Numerical Methods for the Simulation of the Acoustics of Multiphase Flows

2024-09-02

The noise reduction of technical systems has become one of the main challenges in the twenty-first century. In order to tackle this challenge, numerical simulations are a crucial part in the process of understanding the physical mechanisms of sound generation. Nevertheless, experiments have been traditionally used to study the complex phenomenon of sound generated by multiphase flows since there were no suitable numerical methods available. For this reason, a numerical framework for simulating acoustics produced by low Mach number multiphase flows is presented within this work. The motion of the multiphase flow is described by a single set of the Navier-Stokes equations. Various phases in the computational domain are treated as one fluid with variable material properties. The distribution of the phases is advected with the Volume of Fluid method based on a high resolution scheme methodology. To account surface tension, a singular term formulated by the Continuous Surface Tension method is added to the governing equations. For surface tension dominated flows, the accuracy of the forces around the interface is greatly dependent on the interface curvature computation. Therefore, different improvement strategies applied to curvature computation methods along with a machine learning approach are introduced and analyzed. Different orders in energy, length and time scales of the acoustics and the flow lead to a segregated handling. An acoustic/viscous splitting approach is employed for the computation of the acoustics. After the multiphase flow field is obtained, the generation and propagation of the acoustic waves is determined on the basis of the linearized Euler equations. The fluid and acoustic sets of equations are both discretized with the Finite Volume method in the in-house solver FASTEST. A one-way coupling between the two physical disciplines, justified by the difference in the characteristic scales, is accomplished by an acoustic source term derived from the uns

Ph.D. Thesis; NonPeerReviewed; info:eu-repo/semantics/doctoralThesis

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Friedrich, Jonas (2024)Numerical Methods for the Simulation of the Acoustics of Multiphase Flows. Technische Universität Darmstadtdoi: 10.26083/tuprints-00028036 Ph.D. Thesis, Primary publication, Publisher's Version
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TECHNISCHE UNIV DARMSTADT
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