CAE-Companion-2018-2019

Theory WISSEN CAE

One classical application is the analysis of the effects of slosh- ing water in a tank. Fig. 4 shows the relative movement of water during a deceleration of the tank from a certain initial velocity. Not only the connection-forces to the carrying struc- ture can be analyzed but also different measures to lessen the sloshing effects can be simulated and evaluated. In the same manner Fig. 5 shows the effects of water move- ment caused by the drop test of a customary PET-bottle.

and w can

The relation between the three velocities

be derived from the relation of

and leads to

the advective velocity . It constitutes the particle velocity relative to the mesh from the viewpoint of the spatial configuration since both and are variations of the coordinate x . Numerical implementation To deal with the necessary advection for the Eulerian part it has proven useful to split a simulation into a Lagrangian step and an Eulerian step. In the first step all advection is inhibited so there is generally no difference between this step and an ordinary simulation process in structural mechanics. As long as the distortions of the mesh are rea- sonable the Lagrangian formulation is applied. However as soon as the distortions exceed a certain threshold a so called “rezoning” process is executed as shown in Fig. 3.

Figure 5: Movement of Water in a drop-test of a PET-bottle

Another large area for ALE simulation is the capability to simulate shockwave propagations induced by explosions. Fig. 6 shows the propagation of a dust deflagration inside a filter housing. By means of ALE simulations the influence of different measures such as flame traps or gates on the shockwave propagation and thereby on the deformation of the housing can be evaluated.

During this process the nodes of the mesh are moved back to their initial positions. At the same time all material volume and state variables (in Fig. 3 called „Flux“) are transported between the elements in an advection-step. The advection rules however can differ from solver to solver. Examples of application Figure 3: Rezoning Process for highly distorted elements

Figure 4: Water sloshing in a tank

Figure 6: Shockwave propagation in a filter housing resulting from a dust explosion

CAEWissen by courtesy of Heiko Honermeier, Ingenieurbüro Huß & Feickert GbR, www.ihf-ffm.de.

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