16.00 Aerodynamics LectureProf. Annalisa L. Weigel10 February 200410 February 2004 216.00 Aerodynamics LectureLecture outlineq Motivationq Lift• Balloons – buoyancy and Archimedes• Airplanes – airfoils and Bernoulliq Drag• Profile drag• Induced dragq Effects of airfoil geometry on lift and drag10 February 2004 316.00 Aerodynamics LectureWhat is Aerodynamics?q “A branch of dynamics that deals with themotion of air and other gaseous fluids, andwith the forces acting on bodies in motionrelative to such fluids” – Webster’sDictionary10 February 2004 416.00 Aerodynamics LectureLet’s discuss…q What does “aerodynamic” mean to you?q In what other areas or products besidesairplanes does aerodynamics matter?10 February 2004 516.00 Aerodynamics LectureAerodynamics mattersSource: BoeingSource: Gold RacingSource: LexusSource: lancearmstrong.comSource: Japan-Guide.comSource:Land andWater Fundof theRockiesSource:Personalizedgolfballs.com10 February 2004 616.00 Aerodynamics LectureLift and Balloonsq Buoyancy is easiest way of generating liftq Archimedes principle• Difference in pressure on surface of a body =volume displaced• Weight of fluid displaced = buoyant forceq Net force• Fnet = rgVq Static equilibrium• mpayload = (r – rint)V10 February 2004 716.00 Aerodynamics LectureBallooning on Mars?q We want to design a balloon to carry a 2-kg payload on Mars. What gas should weuse in the balloon, and how big does theballoon have to be?q Helpful links:• http://www.members.axion.net/~enrique/density.html• http://www.flyers.org/simulators/atmospheric.htm10 February 2004 816.00 Aerodynamics LectureAirfoil terminologySource: Newman, Dava J., Interactive Aerospace Engineering and Design10 February 2004 916.00 Aerodynamics LectureAspect ratioq Aspect ratio = b2 / S, where b is span; S iswing area• For rectangular wing, AR = b/cq For a table of aspects ratios for differentvehicles, check outhttp://www.aerodyn.org/Wings/ar-tables.html10 February 2004 1016.00 Aerodynamics LectureComparing aspect ratiosSource: BoeingSource: HowStuffWorks.comSource: NASASource:http://www.geocities.com/CapeCanaveral/8629/f14.htmSource: Concordesst.com10 February 2004 1116.00 Aerodynamics LectureFoilSimq NASA software you will use in yourhomework assignmentq http://www.lerc.nasa.gov/WWW/K-12/airplane/foil2.html10 February 2004 1216.00 Aerodynamics LectureLift and drag on airplanesq Lift and drag are mechanical forcesgenerated on the surface of an object as itinteracts with a fluidSource: Newman, Dava J., Interactive Aerospace Engineering and Design10 February 2004 1316.00 Aerodynamics LectureWhat is lift?q Lift is the force that holds an aircraft in theair• L = (Pl – Pu)Sq Coefficient of lift: empirical nondimensionalparameter for easier evaluation of lift• CL = L / (1/2 rn2S)• q = dynamic pressure = 1/2 rn2• Substituting in q, L = qSCL10 February 2004 1416.00 Aerodynamics LectureBernoulli and pitot tubesq Simple form of Bernoulli’s equation• P + 1/2 rn2 = P0q Basis of pitot tube, which measuresairplane velocity ___________• v = √2((P0 – P)/r)Source: Newman, Dava J., Interactive Aerospace Engineering and Design10 February 2004 1516.00 Aerodynamics LectureWhat do pitot tubes look like?10 February 2004 1616.00 Aerodynamics LectureWhat is drag?q Aerodynamic force that opposes anaircraft’s motion through the air, caused byinteraction and contact of a solid body witha fluidq Aerodynamic frictionq Aerodynamic resistance to motionq Depends on wing shape, angle of attack,effects of air viscosity and compressibility10 February 2004 1716.00 Aerodynamics LectureProfile dragq Related to viscous effects of flow overlifting surfaceq Also called “form drag” due to separationof boundary layer around the object’s formSource: Newman, Dava J., Interactive Aerospace Engineering and Design10 February 2004 1816.00 Aerodynamics LectureProfile drag (cont.)q Dimples =greater skinfriction drag= greaterdistance toseparationof flow =lower profiledragSource: Newman, Dava J., Interactive Aerospace Engineering and Design10 February 2004 1916.00 Aerodynamics LectureInduced dragq Arises from 3-dimensional effects of awing caused by downwash velocity nearwing tipq Vortices create a downward velocitycomponent at the wingq Non-dimensional coefficient of induceddrag:• CDI = CL2 / !eAR10 February 2004 2016.00 Aerodynamics LectureInduced dragSource: Newman, Dava J., Interactive Aerospace Engineering and Design10 February 2004 2116.00 Aerodynamics LectureTotal dragq Total drag = profile drag + induced dragq Coefficient of total drag• CDTOTAL = CD0 + CL2 / !eAR10 February 2004 2216.00 Aerodynamics LectureClass exerciseq You and your partner are Senior AerodynamicsConsultants at BlueSky Enterprises. Yourclients have challenged you to apply yourextensive aerodynamics expertise to design aninnovation for an existing product or service ofyour choosing.q They want your answer in 10 minutes.q Prepare a 1-minute pitch on your productinnovation to present to the clients.q Caveat: You can’t pick any of the aerodynamicsapplication areas we discussed earlier! Becreative.10 February 2004 2316.00 Aerodynamics LectureEffects of camberLift CurveDrag Polar CurveSource: Newman, Dava J., Interactive Aerospace Engineering and Design10 February 2004 2416.00 Aerodynamics LectureEffect of skin friction dragLift CurveDrag CurveSource: Newman, Dava J., Interactive Aerospace Engineering and