After running a transient Flow Simulation study, frequency content or spectral information may be of interest. In SOLIDWORKS Flow Simulation, the fast Fourier transform (FFT) is used to convert the time signal to the frequency domain and the resulting FFT plot can be used to evaluate parameters such as time-dependent pressure data. Other resulting quantities that can be plotted include Power Spectral Density indicating the distribution of signal power in the frequency domain, magnitude of the signal, Sound amplitude and sound pressure level (decibel level).
To define FFT plot, users can select FFT plot listed on Flow Simulation results toolbar and any time-dependent goals defined in the flow simulation project.
For the goals, abscissa could be physical time or iteration number. Time-intervals can be customized by changing the start and finish time.
The data plotted can be displayed on the bottom pane or exported to Microsoft Excel. The first image below shows the static pressure on one of the enclosure walls housing computer chips generating heat at different rates for a duration of one second.
To edit minimum and maximum scale values of the plot axes, users can directly click on the minimum or maximum value on the axis and type the desired parameter value in the input box. The FFT Plot feature is available only for time-dependent analyses and requires at least one static pressure goal to be specified in the Flow Simulation study.
FFT plot of the sound pressure level for static pressure goal defined on enclosure wall is shown below.
These plots are also useful for predicting fluid noise levels over a range of frequencies. This is important as acoustic emissions and fan noise are becoming important design criteria.
Let us know how you are using SOLIDWORKS Simulation tools to improve your design and product development processes for things such as defining FFT plot.
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