FLOW SIMULATION OVER AN AIRFOIL IN SOLIDWORKS
AIM: To Simulate Flow over a NACA0017 AIRFOIL using SolidWorks
INTRODUCTION:
An airfoil is the cross-sectional shape of a wing, blade (of a propeller, rotor, or turbine), or sail (as seen in cross-section).
An airfoil-shaped body moving through a fluid produces an aerodynamic force. The component of this force perpendicular to the direction of motion is called lift. The component parallel to the direction of motion is called drag.
The lift on an airfoil is primarily the result of its angle of attack. When oriented at a suitable angle, the airfoil deflects the oncoming air (for fixed-wing aircraft, a downward force), resulting in a force on the airfoil in the direction opposite to the deflection. This force is known as aerodynamic force.
Subsonic flight airfoils have a characteristic shape with a rounded leading edge, followed by a sharp trailing edge, often with a symmetric curvature of upper and lower surfaces. Foils of similar function designed with water as the working fluid are called hydrofoils.
GOVERNING EQUATIONS:
LIFT FORCE –
`L=C_l × (ρ ×V^2)/2 ×A`
DRAG FORCE –
`D= C_d ×(ρ ×V^2)/2 ×A`
where,
`C_l`= Coefficient of Lift
`C_d`= Coefficient of Drag
`ρ`= Density of Fluid (air)
`V`= Velocity of Fluid (air)
`A`= Cross-sectional Area / frontal Area
OBJECTIVE:
- To simulate flow over an Airfoil with varying angle of attacks (0,2,4,6,8,10 degrees)
- To plot graphs of velocity contour, drag force and lift force for each angle of attacks.
PROCEDURE:
- Initially, the Airfoil Sample Data file is used to draw the airfoil spline followed by the line to close the geometry. It is then extruded to a certain extent for desired results. The geometry can be rotated for Varying Angle of attacks.
- Flow Simulation is set up and a Transient Simulation solver is used with a specified velocity of 600 m/s along x-axis. A 2D Computational Domain is assigned with adequate width and height.
- Surface goals comprising of forces in x-direction (Drag Force) and y- direction (Lift Force) are mentioned and a Mesh is defined with a separate local mesh for fluid cells in the periphery of the surface boundaries.
- The simulation is executed and is carried out until the solution converges. A Velocity Cut Plot is proposed and Goal Plots for Drag and Lift Forces.
RESULTS:
Angle of attack = 0 deg
VELOCITY CONTOUR
DRAG FORCE
The drag force reduces drastically after the fluid makes an initial contact with leading edge of the airfoil and then becomes constant.
LIFT FORCE
The lift force is subsequently higher during the emergence of flow and shows sharp ascent and descent over the entire flow simulation.
Angle of attack = 2 deg
VELOCITY CONTOUR
DRAG FORCE
It follows a similar trend to the 0 degrees angle of attack case.
LIFT FORCE
The Lift Force offers an exponential trend. An extremely high value is obtained in the starting but constants out over the passage of time.
Angle of attack = 4 deg
VELOCITY CONTOUR
DRAG FORCE
It also follows a similar trend to that of 0 degrees angle of attack case.
LIFT FORCE
The Lift Force follows a similar trend to that of 2 degrees angle of attack case.
Angle of attack = 6 deg
VELOCITY CONTOUR
DRAG FORCE
A sudden bend is observed at the neck of the plot depicting the approach of angle of stall.
LIFT FORCE
The plot smoothens out after the exponential depicting the smooth flow over and below the airfoil.
Angle of attack = 8 deg
VELOCITY CONTOUR
DRAG FORCE
The bend near neck extends and shows greater chances of stall situation.
LIFT FORCE
The plot follows similar trend to that of 6 degrees angle os attack case.
Angle of attack = 10 deg
VELOCITY CONTOUR
DRAG FORCE
A sudden distortion is observed initially indicating the increase in the frontal area, i.e., the area that comes in contact with the fluid (air). The probability of stall increases.
LIFT FORCE
The plot signifies smoother transition of flow over the airfoil but a sudden dip near the neck region may counter the required motion of flow.
CONCLUSION: The flow over an airfoil gives a clear perspective of the lift force that gradually outshines the drag force in order to make the airplanes and other objects fly. The balance between the two forces yields the required motion and height that we desire.