@article{HasanuzzamanEivaziMerboldetal.2022, author = {Hasanuzzaman, Gazi and Eivazi, Hamidreza and Merbold, Sebastian and Egbers, Christoph and Vinuesa, Ricardo}, title = {Enhancement of PIV measurements via physics-informed neural networks}, doi = {10.1088/1361-6501/aca9eb}, year = {2022}, abstract = {Physics-informed neural networks (PINN) are machine-learning methods that have been proved to be very successful and effective for solving governing equations of fluid flow. In this work we develop a robust and efficient model within this framework and apply it to a series of two-dimensional three-component (2D3C) stereo particle-image velocimetry datasets, to reconstruct the mean velocity field and correct measurements errors in the data. Within this framework, the PINNsbased model solves the Reynolds-averaged-Navier-Stokes (RANS) equations for zeropressure-gradient turbulent boundary layer (ZPGTBL) without a prior assumption and only taking the data at the PIV domain boundaries. The TBL data has different flow conditions upstream of the measurement location due to the effect of an applied flow control via uniform blowing. The developed PINN model is very robust, adaptable and independent of the upstream flow conditions due to different rates of wall-normal blowing while predicting the mean velocity quantities simultaneously. Hence, this approach enables improving the mean-flow quantities by reducing errors in the PIV data. For comparison, a similar analysis has been applied to numerical data obtained from a spatially-developing ZPGTBL and an adverse-pressure-gradient (APG) TBL over a NACA4412 airfoil geometry. The PINNs-predicted results have less than 1\% error in the streamwise velocity and are in excellent agreement with the reference data. This shows that PINNs has potential applicability to shear-driven turbulent flows with different flow histories, which includes experiments and numerical simulations for predicting high-fidelity data.}, subject = {Machine learning; Particle image velocimetry; Turbulent boundary layer; Large Eddy Simulation; Measurement; Maschinelles Lernen; Turbulente Grenzschicht; Physikalisch informiertes neuronales Netz; Messung; Turbulente Grenzschicht; Neuronales Netz; Maschinelles Lernen; Particle-Image-Velocimetry}, language = {en} } @phdthesis{Hasanuzzaman2021, author = {Hasanuzzaman, Gazi}, title = {Experimental investigation of turbulent boundary layer with uniform blowing at moderate and high Reynolds numbers}, doi = {10.26127/BTUOpen-5566}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:co1-opus4-55660}, school = {BTU Cottbus - Senftenberg}, year = {2021}, abstract = {Experimental investigation in turbulent boundary layer flows represents one of the canonical geometries of wall bounded shear flows. Utmost relevance of such experiments, however, is applied in the engineering applications in aerospace and marine industries. In particular, continuous effort is being imparted to explore the underlying physics of the flow in order to develop models for numerical tools and to achieve flow control. Within the scope of this Ph. D. topic, application of active control method such as micro-blowing effect in the incompressible, zero pressure gradient turbulent boundary layer was investigated. Turbulent boundary layer flow is particularly interesting as well as challenging due to the presence of different interacting scales which are increasingly becoming significant as the flow inertial conditions keeps growing. Therefore, energy content of the coherent structures in outer layer becomes stronger and necessitates measurements in relatively large Reynolds number. Present control experiments in turbulent boundary layer can be split into two different work segments, where one is objected towards the data measurements in turbulent boundary layer over smooth surface with and without any external perturbation. Here, perturbation is applied in the form of wall normal blowing while keeping the magnitude of blowing very low compared to the free stream velocity. For the subsequent results reported here, magnitude of blowing ratio was varied between 0\%~6\%. In the first part of the present thesis e.g. 0.415×10e+3≤Reτ≤1.160×10e+3, measurements were performed at the Brandenburg University of Technology wind tunnel. Non-intrusive Laser Doppler Anemometry was applied to carry out a series of measurements on a zero pressure gradient flat plate turbulent boundary layer. Blowing ratio through the perforated surface was varied between 0.17\%~1.52\% of the free stream velocity. To a maximum of 50\% reduction in friction drag was achieved. For the measurements on the upper range of the stated Reynolds number, were conducted at the boundary layer wind tunnel. This boundary layer wind tunnel offers a spatially developed turbulent boundary layer over a flat plate within 2.2×10e+3≤Reτ≤5.5×10e+3 with an excellent spatial resolution. With the help of Stereo Particle Image Velocimetry technique, measurement of the velocity components were obtained covering entire boundary layer in streamwise wall normal plane. In addition, time resolved measurements were also obtained in spanwise and wall-normal plane in order to look into the morphology of turbulent structures immediately above the blowing area.}, subject = {Turbulent boundary layer; Drag reduction; Particle Image Velocimetry (PIV); Laser Doppler Anemometry (LDA); Friction drag; Turbulente Grenzschicht; Particle Image Velocimetry; Laser-Doppler-Anemometrie; Mikro-Ausblasen; Reibungswiderstand; Turbulente Grenzschicht; Particle-Image-Velocimetry; Reibungswiderstand; Laser-Doppler-Anemometrie; Ausblasen}, language = {en} } @misc{Hasanuzzaman2014, type = {Master Thesis}, author = {Hasanuzzaman, Gazi}, title = {Experimental investigation and CFD analysis of wind energy estimation considering building integrated ducts}, doi = {10.26127/BTUOpen-6192}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:co1-opus4-61928}, school = {BTU Cottbus - Senftenberg}, year = {2014}, abstract = {Wind energy is a growing concern over the present awareness of lethal impact of green house gas emission. This energy source has been proven a promising alternative to fossil fuel based energy. Increased onshore wind capacity and decreased amount of low roughness wind sites has inspired the wind energy researchers to explore the possibilities of wind energy from high roughness sites such as urban area. Moreover, exhausted grid capacity between the wind energy producer from remote area and the consumer at city is also a major constrain for wind energy expansion. Driven by such motivation, this thesis has explored possibilities of wind energy conversion from buildings where energy is needed the most. Urban topography is known to be highly turbulent region considering its roughness characteristics. Wind energy yield from urban aerodynamics is a vast arena of experimental research. Within the time frame of the thesis period and available opportunities, a brief description about the wind energy assessment modelling approach from urban flow was outlined. There are several possibilities of wind energy yield from the built structure, but only building integrated duct was focused in this thesis. Time-averaged and global wind speed on the building integrated ducts, flow around the buildings was measured from wind tunnel and numerical analysis. Available wind energy yield and turbulence present in the locations measured from the flow was calculated based on the wind tunnel data and summarized with the pros and cons of the particular geometry. Elliptical duct configuration was found to achieve maximum energy yield from the omnidirectional free stream flow. However, simple rectangular duct configuration was determined as most efficient and optimized considering its simplicity, financial feasibility and relative energy yield with other duct configuration. The thesis also showed that on roof configuration is also very promising for wind energy exploration from the omnidirectional free stream flow. Necessary recommendations were made based on available result for future development of the research approach. Scope and opportunities was mentioned. This investigation has proved that it is possible to extract limited amount of wind energy from building augmented ducts using concentrator effect of the building exterior. Thus, the thesis concluded that the wind energy yield from building augmented ducts using the concentrator effect of the building exterior is a promising renewable energy source.}, subject = {Atmospheric boundary layer; Wind energy; Laser Doppler Anemometry; Numerical simulation; Computational Fluid Mechanics; Atmosph{\"a}rische Grenzschicht; Windenergie; LDA; Numerische Simulation; Windkanal; Windenergie; Windkanal; Atmosph{\"a}rische Grenzschicht; Laser-Doppler-Anemometrie; Numerische Str{\"o}mungssimulation}, language = {en} }