X-Virus-Scanned: clean according to Sophos on Logan.com X-SpamCatcher-Score: 50 [XX] (51%) URL: contains host with port number (-49%) URL: weird port adjustment Return-Path: Received: from alnrmhc13.comcast.net ([206.18.177.53] verified) by logan.com (CommuniGate Pro SMTP 5.1.8) with ESMTP id 2022581 for flyrotary@lancaironline.net; Wed, 02 May 2007 21:41:00 -0400 Received-SPF: none receiver=logan.com; client-ip=206.18.177.53; envelope-from=wschertz@comcast.net Received: from 7n7z201 (c-24-7-194-231.hsd1.il.comcast.net[24.7.194.231]) by comcast.net (alnrmhc13) with SMTP id <20070503013958b1300dplb4e>; Thu, 3 May 2007 01:40:08 +0000 Message-ID: <002501c78d24$09f356f0$6401a8c0@7n7z201> From: "Bill Schertz" To: "Rotary motors in aircraft" References: Subject: Re: [FlyRotary] Complete Presentation Found!: Source Material - Boundary layer with pressure gradient.htm Date: Wed, 2 May 2007 20:40:22 -0500 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0020_01C78CFA.1AD75220" X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2900.3028 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.3028 This is a multi-part message in MIME format. ------=_NextPart_000_0020_01C78CFA.1AD75220 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Ed, I would like it. (I would also like delta-T measurements :-) ) Bill Schertz KIS Cruiser # 4045 ----- Original Message -----=20 From: Ed Anderson=20 To: Rotary motors in aircraft=20 Sent: Wednesday, May 02, 2007 6:54 PM Subject: [FlyRotary] Complete Presentation Found!: Source Material - = Boundary layer with pressure gradient.htm 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 -----=20 From: wrjjrs@aol.com=20 To: Rotary motors in aircraft=20 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 =20 -----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.=20 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.=20 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.=20 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.=20 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 =20 -- 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 ------=_NextPart_000_0020_01C78CFA.1AD75220 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
Ed,
I would like it.
(I would also like delta-T measurements = :-) =20 )
Bill Schertz
KIS Cruiser # 4045
----- Original Message -----
From:=20 Ed=20 Anderson
Sent: Wednesday, May 02, 2007 = 6:54=20 PM
Subject: [FlyRotary] Complete=20 Presentation Found!: Source Material - Boundary layer with pressure=20 gradient.htm

I was certain I must have the = complete=20 presentation (script and slides) of the duct boundary layer=20 separation story stored someplace in the gigabytes of disc = space and=20 I finally found it.  Since it takes up a bit of bandwidth, I will = only e=20 mail it to those interested enough to tell me they want = it.   Its=20 approx 800KB.
 
Attached is one slide that I believe=20 triggered my idea of using a pinched duct to delay boundary layer = separation.
 
Ed
 
 
----- Original Message -----
From:=20 wrjjrs@aol.com=20
To: Rotary motors in = aircraft=20
Sent: Wednesday, May 02, 2007 = 3:24=20 PM
Subject: [FlyRotary] Re: = Source=20 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.comTo:=20 flyrotary@lancaironline.net
Sent:=20 Wed, 2 May 2007 10:34 AM
Subject: [FlyRotary] Source Material - = Boundary=20 layer with pressure gradient.htm

Only for those who (Dave? Bill?, = Rusty?.....) wish to=20 punish themselves with more minutia on air flow in=20 ducts/diffusers.
 
A month or two ago, I posted some slides = extracted=20 from a university study/course on the effects of airflow separation = inside a=20 duct. This involved the boundary layer which appears to act = somewhat=20 different inside the constraining walls of a duct as compared = to its=20 free flow across an airfoil.   The cause of flow = separation in the=20 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=20 layer stay attached to curving duct wall - for a=20 time.  But, this same pressure that helps "push" the = boundary=20 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"=20 design to accelerate the boundary layer and cause it to penetrate = further=20 into the higher pressure area before separation.  I also = inferred that=20 this effect  was what made the Streamline duct of K&W = so=20 effective.  No claim was made that the pinched ducts were = anywhere=20 nearly as effective as the Streamline duct, but were an attempt to = meet a=20 space constraint.
 
Most attempts to use the streamline duct in a space too small = involves=20 truncating the duct from the inlet end.  However, while this = does tend=20 to preserve some of its effectiveness, if the distance is very short = (like=20 my 3 -6 inches) the large expose core area likely increases cooling = drag=20 considerably.  So I decided to keep the inlet small (unlike = what=20 truncating the streamline duct would have resulted in) but to pinch = it down=20 to keep the boundary layer velocity high resulting (hopefully) in = further=20 penetration down the duct before flow separation occurred.
 
Some questioned my interpretation (always a = smart=20 thing to do,  as I only had one short course in aerodynamics as = an=20 Electrical Engineering  student - so my attention was probably = not as=20 keenly focused as it should have been {:>)).  In any=20 case,  I went looking for the source document so that any = interested=20 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=20 frequently do) apparently rotated material presented and removed = this=20  briefing from their website.  This leaves the .html = portion I=20 saved when first reading the presentation which is=20 attached.
 
I was only partially successful in providing = the=20 source  - in that I found the original script that = went with=20 the slide presentation - but unfortunately the slides are not = present with=20 it.  I do have a number of the slides I had previously = extracted (used=20 in my presentation) but since they could be "tainted" by my = "explanation" of=20 the slides, I will not present them.
 
I reviewed the script again and still believe my interpretation = is=20 correct, but others should have the opportunity to decide for=20 themselves. We do that sort of thing on this list.=20
 
 
 But, if you do decide differently, please don't tell my = pinched=20 ducts {:>)
 
 
 
Ed
Ed Anderson
Rv-6A N494BW Rotary Powered
Matthews, = NC
eanderson@carolina.rr.comhttp://members.cox.net/rogersda/rotary/configs.htm#N494BW=
http://www.dmack.net/mazda/index.html
 
  =
AOL now offers free email to everyone. Find out more about what's = free from=20 AOL at AOL.com.

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Homepage:  http://www.flyrotary.com/
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