X-Virus-Scanned: clean according to Sophos on Logan.com X-SpamCatcher-Score: 10 [X] Return-Path: Received: from an-out-0708.google.com ([209.85.132.249] verified) by logan.com (CommuniGate Pro SMTP 5.1.8) with ESMTP id 2022742 for flyrotary@lancaironline.net; Wed, 02 May 2007 23:57:13 -0400 Received-SPF: pass receiver=logan.com; client-ip=209.85.132.249; envelope-from=rotary.thjakits@gmail.com Received: by an-out-0708.google.com with SMTP id c34so356231anc for ; Wed, 02 May 2007 20:56:13 -0700 (PDT) DKIM-Signature: a=rsa-sha1; c=relaxed/relaxed; d=gmail.com; s=beta; h=domainkey-signature:received:received:message-id:date:from:to:subject:in-reply-to:mime-version:content-type:references; b=ofz2zRrIaK7+an+FEdS3WwdsB6RM/eivmDIu3P5peZZbL3CoJ+bo+rpTi94H+RTUovbUWiUUBs64nUZKZpzFGfGh3zoVJJ8ok34wV8mgeDvC7LBmFL/RXwcb6Ei1X3RgHnTuqg+4Snt86i4YxJDMya4bsSji39a8E7XUZXRdI60= DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=beta; h=received:message-id:date:from:to:subject:in-reply-to:mime-version:content-type:references; b=G0xJTlcQbcZ1TW+bQqooAy/VwN9xGHbr415nJuTOd3xFy4tEqG5PKwFWz10MaiI0nanqXbU0ikKDMVDJnKzcDrZpmYwOilC4N3o41HglLbi0uGe0/1uH1xrXRMlmEb6FhHw61PYg25Fng+xCF5nf+yB7WYjcsE7A6bVnlkHdvPA= Received: by 10.100.108.11 with SMTP id g11mr1177486anc.1178164573166; Wed, 02 May 2007 20:56:13 -0700 (PDT) Received: by 10.100.197.4 with HTTP; Wed, 2 May 2007 20:56:12 -0700 (PDT) Message-ID: <63163d560705022056r5a717a3agd4be0b2c05ec9eb7@mail.gmail.com> Date: Wed, 2 May 2007 22:56:12 -0500 From: "Thomas Jakits" To: "Rotary motors in aircraft" Subject: Re: [FlyRotary] Complete Presentation Found!: Source Material - Boundary layer with pressure gradient.htm In-Reply-To: MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_Part_24616_30689173.1178164572977" References: ------=_Part_24616_30689173.1178164572977 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Content-Disposition: inline Hi Ed, please send me the file and any other that deal with the same matter! If you have it up on a website I can download it myself, otherwise please send it (them) to thjakits@gmail.com Thanx! TJ PS: At this time I still have 2835 MB of storage available on this account - so don't be shy!! Gmail rocks! On 5/2/07, Ed Anderson wrote: > > I was certain I must have the complete presentation (script and slides) > of the duct boundary layer separation story stored someplace in the > gigabytes of disc space and I finally found it. Since it takes up a bit of > bandwidth, I will only e mail it to those interested enough to tell me they > want it. Its approx 800KB. > > Attached is one slide that I believe triggered my idea of using a pinched > duct to delay boundary layer separation. > > Ed > > > > ----- Original Message ----- > *From:* wrjjrs@aol.com > *To:* Rotary motors in aircraft > *Sent:* Wednesday, May 02, 2007 3:24 PM > *Subject:* [FlyRotary] Re: Source Material - Boundary layer with pressure > gradient.htm > > > FWIW Ed, > I have always thought your "pinched ducts" were a GOOD idea. > Bill Jepson > > > -----Original Message----- > From: eanderson@carolina.rr.com > To: flyrotary@lancaironline.net > Sent: Wed, 2 May 2007 10:34 AM > Subject: [FlyRotary] Source Material - Boundary layer with pressure > gradient.htm > > Only for those who (Dave? Bill?, Rusty?.....) wish to punish themselves > with more minutia on air flow in ducts/diffusers. > > A month or two ago, I posted some slides extracted from a university > study/course on the effects of airflow separation inside a duct. This > involved the boundary layer which appears to act somewhat different > inside the constraining walls of a duct as compared to its free flow across > an airfoil. The cause of flow separation in the duct being the pressure > build up by the expansion in duct area which led to two counteracting > forces. > > The pressure build up actually helps the boundary layer stay attached to > curving duct wall - *for a time.* But, this same pressure that helps > "push" the boundary layer against the duct wall also slows down the boundary > layer which ultimately leads to flow separation and reversal. > > This "understanding" led me to my "pinched duct" design to accelerate the > boundary layer and cause it to penetrate further into the higher pressure > area before separation. I also inferred that this effect was what made the > Streamline duct of K&W so effective. No claim was made that the pinched > ducts were anywhere nearly as effective as the Streamline duct, but were an > attempt to meet a space constraint. > > Most attempts to use the streamline duct in a space too small involves > truncating the duct from the inlet end. However, while this does tend to > preserve some of its effectiveness, if the distance is very short (like my 3 > -6 inches) the large expose core area likely increases cooling drag > considerably. So I decided to keep the inlet small (unlike what truncating > the streamline duct would have resulted in) but to pinch it down to keep the > boundary layer velocity high resulting (hopefully) in further penetration > down the duct before flow separation occurred. > > Some questioned my interpretation (always a smart thing to do, as I only > had one short course in aerodynamics as an Electrical Engineering student - > so my attention was probably not as keenly focused as it should have been > {:>)). In any case, I went looking for the source document so that any > interested could read it and draw their own conclusion. > > The original source for this material was > http://www.me.dal.ca/site2/courses/mech3300/5_Separation.ppt. However, > they have (as Universities frequently do) apparently rotated material > presented and removed this briefing from their website. This leaves the > .html portion I saved when first reading the presentation which is attached. > > I was only partially successful in providing the source - in that I found > the original script that went with the slide presentation - but > unfortunately the slides are not present with it. I do have a number of the > slides I had previously extracted (used in my presentation) but since they > could be "tainted" by my "explanation" of the slides, I will not present > them. > > I reviewed the script again and still believe my interpretation is > correct, but others should have the opportunity to decide for themselves. We > do that sort of thing on this list. > > But, if you do decide differently, please don't tell my pinched ducts > {:>) > > > > Ed > Ed Anderson > Rv-6A N494BW Rotary Powered > Matthews, NC > eanderson@carolina.rr.com > http://members.cox.net/rogersda/rotary/configs.htm#N494BW > http://www.dmack.net/mazda/index.html > > > > -- > Homepage: http://www.flyrotary.com/ > Archive and UnSub: http://mail.lancaironline.net:81/lists/flyrotary/List.html > > ------------------------------ > AOL now offers free email to everyone. Find out more about what's free > from AOL at *AOL.com* . > > > > -- > Homepage: http://www.flyrotary.com/ > Archive and UnSub: > http://mail.lancaironline.net:81/lists/flyrotary/List.html > > > ------=_Part_24616_30689173.1178164572977 Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Content-Disposition: inline
Hi Ed,
 
please send me the file and any other that deal with the same matter!
 
If you have it up on a website I can download it myself, otherwise please send it (them) to
 
Thanx!
TJ
 
PS: At this time I still have 2835 MB of storage available on this account - so don't be shy!! Gmail rocks!

 
On 5/2/07, Ed Anderson <eanderson@carolina.rr.com> wrote:
I was certain I must have the complete presentation (script and slides) of the duct boundary layer separation story stored someplace in the gigabytes of disc space and I finally found it.  Since it takes up a bit of bandwidth, I will only e mail it to those interested enough to tell me they want it.   Its approx 800KB.
 
Attached is one slide that I believe triggered my idea of using a pinched duct to delay boundary layer separation.
 
Ed
 
 
----- Original Message -----
Sent: Wednesday, May 02, 2007 3:24 PM
Subject: [FlyRotary] Re: Source Material - Boundary layer with pressure gradient.htm

 
FWIW Ed,
I have always thought your "pinched ducts" were a GOOD idea.
Bill Jepson
 
 
-----Original Message-----
From: eanderson@carolina.rr.com
To: flyrotary@lancaironline.net
Sent: Wed, 2 May 2007 10:34 AM
Subject: [FlyRotary] Source Material - Boundary layer with pressure gradient.htm

Only for those who (Dave? Bill?, Rusty?.....) wish to punish themselves with more minutia on air flow in ducts/diffusers.
 
A month or two ago, I posted some slides extracted from a university study/course on the effects of airflow separation inside a duct. This involved the boundary layer which appears to act somewhat different inside the constraining walls of a duct as compared to its free flow across an airfoil.   The cause of flow separation in the duct  being the pressure build up by the expansion in duct area which led to two counteracting forces. 
 
The pressure build up actually helps the boundary layer stay attached to curving duct wall - for a time.  But, this same pressure that helps "push" the boundary layer against the duct wall also slows down the boundary layer which ultimately leads to flow separation and reversal. 
 
 This "understanding" led me to my "pinched duct" design to accelerate the boundary layer and cause it to penetrate further into the higher pressure area before separation.  I also inferred that this effect  was what made the Streamline duct of K&W so effective.  No claim was made that the pinched ducts were anywhere nearly as effective as the Streamline duct, but were an attempt to meet a space constraint.
 
Most attempts to use the streamline duct in a space too small involves truncating the duct from the inlet end.  However, while this does tend to preserve some of its effectiveness, if the distance is very short (like my 3 -6 inches) the large expose core area likely increases cooling drag considerably.  So I decided to keep the inlet small (unlike what truncating the streamline duct would have resulted in) but to pinch it down to keep the boundary layer velocity high resulting (hopefully) in further penetration down the duct before flow separation occurred.
 
Some questioned my interpretation (always a smart thing to do,  as I only had one short course in aerodynamics as an Electrical Engineering  student - so my attention was probably not as keenly focused as it should have been {:>)).  In any case,  I went looking for the source document so that any interested could read it and draw their own conclusion. 
 
  The original source for this material was http://www.me.dal.ca/site2/courses/mech3300/5_Separation.ppt.  However, they have (as Universities frequently do) apparently rotated material presented and removed this  briefing from their website.  This leaves the .html portion I saved when first reading the presentation which is attached.
 
I was only partially successful in providing the source  - in that I found the original script that went with the slide presentation - but unfortunately the slides are not present with it.  I do have a number of the slides I had previously extracted (used in my presentation) but since they could be "tainted" by my "explanation" of the slides, I will not present them.
 
I reviewed the script again and still believe my interpretation is correct, but others should have the opportunity to decide for themselves. We do that sort of thing on this list.
 
 
 But, if you do decide differently, please don't tell my pinched ducts {:>)
 
 
 
Ed
 
 
AOL now offers free email to everyone. Find out more about what's free from AOL at AOL.com .
 

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