ChineseTiger1986
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2017 will also soon have the silver nozzle.
The silver nozzle and black nozzle all belong to the same type of engine, just different variants imo.
Chengdu J-20 5th Generation Aircraft News & Discussions
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2017 will also soon have the silver nozzle.
The silver nozzle and black nozzle all belong to the same type of engine, just different variants imo.
neytirilover
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Plus that, in almost all cases, compressible models are better than incompressible models, the trick is whether you consider the benefit of taking compressibility into consideration worthwhile since the extra coding effort and CPU time you put into it.
Taygibay
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So you have a PhD? GFY ( good for ... )! And I do believe it might be in science because it is obviously not in behavioural psychology, social studies or Internet. Such claims have no place on a forum. Not only are they not required of standard users because of anonymity but they’d also temper with the equalitarian access raison d’être of the Net. Don’t claim you are so good, just show it!
But I’ll take your word for an instant :
I do not have a PhD in science. There are other things I have though. I have piloted airplanes for instance and while not fighters, not on a computer or gaming console, IRL! I can do mechanics work : fix bikes, cars and beyond machinery in general, weapons and heck electronics & computers. I have built a house and a boat for real! Etc. Whatever you think is the sole domain of excellence you practice is more than balanced by real life abilities and experience on my side. When your designs don’t deliver, people like me make them work anyhow.
And while you can counter this by negating its truth quotient, I’ll immediately return the favour as to your PhD.
QED on Internet claims.
Let’s veer to reality :
I’m not certifying anything nor basing my opinion on mere specific resemblances as say between a Mustang P-51 and a Fighting Falcon because of the inlet. . . although ...
Gotta love the Mustang --» GIFT http://www.warbirdheritagefoundation.org/PA_P51_F_0001_W.jpg
I did not say the J-20 was a copy of the MiG-31, in fact almost the contrary. I said there was a filiation, that the original idea was re-used as a base. IRL, outside the lab, this translates into : both planes’ layouts are similar if not identical ( although layout might be too grubby a term, fitted for lowly mechanics and industrial designers more than for your highness? ).
What changed most is not even the application of stealth that is so evident that some think it hides the rest. The body is similar, a very linear fuselage ideal for high speed by aiding penetration through air, cockpit perched aft of the air intakes. Chinese engineers wisely separated the engines more as found in Sukhois because this creates an air flow top ( and bottom depending ) that cools them and reduces heat signature. The wing is similar but bigger due to the trailing edge sweeping back to induce radar reflection scattering. This meant a new rear end, with again SU-like extensions which are found on most modern designs, prolonging air flow again and somewhat hiding the thrusters. For those reasons, the trailing longitudinal surfaces on the underside are now away from the body which is a normal corollary. They’re located in opposition to the now dual & canted vertical fins, as necessary for maximum all-aspects stealth. The body is wider, thicker and flatter to incorporate bays.
The air intakes that used to be on either side of the fuselage are still just about there but wider apart which makes the S-duct routes better. The rear half of these however is nearly the same which shows on even outside views of the ACs. The addition of canards replaces the rear horizontal surfaces that disappeared in the trailing edge design. They’re long moment arm canards with an added Chinese spice in their upward angulation which can be guessed by the preference of the image sourcing for relatively level flight ( meaning that the horizontal axis is stable on pics not that it is parallel to the ground ) views. If they do play on the lift as I wonder, that is an additional quality of importance. I have studied decomposed flight stills and there is a strong possibility that this is true. // You’ll be glad to know that it’s not evident and could only be correctly estimated through serious analysis of entire flight videos. // The cockpit sits higher and looks to be pushed aft mostly due to the long top edge going off the intakes. If there was one thing to accredit a link to the MiG 1.44, the 3/4 rear view of the J-20’s allure and cockpit positioning in particular would be it.
Difference with the Slavic beasts : the absence of the equipment dorsal ridge ( now a channel as said ) for either but more importantly the air intakes design choice as location goes -31like. The dual under nose option found on the MiG 1.44 and the Typhoon as well is a horrid idea. When each engine intake is separate, the likelihood of accident goes down. In a bad case scenario, a single volatile ingestion could affect both paths and suppress power entirely. It fits the single engine F-16 mentioned at the beginning but not a dual engine fighter. That re-positioning alone would severe a link between the J-20 and the 1.44. The rear stabilizer section is of similar intention but realized differently while the top fuselage curvatures are not unlike but the canards are much better located on the J-20 as relative to the pilot.
The Chengdu star is not a paper airplane nor a simple prototype. It shows in every detail. It was not copied on one either. Inspired? Heck, sure since all designers work from a body of knowledge common to aviation but the 31 is a sounder less risky design as an inspiration for the working Black Eagle.
What you described in the second part of your post is quite reasonable too, it just does not come into play in a discussion such as this. Of course the aerodynamics are infinitely superior. Of course the fly-by-wire programming must be a masterpiece by comparison. Yes, specifics performance metrics and objective targets for the design are only known to the makers ( and computer ) and users and only correctly measured in the lab ( anechoic chamber / wind tunnel et al. ). No, they’re not needed to judge layout and evaluate filiation, a rather summary process to begin with. Because unless you also claim to have been on the J-20 design team, it's all opinion really, even for you. Put a clown wig and a red nose on a donkey, it’s still an a.s to the discerning observer!
Even without a PhD!
About which, since you chose the haughty superiority holier than thou and twice as certain route ( Now if you are a well trained PhD, I just might put a little bit of credibility in you. thingie ), a word of advice for the little it’s worth : Good luck backing that!
Under such pretension, trolls will hunt every mistake you produce before I hear of or spot them. They’ll be greedy for doctor’s meat?
As the Eagles famously sang : Every refuge has its price.
. . . The Black Eagles of course!
And yet, no hard feelings! Here's to hoping you for a smoother conversation later, Tay.
P.S. And good luck with the d...egree measuring contest!
But I’ll take your word for an instant :
I do not have a PhD in science. There are other things I have though. I have piloted airplanes for instance and while not fighters, not on a computer or gaming console, IRL! I can do mechanics work : fix bikes, cars and beyond machinery in general, weapons and heck electronics & computers. I have built a house and a boat for real! Etc. Whatever you think is the sole domain of excellence you practice is more than balanced by real life abilities and experience on my side. When your designs don’t deliver, people like me make them work anyhow.
And while you can counter this by negating its truth quotient, I’ll immediately return the favour as to your PhD.
QED on Internet claims.
Let’s veer to reality :
I’m not certifying anything nor basing my opinion on mere specific resemblances as say between a Mustang P-51 and a Fighting Falcon because of the inlet. . . although ...
Gotta love the Mustang --» GIFT http://www.warbirdheritagefoundation.org/PA_P51_F_0001_W.jpg
I did not say the J-20 was a copy of the MiG-31, in fact almost the contrary. I said there was a filiation, that the original idea was re-used as a base. IRL, outside the lab, this translates into : both planes’ layouts are similar if not identical ( although layout might be too grubby a term, fitted for lowly mechanics and industrial designers more than for your highness? ).
What changed most is not even the application of stealth that is so evident that some think it hides the rest. The body is similar, a very linear fuselage ideal for high speed by aiding penetration through air, cockpit perched aft of the air intakes. Chinese engineers wisely separated the engines more as found in Sukhois because this creates an air flow top ( and bottom depending ) that cools them and reduces heat signature. The wing is similar but bigger due to the trailing edge sweeping back to induce radar reflection scattering. This meant a new rear end, with again SU-like extensions which are found on most modern designs, prolonging air flow again and somewhat hiding the thrusters. For those reasons, the trailing longitudinal surfaces on the underside are now away from the body which is a normal corollary. They’re located in opposition to the now dual & canted vertical fins, as necessary for maximum all-aspects stealth. The body is wider, thicker and flatter to incorporate bays.
The air intakes that used to be on either side of the fuselage are still just about there but wider apart which makes the S-duct routes better. The rear half of these however is nearly the same which shows on even outside views of the ACs. The addition of canards replaces the rear horizontal surfaces that disappeared in the trailing edge design. They’re long moment arm canards with an added Chinese spice in their upward angulation which can be guessed by the preference of the image sourcing for relatively level flight ( meaning that the horizontal axis is stable on pics not that it is parallel to the ground ) views. If they do play on the lift as I wonder, that is an additional quality of importance. I have studied decomposed flight stills and there is a strong possibility that this is true. // You’ll be glad to know that it’s not evident and could only be correctly estimated through serious analysis of entire flight videos. // The cockpit sits higher and looks to be pushed aft mostly due to the long top edge going off the intakes. If there was one thing to accredit a link to the MiG 1.44, the 3/4 rear view of the J-20’s allure and cockpit positioning in particular would be it.
Difference with the Slavic beasts : the absence of the equipment dorsal ridge ( now a channel as said ) for either but more importantly the air intakes design choice as location goes -31like. The dual under nose option found on the MiG 1.44 and the Typhoon as well is a horrid idea. When each engine intake is separate, the likelihood of accident goes down. In a bad case scenario, a single volatile ingestion could affect both paths and suppress power entirely. It fits the single engine F-16 mentioned at the beginning but not a dual engine fighter. That re-positioning alone would severe a link between the J-20 and the 1.44. The rear stabilizer section is of similar intention but realized differently while the top fuselage curvatures are not unlike but the canards are much better located on the J-20 as relative to the pilot.
The Chengdu star is not a paper airplane nor a simple prototype. It shows in every detail. It was not copied on one either. Inspired? Heck, sure since all designers work from a body of knowledge common to aviation but the 31 is a sounder less risky design as an inspiration for the working Black Eagle.
What you described in the second part of your post is quite reasonable too, it just does not come into play in a discussion such as this. Of course the aerodynamics are infinitely superior. Of course the fly-by-wire programming must be a masterpiece by comparison. Yes, specifics performance metrics and objective targets for the design are only known to the makers ( and computer ) and users and only correctly measured in the lab ( anechoic chamber / wind tunnel et al. ). No, they’re not needed to judge layout and evaluate filiation, a rather summary process to begin with. Because unless you also claim to have been on the J-20 design team, it's all opinion really, even for you. Put a clown wig and a red nose on a donkey, it’s still an a.s to the discerning observer!
Even without a PhD!
About which, since you chose the haughty superiority holier than thou and twice as certain route ( Now if you are a well trained PhD, I just might put a little bit of credibility in you. thingie ), a word of advice for the little it’s worth : Good luck backing that!
Under such pretension, trolls will hunt every mistake you produce before I hear of or spot them. They’ll be greedy for doctor’s meat?
As the Eagles famously sang : Every refuge has its price.
. . . The Black Eagles of course!And yet, no hard feelings! Here's to hoping you for a smoother conversation later, Tay.
P.S. And good luck with the d...egree measuring contest!
Last edited:
Blue Marlin
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who on earth are you quoting? the j20 does have a few elements of the 1.44 but not enough to say that its an upgraded version of it. shenyang was compeating for the tender too. their plane was bigger than chengdu's and was more suited for strike bombing. but it lost as china needed a more all rounded jet.So you have a PhD? GFY ( good for ... )! And I do believe it might be in science because it is obviously not in behavioural psychology, social studies or Internet. Such claims have no place on a forum. Not only are they not required of standard users because of anonymity but they’d also temper with the equalitarian access raison d’être of the Net. Don’t claim you are so good, just show it!
But I’ll take your word for an instant :
I do not have a PhD in science. There are other things I have though. I have piloted airplanes for instance and while not fighters, not on a computer or gaming console, IRL! I can do mechanics work : fix bikes, cars and beyond machinery in general, weapons and heck electronics & computers. I have built a house and a boat for real! Etc. Whatever you think is the sole domain of excellence you practice is more than balanced by real life abilities and experience on my side. When your designs don’t deliver, people like me make them work anyhow.
And while you can counter this by negating its truth quotient, I’ll immediately return the favour as to your PhD.
QED on Internet claims.
Let’s veer to reality :
I’m not certifying anything nor basing my opinion on mere specific resemblances as say between a Mustang P-51 and a Fighting Falcon because of the inlet. . . although ...
View attachment 280166
Gotta love the Mustang --» GIFT http://www.warbirdheritagefoundation.org/PA_P51_F_0001_W.jpg
I did not say the J-20 was a copy of the MiG-31, in fact almost the contrary. I said there was a filiation, that the original idea was re-used as a base. IRL, outside the lab, this translates into : both planes’ layouts are similar if not identical ( although layout might be too grubby a term, fitted for lowly mechanics and industrial designers more than for your highness? ).
What changed most is not even the application of stealth that is so evident that some think it hides the rest. The body is similar, a very linear fuselage ideal for high speed by aiding penetration through air, cockpit perched aft of the air intakes. Chinese engineers wisely separated the engines more as found in Sukhois because this creates an air flow top ( and bottom depending ) that cools them and reduces heat signature. The wing is similar but bigger due to the trailing edge sweeping back to induce radar reflection scattering. This meant a new rear end, with again SU-like extensions which are found on most modern designs, prolonging air flow again and somewhat hiding the thrusters. For those reasons, the trailing longitudinal surfaces on the underside are now away from the body which is a normal corollary. They’re located in opposition to the now dual & canted vertical fins, as necessary for maximum all-aspects stealth. The body is wider, thicker and flatter to incorporate bays.
The air intakes that used to be on either side of the fuselage are still just about there but wider apart which makes the S-duct routes better. The rear half of these however is nearly the same which shows on even outside views of the ACs. The addition of canards replaces the rear horizontal surfaces that disappeared in the trailing edge design. They’re long moment arm canards with an added Chinese spice in their upward angulation which can be guessed by the preference of the image sourcing for relatively level flight ( meaning that the horizontal axis is stable on pics not that it is parallel to the ground ) views. If they do play on the lift as I wonder, that is an additional quality of importance. I have studied decomposed flight stills and there is a strong possibility that this is true. // You’ll be glad to know that it’s not evident and could only be correctly estimated through serious analysis of entire flight videos. // The cockpit sits higher and looks to be pushed aft mostly due to the long top edge going off the intakes. If there was one thing to accredit a link to the MiG 1.44, the 3/4 rear view of the J-20’s allure and cockpit positioning in particular would be it.
Difference with the Slavic beasts : the absence of the equipment dorsal ridge ( now a channel as said ) for either but more importantly the air intakes design choice as location goes -31like. The dual under nose option found on the MiG 1.44 and the Typhoon as well is a horrid idea. When each engine intake is separate, the likelihood of accident goes down. In a bad case scenario, a single volatile ingestion could affect both paths and suppress power entirely. It fits the single engine F-16 mentioned at the beginning but not a dual engine fighter. That re-positioning alone would severe a link between the J-20 and the 1.44. The rear stabilizer section is of similar intention but realized differently while the top fuselage curvatures are not unlike but the canards are much better located on the J-20 as relative to the pilot.
The Chengdu star is not a paper airplane nor a simple prototype. It shows in every detail. It was not copied on one either. Inspired? Heck, sure since all designers work from a body of knowledge common to aviation but the 31 is a sounder less risky design as an inspiration for the working Black Eagle.
What you described in the second part of your post is quite reasonable too, it just does not come into play in a discussion such as this. Of course the aerodynamics are infinitely superior. Of course the fly-by-wire programming must be a masterpiece by comparison. Yes, specifics performance metrics and objective targets for the design are only known to the makers ( and computer ) and users and only correctly measured in the lab ( anechoic chamber / wind tunnel et al. ). No, they’re not needed to judge layout and evaluate filiation, a rather summary process to begin with. Because unless you also claim to have been on the J-20 design team, it's all opinion really, even for you. Put a clown wig and a red nose on a donkey, it’s still an a.s to the discerning observer!
Even without a PhD!
About which, since you chose the haughty superiority holier than thou and twice as certain route ( Now if you are a well trained PhD, I just might put a little bit of credibility in you. thingie ), a word of advice for the little it’s worth : Good luck backing that!
Under such pretension, trolls will hunt every mistake you produce before I hear of or spot them. They’ll be greedy for doctor’s meat?
As the Eagles famously sang : Every refuge has its price.
And yet, no hard feelings! Here's to hoping you for a smoother conversation later, Tay.
P.S. And good luck with the d...egree measuring contest!
Taygibay
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Blue Marlin
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ok, its getting late, night, bm
General Observer
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Really? It's been a while since I've take aerodynamics, but from what I recall, compressible flow revolves around the acoustic mach number, that is a=dP/d(rho), where rho is the change in density in a infinitesimally small boundary. So with an incompressible model which assumes rho to be constant, how would an compressible model fit=> d(rho)=/=0.
Therefore, without the ability to extract an acoustic mach number, one can't use the isentropic flow equations to deduce pressure/temperature changes across a flow, which all depend on acoustic mach number.
Perhaps, I misunderstood your explanation for something else, like Fanno flow or Rayleigh flow? Where the flow characterization work for both models?
Oh I think I get ya. You mean actually assume compressibility of fluids below Mach .3... I thought you meant earlier assuming constant density but using the compressible model of fluids traveling <.3. Anyhow, definitely agreed. The incompressible model is a good assumption that can be used at a certain range, that is all. You use Ansys for your computations?
Kamil_baku
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mostly, 5th generation jets are built based on their engines...
It is not as easy as you think, to change the engines in a 5th generation jet..
neytirilover
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Anyways, a constant density is a good assumption in many cases, but an assumption is an assumption after all, ideally we want to represent physical processes as accurate as possible, which means the fewer assumptions there are, the better.
I don't use Ansys no more, I use OpenFOAM and developed my own solver based on FOAM basic class library.
So you have a PhD? GFY ( good for ... )! And I do believe it might be in science because it is obviously not in behavioural psychology, social studies or Internet. Such claims have no place on a forum. Not only are they not required of standard users because of anonymity but they’d also temper with the equalitarian access raison d’être of the Net. Don’t claim you are so good, just show it!
But I’ll take your word for an instant :
I do not have a PhD in science. There are other things I have though. I have piloted airplanes for instance and while not fighters, not on a computer or gaming console, IRL! I can do mechanics work : fix bikes, cars and beyond machinery in general, weapons and heck electronics & computers. I have built a house and a boat for real! Etc. Whatever you think is the sole domain of excellence you practice is more than balanced by real life abilities and experience on my side. When your designs don’t deliver, people like me make them work anyhow.
And while you can counter this by negating its truth quotient, I’ll immediately return the favour as to your PhD.
QED on Internet claims.
Let’s veer to reality :
I’m not certifying anything nor basing my opinion on mere specific resemblances as say between a Mustang P-51 and a Fighting Falcon because of the inlet. . . although ...
View attachment 280166
Gotta love the Mustang --» GIFT http://www.warbirdheritagefoundation.org/PA_P51_F_0001_W.jpg
I did not say the J-20 was a copy of the MiG-31, in fact almost the contrary. I said there was a filiation, that the original idea was re-used as a base. IRL, outside the lab, this translates into : both planes’ layouts are similar if not identical ( although layout might be too grubby a term, fitted for lowly mechanics and industrial designers more than for your highness? ).
What changed most is not even the application of stealth that is so evident that some think it hides the rest. The body is similar, a very linear fuselage ideal for high speed by aiding penetration through air, cockpit perched aft of the air intakes. Chinese engineers wisely separated the engines more as found in Sukhois because this creates an air flow top ( and bottom depending ) that cools them and reduces heat signature. The wing is similar but bigger due to the trailing edge sweeping back to induce radar reflection scattering. This meant a new rear end, with again SU-like extensions which are found on most modern designs, prolonging air flow again and somewhat hiding the thrusters. For those reasons, the trailing longitudinal surfaces on the underside are now away from the body which is a normal corollary. They’re located in opposition to the now dual & canted vertical fins, as necessary for maximum all-aspects stealth. The body is wider, thicker and flatter to incorporate bays.
The air intakes that used to be on either side of the fuselage are still just about there but wider apart which makes the S-duct routes better. The rear half of these however is nearly the same which shows on even outside views of the ACs. The addition of canards replaces the rear horizontal surfaces that disappeared in the trailing edge design. They’re long moment arm canards with an added Chinese spice in their upward angulation which can be guessed by the preference of the image sourcing for relatively level flight ( meaning that the horizontal axis is stable on pics not that it is parallel to the ground ) views. If they do play on the lift as I wonder, that is an additional quality of importance. I have studied decomposed flight stills and there is a strong possibility that this is true. // You’ll be glad to know that it’s not evident and could only be correctly estimated through serious analysis of entire flight videos. // The cockpit sits higher and looks to be pushed aft mostly due to the long top edge going off the intakes. If there was one thing to accredit a link to the MiG 1.44, the 3/4 rear view of the J-20’s allure and cockpit positioning in particular would be it.
Difference with the Slavic beasts : the absence of the equipment dorsal ridge ( now a channel as said ) for either but more importantly the air intakes design choice as location goes -31like. The dual under nose option found on the MiG 1.44 and the Typhoon as well is a horrid idea. When each engine intake is separate, the likelihood of accident goes down. In a bad case scenario, a single volatile ingestion could affect both paths and suppress power entirely. It fits the single engine F-16 mentioned at the beginning but not a dual engine fighter. That re-positioning alone would severe a link between the J-20 and the 1.44. The rear stabilizer section is of similar intention but realized differently while the top fuselage curvatures are not unlike but the canards are much better located on the J-20 as relative to the pilot.
The Chengdu star is not a paper airplane nor a simple prototype. It shows in every detail. It was not copied on one either. Inspired? Heck, sure since all designers work from a body of knowledge common to aviation but the 31 is a sounder less risky design as an inspiration for the working Black Eagle.
What you described in the second part of your post is quite reasonable too, it just does not come into play in a discussion such as this. Of course the aerodynamics are infinitely superior. Of course the fly-by-wire programming must be a masterpiece by comparison. Yes, specifics performance metrics and objective targets for the design are only known to the makers ( and computer ) and users and only correctly measured in the lab ( anechoic chamber / wind tunnel et al. ). No, they’re not needed to judge layout and evaluate filiation, a rather summary process to begin with. Because unless you also claim to have been on the J-20 design team, it's all opinion really, even for you. Put a clown wig and a red nose on a donkey, it’s still an a.s to the discerning observer!
Even without a PhD!
About which, since you chose the haughty superiority holier than thou and twice as certain route ( Now if you are a well trained PhD, I just might put a little bit of credibility in you. thingie ), a word of advice for the little it’s worth : Good luck backing that!
Under such pretension, trolls will hunt every mistake you produce before I hear of or spot them. They’ll be greedy for doctor’s meat?
As the Eagles famously sang : Every refuge has its price.
And yet, no hard feelings! Here's to hoping you for a smoother conversation later, Tay.
P.S. And good luck with the d...egree measuring contest!
Thank you for your elaboration, I will find time to read it carefully.
j20blackdragon
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The J-20 doesn't look like an evolution of the MiG-31 to me.
The overall stealth airframe looks like it comes from Lockheed Martin.
The canopy is from the F-22 with a small brace added.
The DSI is from the F-35.
The all-moving vertical stabilizers look like F-35.
The location and configuration of the weapon bays look like F-22.
The EOTS and DAS look like F-35.
The engines look like they come from Salut.
The overall canard configuration/planform along with the ventral fins look like MiG 1.44.
Although the large size of the aircraft and the large intakes do make it look like an interceptor, like the MiG-31.
In my opinion, the J-20 doesn't look like a 'copy' of any one specific plane. It's more of a mish-mash of different technologies from all over the world.
The overall stealth airframe looks like it comes from Lockheed Martin.
The canopy is from the F-22 with a small brace added.
The DSI is from the F-35.
The all-moving vertical stabilizers look like F-35.
The location and configuration of the weapon bays look like F-22.
The EOTS and DAS look like F-35.
The engines look like they come from Salut.
The overall canard configuration/planform along with the ventral fins look like MiG 1.44.
Although the large size of the aircraft and the large intakes do make it look like an interceptor, like the MiG-31.
In my opinion, the J-20 doesn't look like a 'copy' of any one specific plane. It's more of a mish-mash of different technologies from all over the world.
j20blackdragon
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And now a quick summary of the J-20's engine mystery...
The standard AL-31FN looks like this.
Why are the #2016 and #2017 nozzles black, both inside and out?
Why is the silver coating applied over the black?
Why is the new silver nozzle paint scheme different from the old one?
The standard AL-31FN looks like this.
Why are the #2016 and #2017 nozzles black, both inside and out?
Why is the silver coating applied over the black?
Why is the new silver nozzle paint scheme different from the old one?
General Observer
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And now a quick summary of the J-20's engine mystery...
The standard AL-31FN looks like this.
Why are the #2016 and #2017 nozzles black, both inside and out?
Why is the silver coating applied over the black?
Why is the new silver nozzle paint scheme different from the old one?
My assumption,
The silver is just special paint to reduce RCS. Wtih that being said, they probably installed a new engine, which works at a higher temperature at the nozzle, so the design team may have had to put in some time to effectively apply the new coating at high operating temperatures.
Here's a useful equation for determining Power of reflective wave:
Pr = Ps · G · σ/(4 · π · R1^2 )
Pr = reflected power [W]
σ = radar cross section [m2]
R1 = range, distance antenna - aim [m]
Assuming the the entire airframe is painted with RAM reducing material, why not paint the nozzles too? Besides, it's the most exposed area of the aircraft to radar signatures anyhow.
General Observer
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By the way, isentropic temperature ratio for a nozzle:
T0/Te = 1+(Gamma-1)/2*Me^2
T0 = Stagnation temperature
Te = Nozzle exit static temperature
Gamma = 1.4 for air
Me = Mach no. at nozzle exit
If one assumes that the aircraft has a higher thrust, we can increase the exit Mach number, where M = V/sqrt(Gamma*R*T) is higher.
V = Velocity
R = gas constant which is about 8.31J/(Kmol)
T = Static Temperature
Hence, stagnation temperature of the nozzle must be higher. Note, we consider STAGNATION temperature, because it is essentially the TOTAL temperature of the isentropic FLOW, where if the entire flow were to be brought to rest, the temperature. Static temperature only considers temperatures of random motion or excitement* of particles at a certain point, and not the entire flow, hence the term static*.
So there you go, my assumption of why the nozzles are painted back to silver.
Note: We are considering a non-ideal turbojet cycle. Nozzle flow would still be isentropic.
A typical Temperature-Entropy.
Entropy is obtained by combining the 1st and 2nd law of thermodynamics:
T0/Te = 1+(Gamma-1)/2*Me^2
T0 = Stagnation temperature
Te = Nozzle exit static temperature
Gamma = 1.4 for air
Me = Mach no. at nozzle exit
If one assumes that the aircraft has a higher thrust, we can increase the exit Mach number, where M = V/sqrt(Gamma*R*T) is higher.
V = Velocity
R = gas constant which is about 8.31J/(Kmol)
T = Static Temperature
Hence, stagnation temperature of the nozzle must be higher. Note, we consider STAGNATION temperature, because it is essentially the TOTAL temperature of the isentropic FLOW, where if the entire flow were to be brought to rest, the temperature. Static temperature only considers temperatures of random motion or excitement* of particles at a certain point, and not the entire flow, hence the term static*.
So there you go, my assumption of why the nozzles are painted back to silver.
Note: We are considering a non-ideal turbojet cycle. Nozzle flow would still be isentropic.
A typical Temperature-Entropy.
Entropy is obtained by combining the 1st and 2nd law of thermodynamics:
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