Flow over an airfoil

AIM :- To model the flow over a NACA0017 airfoil

ABSTRACT :- In this project we will model an airfoil (from NACA database) in solidworks & then apply flow simulation(2D) for different angle of attacks starting from 0^◦ to 10^◦ with intervals of 2^◦ & study its effect on drag and lift forces.

INTRODUCTION :-

1. Airfoil :- An airfoil is a body of such a shape that when it is placed in an airstream, it produces an aerodynamic force. This can be seen in the cross-section of wings, propeller blades, windmill blades, compressor, and turbine blades in a jet engine.

Fig.1 – Typical airfoil cross-section shape

Terms –

1. Leading edge – It is a part of an airfoil (edge) that hits the air particles first.
2. Trailing edge – It is a part from an aerofoil (edge) that hits the air particles last.
3. Chord Line – It is a straight line joining the leading and trailing edges of an airfoil.
4. Chord – It is a distance between the leading and trailing edges measured along the chord line.
5. Camber – It is a line joining the leading and trailing edges of an aerofoil, equidistant from the upper and lower surfaces.
6. Angle of Attack(α) - It is the angle at which relative wind meets an airfoil. It is the angle formed by the Chord line of the airfoil and the direction of the relative wind. As the angle of attack increases (below the critical limit), relative wind got forced to pass with high velocity from upper surface & with comparatively low velocity from lower surface of airfoil. This develops low pressure on the upper surface & high press. on the lower surface. This imbalance of pressure results in lift force perpendicular(upward) to the direction of wind flow.
7. Drag force - A drag force is the resistance force caused by the motion of a body through a fluid, such as water or air.

2. NACA :- The NACA airfoils are airfoil shapes for aircraft wings developed by the National Advisory Committee for Aeronautics (NACA). The shape of the NACA airfoils is described using a series of digits following the word "NACA”.

NACA0017 details - Chord = 100mm, radius = 0mm, pitch =0^◦

3. CFD :- Computational Fluid Dynamics (CFD) is the science of predicting fluid flow, heat and mass transfer, chemical reactions, and related phenomena using numerical methods. It produces a fairly accurate result with ease and convenience.

PROCEDURE :-

A.) Model setup-

• Import NACA0017 data file on our system. file link -NACA0017
• Make the data in the required format(Sample). Now insert this data in solidworks to create airfoil geometry.

Fig.2 – airfoil geometry

• Select the plane for sketch and then Close this profile (in trailing edge) by using ‘line’ command to make a close contour.
• we convert this geometry into an entity by ‘convert entities’ command.
• Adjust the Angle of attack (0,2,4,6,8,10), according to simulation case by using ‘rotate entities ‘ command under move entities section.
• Now, we will extrude this entity (0.18m) to make an airfoil.

Fig.3 – airfoil model

Now , we head towards flow simulation for analysis, starting with angle of attack of 0^◦.

B.) Flow simulation:-

• Firstly, we create a new project using wizard command, having MKS unit sys. & external flow time dependent simulation with flow type of laminar & turbulent (by default), working fluid as air(rho = 1.225 kg/m³) along with initial condition shown below.

Fig.4 – simulation initial conditions

• From edit definition of computational domain make the simulation 2-D and adjust the computational domain such that the inflow region is 5 times of chord length and outflow region is 20 times of chord length (in flow direction) & proportionally in perpendicular direction to get proper visualisation of the simulation.
• Now, generate a local mesh (with cell refinement of 3), along with global mesh to have proper simulation at fluid-airfoil surface.
• Select goal plots for surface plots , then select force x & force y.
• All set, Run the simulation.
• Look for either drag force or lift force, along with simulation.
• Stop the simulation when the force converges to a value(force curve becomes flat).
• To visualize the simulation make a cut plot along xy plane (plane of airfoil), include contour of velocity.
• For better view, give color refinement of 200.
• Goal Plots will be plotted for drag force & lift force.
• Repeat the same process for different angles of attack.

RESULT :-

Here, Drag_force = integrated force along x-axis = SG Force (X)1

Lift_force = integrated force along Y-axis = SG Force(Y)2

CASE 1 – Angle of attack (α) = 0^◦

a.) Solver result details -

b.) Velocity_contour

c.) Goal_plot results –

d.) Forces –

i.) Drag_Force variation -

ii.) Lift_Force variation -

Here, drag force increases very rapidly & lift force is almost zero & even neg. sometimes.

CASE 2 – Angle of attack (α) = 2^◦

a.) Solver result details –

b.) Velocity_contour -

c.) Goal_plot results –

d.) Forces –

i.)Drag_Force variation –

ii.) Lift Force variation –

As compare to case 1, this time also drag force increases, but considerable increase in lift force is also noticed.

CASE 3 – Angle of attack (α) = 4^◦

a.) Solver result details –

b.) Velocity_contour -

c.) Goal_plot results –

d.) Forces –

i.) Drag_Force variation –

ii.) Lift Force variation –

As AoA is further increased, increment in lift force is more than drag force.

CASE 4 – Angle of attack (α) = 6^◦

a.) Solver result details –

b.) Velocity_contour –

c.) Goal_plot results –

d.) Forces –

i.) Drag_Force variation –

ii.) Lift Force variation –

On further increment of AoA, Lift force dominates drag force with little difference.

CASE 5 – Angle of attack (α) = 8^◦

a.) Solver result details –

b.) Velocity_contour –

c.) Goal_plot results –

d.) Forces –

i.)Drag_Force variation –

ii.) Lift Force variation –

With increase in AoA , lift force increases more rapidly than drag force.

CASE 6 – Angle of attack (α) = 10^◦

a.) Solver result details –

b.) Velocity_contour –

c.) Goal_plot results –

d.) Forces –

i.) Drag_Force variation –

ii.) Lift Force variation –

A sharp increment is noted in lift force & dominates the drag force with large difference.

OBSERVATION :-

Angle of Attack (α)	Avg.Drag Force [F(x)1]	Avg.Lift Force [F(y)2]
(degree)	(N)	(N)
0	1249.84	-2.923
2	1314.841	593.38
4	1357.891	1207.895
6	1444.123	1846.358
8	1577.261	2420.94
10	2866.67	5429.674

NOTE – Here, 1 - 6 nos. on horizontal axis shows the case no.

CONCLUSION :-

1. A successful flow analysis simulation has been carried out over a NACA0017 airfoil for different angles of attack & its effect on various forces acting on airfoil, with the help of Solidworks Flow simulation.
2. When compared for different angles of attack, slope of drag force is very low while slope of lift force is high which means lift force increases more rapidly than drag force.
3. From Velocity contour, it can be clearly seen that with increase in AoA the velocity over the airfoil increases.