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301	The Effect of a Splitter Plate on the Flow around a Surface-Mounted Finite Circular Cylinder 2011 September 1900 (has links) Splitter plates are passive flow control devices for reducing drag and suppressing vortex shedding from bluff bodies. Most studies of splitter plates involve the flow around an “infinite” circular cylinder, however, in the present study the flow around a surface-mounted finite-height circular cylinder, with a wake-mounted splitter plate, was studied experimentally in a low-speed wind tunnel using a force balance and single-component hot-wire anemometry. Four circular cylinders of aspect ratios AR = 9, 7, 5 and 3 were tested for a Reynolds number range of Re = 1.9×10^4 to 8.2×10^4. The splitter plates had lengths, relative to the cylinder diameter, of L/D = 1, 1.5, 2, 3, 5 and 7, thicknesses ranging from T/D = 0.10 and 0.15, and were the same height as the cylinder being tested. The cylinders were partially immersed in a flat-plate turbulent boundary layer, where the range of boundary layer thickness relative to the cylinder diameter was δ/D = 1.4 to 1.5. Measurements were made of the mean drag force coefficient, the Strouhal number at the mid-height position, and the Strouhal number and power spectra along the cylinder height. For all four finite circular cylinders, the splitter plates were effective at reducing the magnitude of the Strouhal number, and weakening or even suppressing vortex shedding, depending on the specific combination of AR and L/D. Compared to the case of an infinite circular cylinder, the splitter plate is less effective at reducing the mean drag force coefficient of a finite circular cylinder. The largest drag reduction was obtained for the cylinder of AR = 9 and splitter plates of L/D = 1 to 3, while negligible drag reduction occurred for the shorter cylinders.
302	Dynamics of Cilia and Flagella / Bewegung von Zilien und Geißeln Hilfinger, Andreas 14 January 2006 (has links) (PDF) Cilia and flagella are hair-like appendages of eukaryotic cells. They are actively bending structures that exhibit regular beat patterns and thereby play an important role in many different circumstances where motion on a cellular level is required. Most dramatic is the effect of nodal cilia whose vortical motion leads to a fluid flow that is directly responsible for establishing the left-right axis during embryological development in many vertebrate species, but examples range from the propulsion of single cells, such as the swimming of sperm, to the transport of mucus along epithelial cells, e.g. in the ciliated trachea. Cilia and flagella contain an evolutionary highly conserved structure called the axoneme, whose characteristic architecture is based on a cylindrical arrangement of elastic filaments (microtubules). In the presence of a chemical fuel (ATP), molecular motors (dynein) exert shear forces between neighbouring microtubules, leading to a bending of the axoneme through structural constraints. We address the following two questions: How can these organelles generate regular oscillatory beat patterns in the absence of a biochemical signal regulating the activity of the force generating elements? And how can the beat patterns be so different for apparently very similar structures? We present a theoretical description of the axonemal structure as an actively bending elastic cylinder, and show that in such a system bending waves emerge from a non-oscillatory state via a dynamic instability. The corresponding beat patterns are solutions to a set of coupled partial differential equations presented herein. Axonem Bewegung bei kleinen Reynolds Zahlen Biophysik Flagellen Geißeln Molekulare Motoren Nodale Zilien Physik Selbstorganisierte Schlagmuster Situs inversus Spermien Wimpern Zilien Situs inversus axoneme biophysics cilia dynein flagella left-right axis formation low Reynolds number dynamics molecular motors nodal cilia physics spermatozoa spontaneous oscillations ddc:530 rvk:UF 5000 Cilie Flagelline Geißel &lt;Biologie&gt; Molekularer Motor Reynolds-Zahl Selbstorganisation Spermium Zilie
303	Ověření tepelně-izolační vlastnosti termoreflexních fóliových izolací / Verification of thermal-insulation properties of the foil materials Šot, Petr January 2014 (has links) The master´s thesis deals with verification of thermal insulating property of thermoreflection foil insulations. The teoretical part of thesis focuses on the energy demand of buildings, the problems of heat transfer material, terms required for study of thermoreflection thermal insulation and experimental methods for determination of thermal insulating properties of insulators. In the next part the chapter is accompanied by an overview of the most common insulation materials which used in construction. The last part of teoretical part is devoted to the description of thermoreflect formation and analysis of the spread of thermal insulating layers of thermoreflection thermal insulation. The first part of thesis is devoted to the use of thermoreflection therm insulation in buildings. The second part of thesis is devoted to the design, assembly and calibration of the measuring device that uses a method of protected warm chamber. It is declared as a binding method of detection of the heat transfer performance of thermoreflection thermal insulation. The developed measuring device allows detection of endpoints in some direction of propagation of heat. Measurment of heat transfer coefficient devoted the third part of practical part. This part contains a description of the samples used for the measurement of the heat transfer coefficient. In the fourth chapter of the practical part are presented the results of the heat transfer coefficient measurments on selected samples of thermoreflection foil insulation. It is shown the characteristic of heat transfer coefficient of individual samples, the dependence of the heat transfer coefficient on the position of the sample in the measuring device and the recommendation of an appropriate use of sample in the works for the climatic conditions of the Czech republic. The work concludes the chapter of comparing and evaluating of all samples with practical recommendations.
304	Dynamics of Cilia and Flagella Hilfinger, Andreas 07 February 2006 (has links) Cilia and flagella are hair-like appendages of eukaryotic cells. They are actively bending structures that exhibit regular beat patterns and thereby play an important role in many different circumstances where motion on a cellular level is required. Most dramatic is the effect of nodal cilia whose vortical motion leads to a fluid flow that is directly responsible for establishing the left-right axis during embryological development in many vertebrate species, but examples range from the propulsion of single cells, such as the swimming of sperm, to the transport of mucus along epithelial cells, e.g. in the ciliated trachea. Cilia and flagella contain an evolutionary highly conserved structure called the axoneme, whose characteristic architecture is based on a cylindrical arrangement of elastic filaments (microtubules). In the presence of a chemical fuel (ATP), molecular motors (dynein) exert shear forces between neighbouring microtubules, leading to a bending of the axoneme through structural constraints. We address the following two questions: How can these organelles generate regular oscillatory beat patterns in the absence of a biochemical signal regulating the activity of the force generating elements? And how can the beat patterns be so different for apparently very similar structures? We present a theoretical description of the axonemal structure as an actively bending elastic cylinder, and show that in such a system bending waves emerge from a non-oscillatory state via a dynamic instability. The corresponding beat patterns are solutions to a set of coupled partial differential equations presented herein. info:eu-repo/classification/ddc/530 ddc:530
305	Tlakové ztráty v otopných soustavách / Pressure losses in heating systems Švanda, Martin Unknown Date (has links) This diploma thesis deals with pressure losses in heating systems. The diploma thesis is divided into three sections. The first part is theoretical and deals with the occurrence of pressure losses. It discusses the properties of the fluid that affect pressure losses. It also deals with hydrodynamic phenomena, flow distribution, pressure loss distribution and its calculations. The aim of the second part, which is practical, was to create a heating project for a selected object. The object is a two-floor kindergarten building located in Velké Němčice. For this project, two heating variants were created. For the first variant, radiators and heating benches were designed and for the second variant, underfloor heating was installed in the building. The goal was to use a source which will gain heat mainly from renewable sources, so the air / water heat pump was chosen as the source of heat production. The project ends with a technical report. The third part of the thesis is dedicated to an experiment which purpose was to find out how the pressure losses of the connecting pieces are reacting to the change with the change of the heating water conditions (flow, temperature). Alongside, two pipes were created which differed in the type of connecting pieces so it allowed to compare how their pressure losses differ. Both pipes were connected by radial pressing, but the fittings differed in the quality of the brass, and therefore in the construction. Also, part of the experimental section of the diploma thesis is a description of the course of radial pressing of fittings from the Herz company.

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