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Processing parallel-disk viscometry data in the presence of wall slip
Leong, Yee-Kwong,Campbell, Graeme R.,Yeow, Y. Leong,Withers, John W. The Korean Society of Rheology 2008 Korea-Australia rheology journal Vol.20 No.2
This paper describes a two-step Tikhonov regularization procedure for converting the steady shear data generated by parallel-disk viscometers, in the presence of wall slip, into a shear stress-shear rate function and a wall shear stress-slip velocity functions. If the material under test has a yield stress or a critical wall shear stress below which no slip is observed the method will also provide an estimate of these stresses. Amplification of measurement noise is kept under control by the introduction of two separate regularization parameters and Generalized Cross Validation is used to guide the selection of these parameters. The performance of this procedure is demonstrated by applying it to the parallel disk data of an oil-in-water emulsion, of a foam and of a mayonnaise.
Processing parallel-disk viscometry data in the presence of wall slip
Yee-Kwong Leong,Graeme R. Campbell,Y. Leong Yeow,John W. Withers 한국유변학회 2008 Korea-Australia rheology journal Vol.20 No.2
This paper describes a two-step Tikhonov regularization procedure for converting the steady shear data generated by parallel-disk viscometers, in the presence of wall slip, into a shear stress-shear rate function and a wall shear stress-slip velocity functions. If the material under test has a yield stress or a critical wall shear stress below which no slip is observed the method will also provide an estimate of these stresses. Amplification of measurement noise is kept under control by the introduction of two separate regularization parameters and Generalized Cross Validation is used to guide the selection of these parameters. The performance of this procedure is demonstrated by applying it to the parallel disk data of an oil-in-water emulsion, of a foam and of a mayonnaise.
A simple method of correcting the parallel plate rim shear stress for non-Newtonian behavior
Pengfei Liu,Yang Wang,Yee-Kwong Leong,Seung Hyuk Kwon,최형진 한국유변학회 2020 Korea-Australia rheology journal Vol.32 No.2
In the rheological characterization of non-Newtonian fluids in a steady torsional shear flow using a parallelplate geometry, there is a need to correct the shear stress at the rim for non-Newtonian behavior. Solving the governing torsional flow equation inversely by Tikhonov regularization using experimental torque vs. rim shear rate data is the most scientific method for obtaining the model independent shear stress. In this short communication, a simple empirical method based on using the derivative of the polynomial fit to torque vs. rim shear rate to correct for the shear stress is presented. This method can be applied to any fluid behavior. The accuracy of this method was confirmed by the outstanding agreement of between the shear stress results of the two methods of polynomial and the inverse problem for magnetorheological fluids. The performance of other correction methods was also discussed.
Flow curve analysis of a Pickering emulsion-polymerized PEDOT:PSS/PS-based electrorheological fluid
Kim, So Hee,Choi, Hyoung Jin,Leong, Yee-Kwong Institute of Physics Publishing 2017 Smart materials & structures Vol.26 No.11
<P>The steady shear electrorheological (ER) response of poly(3, 4-ethylenedioxythiophene): poly(styrene sulfonate)/polystyrene (PEDOT:PSS/PS) composite particles, which were initially fabricated from Pickering emulsion polymerization, was tested with a 10 vol% ER fluid dispersed in a silicone oil. The model independent shear rate and yield stress obtained from the raw torque-rotational speed data using a Couette type rotational rheometer under an applied electric field strength were then analyzed by Tikhonov regularization, which is the most suitable technique for solving an ill-posed inverse problem. The shear stress-shear rate data also fitted well with the data extracted from the Bingham fluid model.</P>
Pek-Ing Au,Benjamin Foo,Yee-Kwong Leong,Wen Ling Zhang,최형진 한국공업화학회 2015 Journal of Industrial and Engineering Chemistry Vol.21 No.1
Based on flow curve of graphene oxide coated polymeric microsphere based electrorheological (ER) fluid,model independent yield stress and shear rate, g˙ ðtÞ, were determined using a Tikhonov regularizationtechnique developed to solve the inverse problem of the shear rate in Couette flow viscometry. Themodel independent yield stress data were compared with that extracted from yield stress fluidmodels ofBingham plastic and Cho-Choi-Jhon (CCJ) used to fit the g˙ ðtÞ data. The agreement between modelindependent and Bingham yield stress was excellent, while the CCJ model yield stresses are generallyslightly higher.