Finding the total pressure acting on a submarine

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Homework Help Overview

The discussion revolves around calculating the total pressure acting on a submarine at a specific depth and speed. The problem involves concepts from fluid dynamics and hydrostatics, particularly focusing on pressure calculations in a marine environment.

Discussion Character

  • Exploratory, Assumption checking, Conceptual clarification

Approaches and Questions Raised

  • Participants discuss the equations relevant to calculating total pressure, including static and dynamic components. There are questions about how to determine static pressure and the implications of speed on pressure measurements. Some participants suggest considering the effects of stagnation points on pressure readings.

Discussion Status

The discussion is ongoing, with participants exploring different aspects of the problem. Some have provided insights into the equations and concepts involved, while others are questioning the assumptions made regarding pressure distribution on the submarine.

Contextual Notes

There is a mention of specific values such as sea-water density and depth, which are critical to the calculations. Participants are also considering the implications of the submarine's speed on the pressure measurements, indicating a need for clarity on how these factors interact.

strine07
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Hello I'm having trouble with answering this question: Certain submarines are capable of speeds in excess of 30 knots. What is the total pressure sensed at the nose of a submarine if the vessel is at periscope depth (5 m) and a speed of 30 knots? (Assume a constant sea-water density of 1030 kg/m3.) What height would the captain read on a mercury manometer that sensed this total pressure?
I know the equations Po=Ps + (1/2)(rho)(V)^2 and dP=(rho)(g)(dh) but am having trouble finding the static pressure in order to find the total pressure.
 
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A depth of 0m corresponds to air pressure (~1.013*10^5 N), your equation for dP allows to add the 5m of water between nose and surface.
 
The second equation should be enough. The submarine will experience this pressure over its surface area. So the mercury manometer will sense this pressure. The hard part would be to calculate the "lift" of the submarine, for which you could use Newton's method.
 
Keep in mind that the nose may see a stagnation point, you won't necessarily see the same total pressure (static and dynamic) as other parts of the vessel.
 

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