Purdue University College of Engineering



AAE 333 Final ProjectFall 2009Due Mon Dec 14No bonus available; no late homework allowedFormatThis project is to be done in teams of two. Send an email to me and the TA’s as soon as you have a team. If you are unable to find a partner by Monday Dec 07, let us know by that date.Turn in one project report for each team. One grade will be assigned to the project. If you feel that your partner is not contributing equally, send me an email. The project is worth two homework assignments and is not optional (in other words, you cannot pass the course with no final project)All materials for the Final Project are stored in the current semester web page in the HOMEWORKS/FINAL_PROJECT directory.Airfoil and Analysis ToolsYou will perform an analysis of the NACA 2415 airfoil, which is slightly fatter than the 2414 airfoil you looked at in HW9 and is chosen because there is experimental data for it available in Abbott & von Doenhoff (A copy is posted in the Project directory)You will use an inviscid/viscous airfoil analysis program called XFOIL written by Professor Mark Drela from MIT. Download the XFOIL tutorial from the FinalProject directory.You may also want to download the more extensive documentation xfoil.doc . A download of the windows executable is also stored in the FinalProject directory. If you want another OS version, go to the XFOIL web site (it is the first hit in a google search on XFOIL.) Getting StartedWork through the tutorial.Create the paneling for the NACA 2415 geometry and plot the airfoilwith the panels. Run XFOIL in inviscid mode at an angle of attack α =4, using the default number of panels. Plot the pressure coefficient, cp(x).Compare to the results from the source/vortex code used in HW9, with a like number of panels. What is the lift coefficient, and how does this value compare to the one found using the earlier matlab code. How does it compare to the experimental data presented in A&vD?Viscous EffectsThe essential task is to “validate” (or “invalidate”, whichever the case may be) the XFOIL code using the experimental lift/drag/moment data presented in A&vD. A secondary task is to understand (and be able to explain) the behavior of the pressure, skin friction and boundary layer thickness distributions produced by XFOIL. Set the Reynolds number to 3 million and the angle of attack to 4 deg. Plot the pressure coefficient for this case, as well as the inviscid solution. Describe how they are different and why. Where does the boundary layer transition from laminar to turbulent flow on the upper and lower surfaces? Mark these transition points on the pressure distribution. Plot the skin friction coefficient. Mark the transition points there too. Does the boundary layer separate and, if so, where? XFOIL shows the airfoil with the boundary layer displacement thickness added to the airfoil geometry and wake. Describe how the boundary layer thickness behaves for the upper and lower surfaces (especially near transition). Repeat 1) at 9 deg aoa. How do the minimum values of pressure compare between the inviscid and viscous analysis?Use the pacc and aseq commands to run XFOIL for a sequence of angles of attack spanning the range reported in the A&vD plots, and for each of the three Reynolds numbers reported there as well as the inviscid case (ignore the “Standard Roughness” data. ) Print the tabulated data for lift, drag and pitching moment. (Note: when you plot a drag polar three plots are created, a drag polar, a lift curve, and a plot of the transition locations. You can either use XFOIL to make the needed plots or you can use Matlab to make the plots from the saved data.) Compare the lift curve and drag polar to the plots of the experimental data from A&vD. Is XFOIL accurate near stall, as the author claims? Describe how the transition locations on the upper and lower surfaces move as the angle of attack is changed.Plot the lift to drag ratio, L/D, as a function of angle of attack for a Re of 3e6 . What is the maximum lift to drag ratio and at what angle of attack does this occur? Mark this point on the drag polar and draw a straight line through (0,0) and this point. Is this line tangent to the drag polar? By plotting the skin friction, you can determine where the boundary layers separates. At what angle of attack does boundary layer separation start to move forward from the trailing edge? When the aoa is 24deg, where does the boundary layer separate?When XFOIL saves the drag data it prints out two drag coefficients: The total drag, and the one including pressure forces only. As the angle of attack changes how does the portion of the drag due to pressure change? At small angles of attack is most of the drag due to pressure or skin friction? What about at large angles of attack?Wrap UpYour final project report should be written using a computer word processing or typesetting program.Your report should start with a brief abstract which describes what you have done, how you did it, and what the main results or conclusions are. Include an introduction that explains what the project is about and what your goals are. Then explain the procedure you use. Next present the results. Discuss any figures or tabulated data you include. (You should not include any figures or tables that are not discussed in the text of your report.) When discussing the figures try to describe the results and discuss any physically meaningful information you can gain from the figures. If trends are shown, discuss those. Finish your report with a brief conclusions section that describes what the project is about, the procedure you used, and the main results or conclusions you reached. ................
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