dynamic pressure on the nose of aircraft?

[dhawal damle]

I am preparing for a exam and in one of the question papers,
there was a question

Q) What is the dynamic pressure an the nose of aircraft?

Maximum or
minimum or
zero.

in the book the ans. is given as zero,but I doubt that could be
printing mistake.

I think the answer shuld be maximum dynamic pressure at the nose.

please correct me.

[Orval Fairbairn]

In article m>,
dhawal damle > wrote:

> I am preparing for a exam and in one of the question papers,
> there was a question
>
> Q) What is the dynamic pressure an the nose of aircraft?
>
> Maximum or
> minimum or
> zero.
>
> in the book the ans. is given as zero,but I doubt that could be
> printing mistake.
>
> I think the answer shuld be maximum dynamic pressure at the nose.
>
> please correct me.

It is certainly a mistake, as the nose (assuming that the airplane is
flying nose-first) is at the stagnation pressure, which is the sum of
the static pressure and dynamic pressure.

Actually, the dynamic pressure is constant for any velocity/density
combination.

Q = Rho*V**2/2

[The Visitor[_2_]]

how do they define dynamic pressure? (as in "changing" pressure.)
Perhaps it is zero if the plane is at a constant speed. And static
pressure is positive(maximum).

dhawal damle wrote:

> I am preparing for a exam and in one of the question papers,
> there was a question
>
> Q) What is the dynamic pressure an the nose of aircraft?
>
> Maximum or
> minimum or
> zero.
>
> in the book the ans. is given as zero,but I doubt that could be
> printing mistake.
>
> I think the answer shuld be maximum dynamic pressure at the nose.
>
> please correct me.
>

[Jim Logajan]

dhawal damle > wrote:
> Q) What is the dynamic pressure an the nose of aircraft?
>
> Maximum or
> minimum or
> zero.
>
> in the book the ans. is given as zero,but I doubt that could be
> printing mistake.
>
> I think the answer shuld be maximum dynamic pressure at the nose.

This is a case where the assumptions (and definitions) in the underlying
model used make a difference in the answer. The dynamic pressure acting
directly on the very center of the nose of an "ideal incompressible
inviscid fluid" is, by definition, zero.

The question, alas, sucks due to unclear context. When I see the word
"nose" I (like you it seems) visualize something other than what the
question writer assumed. "Nose" for the question writer means only the
very center point where the air hits the point - and the air flow
directly on that mathematical point comes to rest. But without context,
when the rest of us see "nose" we think the question is talking about
the dynamic pressure summed up over the _area_ of the nose.

Here's a web page that hopefully provides some insight into the context
the question writer had in mind:

http://www.centennialofflight.gov/essay/Theories_of_Flight/Ideal_Fluid_Flow/TH7.htm

And just to confuse things, here's a web page from the same site that
mentions putting a pitot tube out in front of the nose(!) of a plane for
measuring dynamic pressure (and hence airspeed):

http://www.centennialofflight.gov/essay/Theories_of_Flight/Conservation/TH8.htm