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Experimental validation of active flow concept on wing section
Novotný, Ondřej ; Zima, Martin (referee) ; Popela, Robert (advisor)
The aim of this diploma thesis is experimental validation of active flow concept on the wing section. This concept could be replacement of commonly used high-lift devices. In the be-ginning of the thesis, a different high-lift devices and other experiments of active flow con-trol are described. Practical part of the thesis describes a preliminery of the measurment, such as preparing wind tunnel section, design of the rotary device and models of the wing section. Next chapter describes measuring of the wing section without active flow control and wing section with active flow control. In the end of the thesis the measurement was compared with CFD analysis.
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Wind tunnels for passenger cars
Fabríci, Tomáš ; Zeman, Radek (referee) ; Rudolf, Pavel (advisor)
The bachelor thesis is focused on a wind tunnel usage in the field of automotive industry. Nowadays, they are still the significant part in vehicle aerodynamics research. Specifically, at determining power actuating on vehicle, flow visualization, aero-acoustic measurements. Considering personal vehicles, reducing the drag and reducing the consumption are being accentuated. Aero-acoustic measurements are becoming more and more popular for improvement of driving comfort. Air-flow quality in wind tunnels directly affects the accuracy of the mentioned measurements. The effort is to minimize the accidental turbulence and reach uniform flow quality. Perfect quality of the air-flow will never be reached even though there is an optimal proposal of all sections from which the wind tunnels consist. Very often, we must be satisfied with the accepted flow quality according to the application. However, the progress in the field of computing modeling has reduced the time spent in wind tunnels and moreover it has saved finances. Currently, there is close cooperation between them to reach the best results possible.
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Air flow measurement through compact heat exchanger in wind tunnel
Žůrek, Michael ; Vondruš, Jan (referee) ; Šebela, Kamil (advisor)
This thesis describes Formula Student competition, overview of used aerodynamic devices, placement of compact heat exchangers on these monoposts and current monopost Dragon e2. Next section examines commonly used compact exchangers and their aerodynamic drag, mainly caused by angling and ununiform flow. Subsequently is described the process of preparation, measurement in wind tunnel and measuring devices. An algorithm was created and described, which was used for evaluation of measurement, influence of some factor was commented. On the right-side compact exchanger, methods of measuring were compared, namely pneumatic probe, pressure difference and turbine anemometer. On left side exchanger were observed influence of various aerodynamic elements. Lastly alternative position behind vehicle rear axle was measured.
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A Fuzzy Controller for a Wind Tunnel Model
Piskoř, D. ; Mihálik, O. ; Sýkora, T. ; Arm, J.
In this paper, an alternative approach to control the model of the wind tunnel is proposed. The aim is to find out if it is possible to achieve better results in regulating a system containing nonlinearities when a fuzzy controller is used instead of common linear controllers. The designed fuzzy controller will be implemented into a PLC via automatic code generation in MATLAB later.
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Different Boundary Conditions For LES Solver PALM 6.0 Used for ABL in Tunnel Experiment
Řezníček, Hynek ; Geletič, Jan ; Bureš, Martin ; Krč, Pavel ; Resler, Jaroslav ; Vrbová, Kateřina ; Trush, Arsenii ; Michálek, Petr ; Beneš, L. ; Sühring, M.
We tried to reproduce results measured in the wind tunnel experiment with a CFD simulation provided by numerical model PALM. A realistic buildings layout from the Prague-Dejvice quarter has been chosen as a testing domain because solid validation campaign for PALM simulation of Atmospheric Boundary Layer (ABL) over this quarter was documented in the past. The question of input data needed for such simulation and capability of the model to capture correctly the inlet profile and its turbulence structure provided by the wind-tunnel is discussed in the study The PALM dynamical core contains a solver for the Navier-Stokes equations. By default, the model uses the Large Eddy Simulation (LES) approach in which the bulk of the turbulent motions is explicitly resolved. It is well validated tool for simulations of the complex air-flow within the real urban canopy and also within its reduced scale provided by wind tunnel experiments. However the computed flow field between the testing buildings did not correspond well to the measured wind velocity in some points. Different setting of the inlet boundary condition was tested but none of them gave completely developed turbulent flow generated by vortex generators and castellated barrier wall place at the entrance of the aerodynamic section of the wind tunnel.
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Aspects of Dosage from Short and Long Duration Emissions
Robins, A. ; Hayden, P. ; Gallacher, D. ; Pace, S. ; Chaloupecká, Hana
The objectives of this work were to use wind tunnel concentration measurements to describe the structure of dispersing clouds from an elevated source in a deep turbulent boundary layer and to develop scaling rules that reduce the results to a universal form. The experiments were carried out in the EnFlo meteorological wind tunnel at the University of Surrey. Ensembles of between 100 and 200\nrepeat emissions were used, emission durations between 0.067 and 1.02s and a reference flow speed of 2ms-1. The fetch studied extended to about six source heights downwind (about two boundary layer depths). The structure of the evolving clouds was analysed to determine time of flight, along-wind spread and dosage and to compare the dosage behaviour with the concentration field in a plume from the same source. This illustrated how the two were related and how cloud dosage statistics (mean and\nstandard deviation) could be derived from plume data. It also demonstrated that much larger ensembles were required to reduce the statistical uncertainty in the mean cloud properties. The next steps involve testing these conclusions in a wider range of flow and dispersion conditions, in the presence of obstacles or complex urban areas.
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PHYSMOD 2022 - International Workshop on Physical Modeling of Flow and Dispersion Phenomena
Jurčáková, Klára ; Kellnerová, Radka
The objective of PHYSMOD is to bring together the community active in physical and numerical modeling of flow and dispersion processes occurring in the lowest part of the atmosphere using wind tunnels, water channels, or CFD models. PHYSMOD provides a forum where the most recent advances in fluid modeling, state-of-the-art in experimental work, and newly emerging research areas are discussed in an open-minded and friendly atmosphere. One of the main purposes is to encourage broader collaboration between researchers and transfer knowledge between the laboratories as well as generations. \n\n
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Temporal, Spatial, and Spatio-temporal correlation of the velocity fluctuations
Jurčáková, Klára
Taylor's hypothesis about frozen turbulence [1] says that if the turbulence intensity is small compared to the mean velocity then the advection of a turbulent flow field past a fixed point can be taken entirely due to the mean flow. This means that in the “frozen turbulent field” spatial and temporal dimensions can be interchanged. Although the main assumption of Taylor's hypothesis is not met in the atmospheric boundary layer (the intensity of turbulence is usually between 10 and 20%) the hypothesis is commonly used to calculate integral length scales of turbulent fields from point measurements. Particle image velocimetry with high temporal resolution (TR-PIV) allows us to analyze both temporal and spatial cross-correlations in the turbulent flow fields and to evaluate obtained results.
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Innovative device for the simulation of environmental conditions and testing of building materials
Cacciotti, Riccardo ; Wolf, Benjamin ; Macháček, Michael ; Frankl, Jiří
Excessive humidity influences the performance of building envelopes and the safety of their occupants. Moisture related problems can indeed impose significant health risks for buildings’ users and even lead, under extreme scenarios, to structural failures. This paper investigates an innovative experimental setup for evaluating the influence of changing environmental conditions on the performance of building materials. It stems out from a broader ongoing research aimed at studying the trends of mould growth on wooden building components. The presented results include the design, construction and numerical validation of a small-scale climatic wind tunnel (2m x 1.8m ca.) to be used for the simulation of natural ventilation and daily humidity and temperature fluctuations. Key findings include the final design of a low cost, modular construction which allows gathering reliable data on the response of building materials exposed to changing boundary conditions, intended for improving current mould growth models. Future work is also suggested.
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