On the Comparison of the Long Penetration Mode (LPM) Supersonic Counterflowing Jet to the ..

Classic tonal screech noise created by under-expanded supersonic jets; Long Penetration Mode (LPM) supersonic phenomenon -Under-expanded counter-flowing jet in supersonic free stream -Demonstrated in several wind tunnel tests -Modeled in several computational fluid dynamics (CFD) simulations; Discussion of LPM acoustics feedback and fluid interactions -Analogous to the aero-acoustics interactions seen in screech jets; Lessons Learned: Applying certain methodologies to LPM -Developed and successfully demonstrated in the study of screech jets -Discussion of mechanically induced excitation in fluid oscillators in general; Conclusions -Large body of work done on jet screech, other aero-acoustic phenomenacan have direct application to the study and applications of LPM cold flow jets. For the Oral/Visual Presentation in which this video was presented, please see the following link in the NASA Technical Reports Server (NTRS, ntrs.nasa.gov): hdl.handle.net/...

[@mduvigneaud]

I find this very interesting! A counterflow jet stream to deflect the main shockwave and I think decrease the air resistance. That's really awesome. :D

[@SosirisTseng]

+Martel DuVigneaud And that counter jet creates an 'air shield', preventing the vessel from overheating.

[@mduvigneaud]

Sosiris Tseng Yep! :D

[@beckyfarr6757]

This is the expected result (among others). We need to go back to the wind tunnel. Send money. LOL

[@richardphatthenguyen195]

It is actually nice that this technology is applied elsewhere than pure fundamental fluid mechanic research. Typical counterflow jet start was suggested to be used for mixing fluids. Now, it is quite nice to see that it can be applied in aerospace to reduce the drag effect and thermal stress. I wonder if the velocity ratio could still be applied in supersonic to find instabilities.

[@mrzorg]

This is interesting in a re-entry vehicle as well? Only mentioning it because of the shape of the object. ;-)

[@Aliens-use-cloaking-devices]

So much Info on uap is hidden what about the earth observation vids

[@charybe]

This makes me think of the supercavitating torpedoes going over 400 kmh (250 mph) by exhausting their gases by the front (directed backward), thereby creating their own cavity in the water...

[@beckyfarr6757]

BINGO.

[@ZMacZ]

I guess this is the one thing we needed to start the magnetic accelerator program for getting orbital vehicles up to speed. Normally getting a 'free' 8000 kph (of the total 28.000 kph) at a height of 20.000 feet (6 km) would thermalize the launch vehicle, but with this it should be possible.. For example the space shuttle with it's 2 million kg fuel to 30.000 kilogram payload, would need but a 'mere' 1.5 million kg of fuel and with the same amount of speed achieved that would yield 530.000 kg payload. (roughly) Or, alternately, the launch vehickes could be made smaller, like 40.000 kg payload, but for a 110.000 fuel load.. Cool !!! Also that paves the way towards an actual spacestation, which is one of the few survival strategies against an ELE event..

[@penguin44ca]

Like a spacex entry burn.

[@otivaeey]

What's the implication of counterflow? How's the update?

[@beckyfarr6757]

Nothing has changed, except Bombardier's Antipode concept was published.

[@jaspreetsingh-nr6gr]

but how does this compare to use of an aerodisk spike, the one normally used in external flows?

[@beckyfarr6757]

Aerodisk spike is essentially the same as SPM, it merely moves the shock upstream. The mechanical spike is only tuned to one flight regime, because it is a fixed piece of hardware. LPM disperses the shock and can adjust to a broad range of conditions. All assume since it takes a lot of energy to create a supersonic shock, it must also take a lot of energy to disperse a supersonic shock. This is incorrect thinking and shows ignorance of the Law of Entropy.

[@jaspreetsingh-nr6gr]

i don't have a clear idea about this but a friend of mine said a cavity (indent) on the blunt nose may also dissipate the shock provided it is meshed, do you think this is possible. The flow would be supersonic in the cavity but.

[@beckyfarr6757]

We believe there is a complex interaction with fluid mechanics, thermodynamic gas effects and acoustics in LPM. All work together to create and maintain the effect. This is theory, that suggests data we would need to collect to either refute or further support our thinking. I can see how a cavity of correct volume and location could have similar effect at the correct matching Mach number. Especially if bleed air is injected into the cavity. Such things have been seen in some tests I can not describe further, but usually by accident. This is a good topic for PhD thesis don't you think?