparisons between the straight leading edge and the wavy leading edge cases shows an increase of the maximum lift coefficient as well as stall angle for the wavy leading edge configuration. In addition, at an angle of attack near the stall, the present numerical results shows an increase of the drag coefficient with the wavy leading edge airfoil when compared with the corresponding straight leading edge case.

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