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Meredith Effect - Is this modeled?


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No idea if its modeled and never heard that name used for the effect

 

I came across it before, when reading about the work done to reduce induced drag from both radiators and radial engines.

 

I seem to remember the NACA cowls used on radials employed a similar phenomena to reduce the drag on radials, which were a revelation at the time.

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This effect is not specially modelled... it appearas naturally from the radiator model.

 

The cooler can not only reduce it's drag for zero but under certain conditions can add thrust. But the conditions are - full power, max speed and closed scoop.

Ніщо так сильно не ранить мозок, як уламки скла від розбитих рожевих окулярів

There is nothing so hurtful for the brain as splinters of broken rose-coloured spectacles.

Ничто так сильно не ранит мозг, как осколки стекла от разбитых розовых очков (С) Me

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  • 3 years later...
This effect is not specially modelled... it appearas naturally from the radiator model.

 

The cooler can not only reduce it's drag for zero but under certain conditions can add thrust. But the conditions are - full power, max speed and closed scoop.

 

P-51D_15342_Shutter_Calibrations.thumb.png.60b9ac2b1be87f2a3ba652ada85fd059.png

What do you make of this? In P-51 ingame I reach my top speed with the coolant and oil flaps closed, but that doesn't follow the chart.

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Tested it aswell, temps are match, but speed not.

In game = more you close coolant shutter higher the speed gets.


Edited by grafspee

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  • 6 months later...
  • 7 months later...

If the effect is modeled, why does DCS then not follow the chart I posted above?

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1 hour ago, Magic Zach said:

If the effect is modeled, why does DCS then not follow the chart I posted above?

I don't see any reference in the charts, but anyway, did you match ISA conditions and everything? Indicated airspeed usually doesn't match charts at all unless everything is in the right atmospheric conditions.

 

S!

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8 minutes ago, reece146 said:

Mustang cooling model is b0rked.

Agree

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  • 4 weeks later...
On 6/22/2021 at 1:38 PM, Ala13_ManOWar said:

I don't see any reference in the charts, but anyway, did you match ISA conditions and everything? Indicated airspeed usually doesn't match charts at all unless everything is in the right atmospheric conditions.

 

S!

I have matched the aircraft conditions as listed on the chart ("clean" is with empty bomb racks).  2700RPM, 46".  And while not written on this paper, the aircraft weight was 9760lbs, which I replicated as closely as I could within DCS.  However, I'm unable to get the weight of the bomb racks (though if they're like the A8's bomb racks, in DCS they're weightless).  Weather conditions to no crosswinds, 29.92Hg, 15C.

The chart lists the coolant shutter's recorded position at 0%, 30.6%, 63.9%, and 100% open.  In order, the temperature for each position from the chart is: 130C, 99C, 80C, 72C.
Within DCS, at the same shutter positions, our coolant temperatures are: 116C, 99C, 88C, 84C.  The temperature range is significantly smaller, top and bottom.

The chart lists the oil shutter's recorded position at 0%, 36.1%, 72.2%, and 100% open.  In order, the temperature for each position from the chart is: 90C, 60C, 50C, 50C.
Within DCS, at the same shutter positions, our oil temperatures are: 90C, 65C, 58C, 56C.  Below 90C, the oil temperature is roughly 6C over the line it should follow.

Speeds are a bit harder, since in the chart they do not list what the setting for the momentarily ignored shutter is.  So, I'm going to assume that while the coolant shutter vs speed were recorded, the oil shutter was left in auto.  And while the oil shutter vs speed was recorded, the coolant shutter was left in auto.
In the chart, for the coolant shutter at 0, 30.6%, 63.9% and 100% open, the IAS speeds (reminder, at 1500ft) recorded in order are: 295MPH, 303.5MPH, 302.5MPH, 293.5MPH.
Within DCS, at the same shutter positions, our recorded speeds will be: 316MPH, 313MPH, 308MPH, 299MPH.  Of significant note here, is that not only the speeds don't match...but if graphed, it's not concave down.  As the shutter is closed more and more, the speed increases more and more as well.  This isn't a reflection of the behavior on the chart.

In the chart, for the oil shutter at 0, 36.1%, 72.2%, and 100% open, the IAS speeds recorded in order are: 301MPH, 299MPH, 296MPH, 294MPH.
Within DCS, at the same shutter positions, our recorded speeds will be: 317.6MPH, 313MPH, 313MPH, 312MPH.  It's evident that while the speed is fast, but also notice that the net drag from the shutter seemingly flattens out once the oil shutter is 1/3 open.


Edited by Magic Zach
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