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Aerospace Wind Tunnel Testing - Advice?

  1. Apr 12, 2012 #1
    Hello all,

    I'm in my final year of engineering so I'm required to complete a thesis as part of that. My topic is to investigate the wind loading on a typical conveyor belt + truss arrangement, because there's a lot of uncertainty in industry about drag coefficients etc. I've attached a model of the steel structure below (simplified by removing members parallel to flow), but there's also lots of other services and the conveyor belt itself not pictured. It's 18m long.

    http://i.minus.com/jsD6rCU01EZXt.png [Broken]

    Anyway, my plan is to construct a scale model ~(1:10) and do a variety of wind tunnel tests in my universities wind tunnel (sahweet!) for different arrangements/alignments/etc, with the major output being drag force (assuming the other forces and moments are negligible). The problem is, my supervisor doesn't think the whole project is theoretically complex enough, and I guess he's right - at the end of the day all I'm doing is measuring drag on a model.

    So my question is, how can I make this project more complex? Right now the only real calculations involve some dimensional analysis/similitude (which I'll try to make as elegant and clever as possible). What else can I do/investigate? Essentially I want to show/prove that I've done my research and know the theory behind the results, so I'd love to include some sort of theoretical analysis, but obviously the complicated geometry makes anything I do by hand irrelevant. I was thinking perhaps include flow visualization in some wind tunnel tests and then discuss the boundary layers/flow separation/turbulence onset, but then what's the point? It's not like the dynamic behaviour of the wind will adversely affect its structural integrity.

    Essentially I just want to prove I know my stuff, whilst keeping it relevant to the topic. I'd love to do some sort of CFD analysis, but I fear the geometry is far too complex and I also don't know much about CFD . But if performing a simulation over a small section could provide further insight (and not take forever) I'd love to have a crack!

    Any help/comments are much appreciated
    Last edited by a moderator: May 5, 2017
  2. jcsd
  3. Apr 13, 2012 #2
    I think flow viz could be interesting because the dynamic behavior of the air is certainly important. Turbulence and vortex shedding result in unsteady loading on the body. This unsteady loading can excite certain structural modes and cause serious problems. It also generates noise. I would suggest mini tufts, surface oil flow and smoke wire methods for flow viz.

    You could try various modifications to reduce the drag like fairings.

    You can do pretty interesting things by measuring pressure and velocity components in the wake of a 3D body. For example with measurements from a five hole probe you can decompose the total drag into profile drag and vortex induced drag. But that would take a considerable amount of additional effort.

    If you have the equipment you could perform a simple wake survey with an array of pitot probes and perform a control volume momentum analysis. Or you could make boundary layer measurements and calculate the skin friction.
  4. Apr 15, 2012 #3
    Thanks very much for your reply! Certainly things I can look in to :)
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