Technical Paper
Cycle-to-Cycle Variation of In-Cylinder Tumble Flow by Moment Normalization
2017-10-08
2017-01-2214
The large-scale rotating flow structure in an engine cylinder exhibits features that can be described in generic terms of tumble and swirl. The structural details, nevertheless, vary from cycle to cycle due to fluctuating initial and boundary conditions of the flow. Typical analysis of the flow field cyclic variability - by simple root-mean-square, or additional spatial or temporal filtering, or proper orthogonal decomposition - is based on pointwise deviation of the instantaneous velocity from the ensemble mean. However, that analysis approach is not amenable to the evaluation of spatial variation of the flow structure, in position and orientation, within the flow field. To this end, other studies in the past focused instead on quantifying the variation of the vortex center for the dominant tumble or swirl pattern within the flow field.