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International Journal of Mechanical Engineering and Technology (IJMET) Volume 8, Issue 11, November 2017, pp. 312–318, Article ID: IJMET_08_11_034

Available online at http://www.iaeme.com/IJMET/issues.asp?JType=IJMET&VType=8&IType=11

ISSN Print: 0976-6340 and ISSN Online: 0976-6359

© IAEME Publication Scopus Indexed

CFD ANALYSIS AND COMPARISON USING

ANSYS AND STAR-CCM+ OF MODEL

AEROFOIL SELIG 1223

Narendiranath Babu T

Associate Professor, Department of Mechanical Engineering, VIT University, Vellore, India

Prateek Parmeshwar, Arth Beladiya and Akshay Bhabhra

Department of Mechanical Engineering, VIT University, Vellore, India

ABSTRACT

Airplane structures are highly aerodynamic in nature and the science behind them

generating such significant amounts of lift depends greatly on the aerofoil geometry,

that is the cross-section of their wings. Aerofoils are shaped and designed in such a

way that as they move through a fluid medium they generate certain aerodynamic

forces which helps create a positive pressure difference producing lift. This purpose of

this paper is to analyse airflow across a model aerofoil Selig 1223[4] and determine

airflow patterns along with velocity and pressure profiles. The analysis is performed

in ANSYS Workbench and STAR-CCM+ which are softwares used for a computational

fluid dynamics (CFD). These software give an accurate visual representation of

airflow solving for variables such as pressure values and velocity vectors. Parameters

such as coefficients of lift and drag and their variance with respect to angle of attack

are obtained using the software XFLR5 developed by MIT. Further, observing the

airflow also reveals some key characteristics that might suggest some scope for design

optimisation.

Keywords: CFD analysis, STAR-CCM+ of model aerofoil Selig 1223

Cite this Article: Narendiranath Babu T, Prateek Parmeshwar, Arth Beladiya and

Akshay Bhabhra, CFD analysis and comparison using ANSYS and STAR-CCM+ of

model aerofoil Selig 1223, International Journal of Mechanical Engineering and

Technology 8(11), 2017, pp. 312–318.

http://www.iaeme.com/IJMET/issues.asp?JType=IJMET&VType=8&IType=11

1. INTRODUCTION

A body is said to generate lift when the net forces acting on it have a positive resultant anti-

parallel to the force of gravity. A body is said to generate lift when the net forces acting on it

have a positive resultant anti-parallel to the force of gravity. Airplanes have become a

common sight today and although their whole design is aerodynamic it is the wing geometry

that helps generate such large amounts lift in such heavy structures. Wings have an aerofoil

Narendiranath Babu T, Prateek Parmeshwar, Arth Beladiya and Akshay Bhabhra


cross-section which generate certain aerodynamic forces when moving in a fluid medium. In

simple terms, the aerofoil cross-section creates low pressure regions at the top side and high

pressure regions below it. As such there is a net upward force created by this pressure

difference and when this force created by the pressure difference exceeds the weight, that is

the force of gravity, a resultant upward force comes into picture; a lift is generated [2]. This

pressure difference is a consequence of velocity difference. As the aerofoil moves through a

fluid, say air, the air velocity vectors flow past the wing in a direction opposite to that of the

movement of the wing. These velocity vectors start to form a vortex in a counter-clockwise

direction near the tail of the aerofoil. Now, since angular momentum is conserved, new

vortices need to be generated that move in a clockwise direction. These vortices form around

the cross-section boundary of the aerofoil. As a net effect, we have velocity vectors of airflow

and vortices being added at the top of the aerofoil and the vectors of airflow and vortices

being subtracted below the aerofoil. Thus, velocity is higher at top and lower at bottom. Now

comes the use of Bernoulli's equation which states that the sum of pressure energy, kinetic

energy and the potential energy

1.1. Remains same and thus, a decrease in kinetic energy will result in an increase

in pressure energy provided the potential energy remains constant.

Aerofoils have to be designed in such a way that while producing lift they also minimise

drag. Drag is the aerodynamic force that opposes motion of an object as it moves through a

fluid medium. This is the difference between rectangular aerofoils and tapered aerofoils.

Tapered aerofoils have reduced drag due to less surface area towards the ends of wings. The

accompanied reduction in lift due tapering is insignificant as the majority of the lift is

produced near the fuselage due to finite wing effect. Tapering also serves in reducing the

overall designing, engineering and manufacturing cost due to reduction in the materials

requirement and also reduces weight. These massive wing structures need to be tested for all

these aerodynamic forces such as lift, drag and other parameters such as pressure difference

and airflow velocity across the aerofoil. Testing such components is not only tedious but also

expensive as such large components require huge wind tunnels. As such there is a dire need of

effective simulations which not only predict airflow over aerofoils accurately but also are

relatively much cheap and save a lot of time.

2. CFD ANALYSIS

The Navier-Stokes equations govern the motion of fluids and can be seen as Newton's second

law of motion for fluids. In the case of a compressible Newtonian fluid, this yields[1]

The different terms correspond to the inertial forces, pressure forces, viscous forces, and

the external forces applied to the fluid. These equations are always solved together with the

continuity equation:

The Navier-Stokes equations represent the conservation of momentum, while the

continuity equation represents the conservation of mass. These equations are at the heart of

fluid flow modelling. Solving them, for a particular set of boundary conditions (such as inlets,

outlets, and walls), predicts the fluid velocity and its pressure in a given geometry. Because of

their complexity, these equations only admit a limited number of analytical solutions. As

CFD analysis and comparison using ANSYS and STAR-CCM+ of model aerofoil Selig 1223


these equations are difficult to solve using analytical methods, we employ numerical

techniques such as finite difference and finite volume methods that convert these complex

partial differential equations into simple algebraic equations that are easy to solve and hence

compute. But of course, we cannot solve these equations for the geometry as a whole as

different variables have different values at different points. This is where meshing comes into

picture. Meshing involves dividing the geometry into grids and small finite volume. The sizes

of these grids are such that the solutions to the Navier-Stokes equations can be reasonably

approximated in the volume. The differential equations are solved using numerical methods in

these small nodes and a general picture of the simulation is developed. Naturally, the finer the

mesh size and the smaller the volume of the grid, the more accurate solution gets. CFD

analysis is reaching an optimal mesh count as even though finer mesh will result in accurate

solutions they will cost significant computation time.

2.1. Methodology for modelling

Analysis of the aerofoil Selig 1223 first required its designing and construction [3]. Aerofoils

are smooth and curved structures and as such their construction in any CAD software requires

the use of coordinates which the software then extrapolates to form a wing cross-section. The

coordinates for the aerofoil taken from aerofoil database were imported into SolidWorks, a

CAD software, following which a curve through the points was plotted giving the aerofoil

cross-section. The cross-section was then extruded to give the resulting wing geometry. Now

airflow across this generated CAD had to be simulated and compared in ANSYS and STAR-

CCM+. The lift and drag values for the aerofoil were obtained using another software called

XFLR5.

Figure 1 Aerofoil Cross-section

The basic flow chart for the modelling consisted of the following

a) Flow chart (b) CAD

Figure 2 Modelling of CAD



2.2. Airflow Analysis

The CFD analysis in ANSYS and STAR-CCM+ was performed. The analysis using these

softwares simulated the presence of out aerofoil in a wind tunnel. As such a control volume

had to be setup that simulated wind flow towards the aerofoil accurately. The control volume

was setup and contained air-flow at the speed of 20m/s. The size of the control volume gave

an accurate simulation of the atmosphere and the size was so selected such that no need of

extra unnecessary meshing was required. The control volume setup was followed by meshing.

In STAR-CCM+ the meshing consisted of standard mesh in standard plane areas and the

boundary regions were meshed using finer mesh structures to get an accurate result of the

simulation. After setting up the meshing and subjecting the geometry to the various boundary

and physics conditions such as the properties of the air the given aerofoil was set for

simulation of air-flow.

(a) Domain (b) Boundary Condition

Figure 3 Control Volume STAR-CCM+

(a) Mesh (b) Closer look at mesh

Figure 4 STAR-CCM+

(a) Mesh (b) Closer look at mesh

Figure 5 STAR-CCM+



3. RESULTS AND CONCLUSION

Analysis with STAR-CCM+ with an inlet velocity of 20m/s revealed velocity flow vectors

across the aerofoil and pressure difference across and near the regions of aerofoils. As is

evident from the pressure values that a significant positive lift will be generated due to the

airflow across the aerofoil. It is key to note the airflow near the tail of the aerofoil. We

observe some amount of recirculation of airflow. Recirculation results in excess of air mass

and thus, consequently results in larger pressure values effectively reducing the lift. This

provides scope for the design optimisation of Selig 1223 in order to generate lesser amounts

of airflow recirculation as well as wake regions.

(a) Velocity plot (b) Closer look at plot

Figure 6 STAR-CCM+

(a) Pressure Plot (b) Closer look at plot

Figure 7 STAR-CCM+

(a) Airflow approaching (b) Airflow over aerofoil

Figure 8 STAR-CCM+



(a) Fully developed flow (b) Airflow separation

Figure 9 STAR-CCM+

Figure 10 ANSYS results

Figure 11 XFLR5 Results

Figure 12 XFLR5 Results



REFERENCES

[1] Abdulnaser Sayma Computational Fluid Dynamics.

[2] Karna S. Patel, Saumil B. Patel, Utsav B. Patel, Prof. Ankit P. Ahuja CFD Analysis of an

Aerofoil. UVPCE, Ganpat University

[3] Shreyas Krishnamurthy, Suraj Jayashankar, Sharath V Rao, RochenKrishna ,

Shankargoud Nyaman-navar CFD Analysis of an RC Aircraft Wing.

[4] Airfoil Database: http://m-selig.ae.illinois.edu/ads/coord_database.html

[5] National Aeronautics and Space Administration https://www.grc.nasa.gov/www/k-

12/airplane/liftco.html

[6] MD Khaleel, Marampalli Shilpa and L.Farooq Modeling and CFD Analysis on one Stage

of Turbine of Gas Turbine Engine. International Journal of Civil Engineering and

Technology, 8(5), 2017, pp. 638–645.

[7] Abdul Razzaque Ansari and Prashant Kumar Rana, CFD Analysis of Aerodynamic

Design of Maruti Alto Car. International Journal of Mechanical Engineering and

Technology, 8(3), 2017, pp. 388–399.

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