Shear sine-flow

Figure 5. The stress curves for BK-60 associated with a sine wave strain of amplitude 1.5 x 10 radians and frequency of 0.06 Hz before (A) and-after (B) shearing with steady shear flow (shear rate 60 sec ) for 1 minute.

The sine form of the damping function leads to another major problem, which lays in the occurrence of undesirable oscillations in transient shear flows (Figure 11). This phenomenon may be misleading for example when modelling instabilities in complex flows, since it is then hardly possible to distinguish between real phenomena and those generated by the model itself. 

In the rheological structure of most food systems there is a viscous element present, and the deformation curves are often highly influenced by the rate of the imposed strain. This is due to the fact that the material relaxes (or flows) while tested under compression and the resultant deformation of this flow is dependent on the nature of the viscous element (Szczesniak, 1963 Peleg and Bagley, 1983). In the viscoelastic food systems, where during processing it is caused to oscillate sinusoidally, the strain curve may or may not be a sine wave. In cases when a periodic oscillatory strain is applied on a food system like fluid material, oscillating stress can be observed. The ideal elastic solid produces a shear stress wave in phase with... 

Work is still going on as to what the time domain response of the ER effect really depends on [105] or what is its meaning in terms of the fluid design. The initial and true ER effect in a valve, for example, is not the main concern it is also not the true time of the full pressure rise, the valve geometry, flow rate and other factors being involved. In the shear mode the position is similar yet the torque/input voltage response limit in response to small sine waves has been claimed to be as high as 1000 Hz. 

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