# aerodynamic force

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## Aerodynamic force

The force exerted on a body whenever there is a relative velocity between the body and the air. There are only two basic sources of aerodynamic force: the pressure distribution and the frictional shear stress distribution exerted by the airflow on the body surface. The pressure exerted by the air at a point on the surface acts perpendicular to the surface at that point; and the shear stress, which is due to the frictional action of the air rubbing against the surface, acts tangentially to the surface at that point. The distribution of pressure and shear stress represent a distributed load over the surface. The net aerodynamic force on the body is due to the net imbalance between these distributed loads as they are summed (integrated) over the entire surface. See Boundary-layer flow, Fluid flow

For purposes of discussion, it is convenient to consider the aerodynamic force on an airfoil (see illustration). The net resultant aerodynamic force R acting through the center of pressure on the airfoil represents mechanically the same effect as that due to the actual pressure and shear stress loads distributed over the body surface. The velocity of the airflow V is called the free-stream velocity or the free-stream relative wind. By definition, the component of R perpendicular to the relative wind is the lift, L, and the component of R parallel to the relative wind is the drag D. The orientation of the body with respect to the direction of the free stream is given by the angle of attack, α. The magnitude of the aerodynamic force R is governed by the density &rgr; and velocity of the free stream, the size of the body, and the angle of attack. See Airfoil

An important measure of aerodynamic efficiency is the ratio of lift to drag, L/D. The higher the value of L/D, the more efficient is the lifting action of the body. The value of L/D reaches a maximum, denoted by (L/D)max, at a relatively low angle of attack. Beyond a certain angle the lift decreases with increasing α. In this region, the wing is said to be stalled. In the stall region the flow has separated from the top surface of the wing, creating a type of slowly recirculating dead-air region, which decreases the lift and substantially increases the drag.

## aerodynamic force

[‚e·ro·dī′nam·ik ′fȯrs]
(fluid mechanics)
The force between a body and a gaseous fluid caused by their relative motion. Also known as aerodynamic load.

## Aerodynamic force

The force exerted on a body whenever there is a relative velocity between the body and the air. There are only two basic sources of aerodynamic force: the pressure distribution and the frictional shear stress distribution exerted by the airflow on the body surface. The pressure exerted by the air at a point on the surface acts perpendicular to the surface at that point; and the shear stress, which is due to the frictional action of the air rubbing against the surface, acts tangentially to the surface at that point. The distribution of pressure and shear stress represent a distributed load over the surface. The net aerodynamic force on the body is due to the net imbalance between these distributed loads as they are summed (integrated) over the entire surface.

For purposes of discussion, it is convenient to consider the aerodynamic force on an airfoil (see illustration). The net resultant aerodynamic force R acting through the center of pressure on the airfoil represents mechanically the same effect as that due to the actual pressure and shear stress loads distributed over the body surface. The velocity of the airflow V is called the free-stream velocity or the free-stream relative wind. By definition, the component of R perpendicular to the relative wind is the lift, L, and the component of R parallel to the relative wind is the drag D. The orientation of the body with respect to the direction of the free stream is given by the angle of attack, α. The magnitude of the aerodynamic force R is governed by the density &rgr; and velocity of the free stream, the size of the body, and the angle of attack.

An important measure of aerodynamic efficiency is the ratio of lift to drag, L/D. The higher the value of L/D, the more efficient is the lifting action of the body. The value of L/D reaches a maximum, denoted by (L/D)max, at a relatively low angle of attack. Beyond a certain angle the lift decreases with increasing α. In this region, the wing is said to be stalled. In the stall region the flow has separated from the top surface of the wing, creating a type of slowly recirculating dead-air region, which decreases the lift and substantially increases the drag.

References in periodicals archive ?
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Figure 4 shows an example of the measured data and converted aerodynamic force coefficient.
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The DrivAer geometry has been applied to CFD to simulate open road conditions in order to validate the aerodynamic forces with experimental data as well as set a reference for wind tunnel simulations.
Cheli et al investigated a high-sided lorry in flat ground scenario and measured mean aerodynamic forces and moments by means of a six-component dynamometric balance .
The downwind cases have greater variations in displacement owing to the larger decrease occurred in the aerodynamic force drop.
From definition of aerodynamic force is obvious, that higher speed results in higher energy consumption (1).

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