Unterschiede
Hier werden die Unterschiede zwischen zwei Versionen angezeigt.
| Nächste Überarbeitung | Vorhergehende Überarbeitung | ||
| en:berechnungen:schergeschwindigkeit [2025/07/03 13:32] – angelegt cschall | en:berechnungen:schergeschwindigkeit [2025/09/03 11:48] (aktuell) – [Shear rate] neelest | ||
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| ====== Shear rate und shear deformation ====== | ====== Shear rate und shear deformation ====== | ||
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| + | -> [[..: | ||
| ===== Shear rate===== | ===== Shear rate===== | ||
| + | The shear rate can, as a first approximation, | ||
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| + | $$\dot \gamma = \frac{v_0}{h}$$ | ||
| + | $$\text{with}$$ | ||
| + | $$v_0 = \pi \cdot n \cdot D$$ | ||
| + | |||
| + | and the channel height $h$. | ||
| + | This equation is applied for shear and mixing sections. However, it only describes a simple drag flow of Newtonian fluids. For shear-thinning (pseudoplastic) fluids, the average shear rate is somewhat higher (also due to the superposition with pressure flow). As an approximation for conventional screw channels, the following relation applies: | ||
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| + | $$\dot \gamma = \frac{exp(0, | ||
| + | |||
| + | where $\pi_\dot m$ is the [[schlepp-druckstroemung|dimensionless throughput]] and $\varphi$ is the [[..: | ||
| ===== Shear deformation===== | ===== Shear deformation===== | ||
| + | The shear deformation $\overline{\gamma}$ describes the deformation of a volume element that is sheared due to a shear rate. Thus, shear deformation is the product of shear rate and residence time. | ||
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| + | $$\overline{\gamma}= \dot \gamma \cdot \ t$$ | ||
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| + | This is integrated along the screw length. The cumulative shear deformation gradient is a measure of the laminar mixing effect. | ||
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| + | ===Further topics=== | ||
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