Measurement of the first normal-stress difference at high shear rates for a polyisobutylene/decalin solution ?D2?

The first normal stress difference (N1) as well as shear stress of non-Brownian hard-sphere suspensions in small to large amplitude oscillatory shear flow is investigated.

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Effect of Inner Cavity’s Gas Flow Rate on the Extrusion Forming of Plastic Micro-Pipe

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.842.279 ◽

2020 ◽

Vol 842 ◽

pp. 279-284

Author(s):

Zhong Ren ◽

Xing Yuan Huang

Keyword(s):

Finite Element ◽

Normal Stress ◽

Flow Rate ◽

Gas Flow ◽

Normal Stress Difference ◽

Stress Difference ◽

Gas Flow Rate ◽

Flow Rates ◽

First Normal Stress Difference ◽

Extrusion Forming

During the manufacture of plastic micro-pipe, a certain volume of gas should be properly injected into the inner cavity to overcome the collapse and adhesion problems. In this work, the extrusion forming of plastic micro-tube under the role of inner cavity’s gas were numerically studied. At the same time, the effect of inner cavity’s gas flow rate on the extrusion deformation of plastic micro-pipe was also numerically investigated by using the finite element method. A kind of 2D two-phase fluid geometric model and finite element mesh were established and some reasonable boundary conditions and material parameters were imposed. Under a fixed volume flow rate of melt, different flow rates of inner cavity gas were imposed on the inlet of inner cavity’s gas. The extrusion deformation profile and deformation ratio of plastic micro-pipe under different flow rates of gas were all obtained. To ascertain the mechanisms of effect of inner cavity’s gas flow rate on the extrusion deformation of plastic micro-tube, the flow velocities, pressure, shear rate, normal stress, and the first normal stress difference of melt all obtained and analyzed. Numerical results show that with the increase of inner cavity’s gas flow rate, the radial velocity, axial velocity, pressure, shear rate, normal stress, and the first normal stress difference of melt all increase, which makes the extrusion deformation become more and more serious. In practice, reasonable controlling of the inner cavity’s gas flow rate is very important. In the other hand, it can adjust the size of extruded plastic micro-pipe.

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Normal stresses and microstructure in bounded sheared suspensions via Stokesian Dynamics simulations

Journal of Fluid Mechanics ◽

10.1017/s0022112000008375 ◽

2000 ◽

Vol 412 ◽

pp. 279-301 ◽

Cited By ~ 58

Author(s):

ANUGRAH SINGH ◽

PRABHU R. NOTT

Keyword(s):

Normal Stress ◽

Couette Flow ◽

Normal Stress Difference ◽

Stress Difference ◽

Normal Stresses ◽

Plane Couette Flow ◽

Stokesian Dynamics ◽

First Normal Stress Difference ◽

Particle Pressure ◽

Dynamics Simulations

We report the normal stresses in a non-Brownian suspension in plane Couette flow determined from Stokesian Dynamics simulations. The presence of normal stresses that are linear in the shear rate in a viscometric flow indicates a non-Newtonian character of the suspension, which is otherwise Newtonian. While in itself of interest, this phenomenon is also important because it is believed that normal stresses determine the migration of particles in flows with inhomogeneous shear fields. We simulate plane Couette flow by placing a layer of clear fluid adjacent to one wall in the master cell, which is then replicated periodically. From a combination of the traceless hydrodynamic stresslet on the suspended particles, the stresslet due to (non-hydrodynamic) inter-particle forces, and the total normal force on the walls, we determine the hydrodynamic and inter-particle force contributions to the isotropic ‘particle pressure’ and the first normal stress difference. We determine the stresses for a range of the particle concentration and the Couette gap. The particle pressure and the first normal stress difference exhibit a monotonic increase with the mean particle volume fraction ϕ. The ratio of normal to shear stresses on the walls also increases with ϕ, substantiating the result of Nott & Brady (1994) that this condition is required for stability to concentration fluctuations. We also study the microstructure by extracting the pair distribution function from our simulations; our results are in agreement with previous studies showing anisotropy in the pair distribution, which is the cause of normal stresses.

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Vliv smykové viskozity a elasticity na senzorickou viskozitu modelových kapalných potravin

Czech Journal of Food Sciences ◽

10.17221/10016-cjfs ◽

1999 ◽

Vol 17 (No. 1) ◽

pp. 23-30 ◽

Cited By ~ 3

Author(s):

P. Novotna ◽

M. Houska ◽

V. Sopr ◽

H. Valentova ◽

P. Stern

Keyword(s):

Shear Flow ◽

Normal Stress ◽

Shear Viscosity ◽

Normal Stress Difference ◽

Rheological Parameters ◽

Cellulose Derivatives ◽

Moderate Increase ◽

Stress Difference ◽

First Normal Stress Difference ◽

Normal Difference

The shear flow rheological properties of sugar solutions (70% w/w concentration) modified by different cellulose derivatives have been measured. Thickeners were expected to cause the viscoelastic behaviour of the resulting sol ution. Therefore, the elastic rheological parameters were measured by oscillatory shear technique (phase angle, elastic modulus) and also the first normal stress difference N<sub>1</sub>. The increase of thickener concen tration caused a moderate increase of non-Newtonian behaviour in the shear flow. The sensory viscosity (ra nged between 0 and 100%) was evaluated by five different methods - as an effort for stirring with teaspoon, time for flowing down the spoon, slurping from spoon, compression between tongue and palate and swallowing. The influence of shear viscosity and first normal difference on sensory viscosity was tested. Correlation procedu re between change of sensory viscosity .tlSE and change of shear viscosity .tlJ.Iz showed that only for swallowing there is a statistically evident dependence. The correlation between change of sensory viscosity t.SE and first normal stress difference N<sub>1</sub> is not statistically evident. For all the methods of sensory evaluation the dependence between these parameters is only weak and indirect (with increasing normal stress difference the sensory viscosity is decreasing).

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