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Influence of the Francis turbine stay vane trailing edge shape on generation of Karman vortex street
Novotný, Vojtěch ; Skoták, Aleš (referee) ; Rudolf, Pavel (advisor)
In the flow past bluff bodies for a certain range of velocity a periodical vortex shedding emerges which is known as von Kármán vortex street. This phenomenon causes the periodical alteration of pressure field which affects the body. Should the vortex shedding frequency be similar to the body natural frequency, the amplitude of vibration significantly increases which can lead to fatigue cracking. In the case of water turbines, this phenomenon often affects the stay vanes. Both the vortex shedding frequency and the lift force amplitude can be influenced by the modification of the trailing edge geometry. The aim of this thesis is to use CFD computation in order to find the optimal geometry of the stay vane trailing edge for the specific Francis turbine unit.
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Wind load on cooling tower
Ehrlich, Tomáš ; Kala, Jiří (referee) ; Nevařil, Aleš (advisor)
Thesis is concerned with modeling fluid dynamics and computing wind load on thin-walled structure of cooling tower. Two models for computational fluid dynamics are presented – one with singleton cooling tower and second with group of four cooling tower. Thesis includes also a structural model of cooling tower and methodology of wind load transfer is presented.
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Laboratory Model of the Vortex Speed Indicator
Kazda, Ondřej ; Kolka, Zdeněk (referee) ; Biolková, Viera (advisor)
This work is concerned with posibility of measuring a wind flow by Von Karman vortex sheed structure. The bluff body is situated in the way of air flow propagation and consequentally vortexes will be appeared. Important part of speedmeter design is measurment chamber must allow to vortex sheed propagation. The transient and the reciever are situated vertically to propagation of flow.The Ultrasonic carrier is transmitted and modulated by freqency of vortex sheeding in measurment chamber.Demodulator uses PLL to “focusing“ detection of the ultrasonic beam. This can be indicated like lock and unlock phase loop. From known value of sheed frequency can be directly calculated speed of flow.
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Microfluidic devices
Stehlík, Martin ; Sluše, Jan (referee) ; Rudolf, Pavel (advisor)
The bachelor's thesis deals with the phenomenon of mixing fluid in an equipment with micro scale and its production. The first part is dedicated to describe Reynolds, Peclet and Strouhal number. The second part describes micromixers and their distribution. The final part deal´s with specific examples of manufacturing microfluidc devices.
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Wind loads of building structures
Štěrba, Martin ; Kala, Jiří (referee) ; Hradil, Petr (advisor)
The bachelor thesis deals with the analysis of the effects of wind load on building structures. In the context of the work is solved the numerical modeling of flow around the solid cylindrical bodies at high Reynolds numbers. To the simulations has been used computational software ANSYS CFX. The outputs of the work are the values of Strouhal numbers and the values of drag and lift coefficient depending on the Reynolds number.
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Variation of Strouhal number on iced cable in sub-transitional range
Pospíšil, Stanislav ; Górski, P. ; Kuznetsov, Sergeii ; Tatara, M. ; Marušić, A.
The influence of ice accretion, angle of attack and Reynolds number on the flow field around iced cables of the cable-supported bridges is not clearly understood. The paper presents results of a wind tunnel investigations of Strouhal number of stationary iced cable model of cable-supported bridges. The investigations were carried out in a Climatic Wind Tunnel Laboratory of ITAM. The methodology leading to the experimental icing of the inclined cable model in the climatic section of the laboratory was prepared. For the aerodynamic investigations the iced cable model in a smaller scale was reproduced with combination of photography and 3-D printing procedure. The Strouhal number (St) was determined within the range of the Reynolds number (Re) between 2.4×10^4 and 16.4×10^4, based on the dominant vortex shedding frequency measured in the flow behind the model. The model was orientated at three principal angles of wind attack for each of the Re. Good agreement with the generally reported value in the sub-critical Re range for a circular cylinder was obtained.
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Influence of ice accretion at bridge rope on Strouhal number
Pospíšil, Stanislav ; Gorski, P. ; Kuznetsov, Sergeii
The paper is concerned with the method and results of wind tunnel investigations of the/nStrouhal number (St) of a stationary iced cable model of cable-supported bridges with/nrespect to different angles of wind attack. The methodology leading to the experimental/nicing of the inclined cable model was prepared in a climatic section of the laboratory./nThe St values were determined within the range of the Reynolds number (Re) between/n2.4·104 and 16.5·104, based on the dominant vortex shedding frequencies measured in/nthe wake of the model.
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