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Re: Wind tower design

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Kevin et al,
I went to a technical seminar a while ago sponsored by the local Niagara area building officials where RWDI from Guelph made a presentation. It included a video about simulated wind testing in a water tank with a fine sand about the consistency of icing sugar. The flow of water caused the sand to flow and drift and they were able to measure the results. The tank was relatively small compared to wind tunnel. Perhaps this is the basis for some of this CFD.
Gary

Kevin Below wrote:
So CFD is a method which can be used to simulate air flow around objects, and come up with wind pressures ? I had never heard of it.


On Nov 21, 2007 11:17 PM, Conrad Harrison < sch.tectonic(--nospam--at)bigpond.com <mailto:sch.tectonic(--nospam--at)bigpond.com>> wrote:

    Being as I'm here!

    CFD =computational fluid dynamics

    And from recent articles I have read, it is still early days
    regarding wind loading, and can take hours to days for the
    computer to crunch the numbers. It still largely a research tool
    with few practical programs available.

    It is also used for research into fire behaviour.

    Regards

    Conrad Harrison

    B.Tech (mfg & mech), MIIE, gradTIEAust

    mailto:sch.tectonic(--nospam--at)bigpond.com

    Adelaide

    South Australia

    ------------------------------------------------------------------------

    *From:* Kevin Below [mailto:kbofoz(--nospam--at)gmail.com
    <mailto:kbofoz(--nospam--at)gmail.com>]
    *Sent:* Thursday, 22 November 2007 14:33

    *To:* seaint(--nospam--at)seaint.org <mailto:seaint(--nospam--at)seaint.org>
    *Subject:* Re: Wind tower design

    Harold, what is CFD ?

    On Nov 21, 2007 12:01 PM, Harold Sprague <spraguehope(--nospam--at)hotmail.com
    <mailto:spraguehope(--nospam--at)hotmail.com>> wrote:

    Don't write off circular shapes.  The circular shape may be the
most structurally efficient and most effective for construction. It generally is when it comes to stacks in spite of the vortex shedding problem. Stacks have the same tendency of vortex shedding. It is mitigated
    by strakes or active damping.  The blades themselves of a wind
power generator may mitigate the forming of the vortices. Regardless, my limited experience with high end computer modeling is that a lot of the CFD codes will give you any answer you want. What you need are data points that verify the CFD model. I would
    suggest you speak with Jon Peterka at CPP in Ft. Collins.  He
    knows modeling and he knows the limitations of CFD modeling.  He
may have already modeled this.
    Regards,
    Harold Sprague

    ------------------------------------------------------------------------

    Date: Mon, 19 Nov 2007 12:53:55 -0500


    From: kbofoz(--nospam--at)gmail.com <mailto:kbofoz(--nospam--at)gmail.com>
    To: seaint(--nospam--at)seaint.org <mailto:seaint(--nospam--at)seaint.org>

    Subject: Re: Wind tower design

    Thanks for the feedback Harold,
    I am looking at the probability of wind tunnel testing, as well as
theoretical studies to determine the dynamic properties. I will be asking the wind experts about vortex shedding. I will
    probably be using a non-circular cross-section to reduce the
    vortex shedding, but I don't yet know if a hexagonal or pentagonal
    shape is better than circular.  I believe the best would be
    pentagonal, but that will be a discussion with the wind tunnel
    people.

    Kevin

    On Nov 19, 2007 12:17 PM, Harold Sprague <spraguehope(--nospam--at)hotmail.com
    <mailto:spraguehope(--nospam--at)hotmail.com>> wrote:

        I doubt that you will find any sort of code or design guide on
        this topic.  I would suggest that a wind tunnel study be
        conducted especially if this is for operational wind load
        characteristics.  If this is for extreme wind effects, I would
        think that the dominate issue will be the vortex shedding on
the mast.
        Regards,
        Harold Sprague

        ------------------------------------------------------------------------

        Date: Fri, 16 Nov 2007 22:02:19 -0500
        From: kbofoz(--nospam--at)gmail.com <mailto:kbofoz(--nospam--at)gmail.com>
        To: seaint(--nospam--at)seaint.org <mailto:seaint(--nospam--at)seaint.org>
        Subject: Wind tower design



        Has anybody done any wind tower design work ?  I am doing some
        preliminary work on a concrete tower design, and I am thinking
        about the dynamic behaviour
        and the effect of the passage of the blade when it passes in
        front of the tower.  Does anyone have any information or ideas
        on this ?

        The Germans and the Japanese have actually built some concrete
        towers already.  Apparently steel towers are at about their
        height limit now, and the way to greater efficiency and bigger
        turbines leads to higher towers, which will probably be in
        concrete.

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