Understanding aerodynamics arguing from the real physics
(eBook)

Machine generated contents note: List of symbols Preface 1. Introduction to the conceptual landscape 2. From elementary particles to aerodynamic flows 3. Continuum fluid mechanics and the Navier-Stokes equations 3.1 The continuum formulation and its range of validity 3.2 Mathematical formalism 3.3 Kinematics: streamlines, streaklines, timelines, and vorticity 3.3.1 ... Streamlines and streaklines 3.3.2 ... Streamtubes, stream surfaces, and the stream function 3.3.3 ... Timelines 3.3.4 ... The divergence of the velocity, and Green's theorem 3.3.5 ... Vorticity and circulation 3.3.6 ... The velocity potential in irrotational flow 3.3.7 ... Concepts that arise in describing the vorticity field 3.3.8 ... Velocity fields associated with concentrations of vorticity 3.3.9 ... The Biot-Savart law and the "induction" fallacy 3.4 The equations of motion and their physical meaning 3.4.1 ... Continuity of the flow and conservation of mass 3.4.2 ... Conservation of momentum 3.4.3 ... Conservation of energy 3.4.4 ... Constitutive relations and boundary conditions 3.4.5 ... Mathematical nature of the equations 3.4.6 ... The physics as viewed in the Eulerian frame 3.4.7 ... The pseudo-Lagrangian viewpoint 3.5 Cause and effect, and the problem of prediction 3.6 The effects of viscosity 3.7 Turbulence, Reynolds averaging, and turbulence modeling 3.8 Important dynamical relationships 3.8.1 ... Galilean invariance, or independence of reference frame 3.8.2 ... Circulation preservation and the persistence of irrotationality 3.8.3 ... Behavior of vortex tubes in inviscid and viscous flows 3.8.4 ... Bernoulli equations and stagnation conditions 3.8.5 ... Crocco's theorem 3.9 Dynamic similarity 3.9.1 ... Compressibility effects and the Mach number 3.9.2 ... Viscous effects and the Reynolds number 3.9.3 ... Scaling of pressure forces: the dynamic pressure 3.9.4 ... Consequences of failing to match all of the requirements for similarity 3.10 "Incompressible" flow and potential flow 3.11 Compressible flow and shocks 3.11.1. Steady 1D isentropic flow theory 3.11.2. Relations for normal and oblique shock waves 4. Boundary layers 4.1 Physical aspects of boundary-layer flows 4.1.1 ... The basic sequence: attachment, transition, separation 4.1.2 ... General development of the boundary-layer flowfield 4.1.3 ... Boundary-layer displacement effect 4.1.4 ... Separation from a smooth wall 4.2 Boundary-layer theory 4.2.1 ... The boundary-layer equations 4.2.2 ... Integrated momentum balance in a boundary layer 4.2.3 ... The displacement effect and matching with the outer flow 4.2.4 ... The vorticity "budget" in a 2D incompressible boundary layer 4.2.5 ... Situations that violate the assumptions of boundary-layer theory 4.2.6 ... Summary of lessons from boundary-layer theory 4.3 Flat-plate boundary layers and other simplified cases 4.3.1 ... Flat-plate flow 4.3.2 ... 2D boundary-layer flows with similarity 4.3.3 ... Axisymmetric flow 4.3.4 ... Plane-of-symmetry and attachment-line boundary layers 4.3.5 ... Simplifying the effects of sweep and taper in 3D 4.4 Transition and turbulence 4.4.1 ... Boundary-layer transition 4.4.2 ... Turbulent boundary layers 4.5 Control and prevention of flow separation 4.5.1 ... Body shaping and pressure distribution 4.5.2 ... Vortex generators 4.5.3 ... Steady tangential blowing through a slot 4.5.4 ... Active unsteady blowing 4.5.5 ... Suction 4.6 Heat transfer and compressibility 4.6.1 ... Heat transfer, compressibility, and the boundary-layer temperature field 4.6.2 ... The thermal energy equation and the Prandtl number 4.6.3 ... The wall temperature and other relations for an adiabatic wall 4.7 Effects of surface roughness 5. General features of flows around bodies 5.1 The obstacle effect 5.2 Basic topology of flow attachment and separation 5.2.1 ... Attachment and separation in 2D 5.2.2 ... Attachment and separation in 3D 5.2.3 ... Streamline topology on surfaces and in cross sections 5.3 Wakes 5.4 Integrated forces: lift and drag 6. Drag and propulsion 6.1 Basic physics and flowfield manifestations of drag and thrust 6.1.1 ... Basic physical effects of viscosity 6.1.2 ... The role of turbulence 6.1.3 ... Direct and indirect contributions to the drag force on the body 6.1.4 ... Determining drag from the flowfield: application of conservation laws 6.1.5 ... Examples of flowfield manifestations of drag in simple 2D flows 6.1.6 ... Pressure drag of streamlined and bluff bodies 6.1.7 ... Questionable drag categories: parasite drag, base drag, and slot drag 6.1.8 ... Effects of distributed surface roughness on turbulent skin friction 6.1.9 ... Interference drag 6.1.10. Some basic physics of propulsion 6.2 Drag estimation 6.2.1 ... Empirical correlations 6.2.2 ... Effects of surface roughness on turbulent skin friction 6.2.3 ... CFD prediction of drag 6.3 Drag reduction 6.3.1 ... Reducing drag by maintaining a run of laminar flow 6.3.2 ... Reduction of turbulent skin friction 7. Lift and airfoils in 2D at subsonic speeds 7.1 Mathematical prediction of lift in 2D 7.2 Lift in terms of circulation and bound vorticity 7.2.1 ... The classical argument for the origin of the bound vorticity 7.3 Physical explanations of lift in 2D 7.3.1 ... Past explanations and their strengths and weaknesses 7.3.2 ... Desired attributes of a more satisfactory explanation 7.3.3 ... A basic explanation of lift on an airfoil, accessible to a nontechnical audience 7.3.4 ... More physical details on lift in 2D, for the technically inclined 7.4 Airfoils 7.4.1 ... Pressure distributions and integrated forces at low Mach numbers 7.4.2 ... Profile drag and the drag polar 7.4.3 ... Maximum lift and boundary-layer separation on single-element airfoils 7.4.4 ... Multielement airfoils and the slot effect 7.4.5 ... Cascades 7.4.6 ... Low-drag airfoils with laminar flow 7.4.7 ... Low-Reynolds-number airfoils 7.4.8 ... Airfoils in transonic flow 7.4.9 ... Airfoils in ground effect 7.4.10. Airfoil design 7.4.11. Issues that arise in defining airfoil shapes 8. Lift and wings in 3D at subsonic speeds 8.1 The flowfield around a 3D wing 8.1.1 ... General characteristics of the velocity field 8.1.2 ... The vortex wake 8.1.3 ... The pressure field around a 3D wing 8.1.4 ... Explanations for the flowfield 8.1.5 ... Vortex shedding from edges other than the trailing edge 8.2 Distribution of lift on a 3D wing 8.2.1 ... Basic and additional spanloads 8.2.2 ... Linearized lifting-surface theory 8.2.3 ... Lifting-line theory 8.2.4 ... 3D lift in ground effect 8.2.5 ... Maximum lift, as limited by 3D effects 8.3 Induced drag 8.3.1 ... Basic scaling of induced drag 8.3.2 ... Induced drag from a farfield momentum balance 8.3.3 ... Induced drag in terms of kinetic energy and an idealized rolled-up vortex wake 8.3.4 ... Induced drag from the loading on the wing itself: Trefftz-plane theory 8.3.5 ... Ideal (minimum) induced-drag theory 8.3.6 ... Span-efficiency factors 8.3.7 ... The induced-drag polar 8.3.8 ... The sin-series spanloads 8.3.9 ... The Reduction of Induced Drag in Ground Effect 8.3.10. The effect of a fuselage on induced drag 8.3.11. Effects of a canard or aft tail on induced drag 8.3.12. Biplane drag 8.4 Wingtip devices 8.4.1 ... Myths regarding the vortex wake, and some questionable ideas for wingtip devices 8.4.2 ... The facts of life regarding induced drag and induced-drag reduction 8.4.3 ... Milestones in the development of theory and practice 8.4.4 ... Wingtip device concepts 8.4.5 ... Effectiveness of various device configurations 8.5 Manifestations of lift in the atmosphere at large 8.5.1 ... The net vertical momentum imparted to the atmosphere 8.5.2 ... The pressure far above and below the airplane 8.5.3 ... Downwash in the Trefftz plane and other momentum-conservation issues 8.5.4 ... Sears's incorrect analysis of the integrated pressure far downstream 8.5.5 ... The real flowfield far downstream of the airplane 8.6 Effects of wing sweep 8.6.1 ... Simple sweep theory 8.6.2 ...

Boundary layers on swept wings 8.6.3 ... Shock/boundary-layer interaction on swept wings 8.6.4 ... Laminar-to-turbulent transition on swept wings 8.6.5 ... Relating a swept, tapered wing to a 2D airfoil 8.6.6 ... Tailoring of the inboard part of a swept wing 9 Theoretical idealizations revisited 9.1 Approximations grouped according to how the equations were modified 9.1.1 ... Reduced temporal and/or spatial resolution 9.1.2 ... Simplified theories based on neglecting something small 9.1.3 ... Reductions in dimensions 9.1.4 ... Simplified theories based on ad hoc flow models 9.1.5 ... Qualitative anomalies and other consequences of approximations 9.2 Some tools of MFD (Mental Fluid Dynamics) 9.2.1 ... Simple conceptual models for thinking about velocity fields 9.2.2 ... Thinking about viscous and shock drag 9.2.3 ... Thinking about induced drag 9.2.4 ... A catalog of fallacies 10. Modeling aerodynamic flows in CFD 10.1 Basic definitions 10.2 The major classes of CFD codes and their applications 10.2.1. Navier-Stokes (NS) methods 10.2.2. Coupled viscous/inviscid methods 10.2.3. Inviscid methods 10.2.4. Standalone boundary-layer codes 10.3 Basic characteristics of numerical solution schemes 10.3.1. Discretization 10.3.2. Spatial field grids 10.3.3. Grid resolution and grid convergence 10.3.4. Solving the equations, and iterative convergence 10.4 Physical modeling in CFD 10.4.1. Compressibility and shocks 10.4.2. Viscous effects and turbulence 10.4.3. Separated shear layers and vortex wakes 10.4.4. The farfield 10.4.5. Predicting drag 10.4.6. Propulsion effects 10.5 CFD validation? 10.6 Integrated forces and the components of drag 10.7 Solution visualization 10.8 Things a user should know about any CFD code before running it References.