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Research Papers: Multiphase Flows

Non-Newtonian Drops Spreading on a Flat Surface

[+] Author and Article Information
A. Dechelette, C. R. Wassgren

Maurice J. Zucrow Laboratories, School of Mechanical Engineering, Purdue University, West Lafayette, IN 47907-2014

P. E. Sojka

Maurice J. Zucrow Laboratories, School of Mechanical Engineering, Purdue University, West Lafayette, IN 47907-2014sojka@ecn.purdue.edu

J. Fluids Eng 132(10), 101302 (Oct 20, 2010) (7 pages) doi:10.1115/1.4002281 History: Received May 31, 2007; Revised July 12, 2010; Published October 20, 2010; Online October 20, 2010

The objective of this study is to develop a computational model that accurately describes the dynamic behavior of a non-Newtonian power-law film formed after a drop impinges on a flat surface. The non-Newtonian drop deposition and spreading process is described by a model based on one developed for Newtonian liquids. The effects of variations in non-Newtonian liquid rheological parameters, such as Ren (the non-Newtonian Reynolds number), n (the flow behavior index), and We (the Weber number), are studied in detail. Results show that a reduction in the viscous forces results in enhanced spreading of the film followed by a more rapid recession. An increase in surface tension results in reduced spreading of the film, followed by a more rapid recession. Model predictions of film diameter as a function of time were larger than corresponding experimental values obtained as part of this study. However, the discrepancy never exceeded 21%, demonstrating that the model accurately predicts the phenomena of interest. This comparison also shows that the results are in best agreement for large non-Newtonian Reynolds numbers and small non-Newtonian Ohnesorge numbers (We/Ren).

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Copyright © 2010 by American Society of Mechanical Engineers
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Figures

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Figure 1

Variables used in the theoretical model

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Figure 2

Schematic of the drop impact process considered in the present study

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Figure 3

Comparison of experimental results with model predictions for water-XG 0.05% solution with Ren=1667, We=177, and n=0.70 on a glass substrate (contact angle values as specified in Table 2)

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Figure 4

Comparison of experimental results with model predictions for water-XG 0.20% solution with Ren=822, We=153.5, and n=0.35 on a glass substrate (contact angle values as specified in Table 2). The lower and upper limits on prediction uncertainty due to the uncertainty in the fluid properties are included.

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Figure 5

Spread factor predictions for three different values of n with Ren=5576, We=400, and contact angle values as specified for XG 0.05% in Table 2

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Figure 6

Spread factor values for variations in the Reynolds number Ren with n=0.7, We=400, and contact angle values as specified for XG 0.05% in Table 2

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Figure 7

Spread factor predictions for a decrease of 50% in the Reynolds number Ren with n=0.35, We=397, and contact angle values as specified for XG 0.20% in Table 2

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Figure 8

Spread factor predictions for three different values of We with Ren=2845, n=0.7, and contact angle values as specified for XG 0.05% in Table 2

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Figure 9

Effective viscosity evolution for a water-XG 0.05% solution on a glass substrate. n=0.70, Ren=1667, We=177, and contact angle values as specified for XG 0.05% in Table 2

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Figure 10

Comparison of Newtonian and non-Newtonian diameter predictions on a glass substrate for a water-XG 0.05% deposition (n=0.70, Ren=1667, and We=177) and an analogous Newtonian deposition (n=1, μ=4 mPa s, Ren=1593, and We=177). Contact angle values as specified for XG 0.05% in Table 2.

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