Experiments in Fluids

, Volume 40, Issue 4, pp 577–588 | Cite as

Spatial resolution and noise considerations in determining scalar dissipation rate from passive scalar image data

Research Article
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Abstract

The effects of photonic shot noise and finite spatial resolution on the scalar dissipation rate were investigated for the analytical profile of a passive scalar layer subjected to a compressive strain, and the results were applied to interpret measured data from spray mixing data from an internal combustion engine. A Monte Carlo approach was employed. The measured scalar dissipation rate is underestimated, and the layer width measured at 20% of the peak height is overestimated by the finite resolution. The ratio of the local scalar spread value to the noise level, the spread-noise ratio, was found to describe the noise effects, which principally results in an overestimation of the scalar dissipation rate, especially at high resolution levels. The Nyquist resolution provides a good compromise between the sampling bias at low resolution and the noise bias at high resolution. Top hat filtering the raw data prior to calculation of the scalar dissipation rate was found to, effectively, reduce spatial resolution, whereas median filtering preserved the resolution. Both filters had a comparable effect on noise reduction. The evaluation of experimental data showed that a significant fraction of data reside at low spread-noise ratio and are biased by noise. The peak scalar dissipation rate is, however, not biased by noise and a method of estimating spatial resolution based on the peak scalar dissipation rate is described.

Keywords

Probability Density Function Shot Noise Scalar Dissipation Passive Scalar Joint Probability Density Function 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.
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Notes

Acknowledgements

The efforts of Dan Probst in the early phase of this effort, including the introduction of the spread-noise factor are gratefully acknowledged. This material is based upon work supported by the National Science Foundation under Grant No. 9875726.

References

  1. Bracco FV (1988) Structure of flames in premixed-charge IC engines. Combust Sci Tech 58:209–230CrossRefGoogle Scholar
  2. Buch KA, Dahm WJA (1996) Experimental study of the fine-scale structure of conserved scalar mixing in turbulent shear flows. Part 1. Sc ≫ 1. J Fluid Mech 317:21–71CrossRefGoogle Scholar
  3. Buch KA, Dahm WJA (1998) Experimental study of the fine-scale structure of conserved scalar mixing in turbulent shear flows. Part 2. Sc ∼ 1. J Fluid Mech 364:1–29CrossRefMATHGoogle Scholar
  4. Dahm WJA, Southerland KB (2000) Quantitative flow visualization via fully-resolved four-dimensional spatio-temporal imaging. In: Smits AJ, Lim TT (eds) Flow visualization: techniques and examples. Imperial College Press, London, pp 289–316Google Scholar
  5. Koch JD, Hanson RK (2003) Temperature and excitation wavelength dependencies of 3-pentanone absorption and fluorescence for PLIF applications. Appl Phys B 76:319–324CrossRefGoogle Scholar
  6. Mi J, Nathan GJ (2003) The influence of probe resolution on the measurement of a passive scalar and its derivatives. Exp Fluids 34:687–696CrossRefGoogle Scholar
  7. Paul PH, van Cruyningen I, Hanson RK, Kychakoff G (1990) High resolution digital flowfield imaging of jets. Exp Fluids 9:241–251CrossRefMATHGoogle Scholar
  8. Probst DM, Ghandhi JB (2003) An experimental study of spray mixing in a direct injection engine. Int J Engine Res 4:27–45CrossRefGoogle Scholar
  9. Su LK, Clemens NT (1999) Planar measurements of the full three-dimensional scalar dissipation rate in gas-phase turbulent flows. Exp Fluids 27:507–521CrossRefGoogle Scholar
  10. Su LK, Clemens NT (2003) The structure of fine-scale scalar mixing in gas-phase planar turbulent jets. J Fluid Mech 488:1–29CrossRefMATHGoogle Scholar
  11. Tsurikov MS, Clemens NT (2002) The structure of dissipative scales in axisymmetric turbulent gas-phase jets. AIAA Paper 2002–0164Google Scholar
  12. Van Vliet E, Van Bergen SM, Derksen JJ, Portela LM, Van den Akker HEA (2004) Time-resolved, 3-D, laser-induced fluorescence measurements of fine-structure passive scalar mixing in a turbulent reactor. Exp Fluids 37:1–21CrossRefGoogle Scholar
  13. Wang GH, Clemens NT (2004) Effects of imaging system blur on measurements of flow scalars and scalar gradients. Exp Fluids 37:194–205Google Scholar
  14. Wiles MA (2004) Characterization of operating parameters’ authority on the flow-field mixedness of a DISI engine. MS, Mechanical Engineering, University of Wisconsin-MadisonGoogle Scholar
  15. Wiles MA, Probst DM, Ghandhi JB (2005) Bulk cylinder flowfield effects on mixing in DISI engines. SAE Paper 2005-01-0096Google Scholar

Copyright information

© Springer-Verlag 2005

Authors and Affiliations

  1. 1.Department of Mechanical EngineeringUniversity of Wisconsin-MadisonMadisonUSA

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