X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from misav09.sasknet.sk.ca ([142.165.20.173] verified) by logan.com (CommuniGate Pro SMTP 5.2c1) with ESMTP id 2463516 for flyrotary@lancaironline.net; Fri, 09 Nov 2007 11:41:37 -0500 Received-SPF: none receiver=logan.com; client-ip=142.165.20.173; envelope-from=hjjohnson@sasktel.net Received: from bgmpomr1.sasknet.sk.ca ([142.165.72.22]) by misav09 with InterScan Messaging Security Suite; Fri, 09 Nov 2007 10:40:59 -0600 Received: from sasktel.net ([192.168.234.97]) by bgmpomr1.sasknet.sk.ca (SaskTel eMessaging Service) with ESMTP id <0JR800GTOZOBJK20@bgmpomr1.sasknet.sk.ca> for flyrotary@lancaironline.net; Fri, 09 Nov 2007 10:40:59 -0600 (CST) Received: from [192.168.234.25] (Forwarded-For: [24.72.101.251]) by cgmail1.sasknet.sk.ca (mshttpd); Fri, 09 Nov 2007 10:40:59 -0600 Date: Fri, 09 Nov 2007 10:40:59 -0600 From: H & J Johnson Subject: Re: [FlyRotary] Re: Total,duct, Ambient or Velocity???? To: Rotary motors in aircraft Message-id: MIME-version: 1.0 X-Mailer: Sun Java(tm) System Messenger Express 6.1 HotFix 0.20 (built Feb 27 2006) Content-type: text/html; charset=us-ascii Content-language: en Content-transfer-encoding: 7BIT Content-disposition: inline X-Accept-Language: en Priority: normal

> But, semantics aside, yes, I agree, lower exit pressure is what
> you are after and that does not always equate to larger exit duct
> area. In fact, if the air heated by the core flows through a
> nozzle it might even produce thrust and lower exit pressure using
> a smaller exit. But, in general, I still believe that in most of
> our cases, we are short of the level of duct design that would
> reliably permit that. What we need is someone to invest in one of
> those $$$$ Computer Fluid Flow software programs and see what they
> would reveal.
>
> Ed
>
>
> Ed,
>
> I have to disagree with the big $$$ CFD idea. Until I see proper
> exit ducts and every effort made to do things right inlet
> wise....CFD is a waste of time. I have yet to see an installation
> at the level of refinement where CFD would start to make sense.
> You can get to 90% of optimum by following a few simple guidelines
> and some fairly simple math.
>
> 1.) do a heat balance at the cruise condition to figure out how
> much air you need to ingest.
>
> 2.) Size your inlet appropriately.
>
> 3.) Provide a real exit duct.
>
> 4.) Use a cowl flap.
>
> 5.) Do some testing with oil and tufts to make improvements.
>
> A properly done CFD will only get you another 5% beyond these
> simple steps that are within reach of mere mortals. In fact if the
> guy/gal doing the CFD work is not intimately familiar with the
> situation and what sort of assumptions to make/conditions to
> assign it is very likely that the results will be less successful
> that the empirical method.
>
> In other words CFD=decimal dust.
>
>
> Monty

Well.. I haven't spent $$$ on it but SolidWorks now comes w/ a version of

CosmosFloWorks in the package in 2008.. I've got the software so I may give it

a whirl.. I was waiting to test it before I commented but.. since people are talking

directly about it.. :-)

Jarrett