Mar 18, 2019 20:43
5 yrs ago
1 viewer *
English term
a forward Mach number
English to French
Tech/Engineering
Patents
(in a patent) METHOD OF DETECTING COKING IN A COMBUSTION CHAMBER FUEL INJECTOR
the cruise conditions may correspond to: a forward Mach number of 0.8; a pressure of 23000 Pa; and a temperature of -55 deg C.
Proposed translations
(French)
| 3 | une vitesse avant de Mach 0,8 |
florence metzger
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| 5 -1 | Un nombre de Mach critique |
Samuel Clarisse
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References
| NASA and propeller blades ... |
Daryo
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Proposed translations
4 mins
Selected
une vitesse avant de Mach 0,8
une suggestion...
Peer comment(s):
| agree |
Daryo
2 days 2 hrs
|
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merci
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| disagree |
Samuel Clarisse
: We have a technical term for this in French= Mach critique
2 days 2 hrs
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4 KudoZ points awarded for this answer.
Comment: "merci!"
-1
1 day 15 hrs
Samuel Clarisse
France
France
Native in French
France
Always keeping in mind the audience
Native in: French (Variants: Standard-France, Swiss, Canadian, Belgian, Luxembourgish) 
Works in: English to French, Spanish to French
Related KudoZ points
:
68
Un nombre de Mach critique
Le mach de cet appareil correspond en fait ici à 80 % de la vitesse du son.
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Note added at 2 days 4 hrs (2019-03-21 00:47:16 GMT)
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One last thing, it's not because it's written "critical" in French that this is a bad thing...
It is indeed a factual speed.
Sometimes, specific terms can be weird even for a native like me.
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Note added at 2 days 4 hrs (2019-03-21 00:47:16 GMT)
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One last thing, it's not because it's written "critical" in French that this is a bad thing...
It is indeed a factual speed.
Sometimes, specific terms can be weird even for a native like me.
Peer comment(s):
| disagree |
Daryo
: can't see where do you see any notion of "critical" speed in the ST - all I can see is a simple factual "speed" as measured in the direction of movement. Nothing to imply that above that speed gremlins will be unleashed...
11 hrs
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Because maybe not everything is literal in translation... duh. Forward mach= the speed at which the cruise will reach the speed of sound (Mach), in this case at 80% of Mach= in other words, called "Mach critique" in French.
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Reference comments
2 days 23 hrs
Reference:
NASA and propeller blades ...
An investigation of the characteristics of a full-scale supersonic type propeller has been made in the Langley 16-foot transonic tunnel with the 6000-horsepower propeller dynamometer. The tests covered a range of blade angles from 20.20 to 60.20 at forward Mach numbers up to 0.96.
The results showed that envelope efficiency at an advance ratio of 2.8 decreased from 86 percent to 72 percent when the forward Mach number was increased from 0.70 to 0.96. A comparison of the experimental results with calculated results showed that maximum propeller efficiency' can be calculated with good accuracy by using ordinary subsonic strip theory when the blade-section speeds are supersonic. The investigation also showed favorable power-absorption properties of the supersonic type propeller at high speeds.
...
https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/199300...
from how "forward Mach numbers" was used in this text, it's pretty clear that it's simply the (forward) speed of the airplane in relation to the surrounding air mass.
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Note added at 2 days 23 hrs (2019-03-21 20:07:49 GMT)
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also:
http://naca.central.cranfield.ac.uk/reports/1954/naca-report...
The results showed that envelope efficiency at an advance ratio of 2.8 decreased from 86 percent to 72 percent when the forward Mach number was increased from 0.70 to 0.96. A comparison of the experimental results with calculated results showed that maximum propeller efficiency' can be calculated with good accuracy by using ordinary subsonic strip theory when the blade-section speeds are supersonic. The investigation also showed favorable power-absorption properties of the supersonic type propeller at high speeds.
...
https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/199300...
from how "forward Mach numbers" was used in this text, it's pretty clear that it's simply the (forward) speed of the airplane in relation to the surrounding air mass.
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Note added at 2 days 23 hrs (2019-03-21 20:07:49 GMT)
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also:
http://naca.central.cranfield.ac.uk/reports/1954/naca-report...
Discussion
BTW "Most commercial jetliners cruise somewhere between 30,000 and 45,000 feet above mean sea level. " i.e. between 9.1 and 13.7 km above sea level so 10.9 km could be seen as a kind of "representative average".
https://www.mide.com/pages/air-pressure-at-altitude-calculat...
https://www.geol.umd.edu/~jmerck/geol100/lectures/33.html
https://www.physlink.com/Education/AskExperts/ae610.cfm
A long-winded way to confirm that it's about bog standard parameters for cruising, nowhere near pushing an airplane to its limits - and "nombre de Mach critique" IS A LIMIT:
"En aérodynamique, le nombre de Mach critique d'un aéronef est le nombre de Mach le plus bas à partir duquel l'écoulement de l'air atteint la vitesse du son en un point au moins de l'appareil"
Besides the fact the ST is simply stating a speed without any hint of that speed being special in any way, if you read the article, you'll find that passing this limit can lead to lost of control - what sane pilot would be cruising at a speed that is at the limit of losing him control over the airplane?