the sources of all aerodynamic forces

THE SOURCE OF ALL AERODYNAMIC FORCES

• A knowledge of four basic aerodynamics quantities (P,𝞺,T and v ) at each point of the flow fully defines the flow field 
• The air flow over the surface of any body in the flow creates anaerodynamic force on the body
• the aerodynamic forces by the airflow on the surface of an airplane,missile,.....etc stems from only two natural sources

                                        1. pressure distribution on the surface

                                        2. shear stress distribution on the surface

• pressure exerted by the gas on the solid surface of the object always acts normal to the surface
• the net unbalance of the varying pressure distribution over the surface of airplane creates an aerodynamic force which is known as lift
• the shear stress acting on the surface is due to the friction between surface and fluid particles as flow moves around the body
• the shear stress ' τ_w  ' is defined ass the force per unit area acting tangentially on the surface due to friction
• the aerodynamic force created due to shear stress distribution is known as drag
• prediction of pressure and shear stress distribution on the surface requires knowledge of flow field around the body