The design task facing us is to shape the wing to realize aerodynamic characteristics well suited to the mission. Doing this requires a prediction method of either L1, L2, or L3 genus that maps the given geometry to its pressure field and ultimately to its performance. An early multidisciplinary design and optimization activity is the cycle 1 parametric design of the clean wing, A parametric design study evaluates the aircraft baseline configuration and it has the ability to arbitrarily vary those parameters that influence its shape and hence its performance. It determines the sensitivity of the vehicle effectiveness against some of the established requirements. The parametric effects of, for example, varying the wing planform are assessed, leading toward optimization of the layout by some measure of effectiveness. L0 and L1 tools are enhanced with surrogate models to speed up the aerodynamic evaluations. The vortex lattice method is presented as a mainstay tool in the clean-wing design process and is illustrated using a number of examples. The discussion of the design task continues for high-speed flight missions, indicating where the fidelity must be increased to L2 and L3 tools.

Having constructed the initial wing shape as a stack of airfoils, the 2D flow around an airfoil can tell us much about the 3D flow around a finite wing. In particular, exploring first in 2D the mapping from shape to flow to performance and its inverse tells us much about the roles that thickness and camber play in attaining sought-after performance. A rapid, special-purpose tool for airfoil analysis greatly aids the aerodynamic designer if results can be run in seconds on a laptop computer. This chapter describes one such tool, MSES, a surrogate model to the Reynolds-averaged Navier–Stokes (RANS) methodology, which very rapidly solves the steady Euler equations coupled to the integral boundary-layer equations. As a rule, a RANS code is too slow for routine design work and has not yet shown any accuracy advantages over the much faster zonal approaches. However, it is more robust with respect to Mach number and flow separation and can compute the entire shock stall phenomenon, as we saw in the steady-flow example in Chapter 6. Examples are given showing MSES applied to airfoil designs in both direct and inverse modes. MSES together with RANS completes the computational fluid dynamics tool kit needed for the applications in the remaining chapters.

Applying the computational fluid dynamics tool kit to the analysis and design of airfoil aerodynamics, this chapter explores the details of the shape-to-performance mapping under a variety of flight conditions, from low subsonic to transonic and supersonic speeds. The mappings change with the intended design goal, be it more laminar flow, higher maximum lift coefficient, or increased drag divergence speed. Through computations one sees correlations between these performance measures and shape factors such as thickness and camber distributions. One also sees clear historical progress in design methods. The earliest NACA airfoils during the 1920s were designed mainly in a cut-and-try approach. Aided by a theoretical method for predicting airfoil aerodynamics, the designs in the 1930s–1950s improved performance significantly. During the 1970s, NASA then resumed work combining a computational inverse procedure with supportive wind-tunnel measurements that produced the new technology family of NASA airfoils. This chapter investigates and compares some of them. It continues with a high-lift example analyzing the three-element slat-airfoil-flap test case L1T2 and comparing the predicted increases in lift with that measured in experiments for these high-lift devices. The final example – airfoil design by mathematical single-point optimization – reshapes the RAE2822 airfoil to minimize the wave drag at cruise conditions.

The prime focus of aerodynamic design is the shaping and layout of the aircraft's lifting surfaces. Introducing the subject matter of the book, this chapter also conveys some appreciation for, and fundamental insight into, how and why wings evolve into the configurations we see flying. Typical of the development process is that the new aircraft evolves in a succession of design cycles. This chapter describes three early design cycles. As Theodore von Karman implies, creativity lies at the heart of any engineering activity. Belonging to the cognitive aspects of the human brain, creativity is not in the realm of technology, but we indicate how and where it enters into the design process and encourage students to "think outside the box." The fundamental aerodynamic quantities of lift and drag are key to performance. Sizing the wing surface to the design mission is a crucial step in determining the baseline configuration, which then develops further in cycles 2 and 3. The chapter introduces the tools, tasks, and workflows of the three design cycles, explains how computational fluid dynamics and optimization procedures are involved, and maps out where in the coming chapters each of these is treated in depth.

Acoustic design of ductworks such as fluid machinery intake and exhaust systems usually requires a large number of iterations for concept validation and prototype development. The network approach is ideally suited for this purpose, but systematic search and optimization methods are indispensable for quick and efficient progress. The last chapter, Chapter 13, discusses the acceleration of iterative design calculations and handling uncertainties about model parameters. We also present an approach which brings an inverse perspective to the conventional target based acoustic design calculations.

Chapter 10 describes analytical actuator-disk models for the basic acoustic source mechanisms, namely, non-steady mass and heat injection and force application, applications of which are demonstrated on internal combustion engines, turbomachinery and combustion chambers.

Chambers and resonators are used as noise control devices in almost all industrial duct systems. In Chapter 5, transmission loss is defined and, using the acoustic models and the assembly techniques described in previous chapters, transmission loss characteristics of various chamber and resonator types are demonstrated. Also discussed are the calculation of the shell noise and mean pressure loss (or back pressure), which may impose trade-offs on effective use of these devices in duct-borne noise control.

Chapter 6 introduces the three-dimensional analytic theory of sound propagation in ducts and presents acoustic models of hard-walled and lined uniform ducts. Also discussed are the effects of gradual cross-section non-uniformity, circular curvature of the duct axis, and sheared and vortical mean flows.

Chapter 12 describes the contemporary measurement methods in duct acoustics. Acoustic measurements are necessary in order to validate theoretical models and also to develop acoustic models when theoretical approaches tend to be inadequate or impossible. The multiple wall-mounted microphone method is introduced from first principles and its applications to the measurement of the characteristics of acoustic sources and of passive system elements are described.

This chapter describes a block diagram based network approach for construction of acoustic models of duct systems from the simpler components in one dimension and three dimensions. This topic is considered early in the book, because it describes the format used in later chapters in mathematical representation of acoustic models of ductwork components and their assemblies.

This chapter introduces the general analytic theory of one-dimensional sound propagation in ducts and presents acoustic models for uniform, non-uniform and inhomogeneous ducts with hard or finite impedance walls and parallel sheared mean flow.

Chapter 11 describes calculation of the sound pressure level at a point in the acoustic field of an in-duct source. Insertion loss of a silencer is shown to be represented approximately by source-independent parameters under certain conditions. The discussion encompasses multi-modal sound propagation and radiation and the ASHRAE method of silencer sizing in ventilation and air distribution systems.