Meredith Effect - Is this modeled?

[Enduro14]

1 minute ago, Yo-Yo said:

Meredith is not a myth, the effect is very common, just a ram-jet. It can not give a significant thrust, though, but can reduce cooling losses. For sure, it's a matter of high speed, where the air passage area can be reduced significantly forming a nozzle to use added enthalpy.

Yes that is my meaning, "myth" as in it produces so much thrust it increases top speed such and such......, lots of Folks in the ww2 community seem to think its a Booster of Thrust so to speak.  Heck even a Airshow pilot I saw on youtube and some documentaries have even stated it produced so much thrust it overcame any and all drag.  So Find it always interesting to see the discussions on it.  I always learn when you Post Yo-Yo,  thanks.

[OutOnTheOP]

57 minutes ago, NineLine said:

You should be able to delete your own posts now, editing your own posts has always been allowed and I don't know what you mean about 10 minutes to save. 

 
I meant what I said: that I had to click "submit", then wait almost 10 minutes before the post would complete.  It did not appear to be linked to the internet connectivity on my side, as I had no issues at that time with high-data-throughput tasks like streaming video at the exact same time that the ED forum was taking so long to complete the post.  Perhaps your server was undergoing maintenance

[scoobie]

(Off-topic)

9 hours ago, OutOnTheOP said:

I had to click "submit", then wait almost 10 minutes before the post would complete

So it does eventually complete! Good to know!
If you keep getting this issue (then it's probably the same thing as on my end), you can "test" your post by clicking "Preview" - if the preview shows nothing (whitespace), don't click "Submit Reply", but press F5 instead (refresh page in the browser). Your post is now gone, but don't worry. Click "Reply to this topic" again and your text will reappear. This time "Submit Reply" should work immediately.
Basically whenever "Preview" does actually show your post, you're good to click "Submit Reply". Otherwise F5 etc.

I don't know why this happens.

 

Edited October 5, 2021 by scoobie

[NineLine]

9 hours ago, OutOnTheOP said:

 
I meant what I said: that I had to click "submit", then wait almost 10 minutes before the post would complete.  It did not appear to be linked to the internet connectivity on my side, as I had no issues at that time with high-data-throughput tasks like streaming video at the exact same time that the ED forum was taking so long to complete the post.  Perhaps your server was undergoing maintenance

No idea, I have never seen such an issue, and first I have heard of it, will ask our IT fellow.

[Magic Zach]

On 10/2/2021 at 2:33 AM, Yo-Yo said:

The drag is not minimized at the certain coolant shutter position. The fundamental dependance is monotone. The modal character of speed curve vs coolant shutter position is due to the common airflow pass for engine cooler and aftercooler radiators. As the shutter is closed, the drag is minimal (or even slightly negative) but the air charge temperature rises significantly decreasing engine power.

So you are saying that while the shutter closes, the aftercoolant temperature rises, rising the fuel/air mix temperature and decreasing engine power.  This clicks.
However, we apparenlty don't see this loss in BHP within the DCS P-51D.

Quote

The last factor is the most uncertain regardles references to fine tune the whole system (prop thrust, exhaust thrust and radiators drag), because they are cross-dependant.

So, the primary source cannot be followed because it's unreliable?  While the term "air charge" was new to me, I believe that the idea of cooling the air and/or mixture is universal virtue of all our engines, the P-47 notoriously so with the intercooler.  I can't see what permits this BHP-loss phenomenon to be ommitted from our Mustang.  We have a primary source, and while more would be ideal, it is better than nothing.  The idea of not implementing features because some but not all possible source exists isn't doing DCS module fidelity any favors.  One source is better than none, and I believe it's better to act on it than ignoring such a feature for a module entirely.

I need to also rehash some things.  In my prior charts, I made a critical mistake.  I misread the original source and thought 44-15342's tested shutter altitude was at 5,000ft.  It is not.  It is at 15,000ft, and I have since redone all my DCS mimic trials.  It now also makes sense as to why 46" was chosen as the throttle setting, because at that altitude and density, I can only attain 44-46" of manifold pressure myself.  Also, I have redone them all with the momentarily-ignored shutter full 100% open, instead of left in auto as before.
Regardless, here is the redone charts
 

Of note:
-The speeds attained are really not that different.  At most, it is a 3mph difference between 44-15342 and DCS.  It's not that significant in my opinion, but others may have a different take on it.
-Of major note, the temperature range is still greatly, if not more reduced.  While 44-15342's has the ability to influence its oil temperature anywhere from 90C to 48C (a 42C range), our DCS Mustang can only change its temperature from 76C to 51C (a 25C range).  This is nearly half of the capability of 44-15342.
 

Of note:
-The coolant temperature vs shutter position lines are incredibly close between the real Mustang and ours in DCS.  Close enough I'd say it's rather accurate!
-The speed benefits still do not stop their linear progression with the DCS Mustang, and this permits the DCS P-51 to attain rather fast speeds with the shutter fully closed.  The DCS speed line doesn't follow anywhere near the same shape as with the real Mustang.  This is (as talked about above) possibly due to the loss of BHP not being modeled within DCS.

Replay tracks provided, created in the new DCS 2.7.7

(P.S. Why is our DCS P-51's oil thermostatically controlled to maintain 85C oil temperature when attainable, 5C on the hot side of the green?  What was the source for this decision?  The primary source above was attempting to set the control to 70C oil, at the bottom end of the green on the gauge.  And likewise 107C for the coolant.  Even within ED's own P-51 English Manual, it lists 70-80C as the desired oil operating temperature)
 

MUSTANG SHUTTER TRIALS.zip

Edited October 23, 2021 by Magic Zach
oil thermostat questions

[Magic Zach]

@Yo-Yo Hello?  Been 10 days

[NineLine]

What would you like him to answer further from what he has already answered? He is a very VERY busy man, is is responsible for many FMs in and in development. What else do you need to know? Regardless of new tests, it seems he answered most if not all the questions. It seems that the effect is not a wonder mechanism, nor is it 100% predictable/consistent. 

[Magic Zach]

13 hours ago, NineLine said:

What would you like him to answer further from what he has already answered?...What else do you need to know? Regardless of new tests, it seems he answered most if not all the questions.

The questions that have been left unanswered.  Previously, his answers have brought up new ones.  There is still a performance error and the goal is to try to determine what is the reason or cause.  It was explained in Yo-Yo's October 2nd post that the performance loss was due to air charge temperature increasing, and the loss of BHP that slowed the Mustang down again as the shutter closed completely and the aftercoolant and coolant temperatures rose.
And regarding the applicability of the data we have, even if singular sources might not be optimum at all, only have one I don't believe warrants not modeling the result, and ignoring it completely.
Additionally the temperature range for the oil still falls short on both ends, it can't get as hot, or as cold.  By a very large margin
And also, why is the oil temperature in our DCS P-51 thermostatically set for 85C, and not 70 or 75C?  Our oil is themostatically set to be hot, and above the prescribed limits.
This was all mentioned in more detail above in my last post.

Edited November 4, 2021 by Magic Zach

[NineLine]

Honestly I dont think its worth talking about until the new cooling system is in place. Many of your questions focus on that. 

I think you should let it go for now and retest when the new system is added, then see if other questions still remain.

Thanks.

[Yo-Yo]

The oil thermostat adjusted exactly as the manual directed.

[grafspee]

5 hours ago, Yo-Yo said:

The oil thermostat adjusted exactly as the manual directed.

Maintenance manual?

[Yo-Yo]

5 hours ago, grafspee said:

Maintenance manual?

Yes.