scholarly journals Shear Stress Dependence of Flow Properties of Gelatinized Modified Starch Suspensions.

1996 ◽  
Vol 43 (1) ◽  
pp. 56-63 ◽  
Author(s):  
Hitoshi ASADA ◽  
Kanichi SUZUKI
Keyword(s):  
Shear Stress ◽  
Modified Starch ◽  
Stress Dependence ◽  
Flow Properties

scholarly journals Derivation of Ice Sliding Properties from The Numerical Modelling of Surging Ice Masses

1979 ◽  
Vol 23 (89) ◽  
pp. 420-421 ◽  
Author(s):  
W. F. Budd ◽  
B. J. McInnes ◽  
I. Smith
Keyword(s):  
Shear Stress ◽  
Numerical Modelling ◽  
Sliding Friction ◽  
Two Dimensional ◽  
Dimensional Model ◽  
Flow Properties ◽  
Two Dimensional Model ◽  
Two Parameters ◽  
Basal Shear ◽  
Best Fit

Abstract It is difficult to deduce sliding properties from the numerical modelling of ordinary glaciers because the flow law of ice is still not known well enough to clearly differentiate sliding from internal deformation of the ice. For glaciers undergoing high-speed surges it appears that the majority of the total speed is due to sliding. Furthermore the average basal shear stress of the ice mass is lowered during the surge. This suggests that surging glaciers can be modelled by incorporating a sliding friction law which has the effective friction coefficient decreasing for high velocities. A relation of this type has been found for ice sliding on granite at −0.5°C by Barnes and others (1971) and has also been obtained for rough slabs with ice at the pressure-melting point by Budd and others (1979). A simple two-dimensional model was developed by Budd and McInnes (1974) and Budd (1975), which was found to exhibit the typical periodic surge-like characteristics of real ice masses. Since the sliding-stress relation for the low velocities and stresses was not known, and was not so important for the surges, it was decided to use the condition of gross equilibrium (i.e. that the ice mass as a whole does not accelerate) together with a single-parameter relation for the way in which the friction decreases with stress and velocity to prescribe the basal shear-stress distribution. The low-stress-velocity relation can thus be obtained as a result. This two-dimensional model has now been parameterized to take account of the three-dimensional aspects of real ice masses. A number of ice masses have since been closely matched by the model including three well-known surging ice masses: Lednik Medvezhiy, Variegated Glacier, and Bruarjökull. Since the flow properties of ice are so poorly known—especially for longitudinal stress and strain-rates—the model has been run with two unknown parameters: one a flow-law parameter (η) and the other a sliding parameter (ø). The model is run over a wide range of these two parameters to see if a good match can be made to the real ice masses and if so what the values of the parameters η and ø are for best fit. The matching of the three above ice masses gave very similar values for each of the two parameters η and ø, the value of η being within the range of values expected for the flow properties of temperate ice as determined by laboratory experiments. Using the same values of η and ø it is found that the ordinary glaciers modelled so far do not develop surging but that they could do if the value of ø were increased or if the mass-balance input were sufficiently increased. For Lednik Medvezhiy a detailed analysis of the friction coefficient with velocity was carried out and it was found that the values required for best fit showed a very close agreement to the sliding friction curve of Barnes and others (1971) at −0.5°C. It is concluded that this type of sliding relation can account for the major features of glacier surge phenomena. Finally it is apparent that the numerical modelling technique can be used very effectively to test any large-scale bulk sliding relation by the analysis of real surges of ice masses and in addition can provide further insight into the sliding relation in association with other stresses in the ice mass.

Flow Behaviors of Commercial Food Thickeners Used for the Management of Dysphagia: Effect of Temperature

2012 ◽  
Vol 8 (2) ◽  
Author(s):  
Se-Ra Hong ◽  
Dong-Soo Sun ◽  
Whachun Yoo ◽  
Byoungseung Yoo
Keyword(s):  
Shear Stress ◽  
Yield Stress ◽  
Flow Behavior ◽  
Effect Of Temperature ◽  
Rheological Parameters ◽  
High Shear ◽  
Flow Properties ◽  
Different Temperatures ◽  
Management Of Dysphagia ◽  
Arrhenius Temperature

Gum-based food thickeners are widely used to care for patients with dysphagia in Korea. In this study, the flow properties of commercially available gum-based food thickeners marketed in Korea were determined as a function of temperature. The flow properties of thickeners were determined based on the rheological parameters of the power law and Casson models. Changes in shear stress with the rate of shear (1-100 s-1) at different temperatures (5, 20, 35, and 50 oC) were independent of the type of thickener. All thickeners had high shear-thinning behavior (n=0.08-0.18) with yield stress at the different temperatures tested. In general, apparent viscosity (na,50) values progressively decreased with an increase in temperature. In addition, the consistency index (K) and Casson yield stress (σoc) values did not change much upon an increase in temperature from 5 to 35 oC, except for sample B. In the temperature range of 5-50 oC, the thickeners followed an Arrhenius temperature relationship with a high determination coefficient (R2=0.93-0.97): activation energies (Ea) for the flow of thickeners were in the range of 2.44 - 10.7 kJ/mol. Rheological parameters demonstrated considerable differences in flow behavior between the different gum-based food thickeners, indicating that their flow properties are related to the type of thickener and the flow properties of gum.

Influence of fibrinogen on flow properties of erythrocyte suspensions

1964 ◽  
Vol 207 (5) ◽  
pp. 1035-1040 ◽  
Author(s):  
Roe E. Wells ◽  
Thomas H. Gawronski ◽  
Paul J. Cox ◽  
Richard D. Perera
Keyword(s):  
Shear Stress ◽  
Shear Rate ◽  
Cell Aggregation ◽  
Cell Suspensions ◽  
Fibrinogen Concentration ◽  
Sedimentation Rates ◽  
Cell Aggregates ◽  
Red Cell ◽  
Flow Properties ◽  
Yield Value

The influence of fibrinogen on the flow properties of red cell suspensions (hematocrit 41) was studied by viscometry at low rates of shear (0.1–20 sec–1). These findings were correlated with sedimentation rates and photomicrographical studies of cell aggregation. Fibrinogen concentration was varied from 0.3 to 2.0 g/100 ml. The viscosity of the pure solutions of fibrinogen was independent of shear rate, ranging from 0.87 to 1.7 centipoise (cp) at 37 C. The viscosity of the cell suspensions at 10 sec–1 varied from 4.3 cp in 0.3 g/100 ml fibrinogen to 14 cp in 2 g/100 ml fibrinogen. All suspensions were markedly dependent on shear rate, viscosity increasing in exponential-like fashion as shear rate decreased. Extrapolation of plots of shear stress1/2 versus shear rate1/2 revealed the suspensions to sustain a finite stress without deformation or flow, the "yield value" increasing as fibrinogen concentration increased. Photomicrographs of dilute cell suspensions revealed the formation of cell aggregates and rouleaux, increasing in size and descent velocity as fibrinogen concentration increased.

scholarly journals Surface shear stress dependence of gas transfer velocity parameterizations using DNS

2016 ◽  
Vol 121 (10) ◽  
pp. 7369-7389 ◽  
Author(s):  
S. T. Fredriksson ◽  
L. Arneborg ◽  
H. Nilsson ◽  
R. A. Handler
Keyword(s):  
Shear Stress ◽  
Gas Transfer ◽  
Surface Shear Stress ◽  
Stress Dependence ◽  
Transfer Velocity ◽  
Surface Shear ◽  
Gas Transfer Velocity

scholarly journals Determination of loading capacity depending on bevel angle of the wooden bonded scarf joint

2010 ◽  
Vol 56 (No. 4) ◽  
pp. 159-165 ◽  
Author(s):  
O. Dajbych ◽  
D. Herák ◽  
A. Sedláček ◽  
G. Gűrdil
Keyword(s):  
Shear Stress ◽  
Normal Stress ◽  
Theoretical Method ◽  
Loading Capacity ◽  
Stress Dependence ◽  
Method Of Determination ◽  
Scarf Joint ◽  
Formula Derivation ◽  
Mohr’S Circle

The paper is focused on comparison of experimental and simple theoretical method of determination of loading capacity depending on bevel angle of wooden bonded scarf joint. The Mohr's circle principle, thus shear stress dependence on normal stress, is used for loading capacity formula derivation. It has been established that for random bevel angle under approximately 70 degrees the future loading capacity can be calculated from knowledge of ultimate force for bevel angle 0 and 90 degrees.

scholarly journals Shear Stress Dependence of Melt Viscosity for Polypropylene

1965 ◽  
Vol 22 (244) ◽  
pp. 513-519
Author(s):  
Nobuo Yamada ◽  
Naoyuki Kishi ◽  
Hiroyuki Iizuka
Keyword(s):  
Shear Stress ◽  
Stress Dependence ◽  
Melt Viscosity

A Reduced-Order Model of the Mean Properties of a Turbulent Wall Boundary Layer at a Zero Pressure Gradient

2014 ◽  
Vol 136 (3) ◽  
Author(s):  
Lei Xu ◽  
Zvi Rusak ◽  
Luciano Castillo
Keyword(s):  
Boundary Layer ◽  
Shear Stress ◽  
Reynolds Shear Stress ◽  
Streamwise Velocity ◽  
Similarity Function ◽  
Mixing Length ◽  
Flow Properties ◽  
Normal Coordinate ◽  
Streamwise Location ◽  
The Mean

A novel two-equations model for computing the flow properties of a spatially-developing, incompressible, zero-pressure-gradient, turbulent boundary layer over a smooth, flat wall is developed. The mean streamwise velocity component inside the boundary layer is described by the Reynolds-averaged Navier–Stokes equation where the Reynolds shear stress is given by an extended mixing-length model. The nondimensional form of the mixing length is described by a polynomial function in terms of the nondimensional wall normal coordinate. Moreover, a stream function approach is applied with a leading-order term described by a similarity function. Two ordinary differential equations are derived for the solution of the similarity function along the wall normal coordinate and for its streamwise location. A numerical integration scheme of the model equations is developed and enables the solution of flow properties. The coefficients of the mixing-length polynomial function are modified at each streamwise location as part of solution iterations to satisfy the wall and far-field boundary conditions and adjust the local boundary layer thickness, δ99.4, to a location where streamwise speed is 99.4% of the far-field streamwise velocity. The elegance of the present approach is established through the successful solution of the various flow properties across the boundary layer (i.e., mean streamwise velocity, viscous stress, Reynolds shear stress, skin friction coefficient, and growth rate of boundary layer among others) from the laminar regime all the way to the fully turbulent regime. It is found that results agree with much available experimental data and direct numerical simulations for a wide range of Reθ based on the momentum thickness (Reθ) from 15 up to 106, except for the transition region from laminar to turbulent flow. Furthermore, results shed light on the von Kármán constant as a function of Reθ, the possible four-layer nature of the mean streamwise velocity profile, the universal profiles of the streamwise velocity and the Reynolds shear stress at high Reθ, and the scaling laws at the outer region.

scholarly journals Alkyl-Chitosan-Based Adhesive: Water Resistance Improvement

Molecules ◽  
2019 ◽  
Vol 24 (10) ◽  
pp. 1987 ◽  
Author(s):  
Narimane Mati-Baouche ◽  
Cédric Delattre ◽  
Hélène de Baynast ◽  
Michel Grédiac ◽  
Jean-Denis Mathias ◽  
...  
Keyword(s):  
Shear Stress ◽  
Bond Strength ◽  
Chemical Modification ◽  
Chemical Structure ◽  
Water Resistance ◽  
Flow Properties ◽  
Adhesive Properties ◽  
Alkyl Chains ◽  
Modified Polymers ◽  
Resistance Improvement

A chemical modification by grafting alkyl chains using an octanal (C8) on chitosan was conducted with the aim to improve its water resistance for bonding applications. The chemical structure of the modified polymers was determined by NMR analyses revealing two alkylation degrees (10 and 15%). In this study, the flow properties of alkyl-chitosans were also evaluated. An increase in the viscosity was observed in alkyl-chitosan solutions compared with solutions of the same concentration based on native chitosan. Moreover, the evaluation of the adhesive strength (bond strength and shear stress) of both native and alkyl-chitosans was performed on two different double-lap adherends (aluminum and wood). Alkyl-chitosans (10 and 15%) maintain sufficient adhesive properties on wood and exhibit better water resistance compared to native chitosan.

Sign in / Sign up

Export Citation Format

Share Document