Читать книгу The Rheology Handbook - Thomas Mezger - Страница 9

Figure 2.1: The Two-Plates model for shear tests to illustrate the velocity distribution of a flowing fluid in the shear gap

Figure 2.2: Laminar flow in the form of planar fluid layers

The Two-Plates model is used to define fundamental rheological parameters (see Figure 2.1). The upper plate with the (shear) area A is set in motion by the (shear) force F and the resulting velocity v is measured. The lower plate is fixed (v = 0). Between the plates there is the distance h, and the sample is sheared in this shear gap. It is assumed that the following shear conditions are occurring:

1 The sample shows adhesion to both plates without any wall-slip effects.

2 There are laminar flow conditions, i. e. flow can be imagined in the form of layers. Therefore, there is no turbulent flow, i. e. no vortices are appearing.

Accurate calculation of the rheological parameters is only possible if both conditions are met.