with <linearly> variable thickness blades

alexeru653280

Senior Member
Iran
Is use of "linearly " in the following sentences correct grammatically and conceptually? If it is not , kindly suggest ways to make it clearer.

They experimentally investigated the turbines with linearly variable thickness blades.
explanations:

Thickness of the blades increase from hub to tip but cord length of blades is constant from hub to tip.

My means regarding to "linearly" is the following figure (please see the figure)

Blade geometry3.jpeg



This is non-linearly:

Capture.PNG
 
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  • Franco-filly

    Senior Member
    English - Southern England
    Perhaps "tapered blades"? or "blades whose thickness and width taper [or gradually increase] from hub to nib [or along their length]."
    I feel the word "variable" gives the impression of the thickness "varying" in different areas along the length rather than progressively increasing from the hub to the tip.
     

    manfy

    Senior Member
    German - Austria
    Hmmm, no, sorry! That doesn't work.
    "Linearly variable thickness blades", from a purely grammatical perspective, must be interpreted as 'thickness blades' that are linearly variable. :eek: So, that combination of adverb, adjective, nouns doesn't work grammatically.
    Besides, linear variability of thickness would also be possible with convex and concave blades as seen in the bottom picture, isn't it?

    As a non-specialist in turbine design, I'd call the the edges of the top blade "straight" (as opposed to the curved cross-section of convex/concave blades).
    Are you trying to express that the geometric shape of the cross-section was fixed except for its thickness?
     

    Egmont

    Senior Member
    English - U.S.
    The shape in the first figure is usually described as a linear taper.

    (By the way, the word you want is chord, not cord. They sound the same. but they are different words with different meanings.)
     

    alexeru653280

    Senior Member
    Iran
    Hmmm, no, sorry! That doesn't work.
    "Linearly variable thickness blades", from a purely grammatical perspective, must be interpreted as 'thickness blades' that are linearly variable. :eek: So, that combination of adverb, adjective, nouns doesn't work grammatically.
    Besides, linear variability of thickness would also be possible with convex and concave blades as seen in the bottom picture, isn't it?

    As a non-specialist in turbine design, I'd call the the edges of the top blade "straight" (as opposed to the curved cross-section of convex/concave blades).
    Are you trying to express that the geometric shape of the cross-section was fixed except for its thickness?
    Besides, linear variability of thickness would also be possible with convex and concave blades as seen in the bottom picture, isn't it?
    No No, the blades is as follows:



    I am trying to express geometric shape of blade in terms of the thickness along the height of blade.
     

    alexeru653280

    Senior Member
    Iran
    Sorry, i had a problem in typing!

    Besides, linear variability of thickness would also be possible with convex and concave blades as seen in the bottom picture, isn't it?
    No, the blades is as follows:

    untitled2.png


    untitled3.png


    I re-type as follows:

    They experimentally investigated the turbines with variable thickness blades. The improved turbines under this investigation are created by linearly growing blade thickness with radius.
    Is it OK?

    Are you trying to express that the geometric shape of the cross-section was fixed except for its thickness?
    I am trying to express geometric shape of blade in terms of the thickness along the height of blade.
     

    manfy

    Senior Member
    German - Austria
    I am trying to express geometric shape of blade in terms of the thickness along the height of blade.
    Just to make sure: "height of blade" is the distance from hub to tip, right? And the change in blade thickness from hub to tip is linear, with small thickness at the hub and the thick end at the tip.

    If so, I'd slightly rephrase your sentence.
    The collocation of "experimentally investigated" and "variable thickness blades" sounds as if they had used dynamically adjustable blades. And that's because "experimentally" implies testing with many different shapes, parameters, etc.
    I doubt that they used dynamically variable blades, therefore I'd say:

    "They experimentally investigated the turbines with tapered blades of varying thickness. The improved turbines under this investigation are were created by linearly growing increasing blade thickness with radius."

    * the first sentence doesn't clearly define the nature of the taper now, but the next sentence clarifies this. Also, "of varying thickness" suggests that they tested different blade thicknesses and that they played with the taper parameters (well, at least it allows the reader to draw that conclusion)
    * since the investigation resulted in the improved version, it's better to use simple past 'were created'
    * using your 'growing' instead of my 'increasing' is not really wrong, but I dislike 'growing' in this context

    PS: If you feel that the fact of tapered thickness is crucial in the first sentence, you might also say: "They experimentally investigated the turbines with thickness-tapered blades." (But then the second sentence loses some "bite")
     
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    Uncle Bob

    Senior Member
    British English
    I suggest "...investigation had blade thickness increasing linearly with radius*" i.e. turned round and without the "created", which is unnecessary.

    * "distance from the hub" may be better than "radius".
     
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    alexeru653280

    Senior Member
    Iran
    Another questions:

    1. According above posts, so, noun phrase "constant chord blade" is wrong?

    For example, the following sentences is wrong?

    In another study [11], the characteristics of a Wells turbine with NACA0021 constant chord blades were investigated.
    2. or noun phrase variable thickness blade is wrong?

    In this study, two kinds of blade profile are investigated that one is constant thickness blade (original turbine) and other is variable thickness blade (proposed design).
    Thickness or chord are not a adjective for the blade, so i think that above noun phrases are wrong. Am i right?
     
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    manfy

    Senior Member
    German - Austria
    Thickness or chord are not a adjective for the blade, so i think that above noun phrases are wrong. Am i right?
    No, those words are fine -- I think !!
    When it comes to compound words with more than 2 individual words, you have to look at individual word pairs and you have to decide whether they make sense as a word pair; if yes, then you have to check whether this word pair makes sense in combination with the additional word you want to compound.
    E.g., a "chord blade" or "thickness blade" in itself doesn't make any sense to me, but a "constant chord blade" does; it is a blade with a constant chord. (I don't really know what that is because I'm not a mechanical engineer, but grammatically and semantically it seems to be a valid compound word -- same as a "constant thickness blade" with 'constant thickness' as the first connected word pair).

    In your second sentence I still don't like the term "variable thickness blade" because 'variable' conveys the idea of 'ability to vary', which is not the case. You're talking about a geometrically fixed design with tapered thickness instead of the conventional constant thickness; i.e. I'd say:

    "In this study, two kinds of blade profiles are being investigated, one with a constant thickness blade (original turbine) and another with a tapered blade (proposed design)."
     

    alexeru653280

    Senior Member
    Iran
    No, those words are fine -- I think !!
    When it comes to compound words with more than 2 individual words, you have to look at individual word pairs and you have to decide whether they make sense as a word pair; if yes, then you have to check whether this word pair makes sense in combination with the additional word you want to compound.
    E.g., a "chord blade" or "thickness blade" in itself doesn't make any sense to me, but a "constant chord blade" does; it is a blade with a constant chord. (I don't really know what that is because I'm not a mechanical engineer, but grammatically and semantically it seems to be a valid compound word -- same as a "constant thickness blade" with 'constant thickness' as the first connected word pair).

    In your second sentence I still don't like the term "variable thickness blade" because 'variable' conveys the idea of 'ability to vary', which is not the case. You're talking about a geometrically fixed design with tapered thickness instead of the conventional constant thickness; i.e. I'd say:

    "In this study, two kinds of blade profiles are being investigated, one with a constant thickness blade (original turbine) and another with a tapered blade (proposed design)."
    Thanks...

    I searched now and i see that there is published papers that "variable thickness blade" is used in those.......please see the following link:

    "variable thickness blade" - Google Scholar

    I would like write as follows:

    In this study, two kinds of blade profiles are being investigated, one with a constant thickness blade (original turbine) and another with a variable thickness blade (i.e. tapered blades of varying thickness-proposed design).
    Are the sentences formal for abstract of a technical paper, particularly words within parenthesis?
     

    manfy

    Senior Member
    German - Austria
    I'm not convinced! And that's because you get a small number of hits AND the surrounding text doesn't fit (unfortunately I can't see the full papers without registration or payment). I still prefer "tapered thickness blade" -- the google search returns only 7 hits, but the surrounding text feels right.

    Anyway, I don't want to talk you out of "variable thickness blade"; it is your paper, i.e. your freedom to choose. Whatever you choose, it's clear that this word is technical jargon and any layman might not understand (or might not even care to understand ;) ) the idea behind it. You have to choose your words based on the audience you want to reach.

    In this study, two kinds of blade profiles are being investigated, one with a constant thickness blade (original turbine) and another with a variable thickness blade, i.e. blades tapered in thickness (proposed design).
    I'd put the description of variable thickness blade outside the brackets; this way the description 'proposed design' complements the description 'original turbine' better.
     

    Packard

    Senior Member
    USA, English
    This sounds like one of those cases where an illustration would solve a lot of problems.
     

    manfy

    Senior Member
    German - Austria
    This sounds like one of those cases where an illustration would solve a lot of problems.
    Not necessarily! Earlier on I looked at some google results for rotor blade designs which came with multiple drawings, and that seemed utterly confusing.
    I guess there's a fine line between too little and too much information, be it verbal or illustrative. :D
     

    Edinburgher

    Senior Member
    German/English bilingual
    Anyway, I don't want to talk you out of "variable thickness blade"
    But I do. For me the term "variable thickness" can carry a suggestion that the thickness itself is variable at each point, i.e. the blade can be dynamically reconfigured to change its thickness (imagine the blade skin being flexible and its body filled with hydraulic fluid of which the pressure can be varied).
    It's OK to say that the thickness varies linearly (from hub to tip), but not OK (I suggest) to say that it has (linearly) variable thickness.
     

    Packard

    Senior Member
    USA, English
    Not necessarily! Earlier on I looked at some google results for rotor blade designs which came with multiple drawings, and that seemed utterly confusing.
    I guess there's a fine line between too little and too much information, be it verbal or illustrative. :D
    I guess it turns on who is doing the illustrations. The ones I've seen seemed perfectly clear. Here are some examples: rotor blade design - Google Search

    Here's one:

     

    manfy

    Senior Member
    German - Austria
    I just found one piece of proof that confirms Edinburgher's and my opinion that "variable <something>" is usually understood as "something that can be changed/varied dynamically". This Wiki article talks about wing configurations and variable chord, variable thickness:
    Variable thickness: the upper wing centre section can be raised to increase wing thickness and camber for landing and take-off, and reduced for high speed. Charles Rocheville and others flew some experimental aircraft.
    I don't want to deny that the term "variable chord/thickness/whatever blade" may exist in this field of fluid dynamics, but if it is used to describe a fixed tapered shape then it is simply a misuse of the word "variable".
     
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