Flow over an airfoil

Aim/Objective: Flow over an air-foil simulation using solidworks.

Theory:

Airfoil is defined as the cross-section of a body that is placed in an airstream in order to generate useful aerodynamic force.

Computational Fluid Dynamics (CFD) has fascinated researchers, as it is a fast, accurate and reliable method of analyzing the variation of hydrodynamic properties of the flow over and within a body. Computational Fluid Dynamics (CFD) is a branch of fluid mechanics that uses numerical methods and algorithms to solve complex problems involving fluid flow.

Angle of attack is the angle between the oncoming air or relative wind and a reference line on the airplane or wing. Sometimes, the reference line is a line connecting the leading edge and trailing edge at some average point on the wing.

Effect of angle of attack:

• Increases as the angle of attack increase the lift force increase proportionately. And a certain point, called critical angle of attack, upper surface flow is more separated and the airfoil or wing is producing its maximum coefficient of lift.
• The study of airfoil behavior to varying angle of attacks is made in order to determine the best possible dimensions for practical conditions. In most airplanes, this is about 16 to 18 degrees. During a cruise, the requirement is to maintain the angle of attack where the total drag on the airplane is minimum so as to use the minimum thrust and therefore, minimum fuel consumption. This could occur at an angle of about 3 to 5 degrees.

3D Cad Model:

Boundary Conditions:

Procedure:

• An airfoil is created by using convert entities then line command.
• For the different angle of attacks rotate entities is used.
• The airfoil is extruded to 0.5 mm. Now save the file.
• The flow simulation is created using the wizard menu.
• The analysis type is selected as external. Time-dependent is selected.
• Total analysis time is selected as 5 sec and output time is 1sec.
• The fluid is selected as air and velocity parameter over X-direction is selected as 600m/s and then click finish.
• Now a computational domain is created by using the 2D option.
• The computational domain is expanded along both y-directions and x-direction in such a way that the length after the wake region should be 5 times the length ahead of wake region.
• The Global mesh is defined and the local mesh is defined by selecting the surface. It is refined up to a level of 3.
• The goals option is selected then force x and force y selected after selecting the surface.
• Run the simulation.
• Now a cut plot is made along x-direction and velocity over the airfoil is selected.
• Color refining is given 200.
• A goal plot is plotted between drag force along the x-direction and lift along the y-axis.
• The above procedure is followed for different attack angles and the following results are used to plot the necessary graphs.

5. Results:

Case 1: Angle of attack at 0°

Drag force and Lift force

Drag Force: 300.862N

Lift Force: 0.01548N

Case 2: Angle of attack 2°

Drag force and Lift force

Drag Force: 333.0128N

Lift Force: 835.6774N