Inertia effects in rheometrical flow systems

The flow field of a linear viscoelastic material in the orthogonal rheometer, taking fluid inertia into account, has been studied theoretically and an exact solution is given. The flow field of a Newtonian liquid is included in this solution as a special case. The forces on the plates are readily deduced from this solution. The paper concludes with an energy consideration

Inertia effects in rheometrical flow systems Part 2: The balance rheometer

The flow field of a linear viscoelastic fluid in the balance rheometer, taking fluid inertia into account, has been studied theoretically and an exact solution is given. The flow field of a Newtonian fluid is included in this solution as a special case. The forces and couples on the hemispheres are readily deduced from this solution

Relations between loss angles in isotropic linear viscoelastic materials

Starting from the relations between complex dynamic moduli simple diagrams are deduced connecting the locus of complex Poisson's ratiov* ≡v′ +iv″ in the complexv* plane with differences between various loss angles. From these diagrams the sequence of magnitudes of several loss angles appearing in linear viscoelastic theory is deduced. Although theoretically this sequence depends on the values ofv′ andv″, it is found experimentally that for polymeric materials, due to the fact that the values ofv′ andv″ are constrained to limited ranges, general rules can be given. The sequences deduced are compared with experimental data. Finally some relations are used to illustrate the phase relationships between stress and deformations in an uniaxial stress experiment. From these relations a new method for measuring the loss angle in compression is suggested

Community Engagement as a Student-Athlete

Hannah Waterman discusses student engagement at Linfield College with regard to her involvement with the volleyball team.https://digitalcommons.linfield.edu/inauguration2019_students/1020/thumbnail.jp

Place, space and the reinvention of social emancipation on a global scale : second thoughts on the Third World Social Forum

empowerment;trade unions;internationalism;social movements

Inertia effects in rheometrical flow systems Part 3: Some energy considerations with respect to the flow field in the balance rheometer

Following up a previous paper by one of the presents authors on the flow field in the balance rheometer, inertia effects being included, in this paper some energy considerations with respect to this flow field are presented. It is shown that in a frame rotating with the same angular velocity as the hemispheres the power supplied by these hemispheres equals the rate of energy dissipation in the sample, i.e. in this coordinate system there is no “stress power paradox”. Further it is shown that the “elastic” couple for a Newtonian liquid, appearing in the calculations, stems from the extra kinetic energy caused by the deviation of the actual flow field from the flow field that appears when inertia effects are ignored