I am trying to perform an FFT on data from a simulation that has an oscilating shape. When I run the scipy FFT, the output is the same as the input and I can't figure out why. My code is below: tstart = 7.5000000000039813e-2 rho = 0.80272956E-04 V = 4773.706375394508 Aref = 0.203911 Pnondim = 0.5 * rho * V**2 * Aref df1 = pd.read_csv('screenP.csv') P1 = -np.array(df1[:])/Pnondim CT = 1.52 Ax1 = P1 + CT steps1 = len(P1) dt1 = 2e-7 tend1 = tstart + steps1*dt1 t1 = np.linspace(tstart,tend1,steps1) * 1000 plt.plot(t1,Ax1) plt.show() X = fftpack.rfft(Ax1) freq = fftpack.rfftfreq(len(Ax1), dt1) plt.plot(freq, np.abs(X)) plt.xlabel('Frequency (Hz)'), plt.ylabel('Power') plt.show() where screenP is data output from a CFD solver. The original curve and the fft output are shown below. https://i.sstatic.net/8iPa8.png https://i.sstatic.net/1Eja9.png Any help would be much appreciated. Continue reading...
