Stagnation point

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Photo showing stagnation point and attached vortex at an un-faired wing-root to fuselage junction on a Schempp-Hirth Janus C glider.

The stagnation point is a point on the surface of a body submerged in a fluid flow where the fluid velocity is zero. The Bernoulli equation shows that the static pressure is highest when the velocity is zero. The velocity is zero at stagnation points so the pressure around the submerged body is highest at the stagnation points. This pressure is called the stagnation pressure.

The Bernoulli equation shows that the stagnation pressure is equal to the dynamic pressure plus free-stream static pressure. We can use this information in the equation for finding pressure coefficient $C p$ :

$C_p={p-p_\infty \over q_\infty}$

where:

C p

is pressure coefficient

p

is static pressure at the point at which pressure coefficient is being evaluated

$p_\infty$ is pressure at points remote from the body (free-stream static pressure)

$q_\infty$ is dynamic pressure at points remote from the body

Stagnation pressure minus static pressure is equal to dynamic pressure; therefore the pressure coefficient $C p$ at stagnation points is 1.

On a streamlined body fully immersed in a potential flow, there are two stagnation points. On a body with a sharp point such as the trailing edge of a wing, the Kutta condition specifies that a stagnation point is at that location. The streamline at a stagnation point is perpendicular to the surface of the body.