center of pressure


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Center of pressure

A point on a plane surface through which the resultant force due to pressure passes. Such a surface can be supported by a single mounting fixture at its center of pressure if no other forces act. For example, a water gate in a dam can be supported by a single shaft at its center of pressure. See Resultant of forces

Center of Pressure

 

the point at which the line of action of the resultant of the forces due to pressure on a body at rest or in motion in an ambient medium intersects some plane drawn in the body. The ambient medium may be a liquid or a gas.

For example, the center of pressure for an airplane wing (Figure 1) is the point of intersection of the line of action of the resultant aerodynamic force and the plane of the wing chord. For a body of revolution—such as the fuselage of a rocket or the body of a dirigible or mortar shell—the center of pressure is the point of intersection of the resultant aerodynamic force and the body’s plane of symmetry perpendicular to the plane passing through the axis of symmetry and through the velocity vector of the body’s center of gravity.

Figure 1. Location of the center of pressure for a wing: (b) chord length, (α) angle of attack, (v) free-stream velocity vector, (R) resultant aerodynamic force, (Xcp) distance from the center of pressure to the leading edge of the wing

The location of the center of pressure depends on the shape of the body; for a moving body, it may also depend on the direction of motion and on the properties of the ambient medium, for example, its compressibility. Thus, depending on the shape of the wing section, the location of the center of pressure for an airplane wing may vary with the angle of attack a or may be constant. If the location of the center of pressure is constant, the wing is called a constant center of pressure wing and xcp ≈ 0.25b (Figure 1). During supersonic motion, the center of pressure is shifted substantially toward the trailing edge of the wing because of the effect of the compressibility of air.

A change in the location of the center of pressure has a considerable effect on the dynamic stability of a moving body, such as an airplane, a rocket, or a mortar shell. For the motion to be stable upon a random variation of the angle of attack α, the center of pressure should shift in such a way that the aerodynamic moment causes the body to return to its original position. For example, as α increases, the center of pressure should shift toward the tail. To ensure dynamic stability, a body intended for flight is often provided with an appropriate tail assembly.

REFERENCES

Loitsianskii, L. G. Mekhanika zhidkosti i gaza, 3rd ed. Moscow, 1970.
Golubev, V. V. Lektsiipoi teorii kryla. Moscow-Leningrad, 1949.

center of pressure

[′sen·tər əv ′presh·ər]
(aerospace engineering)
The point in the chord of an airfoil section which is at the intersection of the chord (prolonged if necessary) and the line of action of the combined air forces (resultant air force).
(fluid mechanics)
For a body immersed in a fluid, the point through which the resultant of the forces on the surface of the body due to hydrostatic pressure acts.

center of pressure (C of P)

center of pressure (C of P)click for a larger image
The point, usually on the chord line, through which the total reaction (sum total of all aerodynamics forces) may be considered to act. The center of pressure is not a fixed point but moves with changes to the angle of attack.
References in periodicals archive ?
Converting Chattecx Balance System vertical reaction force measurements to center of pressure excursion measurements.
This allows to establish that subjects' height does not condition the displacement of the plantar center of pressure induced by anteposition of the skull.
Center of pressure progression characteristics under the plantar region for elderly adults.
Several years ago, Collins recognized that the location of the center of pressure, as measured on a sensitive apparatus known as a force platform, follows a specific type of random walk.
Center of pressure (CoP) is one of the kinetic-related variables which can present the whole body balance dynamics.
While only discreet points were pulled off of the KAM and LMF curves, it may be beneficial for future research to perform a principal component analysis in order to further examine the time-series curves of the variables of interest, as well as incorporating other possible explanatory variables such as center of pressure or GRF lever arms.
The holding had long been at the center of pressure from regulators for its alleged support of Turkish Islamic scholar Fethullah GE-len, whom President Recep Tayyip Erdoy-an launched a witch hunt against and started calling the leader of a terrorist organization following the publication of a corruption scandal that implicated then-Cabinet members and the son of the president in December 2013.
Also of importance is the wing's center of lift (CL), or center of pressure, which is represented by the bluw/white point in the diagrams.
Although timed tests of functional ambulation offer an easy and efficient measure of gait performance in the clinical setting, they do not expose underlying challenges in the motor control of changing directions during walking that can be determined by examining the center of pressure (COP) trajectory.
In a separate study, individuals with diabetic peripheral neuropathy demonstrated a significantly greater center of pressure excursion during sensory conditions when compared to individuals with diabetes and no neuropathy and individuals with neither diabetes nor neuropathy (44).
Kinetic variables (vertical, medio-lateral [ML], anteroposterior [AP] maximum ground reaction forces [GRF], and center of pressure [COP] ML and AP) were measured by a Bertec force platform at 1000 Hz with participants S and BF.

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