Comparative Analysis of Velocity Decomposition Methods for Internal Combustion Engines

Abstract

Different signal processing technique performances are compared to each other with regard to separating the mean and fluctuating velocity components of a simulated one-dimensional unsteady velocity signal comparable to signals observed in internal combustion engines. A simulation signal with known mean and fluctuating components was generated using experimental data and generic turbulence spectral information. The simulation signal was generated based on observations on the measured velocity data obtained using LDV in a motored Briggs-and-Stratton engine at about 600 RPM. Experimental data was used as a guide to shape the simulated signal mean velocity variation; fluctuating velocity variations with specified spectrum and standard deviation was used to mimic the turbulence. Cyclic variations were added both to the mean and the fluctuating velocity signals to simulate prescribed cyclic variations. The simulated signal was introduced as input to the following algorithms: ensemble averaging; high-pass filtering; Proper-Orthogonal Decomposition (POD); Wavelet Decomposition (WD) and Wavelet Decomposition/Principal Component Analysis (WD/PCA). The results were analyzed to determine the best method in correctly separating the mean and the fluctuating velocity information, indicating that the WD/PCA performs better compared to other techniques.

Cross-Correlation of POD Spatial Modes for the Separation of Stochastic Turbulence and Coherent Structures

“…There have been multiple approaches suggested in literature to achieve velocity field decomposition. Ölçmen et al [1] present a comparative analysis of suggested approaches-Reynolds decomposition (referred to as ensemble averaging in that study), proper orthogonal decomposition (POD) and frequency filtering amongst others.…”

Methodology for the large-eddy simulation and particle image velocimetry analysis of large-scale flow structures on TCC-III engine under motored condition

“…Hence, many researchers have investigated the separation between “true” turbulence and cyclic variation using a frequency filtering method. 57–59 However, this method has a difficulty that the cut off frequency is empirically determined and it cannot be physically defined. Therefore, in the present study, the ensemble average method is employed in order to focus on the application of the integral length scale analysis on ICE using numerical and experimental study.…”

Influence of asymmetric valve strategy on large-scale and turbulent in-cylinder flows

“…Spatial filtering techniques based on fast Fourier transform (FFT) have been used in studies. 3–6 Olçmen et al 7 gives a comprehensive comparison of methods including ensemble averaging, wavelet decomposition, proper orthogonal decomposition (POD) and combinations of these methods. The work concludes that a method involving POD yielded the best results.…”