Structural mechanics

vibration behavior determination of a smart density meter for slurries.

In the dredging industry, different types of materials can be dredged, for example to win construction materials or for reclamation. The dredged material is a mixture of water and typically sand, clay or boulders and this mixture is called slurry, which is transported through pipes. Measuring the density of the slurry is important for process control. Traditionally, slurry density is measured from outside the pipe using gamma radiation, which naturally entails safety risks and complicates day-to-day operations. This drawback is overcome by the Alia Density Meter (ADM) developed by Alia Instruments. They developed a smart density meter together with Demcon that works more safely and reliably, non-nuclear. The instrument works according to a mechanical measuring principle and is equipped with an electromagnetic actuator and accelerometers.



The working principle of the ADM is based on Newton’s second law (F = m*a): an electromagnetic actuator exerts a force with a known value and frequency on a pipe segment through which slurry is flowing, and an accelerometer measures the acceleration of the pipe. The mass can then be extracted, and as the volume is known, the density can be extracted as well. For optimal performance, the dynamic behaviour of the vibrating tube should be determined and understood. At Demcon multiphysics we modelled the vibrating behaviour of the tube to gain an understanding of different designs.

Slurry density

our approach.

Eigenfrequencies and their eigenmodes describe how the tube is sensitive to vibrations at a certain frequency. Hence, the eigenmodes are determined first, using Modal Analyses with Ansys Mechanical. Next, insight into the deformations of the vibrating structure is obtained then. It depends on the magnitude and direction of the actuation force which deformations and accelerations will be generated. These are important, to determine the relation between the electromagnetic actuator and the accelerometers and thus, to predict an accurate density of the slurry. This last part has been determined using Harmonic Response Analyses to generate Frequency Response Functions (FRF).


Demcon multiphysics.

Demcon multiphysics is an engineering agency with high-end expertise in the area of heat transfer, fluid dynamics, structural mechanics, acoustics, electromagnetism and nuclear physics. We support clients from a wide variety of market sectors and help them achieve their goals in research and development with deep physical insights.

We combine fundamental physical knowledge from an analytical approach with Computer Aided Engineering (CAE) simulations tools from ANSYS, MATHWORKS, COMSOL, STAR-CCM+ and FLUKA to setup, execute, analyze and evaluate numerical simulations. The use of Computational Fluid Dynamics (CFD), Finite Element Analysis (FEM / FEA), Lumped Element Modelling (LEM), Computational Electromagnetics (CEM) and Monte Carlo simulations enables us to make a virtual prototype of your design. With these techniques we can simulate the fluid and gas flows, energy exchange, heat and mass transfer, stresses, strains and vibrations in structures and the interaction of electromagnetic fields with other physical aspects like heat generation. Simulation-driven product development increases the development efficiency and reduces the product development time. Our services can therefore fully support you in the designing phase, from idea up to prototype, from prototype to final design.