On the Meredith Effect

[wuzak]

Looking at the P-40F

View attachment 573550

Is that the XP-40F?

Looks like the XP-60, but with P-40 wings and undercarriage.

 

[Shortround6]

It is an experimental P-40F testing a different radiator setup (obviously) results seem to be unknown/not published but since they didn't change the production versions (or the Ls) any possible gains must have been minimal.

edit. The plane pictured was the 3rd production P-40F. It is supposed to have been changed back to normal configuration, which should lay to rest any speculation on CUrtiss selling North American any good information on radiator design with the P-46 data/information back in 1940. I mean if CUrtiss is still fumbling about in 1942 trying to do better than the P-40 "chin" radiator set up how good could their information have been in 1940?

 

[Zipper730]

What kind of cowling would you need for a radial to make use of the Meredith effect to good degree?

 

[swampyankee]

What kind of cowling would you need for a radial to make use of the Meredith effect to good degree?

A well-designed NACA cowling.

 

[Shortround6]

A well-designed NACA cowling.

Very, very, very well designed

 

[MIflyer]

Very, very, very well designed

And preferably with a jet engine - or a Power Recovery Turbine - in the back of it.

 

[Zipper730]

How comes that basic shape seems good?

It'd look good if it had a splitter...

 

[pbehn]

It'd look good if it had a splitter...

Hawkers experimented with a set up like that for the Typhoon/Tornado but stuck with the chin radiator.

 

[tomo pauk]

It'd look good if it had a splitter...

Disagree...

 

[Zipper730]

Very, very, very well designed

It would require an elaborate bell-mouth shape. The problem would be ensuring adequate cooling while keeping drag low.

Disagree...

You might very well be right.

 

[wuzak]

Hawkers experimented with a set up like that for the Typhoon/Tornado but stuck with the chin radiator.

Tornado was originally designed that way, but quickly changed to the chin radiator.

I've seen it that the Typhoon was always to have a chine radiator and also that the chin radiator was adopted after initial flights of the Tornado.

The Typhoon's first flight was several months after the Tornado's, which makes the latter possible.

The former is also possible, but I struggle to believe that Hawker would design two nearly identical airframes with two different cooling systems.

 

[Shortround6]

It would require an elaborate bell-mouth shape. The problem would be ensuring adequate cooling while keeping drag low.

In actuality many/most of the WW II radial engine fighters had more cooling intake area than they needed for high speed flight. The problem/s were insuring adequate air flow on the ground or in a long climb.

Problems in getting the Meredith effect to work on air cooled engines are;
1. not slowing the airflow down too much as it goes through the cowl/baffles/fins. Some slow down is beneficial as the lower speed airstream will have lower drag going though the labyrinth of baffles.
2, not introducing too much turbulence as it does so.
3. having adequate space behind the cylinders to smooth the airflow and compress it as it approaches the exit/s without introducing any(much) turbulence.
4 having outlets of proper size to get the exit speed of the cooling air up to the required speed.
5, having the cooling air outlets somewhat aligned with the direction of travel without creating drag.
6. having to deal with real world problems. Some radial engines had parts of the cowl flaps wired or screwed shut on later versions to keep the engine from dumping oil on the windscreen which means different length paths for the air to get out which means, without very careful baffling/testing different speeds for the air (turbulence).

 

[pbehn]

Tornado was originally designed that way, but quickly changed to the chin radiator.

I've seen it that the Typhoon was always to have a chine radiator and also that the chin radiator was adopted after initial flights of the Tornado.

The Typhoon's first flight was several months after the Tornado's, which makes the latter possible.

The former is also possible, but I struggle to believe that Hawker would design two nearly identical airframes with two different cooling systems.

Maybe not exclusively about aerodynamics it takes the place where a bomb or tank goes.

 

[Zipper730]

In actuality many/most of the WW II radial engine fighters had more cooling intake area than they needed for high speed flight.

Where the airflow into them is nice and high.

The problem/s were insuring adequate air flow on the ground or in a long climb.

How would one have gotten around that problem?

Problems in getting the Meredith effect to work on air cooled engines are;
1. not slowing the airflow down too much as it goes through the cowl/baffles/fins. Some slow down is beneficial as the lower speed airstream will have lower drag going though the labyrinth of baffles.

I'm guessing slowing it down too much would mean it wouldn't have enough speed to flow over the cylinders effectively, and carry away the heat in the process?

2, not introducing too much turbulence as it does so.

How would one have avoided this problem?

3. having adequate space behind the cylinders to smooth the airflow and compress it as it approaches the exit/s without introducing any(much) turbulence.
4 having outlets of proper size to get the exit speed of the cooling air up to the required speed.

So you'd want the space behind the cylinders to be of convergent design, thus allow the airflow to accelerate, but long enough to ensure the airflow smooths out after flowing over the cylinders, while not being too long, as to produce losses?

5, having the cooling air outlets somewhat aligned with the direction of travel without creating drag.

The cooling-air outlets are located in the rear part off the cowling, behind the cylinders, correct?

6. having to deal with real world problems.

I'm curious about the gill arrangement seen in the Tempest Mk.II. How hard that kind of set-up to work? It looked very aerodynamic, as it didn't protrude into the wind like general cowl-flaps.

 

[wuzak]

How would one have avoided this problem?.

Use a liquid cooled engine.

I'm curious about the gill arrangement seen in the Tempest Mk.II. How hard that kind of set-up to work? It looked very aerodynamic, as it didn't protrude into the wind like general cowl-flaps.

Inspired by captured Fw 190As.

 

[Shortround6]

You have exhaust thrust and perhaps the rush of the exhaust pulls air out of the engine compartment but that is not Meredith effect.
Perhaps the exhaust mixes with the air leaving the engine compartment and the resulting mass/velocity of the combined stream results in higher thrust than the exhast alone. I don't know, but it is still not Meredith effect.
To get Meredith effect the velocity of the air leaving through the "gill" has to be higher than the airspeed of the aircraft. since the air is also leaving at an angle to the line of flight you have to figure the vector to get the actual thrust.

tempest engine

trying to get a smooth airflow through that mess is not easy.

Please note I am not saying they didn't do a good job or didn't do careful testing and engineering but the chances of the cooling air leaving the plane at a higher speed than it went in the front of the cowing seem pretty slim. I could be wrong.

 

[Bottlehead]

TP de Paravicini. Or Thomas Pitt de Paravicini.

His name was indeed Thomas Pitt de Paravicini.
But for patents the name filed is just TP de Paravicini.
Another pic from another patent

TP de Paravicini. Or Thomas Pitt de Paravicini.

 

[Bottlehead]

I realize that, because the powerplant used in it was very similar to the Rolls Royce Goshawk, which was also an evaporatively cooled engine. And look at how successful that was. I'm not sure, but did the Germans try this on other aircraft, other than the He100 fighter? The British used this on a number of flying machines built, and was also proposed for such designs as RJ Mitchell's design for the Type 232, his contribution being a gull winged four engine patrol flying boat of the Sundeland class. In this case, the intake for the condensers being the entire leading edge of the wings.

My thought is if something similar to the belly scoop on the P51(as well as the MB5 and the Australian Mustang lookalike, but not scoop shaped, but one with an equal amount of area, could be doable.

I'm not sure if the Germans were even aware of the Meredith Effect, even though at the time of the 119m they might've had more than a few Mustangs brought down that they might have studied. I dunno, but if they weren't(and I have yet to learn that they did know of it, if only by dint of studying the Mustand cooling system in toto), wouldn't something like this be useful now, given advancement in materials technology since the War? I'm speaking as as mechanic who has been doing too much thinking. so perhaps I'm sorely mistaken in my assumptions. Still, it might be something worth consideration, 'cause an engine that can dissipate engine waste heat at a higher rater due to higher temp/ambient temp differential.

This is what I get for being the kind of person who thinks a few miles outside the litter pan.

Original patentView attachment 574159

I realize that, because the powerplant used in it was very similar to the Rolls Royce Goshawk, which was also an evaporatively cooled engine. And look at how successful that was. I'm not sure, but did the Germans try this on other aircraft, other than the He100 fighter? The British used this on a number of flying machines built, and was also proposed for such designs as RJ Mitchell's design for the Type 232, his contribution being a gull winged four engine patrol flying boat of the Sundeland class. In this case, the intake for the condensers being the entire leading edge of the wings.

My thought is if something similar to the belly scoop on the P51(as well as the MB5 and the Australian Mustang lookalike, but not scoop shaped, but one with an equal amount of area, could be doable.

I'm not sure if the Germans were even aware of the Meredith Effect, even though at the time of the 119m they might've had more than a few Mustangs brought down that they might have studied. I dunno, but if they weren't(and I have yet to learn that they did know of it, if only by dint of studying the Mustand cooling system in toto), wouldn't something like this be useful now, given advancement in materials technology since the War? I'm speaking as as mechanic who has been doing too much thinking. so perhaps I'm sorely mistaken in my assumptions. Still, it might be something worth consideration, 'cause an engine that can dissipate engine waste heat at a higher rater due to higher temp/ambient temp differential.

This is what I get for being the kind of person who thinks a few miles outside the litter pan.

Patent filed 1936 by TP de Paravicini. Mustang is similar but later. So used this basic patent.

 

[Bottlehead]

His name was indeed Thomas Pitt de Paravicini.
But for patents the name filed is just TP de Paravicini.
Another pic from another patent

Where does the bold in your post come from with regard to me? The Meredith effect is quite easy to explain much harder to do effectively. The Spitfire used it but not very well. The inlet was on the wing surface and had problems with the boundary layer, the outlet was also poor. Despite this Supermarine kept it as it was, even on the successors to the Spitfire. Hawkers tried a cooling system with the inlet under the fuselage on the Typhoon/Tempest but reverted to the chin type, it isn't easy to change things about once a design is made.

The wing inlets that TP de Paravicini showed in several
Patents was not executed because the wing designers did not want to redesign the structure to accommodate the flow.
Hence the underbelly or chin cowled chamber.

the Math was well understood by TP de P because Rolls Royce valued his mathematical skills.
He came under Roweledge and Mellor.

 

[mvdmitri]

Very good article on Meredith jet effect calculation for high altitude piston propeller aircrafts:

http://www.arpnjournals.org/jeas/research_papers/rp_2016/jeas_0316_3840.pdf

http://www.arpnjournals.org/jeas/research_papers/rp_2016/jeas_0416_3963.pdf

http://www.arpnjournals.org/jeas/research_papers/rp_2016/jeas_0416_3979.pdf

http://www.arpnjournals.org/jeas/research_papers/rp_2016/jeas_0516_4164.pdf

http://www.arpnjournals.org/jeas/research_papers/rp_2017/jeas_0417_5885.pdf

Aerodynamics of heat exchangers for high-altitude aircraft
https://ntrs.nasa.gov/api/citations/19960033266/downloads/19960033266.pdf

Meredith effect also was calculated for a steam condenser-radiator of a steam turbine propeller aircraft:
https://digital.library.unt.edu/ark:/67531/metadc58164/m2/1/high_res_d/19930085809.pdf