 Evolution of Turbulent Energy Spectrum THESIS TOPIC PROPOSAL Institute: Budapest University of Technology and Economics mechanical engineering Géza Pattantyús-Ábrahám Doctoral School of Mechanical Engineering Thesis supervisor: Gergely Kristóf Location of studies (in Hungarian): BME Department of Fluid Mechanics Abbreviation of location of studies: ÁT Description of the research topic: a.) Preliminaries: Turbulence modeling remains challenging due to the wide range of spatial and temporal scales involved. Current approaches, such as RANS and LES, provide limited information on the turbulent energy spectrum, leading to uncertainties in predicting flow characteristics. b.) Aim of research: The main objective of the research is to provide a mathematical description of the turbulent energy spectrum's evolution, to connect new models with general-purpose numerical flow models, and to apply them to solve practical problems. Our goal is to produce the complete turbulent energy spectrum at significant points in the flow field using available turbulence information (CFD model results) and the numerical solution of the Kolmogorov equation, verifying the reliability of the underlying flow model and enabling more accurate determination of transport coefficients, and provision of acoustic sources and mechanical excitations for further analysis. c.) Tasks, main items, necessary time: In this exciting PhD project, you will have the opportunity to develop a cutting-edge turbulence model by combining various formulations of energy flux between scales, such as the Obukhov model and local models like Pao (1965). You will contribute to advancing turbulence modeling by validating and refining the model using Direct Numerical Simulation (DNS) results for decaying and equilibrium turbulence. During the four-year project, you will work on implementing the model in computational frameworks, applying it to real-world engineering problems, and collaborating with industrial partners. You will have access to state-of-the-art experimental facilities, such as wind tunnels, Particle Image Velocimetry (PIV), and Laser Doppler Velocimetry (LDV) devices, enabling you to obtain high-quality validation data. The project will result in the development of an open-source turbulence modeling tool, with your work published in high-impact journals and presented at international conferences. This PhD project offers a unique opportunity to make a lasting impact on turbulence research, while collaborating with prestigious institutions and engaging with industry partners to apply your findings to practical engineering challenges. Year 1: • Conduct an extensive literature review on energy flux models • Develop a comprehensive flux model combining Obukhov and Pao (1965) models • Implement the combined flux model and the solution method in Python • Perform initial validation using DNS results for decaying and equilibrium turbulence • Refine the model based on the validation results Year 2: • Apply the refined flux model to various turbulence scenarios • Obtain validation data using wind tunnels, PIV, and LDV devices • Collaborate with partner institutions for additional validation data • Refine the model based on new validation results • Begin preparing publications for high-impact journals Year 3: • Develop user guides and best practices for the spectral model • Establish collaborations with interested industrial partners • Apply the model to real-world engineering problems in collaboration with partners • Prepare and submit publications to high-impact journals • Present findings at international conferences and workshops Year 4: • Finalize the spectral model for open-source release • Create an open-source repository for the model and related resources • Promote the availability and benefits of the open-source tool • Engage with more industrial partners for potential collaborations • Complete any remaining publications and conference presentations d.) Required equipment: The necessary measuring devices and computing equipment are available at the BME Department of Fluid Mechanics. e.) Expected scientific results: 1. Spectral model, which provides more detailed information about turbulence in certain points of the flow space than current CFD models. 2. A flux model suitable for a more precise description of the energy exchange between turbulent scales. 3. Method for generating the boundary conditions (sources) of the spectral model. 4. Method for selecting the important points of the flow field from the point of view of acoustic and dynamic use. f.) References: • Ferziger, J. H., & Peric, M. (2002). Computational methods for fluid dynamics. Springer Science & Business Media. • Pope, S. B. (2000). Turbulent Flows. Cambridge University Press. • KRISTÓF, Gergely; PAPP, Bálint. Application of GPU-based Large Eddy Simulation in urban dispersion studies. Atmosphere, 2018, 9.11: 442. • Kristóf, G.; Papp, B.; Wang, H.; Hang, J. Investigation of the flow and dispersion characteristics of repeated orographic structures by assuming transient wind forcing. Journal of Wind Engineering and Industrial Aerodynamics, 2020, 197, 104087. https://doi.org/10.1016/j.jweia.2019.104087 • Papp, B., Kristóf, G., Istók, B., Koren, M., Balczó, M., Balogh, M. (2021). Measurement-driven Large Eddy Simulation of dispersion in street canyons of variable building height. Journal of Wind Engineering and Industrial Aerodynamics, 211, 104495. https://doi.org/10.1016/j.jweia.2020.104495 • Papp, B., Kristóf, G., Gromke, C. (2021). Application and assessment of a GPU-based LES method for predicting dynamic wind loads on buildings. Journal of Wind Engineering and Industrial Aerodynamics. https://doi.org/10.1016/j.jweia.2021.104739 Required language skills: English Number of students who can be accepted: 1 Deadline for application: 2024-10-15 |