Much of the terminology associated with pulsation analysis is specific to time-frequency analysis and/or to vibrational analysis. The following words have been defined for ease of comprehension when working with the PFA module. Note that most of the defined words include page numbers and, occasionally, equation numbers. All of these references can be found in the document referenced at the end of this page.

• Block Size - The number of samples in a set amount of time that are frequently calculated in powers of 2 (Page 14, Equation 26)

• Low-Pass Filter (LPF) - A mathematical filter that permits all frequencies at and below the specified frequency (termed the cutoff frequency) for analysis, and rejects all frequencies above the cutoff frequency (Page 7)

• Sample Rate - The inverse of the time step (Page 14)

• Harmonic Frequencies - Multiples of the base frequencies that excite the system

• Forcing Function - This is the function that will be used to “ring” the system. This function can be the pulse in a non-low-pass-filtered system, or can be determined by the cutoff frequency that is determined by using FFT and LPF functions (Page 7)

• Pulse - The near-instantaneous increase, then normalization, of flow

• Fast Fourier Transform (FFT) - A method used to transpose the time-domain (flow vs. time) into the frequency-domain (magnitude vs. frequency)

• dta - The initial time step, calculated by 1/2fc (Page 4, Equation 7)

• dtb - The selected time step, filling the criteria that dtb is less than or equal to dta/3 (Page 5)

• Cutoff frequency (fc) - This is the frequency that is the maximum frequency that will be analyzed in the system. Calculated by nN/10, where n is the maximum pump speed (with buffer) and N is the number of pump heads in the pump (Page 4, Equation 6)

References

1. Blanding, James M., Ph.D., and Trey Walters, PE. Pulsation Analysis in Positive Displacement Pump Systems Using Waterhammer, Modal, and Animation Software. Houston, TX: 45th Turbomachinery & 32nd Pump Symposia, Sept. 2016. http://www.aft.com/documents/TechnicalPapers/2016/TPS2016-PulsationAnalysis.pdf