Experimental uncertainties in extensional rheometry of liquids by fiber drawing

Lubricated squeezing flow experiments on wheat flour dough have been performed in constant plate speed and constant extension rate modes. The objective of this work was to assess the effects of the target values on the attained results obtained during wheat dough rheological properties measurement. Different rheometers were used to allow these operations. In both cases, each constant target speed used increases with the increasing time before reaching its stability. These increasing effects versus time are higher with greater speeds. It was obtained 20.1-41.5% of increasing time ratio between the two modes from the lower to higher speeds and for each given speed (0.005-1.5 [mm·s −1 or s −1 ]). The target speed increasing in order to reach the attained value caused sample dough deformation. These strain effects of dough are more important for high initial thickness of dough. Whatever the types of dough strain needed and target speed level used, the limit force measurable in many cases was 40 N (newton). It was a constrain factor for measured values. The data processing to obtain dough rheological properties remains too long and difficult with both measurement methods. PRACTICAL APPLICATIONSIn search of viable ways to study dough rheological properties, the uses of empirical and fundamental methods are of appropriate possibility. Several methods are further able to be used to measure and record dough rheological properties under conditions of unsteady flow. They are used to assess flour ability and provide dough with good breadmaking performance, to mimic dough stretching and to measure its resistance to rupture. Consequently, efficient and versatile methods have opened new possibilities for studying viscoelasticity behaviors related to cereals science and processing. These benefit effects make basic new methods used in breadmaking process, a powerful tool for monitoring the consistency and structural changes in dough and final bread. Because of their major importance in breadmaking process, it is essential in this study to assess the effects of the target values on the attained results in dough rheological properties measurement methods. They can help understand their implications on the data processing of these tests for reliable research on dough rheology. Journal of Texture Studies ISSN 1745-4603

show abstract

“…The conditions described by Secor et al . () and Macosko () considering wheat flour dough viscous properties were used.…”

Section: Methodsmentioning

confidence: 99%

Wheat Flour Dough Rheological Properties Measurement: Effects of the Target Values on the Attained Results

Kouassi-Koffi

Mureșan

Gnangui

et al. 2015

Journal of Texture Studies

View full text Add to dashboard Cite

show abstract

“…6 and 9 suggest that, for nearly head-on collisions, the droplets experience extensional flow rather than shear flow. At the high deformation rates investigated in our experiments, the Trouton ratio (ratio of extensional-to-shear viscosity) for xanthan solutions of comparable concentration is found to be much more than the value of 3 valid for Newtonian fluids, as shown in the works of Secor et al (1989);Fuller et al (1987); Khagram et al (1985). For the 500 ppm xanthan solution, the extensional viscosity was found to be almost two orders of magnitude higher than the corresponding shear viscosity, Tr =104.9, Fuller et al (1987).…”

Section: Energy Dissipation and Extensional Effectmentioning

confidence: 44%

Experimental investigation of non-Newtonian droplet collisions: the role of extensional viscosity

Finotello

Vrouwenvelder

et al. 2018

Exp Fluids

View full text Add to dashboard Cite

We investigate the collision behaviour of a shear thinning non-Newtonian fluid xanthan, by binary droplet collision experiments. Droplet collisions of non-Newtonian fluids are more complex than their Newtonian counterpart as the viscosity no longer remains constant during the collision process. Despite the complex collision dynamics, we are able to present a complete regime map based on non-dimensional Weber (We) number and impact parameter (B). We compare the collision outcomes of xanthan, glycerol and a milk concentrate at similar impact conditions. These experiments reveal very rich and complex collision morphologies for shear thinning xanthan solution, strikingly different from Newtonian droplet collisions. Unlike glycerol and milk, xanthan collisions show no reflexive separation even at very high We number. Instead of breakup, we observe disc-like shapes with an oscillating behaviour of the colliding droplets. A detailed analysis reveals that this outcome is related to increased viscous energy dissipation and extensional effects.

show abstract

“…Secor et al [5], developed an approximate analysis by applying an energy balance to the flow. Again, an ideal planar extensional velocity field is assumed for the test fluid.…”

Section: Methodsmentioning

confidence: 99%

“…The first two, due to Williams and Williams [6] and Secor et al [5] rely essentially on the suppositions that the sample velocity field is determined a priori and is free of shear. This is in contrast to the third method, an adaption of a contraction analysis developed by Binding [10] in which shear is permitted and account is taken of its contribution.…”

Section: Data Interpretationmentioning

confidence: 99%

“…Even this approach, however, is not entirely successful. Secor et al [5] studied lubricated planar stagnation flows and their numerical analysis demonstrated that pure planar extension throughout the die was prevented by the interaction of the die shape with the viscous normal stresses at the lubricant/sample interface. Nevertheless regions of approximately extensional flow were identified and an approximate analytical solution was proposed.…”

Section: Introductionmentioning

confidence: 98%

See 1 more Smart Citation

On the interpretation of data from Converging Flow Rheometers

Binding

Jones

1989

Rheol Acta

View full text Add to dashboard Cite

A reappraisal of data obtained from a Converging Flow Rheometer (CFR) is presented, together with new results for a specific polymer solution.Particular emphasis is placed on the interpretation of the experimental pressure data in terms of a planar extensional viscosity. It is suggested that previous interpretations, while yielding viscosity levels that appear reasonable, nevertheless fail to give the qualitative behaviour that might be expected on the basis of predictions from well accepted constitutive models. This, in the authors' opinions, arises because certain fluids, i.e. those that are highly tension-thickening, cease to flow in accordance with the assumed kinematics at high flow rates.By adapting a recently proposed approximate analysis for flow through a contraction it is shown that better qualitative behaviour, for the planar extensional viscosity, can be obtained from the Converging Flow Rheometer.

show abstract

Experimental uncertainties in extensional rheometry of liquids by fiber drawing

Cited by 16 publications

References 0 publications

Wheat Flour Dough Rheological Properties Measurement: Effects of the Target Values on the Attained Results

Wheat Flour Dough Rheological Properties Measurement: Effects of the Target Values on the Attained Results

Experimental investigation of non-Newtonian droplet collisions: the role of extensional viscosity

On the interpretation of data from Converging Flow Rheometers

Contact Info

Product

Resources

About