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From: "Ed Anderson" <eanderson@carolina.rr.com>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
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Subject: Re: [FlyRotary] Re: K & W Konfusion
Date: Sun, 11 Sep 2011 18:59:11 -0400
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One, additional thing might be worth porting out is that with the vector 
quantity Vb = Vi +Vt with Vt the component tangential to the face of the 
core - as you might imagine, you don't get a lot of cooling contribution due 
to Vt, as theoretically it doesn't contribute (much) to the flow through the 
core (at least that is how I read it).  Therefore the condition where vb = 
vi with vt = 0 probably means maximum cooling effect from the air flow which 
(one reason) is why straight in flowing ducts (where Vb = Vi) cool better 
than one with twists and turns.

Ed
--------------------------------------------------
From: "Ed Anderson" <eanderson@carolina.rr.com>
Sent: Sunday, September 11, 2011 6:08 PM
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
Subject: [FlyRotary] Re: K & W Konfusion

> Hi Charlie,
>
> Having pulled my hair out over some things in Chapter 12 of K& W,  I can 
> empathize.  Let me see if I can help you with this particular question.
>
> As you know, Vb is a vector quantify having both magnitude and direction 
> and here is composed of two vector quantities:  Vi - (vector  in line or 
> incident with the core)  and Vt (vector tangential to the face of the 
> core). In this case ( a special case of the straight duct) Vt = 0.  No, 
> the first chapter does NOT spell this out, so you did not miss it, but 
> when you examine figure 12.6  you will see it.
>
> In your first reference the Vt value = 0 (they do not point this out) and 
> Vb is therefore equal solely to Vi (or the vector  parallel to the duct, 
> straight into the core).  So here Vb = Vi because Vt = 0, straight duct 
> condition only.
>
> Now in figure 12.6 the incoming oblique air flow does have two components 
> (Vi and Vt) relative to the orientation of the block - Vt is not zero here 
> and of course neither is Vi.  So Vb = Vi + Vt.  If you have a good copy 
> and look carefully you can see that at the bottom of the vector triangle 
> it shows Vb as the vector sum of Vi and Vt- and Vb is pointed in the 
> direction of the airflow through the core (or parallel to the holes 
> through the core or perpendicular to the core face).
>
>  If you look at figure 12-7, the same vector combination is there and a 
> bit easier to see.   So in effec,t your first reference to Vb in chapter 
> 12 is a special case of the overall vector components of the airflow (Vi 
> and Vt) except in that case Vt = 0 and Vb = Vi.
>
> So it is probably more correct to say that Vb is the vector sum of the 
> incident and tangential vectors of airflow  or Vb is the vector expression 
> of the airflow through the core.
>
> What is missing in figure 12.6 is the showing the vector sum of Vb AFTER 
> it exits the core.    If they did, what you would probably see is Vt much 
> smaller or zero and Vb = Vi (since the duct is straight after the core). 
> So if the vector sum on the one side of the core is Vb then it will also 
> be Vb on the opposite side of the core - however the values of the vector 
> components vi and vt will be different (if not a straight duct) - but 
> their sum will remain the same - vb.
>
> At least that is the way I read it - and no, I've never found and K&W for 
> dummies - if you do please let me know.
>
>
> Dummy Ed
>
> Edward L. Anderson
> Anderson Electronic Enterprises LLC
> 305 Reefton Road
> Weddington, NC 28104
> http://www.andersonee.com
> http://www.eicommander.com
>
>
> --------------------------------------------------
> From: "Charlie England" <ceengland@bellsouth.net>
> Sent: Sunday, September 11, 2011 3:13 PM
> To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
> Subject: [FlyRotary] K & W Konfusion
>
>> Anyone else having problems interpreting K & W's chapter 12 on cooling?
>>
>> I confess to only having available (downloaded) chapters  on inlets & 
>> cooling, but their use of terms is a bit hair-pulling for me. For 
>> instance, VsubB is defined on the 1st page of the chapter as 'velocity of 
>> the air ahead of the block' & diagrammed that way in fig 12-1, then it's 
>> apparently diagrammed as the velocity *leaving* the cooling block in fig 
>> 12-6. And quite a few of the terms don't seem to be defined at all (this 
>> may be due to my failure to take a physics course in college, & the 30+ 
>> year interval since my one semester of Calculus...).
>>
>> If there's a 'K&W for Dummies' book, please recommend a source...
>>
>> Charlie
>>
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>
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