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Help with pressure wave analysis

  1. Aug 10, 2010 #1
    For my work I am analyzing pressure waves. I am new to this however, and do not know very much. I have attached two plots of the same wave. One plot is a line plot, and the other is a dot plot. For my analysis, I am using MATLAB.

    As can be seen from the two plots, my data is very noisy. There is nothing I can do about this however, so I will have to work with what I am given. I would like to use a filter, a moving average, or perhaps a combination to better understand the data, but I do not know which to use, why one would be better than the other, advantages, disadvantages, etc.

    Any help would be appreciated.

    Thanks,

    Nate
     

    Attached Files:

  2. jcsd
  3. Aug 10, 2010 #2

    minger

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    Science Advisor

    Without knowing your problem, it's hard to say which "peaks" are real and which ones are noise. Typically when I look at pressures in a CFD problem, I will perform FFT analysis afterward to see what frequencies show up in the solution.

    Can you explain a little more about your setup and what exactly you're measuring?
     
  4. Aug 10, 2010 #3

    minger

    User Avatar
    Science Advisor

    Without knowing your problem, it's hard to say which "peaks" are real and which ones are noise. Typically when I look at pressures in a CFD problem, I will perform FFT analysis afterward to see what frequencies show up in the solution.

    Can you explain a little more about your setup and what exactly you're measuring?
     
  5. Aug 10, 2010 #4
    I am measuring the blast wave from a 105mm cannon. The data was collected using a static pressure gage. The pressure gage was located at the level of the cannon 10m away at a 45 degree angle, so the gage is actually 14.14m from the muzzle.

    I tried performing an fft analysis and the attachment will show what I came up with.
    This is the MATLAB code that I used:

    figure
    plot(fft(yvalues))

    I don't think this is right though. I will look further into fft analysis.
     

    Attached Files:

  6. Aug 10, 2010 #5

    minger

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    Science Advisor

    No, most FFT plots I've seen/done are a simple line plot. On the x-axis you have frequency, and on the y-axis, you have magnitude. For example, if you're data plot was really y=sin(wt), on the FFT plot you would show a spike on the x-axis at w, and ideally zero everywhere else.

    Unfortunately, you only have one "blast" from the cannon. You need at least a few pulses to get an accurate FFT.

    What is the goal here? Are you simply trying to remove the noise?
     
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