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ISBN 9783843928113

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978-3-8439-2811-3, Reihe Ingenieurwissenschaften

Dominik Staab
Numerical treatment of multiphase flows coupled with acoustics for surface tension dominated flows

188 Seiten, Dissertation Technische Universität Darmstadt (2016), Softcover, A5

Zusammenfassung / Abstract

In many areas of industry and science one is concerned with the improvement of multiphase flow processes. In order to effectively improve these processes, multiphase flows and acoustic fields are predicted with the help of numerical simulations. The goal of this study was therefore to develop a flow solver for heterogeneous media with the ability to predict the resulting sound.

To calculate multiphase flows, the Volume-of-Fluid-Method (VOF) was used, which was integrated into the flow solver FASTEST. This method was chosen because of its robustness with respect to the coalescence and the rupture of bubbles and droplets, but also because of its conservativity. The implementation was tested by verification and comparison with already validated solvers.

In order to include the effects of surface tension between two phases, efficient models from the literature were implemented and evaluated. This includes the implementation of the Level-Set-Method, which was coupled with the VOF to compute highly accurate surface tensions. In addition, a new efficient surface tension model was developed and verified. The new model was compared with other models, which demonstrated that it calculates the surface tension quickly and accurately.

To solve the acoustic system, the linearized Euler equations (LEE) were coupled to the multiphase flow equations. The already implemented single-phase LEE have been extended and verified for heterogeneous media. The resulting system is able to calculate the acoustic fields and to transport the sound waves through phase interfaces, taking into account transmission and refraction.

A holistic concept for the efficient calculation of multiphase flows coupled with the acoustics was developed. This concept includes the aforementioned components, but also the ability to move the grid. This was analyzed based on rigid body motions. In this case, an equation of motion for the translational movement of floating and sinking objects in the context of multiphase flow was implemented and verified. This concept is also able to calculate the sound generation based on the multiphase flows, which was made plausible by the test case of an oscillating drop.