Friedrich, Jonas (2024)
Numerical Methods for the Simulation of the Acoustics of Multiphase Flows.
Technische Universität Darmstadt
doi: 10.26083/tuprints-00028036
Dissertation, Erstveröffentlichung, Verlagsversion
Kurzbeschreibung (Abstract)
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 unsteady flow field. By adapting the acoustic source term to the multiphase environment, the difficulties of a moving interface are overcome. The coupled validation test cases show the expected results. For the final part of this work, the developed numerical methods are applied on a three-dimensional test case. A complex and not yet fully understood example of multiphase acoustics is the sound of a water drop impacting into a water pool, as can be heard from a tripping tap. First, the necessary of a very high resolution in space and time as well as an accurate curvature model is demonstrated. Afterwards, the results of the simulations are compared to experimental data with satisfactory agreement and further insights on the sound producing physics are given.
Typ des Eintrags: | Dissertation | ||||
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Erschienen: | 2024 | ||||
Autor(en): | Friedrich, Jonas | ||||
Art des Eintrags: | Erstveröffentlichung | ||||
Titel: | Numerical Methods for the Simulation of the Acoustics of Multiphase Flows | ||||
Sprache: | Englisch | ||||
Referenten: | Schäfer, Prof. Dr. Michael ; Weeger, Prof. Dr. Oliver | ||||
Publikationsjahr: | 2 September 2024 | ||||
Ort: | Darmstadt | ||||
Kollation: | ix, 111 Seiten | ||||
Datum der mündlichen Prüfung: | 9 Juli 2024 | ||||
DOI: | 10.26083/tuprints-00028036 | ||||
URL / URN: | https://tuprints.ulb.tu-darmstadt.de/28036 | ||||
Kurzbeschreibung (Abstract): | 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 unsteady flow field. By adapting the acoustic source term to the multiphase environment, the difficulties of a moving interface are overcome. The coupled validation test cases show the expected results. For the final part of this work, the developed numerical methods are applied on a three-dimensional test case. A complex and not yet fully understood example of multiphase acoustics is the sound of a water drop impacting into a water pool, as can be heard from a tripping tap. First, the necessary of a very high resolution in space and time as well as an accurate curvature model is demonstrated. Afterwards, the results of the simulations are compared to experimental data with satisfactory agreement and further insights on the sound producing physics are given. |
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Status: | Verlagsversion | ||||
URN: | urn:nbn:de:tuda-tuprints-280364 | ||||
Sachgruppe der Dewey Dezimalklassifikatin (DDC): | 600 Technik, Medizin, angewandte Wissenschaften > 620 Ingenieurwissenschaften und Maschinenbau | ||||
Fachbereich(e)/-gebiet(e): | 16 Fachbereich Maschinenbau 16 Fachbereich Maschinenbau > Fachgebiet für Numerische Berechnungsverfahren im Maschinenbau (FNB) |
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Hinterlegungsdatum: | 02 Sep 2024 09:16 | ||||
Letzte Änderung: | 03 Sep 2024 05:40 | ||||
PPN: | |||||
Referenten: | Schäfer, Prof. Dr. Michael ; Weeger, Prof. Dr. Oliver | ||||
Datum der mündlichen Prüfung / Verteidigung / mdl. Prüfung: | 9 Juli 2024 | ||||
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