First Look: LCA Mk.2 Air Intake Wind-Tunnel Model

[Srinivas]

First Look: LCA Mk.2 Air Intake Wind-Tunnel Model

Found this interesting picture from NAL that shows a 1:7 wind tunnel model of the LCA Tejas Mk.2 redesigned air-intake for the F414-GE-INS6 turbofan. No real change, is there?





Livefist

 

[S-DUCT]

Hmm..changes in airintakes are indistinguishable form naked eye.A senior member in BRF had a conversation with CD balaji,head of inchage of lca Navy programme,he said that air intakes would be widen by only 10mm only.

 

[narcon]

Was Arihant submarine tested against wind tunnel?

 

[SQ8]

Was Arihant submarine tested against wind tunnel?

You would not test a sub against wind.. at most you would use a fludic test area.. filled with colored water to look at the hydrodynamics... @Capt.Popeye

 

[narcon]

You would not test a sub against wind.. at most you would use a fludic test area.. filled with colored water to look at the hydrodynamics... @Capt.Popeye

"Because air works in the same way as a liquid, wind tunnels can be used to simulate the effects of water on a submarine hull".

 

[SQ8]

"Because air works in the same way as a liquid, wind tunnels can be used to simulate the effects of water on a submarine hull".

yes.. but something called density also comes into play..

this is what you use
Water tunnel (hydrodynamic) - Wikipedia, the free encyclopedia

 

[killerx]

yea black paint makes it look stealthy but the the air frame in the same

 

[Capt.Popeye]

"Because air works in the same way as a liquid, wind tunnels can be used to simulate the effects of water on a submarine hull".

Both are fluids alright and principles of fluid hydrodynamics are similar; e.g drag and lift. But they are not the same.
I wonder if anybody tested a model of the Arihant in a wind tunnel. But I am absolutely sure that they tested it in a Wave-Tank.
With both sinusoidal and non-sinusoidal wave forms. How would anybody simulate that in a wind-tunnel?

Just as the Porsche 911 was extensively tested in a wind-tunnel ( I read about that) but was it intended to swim or to fly?

yes.. but something called density also comes into play..

this is what you use
Water tunnel (hydrodynamic) - Wikipedia, the free encyclopedia

That is there of course. Then there is the additional study required of wave-resistance wrt waves of different forms. Which can create slamming resistance forces. How do you do that in a wind tunnel?

 

[narcon]

yes.. but something called density also comes into play..

this is what you use
Water tunnel (hydrodynamic) - Wikipedia, the free encyclopedia

Lamantabily the wiki source does not use the word "density" even once.

But anyway. That statement was from NASA.

Here is the mock up of US submarine being tested under the wind tunnel:

NASA - Submarine in a Wind Tunnel

 

[SQ8]

Lamantabily the wiki source does not use the word "density" even once.

But anyway. That statement was from NASA.

Here is the mock up of US submarine being tested under the wind tunnel:

NASA - Submarine in a Wind Tunnel

Nevermind the wiki.. its the least reliable of sources.. only good for a general idea.

How does that answer Capt Popeye's and mine's question?
If density does not matter.. then there would be no need for this.
pub - memphis

So yes, fluid flow may be very well simulated.. but exact results on acoustics and the lot would not matter.

Free surface and dynamic testing needs to be carried out in a towing tank and water
tunnel. Dynamic testing, although possible in a wind tunnel, has the impossible difficulty
of the added mass that is not present in a water tunnel.

from http://www.dsto.defence.gov.au/publications/3442/DSTO-TR-1622.pdf

 

[Capt.Popeye]

Lamantabily the wiki source does not use the word "density" even once.

But anyway. That statement was from NASA.

Here is the mock up of US submarine being tested under the wind tunnel:

NASA - Submarine in a Wind Tunnel

Why can't a model of a sub be tested in a wind-tunnel, if the model of a sportster can be tested in one?

But that would hardly be a substantive or conclusive test of a hull form. Hull forms of both surface vessels and sub-surface craft are subject to impact by waves. These can only be replicated/simulated in a Hydrodynamic Testing Tank aka a Wave Testing Tank. Those tests are all important.

 

[INDIAISM]

Thank God at last some sense prevailed in DRDO as their is not much change in design of Mk1 and Mk2....As more change would have meant more delay and that's what LCA Tejas project and our defence establishment....

 

[narcon]

From your source:

In order to proceed with such concepts it is vital to have a database. Our current
submarine, the Collins class, should be the base from which all changes and proposals are
measured. It is suggested detailed wind tunnel studies should be undertaken concurrently
with computational fluid dynamic (CFD) evaluations. The results should then be
compared with full scale trials to establish propeller efficiencies and roughness factors as
well as the contributions for each feature, hull, sail, control fins, masts and snorkels, flood
openings and others. This database will allow more precise comparisons for any
improvements which may be considered in a future design.

Reynolds number allows us to examine flow on a real submarine in seawater by testing a
model in, for example, a wind tunnel. If the Reynolds numbers are the same in each
situation then we have similarity in the results.

BTW what is a fluid mechanism, dimensional analysis, without Reynolds numbers?

So first step it is!
NASA aint wrong.

 

[Screambowl]

intakes are totally new design.

 

[Capt.Popeye]

From your source:

BTW what is a fluid mechanism, dimensional analysis, without Reynolds numbers?

So first step it is!
NASA aint wrong.

It is ONLY the first step; NOT the last word.

NASA may not be wrong, but the USN or IN (or any Naval Design Bureau) would be; it they stopped testing there......