How do altimeters react in high acceleration flow?

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SUMMARY

The discussion focuses on the behavior of barometric altimeters in high acceleration flow, particularly in subsonic conditions. It is established that the readings of a barometric altimeter can be influenced by horizontal pressure gradients, especially when a missile accelerates horizontally. The placement of static ports is critical; they must be positioned to ensure airflow velocity matches the freestream to provide accurate readings. Computational Fluid Dynamics (CFD) modeling is essential for understanding airflow disturbances around airframes and calibrating static port data against clean reference data.

PREREQUISITES
  • Understanding of barometric altimeter functionality
  • Knowledge of static port placement and its impact on airflow
  • Familiarity with Computational Fluid Dynamics (CFD) modeling
  • Basic principles of aerodynamics in subsonic flight
NEXT STEPS
  • Research barometric altimeter calibration techniques
  • Explore the principles of airflow around airframes using CFD
  • Learn about the design and placement of static ports in aerospace engineering
  • Investigate the effects of horizontal pressure gradients on flight instruments
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Aerospace engineers, flight test engineers, and anyone involved in the design and calibration of flight instrumentation, particularly in high-speed and high-acceleration environments.

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How will barometric altimeter react to horizontal pressure gradient when missile accelerate horizontally, in subsonic regime?
Will he change reading even if he fly at same altitude?
 
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Air pressure which barometric altimeter measures depends on position of the missile surface where altimeter is. Head air pressure is higher than the Tails. Higher altitude air pressure is lower than the lowers.
 
Last edited:
anuttarasammyak said:
Air pressure which barometric altimeter measures depends on position of the missile surface where altimeter is. Head air pressure is higher than the Tails. Higher altitude air pressure is lower than the lowers.
Yes but static ports must be place in position where airflow velocity is same as freestream.

Here is static port at rocket.
1YABh.webp
 
Bit late to the party, but…

Static ports are not perfect. There’s always some disturbance from airflow around the airframe that needs to be accounted for. CFD modeling helps a great deal for that these days, but at least for larger jets, there will usually be a static port run out on a line, often from the tip of the vertical stabilizer, to provide clean air to reference against. The flight test program then compares the “clean” data against the data from the production static ports and then uses that comparison to create a calibration database.

Hopefully this helps.
 
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