Radial vs in-line engines

[Crumpp]

Meredith effect on the Mustang.



Only the RAE bought into the thrust production theory. Both the NACA and the RLM disagreed.

Understand that of the three, it was the RAE that was trailing in aerodynamics. The British engines were good, probably the best of all the combatants but their aerodynamic sciences was behind the other major combatants. That is why you have RAE claims for things like Mach .98 dives out of the Spitfire that later get retracted as they discovered the static port placement was completely wrong for any degree of accurate speed measurement in the transonic realm.

[Sternjaeger II]

Originally Posted by Crumpp

Meredith effect on the Mustang.



Only the RAE bought into the thrust production theory. Both the NACA and the RLM disagreed.

Understand that of the three, it was the RAE that was trailing in aerodynamics. The British engines were good, probably the best of all the combatants but their aerodynamic sciences was behind the other major combatants. That is why you have RAE claims for things like Mach .98 dives out of the Spitfire that later get retracted as they discovered the static port placement was completely wrong for any degree of accurate speed measurement in the transonic realm.

I'm not discussing the quality of British aerodynamic research, I'm just saying that the Meredith effect is not a made up thing, and the Mustang is probably the design that benefits most from it.
As you know, they took a great deal of care in the design of the radiator system on the P-51: the radiator intake is detached from the fuselage to avoid turbulent airflow from the fuselage, and the radiator exhaust port could be opened/shut automatically so that it wouldn't bother the pilot. It surely was an efficient and revolutionary system, which allowed for a better performance with a very low drag coefficient (if compared to others) because of its design.

Its clever aerodynamics, light weight and reliability made for a superb system compared to the conventional turbo supercharged radials.

[Sternjaeger II]

uh, I forgot to ask Crumpp, can you please point me to the source of that page? Sounds like an interesting read.

[Crumpp]

It is from The American Institute of Aeronautics and Astronautics (AIAA) library database and is from a presentation at an engineering conference. It is from the only modern design analysis on the P-51 Mustang and was done with an eye on improvements for one of the Reno racers. That being said, I got my copy directly from the author and can give you one if you like.

[Sternjaeger II]

Originally Posted by Crumpp

It is from The American Institute of Aeronautics and Astronautics (AIAA) library database and is from a presentation at an engineering conference. It is from the only modern design analysis on the P-51 Mustang and was done with an eye on improvements for one of the Reno racers. That being said, I got my copy directly from the author and can give you one if you like.

yes please!

[Crumpp]

Certainly. Send me a PM with your email and I will get you a copy.

You do realize it contradicts almost everything you posted in your last post about the P51.

Particularly:

they took a great deal of care in the design of the radiator system on the P-51

It surely was an efficient and revolutionary system

Supersonic aerodynamics and compressibility were still pretty new and not well understood at the time the P51's radiator was designed. Therefore, they did not correctly slope the intake for normal shock formation. The slope was too steep and separation occurred.

That means high drag. This is confirmed in both later NACA wind tunnel testing and RAE flight testing. It is highly unlikely the P-51 series achieved any of its designers goals of laminar flow or Meredith effect. Interesting enough, the B-24 with the Davis wing in a complete accident of fate, did achieve laminar flow!

[Sternjaeger II]

Originally Posted by Crumpp

Certainly. Send me a PM with your email and I will get you a copy.

You do realize it contradicts almost everything you posted in your last post about the P51.

Particularly:

Supersonic aerodynamics and compressibility were still pretty new and not well understood at the time the P51's radiator was designed. Therefore, they did not correctly slope the intake for normal shock formation. The slope was too steep and separation occurred.

That means high drag. This is confirmed in both later NACA wind tunnel testing and RAE flight testing. It is highly unlikely the P-51 series achieved any of its designers goals of laminar flow or Meredith effect. Interesting enough, the B-24 with the Davis wing in a complete accident of fate, did achieve laminar flow!

Hang on, why you're taking supersonic aerodynamics and compressibility into the equation? No plane of the era was designed to operate at such speeds.

My point was that if compared to other radiators of the era, the Mustang one was by far the more aerodynamically efficient, and surely superior to radial engines.

So you're now telling me that the Mustang wing is not a laminar design?