Derivation of Dynamic Pressure

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SUMMARY

The dynamic pressure formula, expressed as 1/2PV^2, derives from Newton's Second Law applied to fluid dynamics. In this context, P represents density and V denotes velocity. The proportionality of dynamic pressure to V^2 arises from the relationship between the momentum change of air displaced by an object and its velocity, where the mass current is also proportional to V. This integration of fluid dynamics principles confirms that dynamic pressure increases with the square of the velocity.

PREREQUISITES
  • Understanding of Newton's Second Law
  • Basic principles of fluid dynamics
  • Knowledge of momentum and its relation to force
  • Familiarity with the concept of density in physics
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  • Study the derivation of the Bernoulli equation
  • Explore the concept of momentum in fluid mechanics
  • Learn about the applications of dynamic pressure in aerodynamics
  • Investigate the relationship between velocity and pressure in fluid flow
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Aerospace engineering students, physics enthusiasts, and anyone interested in the principles of fluid dynamics and aerodynamics will benefit from this discussion.

arithhuh
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Dear All, I need your help with a present problem -

I am a student pilot, and want to see the derivation for the dynamic pressure formula - which is 1/2PV^2 where P - Density, V-Velocity

I was asked an interesting question by my a fellow student: Why is dynamic pressure directly proportional to v^2 and not just V?

Kindly explain to me these points.

Thank you,
~ Aditya.
 
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It comes from looking at Newton's Second Law for a fluid particle along a streamline. In a nutshell, the term is the result of an integration of the term
\rho V \frac{\partial{V}}{\partial{s}}

How much detail do you want to get into?
 
Here is a simple argument why the pressure is proportional to v^2:

The object flying through air must remove air in front of it. If you assume that the change of air velocity is proportional to the speed of the object, then the change of momentum of air (pushed away in a certain time) is proportional to v^2 (because the mass current is also proportional to v). Force equals the change of momentum/change of time, so force is also proportional to v^2.
 

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