Aerodynamic forces shear force

The pressure (p) and shear stress (tj distributions over an airfoil-shaped body are shown schematically in Figure 1. The pressure and shear stress distributions exerted on the body surface by the moving fluids are the two hands of nature that reach out and grab the body, exerting a net force on the body—the aerodynamic force. 

A review of the past literature on the available correlations on the mean droplet size produced by splash plate nozzles shows that there are large discrepancies between the results. The prediction of the droplet sizes generated by splash plate nozzles is based on the Kelvin-Helmholtz (K-H) instability theory for a liquid sheet. Dombrowski and Johns [14], Dombrowski and Hooper [18] and Fraser et al. [13] developed such a theoretical model to predict droplet sizes from the breakup of a liquid sheet. They considered effects of liquid inertia, shear viscosity, surface tension and aerodynamic forces on the sheet breakup and ligament formation. Dombrowski and Johns [14] obtained the following equation for droplets produced by a viscous liquid sheet ... 

The drug particles are then entrained by the air flow due to the shear forces during inhalation (Fig. 14.2). The large carrier particles, which mainly craisist of a-lactose monohydrate for marketed products, get impacted in the throat due to inertia, while fine particles follow the air stream into the deeper airways to reach bronchioles and alveoli according to its aerodynamic diameter [2]. The fraction of interest the so-called Fine Particle Fraction (FPF) comprises all drug particles of an aerodynamic diameter <5 pm [12]. 

The shearing stress, r, exerted by the wind on the ground entails a downwards flux of momentum. In the aerodynamic boundary layer above the surface, the momentum is transferred by the action of eddy diffusion on the velocity gradient. The friction velocity is defined by w = t/pa and is a measure of the intensity of the turbulent transfer. Near to a rough surface, the production of turbulance by mechanical forces... 

Small particles in a shear field as shown in Fig. 15 experience a lift force perpendicular to the direction of flow. The shear lift origmates from the inertia effects in the viscous flow around the particle and is fundamentally different from aerodynamic lift force. The expression for the inertia shear lift was first obtained by... 

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