For This Problem, the Default Geometry from Flowlab Was Used

FLOWLAB SOLUTION

9.111 Use the clarky template from FlowLab to investigate the effects of angle of attack, a, on the lift and drag coefficients, CL and CD. Alter the angle of attack from α = –5° to 10°, in increments of 5°. Assume that this airfoil section is part of the wing of an aircraft that is flying through incompressible, viscous air at U = 200 mph and an altitude of h = 15,000 ft in a standard atmosphere. Generate plots of CL and CD as functions of α similar to Figure 9.33 and explain the trends seen in both the lift and drag coefficients as a is increased.

Problem Setup

For this problem, the default geometry from FlowLab was used:

The flow was set to Viscous and the Boundary Condition settings were altered to achieve the stated flight conditions.

It is expected that the student will calculate the correct values for ambient pressure and temperature and the Mach number given the conditions in the problem statement. The 0º angle of attack settings are shown below.

For all simulations, the medium mesh resolution was used for the grid setup. A sample of this grid is shown in the following figure.

A close-up of the grid around the airfoil is shown in the following figure.

Answer

For the simulations, the default convergence limit was set to 1x10-4. A plot of the residual history for the 0º angle of attack case is shown below.

The focus of the problem is to investigate the effects of changes in angle of attack on the lift and drag coefficients. The student is required to run simulations at four different angles of attack and record the lift and drag coefficients. These results are presented below.

-5º angle of attack

0º angle of attack

5º angle of attack

10º angle of attack

The student is also asked to generate plots of CL and CD as a function of a and to discuss the trends. These plots are given in the following two figures.

The plots show the expected trends in the lift and drag coefficients with respect to the angle of attack. The students should discuss the primary features of the graph as it relates to Chapter 9 material of the text.

Additional Material

The following plots show the velocity contours for a = 5º and 10º, respectively. These results are not required in the problem statement, but included as additional material for this problem.