Semi--numerical Simulation of a Miniaturized Vibrating Membrane--Rheometer
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Sensor+Test 2009 Konferenz
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For online process monitoring purposes micro--rheometers based upon quartz resonators are commonly used but suffer from weak comparability of the results compared to those obtained from traditional laboratory viscometers. This discrepancy is partly be explained by the low agitation of the measured liquid within these micro--rheometers -- this issue is addressed by larger deformation at lower frequencies in our present measurement setup. In our contribution we investigate a miniaturized clamped membrane device. This system consists of a sample cell filled with the liquid under test. Its bottom and top side both are sealed by PMMA-membranes which are excited to vibrations. For the analysis of this problem finite element (FE) solvers fail due to the large amount of elements required for adequate discretization. The viscosity coefficient of the liquid under test is linearly related to the power dissipation due to shear velocity gradients in the sample fluid which causes a finite Q--factor of the resonance peak.