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Computation of vehicle aerodynamic characteristics
Čavoj, Ondřej ; Porteš, Petr (referee) ; Vančura, Jan (advisor)
This Diploma thesis deals with CFD simulations of flow around vehicles subjected to a crosswind with MIRA Reference Car in three body shapes with a diffuser serving as a vehicle. It contains tuning of computational grid and chosen solver settings in Fluent, mostly for v2f turbulence model. The main output of this thesis is a simulation of all body shapes in several crosswind angles in steady state and one chosen body shape with one chosen crosswind angle in unsteady state. All results are validated against measurements taken with full scale models in MIRA windtunnel.
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Formula Student aerodynamics
Egorov, Artemii ; Vančura, Jan (referee) ; Čavoj, Ondřej (advisor)
This bachelor thesis focuses on summarizing knowledge in the field of aerodynamic elements development on formula student cars. The introductory part deals with an overview of the history and rules of Formula student competition. The second part is devoted to the description of aerodynamic elements themselves and their development methods.
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Condition Simulation in Vehicle Aerodynamics Computation
Čavoj, Ondřej ; Sloupenský, Zdeněk (referee) ; Popela, Robert (referee) ; Píštěk, Václav (advisor)
Several types of discrepancies have been examined between CFD simulations, wind tunnel measurements and real world conditions. The results of different wheel rotation methods show that while stationary approaches can often substitute real unsteady wheel rotation, they can also be very sensitive to the exact angular positioning of wheel rims. Using both measured and computed flow fields, the lower part of wheel wake was identified as a key area, showing differences between rotation methods and sources of simulation errors in general. It was also shown that the level of detail in tyre geometry and its deformation near contact patch do not have a large impact on accuracy. Due to the absence of tyre rotation, the tyre sidewall was identified as an important place of flow separation with large effect on flow field and forces. Angle of attack study confirmed that assessing purely straight-line drag causes its under prediction compared to real-world values. This judgement would however benefit from obtaining data in more adverse conditions compared to those currently available. Finally, tyre radial expansion was investigated, causing a drop in drag with increasing vehicle velocity and altering the flow around the rear bodywork. Ignoring this effect can therefore negatively influence the aerodynamic development of a vehicle.
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The beginnings of automotive aerodynamics
Sunek, Ondřej ; Vančura, Jan (referee) ; Čavoj, Ondřej (advisor)
This bachelor thesis is concerned with charting the early phase of development of automobile aerodynamics around the first half of the 20th century. Further on, it describes some procedures which were used for designing of each car and the circumstances that led to the design of breakthrough cars. Simultaneously the thesis states some aerodynamic deficiencies of the cars of the period as viewed from today´s perspective.
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Transitional effects in road vehicle aerodynamics
Kroupa, Michal ; Vančura, Jan (referee) ; Čavoj, Ondřej (advisor)
This bachelor thesis deals with transient phenomena in vehicle aerodynamics with the focus on describing and proposing of unsteady mechanisms. First part investigates transient phenomena during crosswind gusts. Next part deals with unsteady pressure distribution around the vehicle during passing and overtaking manoeuvre. Final part investigates transient phenomena during dynamic pitching motion.
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Racing car technology in the period of World Wars
Ducheček, Martin ; Vančura, Jan (referee) ; Čavoj, Ondřej (advisor)
This bachelor thesis describes developement and historical racing vehicles especially in interwar period and looks into their influence to cars. In the next section, rules and conditions of competition, the first important race and start of Grand Prix, are briefly explained. A purpose of this thesis is to introduce important technology progress and inovations of this period, which have influenced a construction of cars for long decades, many of them are used to this day.
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CFD simulation of a crosswind gust
Kroupa, Michal ; Vančura, Jan (referee) ; Čavoj, Ondřej (advisor)
This thesis deals with the investigation of unsteady effects on vehicle that has been exposed to a crosswind gust. First crosswind velocity function was created, which is a function of both time and space. A comparison of continual and trapeze gust model was carried out. Next step was to compare unsteady and quasi-steady evolution of the aerodynamic loads using accumulated forces, surface pressures and flow field around the car. The penultimate part deals with investigation of unsteady behaviour of drag and in the last part the influence of rear geometry of the car on unsteady phenomena was investigated.
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Motor Vehicles Non-Synchronous Transmission
Červenka, Filip ; Čavoj, Ondřej (referee) ; Hejtmánek, Petr (advisor)
The topic of this bachelor thesis is Motor Vehicles Non-synchronous Transmission. The thesis is focused on the basic calculation formulas used in the design of gearboxes, the classification of gearboxes, the description of non-synchronous transmissions, including the description of their construction and the comparison between synchronous and non-synchronous transmissions. Also included are the principles of quickshift gearboxes. The thesis concludes with a list of several manufacturers of non-synchronous transmissions.
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Methods for determining aerodynamic properties of vehicles
Páleš, Patrik ; Blaťák, Ondřej (referee) ; Čavoj, Ondřej (advisor)
The aim of the bachelor’s thesis is a description of methods being used for measurements of aerodynamic characteristics of automobiles. The exact determination of the aerodynamic characteristics requires sophisticated testing equipment and advanced engineering procedures. The research comprises several approaches. Computational fluid dynamics (CFD) is based on turbulent models application such as RANS, LES and DNS. Pressure distribution on a vehicular body surface and an air flow along the vehicle are monitored in wind tunnels. Flow visualization is carried out by optical (PIV, LDA) and non-optical methods. Experimental road testing methods are focused on multiple parameters including a vehicle directional stability, its cross-wind sensitivity, engine cooling system and many others.
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