Kooperativer Bibliotheksverbund

UID:

Umfang: 1 online resource (xxvi, 398 pages).

Serie: Dissertationsreihe am Institut für Hydromechanik der Universität Karlsruhe (TH) ; Band 2

Inhalt: Shallow turbulent wake flows are generated by large obstacles - like islands or headlands - introduced to shallow turbulent open-channel flows. Large-scale quasi two-dimensional vortices may shed off from an obstacle, and advect downstream in a vertical shear flow with predominantly small-scale turbulence induced by bottom friction. Experimental, analytical, and numerical techniques are employed in the present study to characterize the mean flow and turbulence properties of shallow wakes; mechanisms of generation and decay of large-scale vortical structures are clarified, as is their influence on momentum and mass transport in shallow wakes; the global and local stability of shallow wakes is analyzed and evidenced from experimental data. Part I of this work covers non-intrusive optical measurement techniques especially adapted to investigate shallow shear flows. Flow velocities and mass concentrations are obtained (i) point-wise with high spatiotemporal resolution using a combinded LDV-LIF system, and (ii) field-wise using near-surface PIV and depth-averaged PCA systems with a coupling by phase-resolved averaging. Improved algorithms for the evaluation of mass concentrations are based on hydro-optical models of the underlying fluorescence and light attenuation processes. Part II addresses the time-mean description of shallow wake flows. The stochastic description of the turbulence fields displays a characteristic spectral distribution both of kinetic energy and of mass variance, which is partially consistent with the theory of unbounded 2D turbulence at large scales, and with the theory of homogeneous 3D turbulence at small scales. An integral wake model including the effect of bottom friction is derived analytically, and is validated by experimental data. The time-mean distributions of flow velocities and of mass concentration allow to identify wake near fields and far fields with specific asymptotic wake developments. Wake stability classes are associated with local stability regions suggested by linear stability analyses. Part III elaborates the structure and dynamics of quasi-periodic wake flows and the significance of large-scale eddies. This involves a structure identification scheme to educe individual vortices, and a phase-resolved averaging procedure to decompose the flow fields into large-scale coherent and small-scale turbulent parts. A Numerical Particle Tracking technique is employed to model the mass transport and to elucidate different diffusion and dispersion effects.

Anmerkung: English.

Weitere Ausg.: ISBN 1000003453

Sprache: Englisch

UID:

Umfang: 1 online resource (xxvi, 398 pages).

Serie: Dissertationsreihe am Institut für Hydromechanik der Universität Karlsruhe (TH) ; Band 2

Inhalt: Shallow turbulent wake flows are generated by large obstacles - like islands or headlands - introduced to shallow turbulent open-channel flows. Large-scale quasi two-dimensional vortices may shed off from an obstacle, and advect downstream in a vertical shear flow with predominantly small-scale turbulence induced by bottom friction. Experimental, analytical, and numerical techniques are employed in the present study to characterize the mean flow and turbulence properties of shallow wakes; mechanisms of generation and decay of large-scale vortical structures are clarified, as is their influence on momentum and mass transport in shallow wakes; the global and local stability of shallow wakes is analyzed and evidenced from experimental data. Part I of this work covers non-intrusive optical measurement techniques especially adapted to investigate shallow shear flows. Flow velocities and mass concentrations are obtained (i) point-wise with high spatiotemporal resolution using a combinded LDV-LIF system, and (ii) field-wise using near-surface PIV and depth-averaged PCA systems with a coupling by phase-resolved averaging. Improved algorithms for the evaluation of mass concentrations are based on hydro-optical models of the underlying fluorescence and light attenuation processes. Part II addresses the time-mean description of shallow wake flows. The stochastic description of the turbulence fields displays a characteristic spectral distribution both of kinetic energy and of mass variance, which is partially consistent with the theory of unbounded 2D turbulence at large scales, and with the theory of homogeneous 3D turbulence at small scales. An integral wake model including the effect of bottom friction is derived analytically, and is validated by experimental data. The time-mean distributions of flow velocities and of mass concentration allow to identify wake near fields and far fields with specific asymptotic wake developments. Wake stability classes are associated with local stability regions suggested by linear stability analyses. Part III elaborates the structure and dynamics of quasi-periodic wake flows and the significance of large-scale eddies. This involves a structure identification scheme to educe individual vortices, and a phase-resolved averaging procedure to decompose the flow fields into large-scale coherent and small-scale turbulent parts. A Numerical Particle Tracking technique is employed to model the mass transport and to elucidate different diffusion and dispersion effects.

Anmerkung: English.

Weitere Ausg.: ISBN 1000003453

Sprache: Englisch

UID:

Umfang: 1 online resource (xxvi, 398 pages).

Serie: Dissertationsreihe am Institut für Hydromechanik der Universität Karlsruhe (TH) ; Band 2

Inhalt: Shallow turbulent wake flows are generated by large obstacles - like islands or headlands - introduced to shallow turbulent open-channel flows. Large-scale quasi two-dimensional vortices may shed off from an obstacle, and advect downstream in a vertical shear flow with predominantly small-scale turbulence induced by bottom friction. Experimental, analytical, and numerical techniques are employed in the present study to characterize the mean flow and turbulence properties of shallow wakes; mechanisms of generation and decay of large-scale vortical structures are clarified, as is their influence on momentum and mass transport in shallow wakes; the global and local stability of shallow wakes is analyzed and evidenced from experimental data. Part I of this work covers non-intrusive optical measurement techniques especially adapted to investigate shallow shear flows. Flow velocities and mass concentrations are obtained (i) point-wise with high spatiotemporal resolution using a combinded LDV-LIF system, and (ii) field-wise using near-surface PIV and depth-averaged PCA systems with a coupling by phase-resolved averaging. Improved algorithms for the evaluation of mass concentrations are based on hydro-optical models of the underlying fluorescence and light attenuation processes. Part II addresses the time-mean description of shallow wake flows. The stochastic description of the turbulence fields displays a characteristic spectral distribution both of kinetic energy and of mass variance, which is partially consistent with the theory of unbounded 2D turbulence at large scales, and with the theory of homogeneous 3D turbulence at small scales. An integral wake model including the effect of bottom friction is derived analytically, and is validated by experimental data. The time-mean distributions of flow velocities and of mass concentration allow to identify wake near fields and far fields with specific asymptotic wake developments. Wake stability classes are associated with local stability regions suggested by linear stability analyses. Part III elaborates the structure and dynamics of quasi-periodic wake flows and the significance of large-scale eddies. This involves a structure identification scheme to educe individual vortices, and a phase-resolved averaging procedure to decompose the flow fields into large-scale coherent and small-scale turbulent parts. A Numerical Particle Tracking technique is employed to model the mass transport and to elucidate different diffusion and dispersion effects.

Anmerkung: English.

Weitere Ausg.: ISBN 1000003453

Sprache: Englisch

UID:

Umfang: 1 online resource (154 pages)

Inhalt: Zur Bestimmung der Anzahl und Lage von Hubstandorten sowie der Transportmengen auf einzelnen Transportrelationen wird ein Hub-Location-Problem mit Direktverkehrsrelationen und beschränkter Sortierkapazität der potentiellen Hubstandorte als gemischt binäres lineares Optimierungsproblem modelliert. Somit werden bereits in der Planungsphase die Kapazitätsrestriktionen der Hubs berücksichtigt und dadurch mögliche Kapazitätsüberlastungen der Hubs sowie die daraus resultierende Errichtung von Sekundäarhubs vermieden.Zur optimalen Lösung des Hub-Location-Problems wird ein Branch-and-Bound-Verfahren eingesetzt, für das ein effizientes Näherungsverfahren zur Bestimmung von unteren Schranken in den Knoten des Suchbaums entwickelt wird. Zur Bestimmung einer Eröffnungslösung werden die heuristischen Add- und Drop-Verfahren eingesetzt. Für die im Rahmen der Eröffnungsverfahren notwendigen Berechnungen von Allokationslösungen wird ein modifizierter Tripel-Algorithmus entwickelt. Im Verlauf des Branch-and-Bound- Verfahrens werden erstmalig logische Tests bei einem Hub-Location-Problem mit dem Ziel eingesetzt, noch freie Entscheidungsvariablen des Suchbaums vorzeitig zu fixieren.Mit Hilfe der entwickelten Verfahren werden Problemgrößen mit bis zu 100 potentiellen Hubstandorten optimal gelöst. Dies ist auf den Einsatz der logischen Tests sowie die effizient Berechnung der unteren Schranken zurückzuführen. Der Einsatz der logischen Tests bewirkt eine Reduzierung der Rechenzeit um bis zu 80%.

Weitere Ausg.: ISBN 1000003457

Sprache: Deutsch

UID:

Umfang: 1 online resource (xvi, 138 pages)

Inhalt: Pyramidal buildings are undergoing a renaissance in todays architectural design due to their attractive mystery that has fascinated many architects. From an aerodynamic engineering point of view, structural buildings with the shape of a pyramid have their own interesting and particular aerodynamic characteristics as compared to other usual structural buildings (i.e. cuboidal).However, despite its distinct aerodynamic characteristics compared to other usual structural buildings, the flow and pressure characteristics around pyramidal structures have not yet been investigated completely. Very limited studies about pyramidal buildings can be found in the literature.Consequently, the technical layout with respect to wind load assumption of pyramidal buildings are usually not listed in standard tables which underlines the need of systematic investigations for pyramidal structures.In this study, pyramids with a wide range of base angle variation (theta = 30°, 40°, 45°, 50°, 55°, 60°, 70°) have been investigated intensively through a detailed and accurate laboratory experiments at the Laboratory of Building- and Environmental Aerodynamics, Institute for Hydromechanics, at the University of Karlsruhe. The flow measurements were performed using a 2-D Laser Doppler anemometry (LDA) and The pressure measurements were carried out using a standard pressure tapping technique. The present study focuses on the most important parameters affecting the flow and pressure characteristics that include the influence of base angles, the influence of wind directions and the influence of the pyramid heights with respect to a characteristic length. Besides the experimental investigations, numerical investigations with the aid of a software package called FLOVENT were also additionally performed in order to prove, whether experimental and numerical studies deliver the same results.Based on the flow measurement results, this study was able to distinguish the general characteristics of flow around pyramid building when compared to other type of structures (i.e. cuboidal structure). A set of equations to calculate the reattachment length at the leeward side of the pyramid was generated. In addition, an equation to estimate the zero streamline and an area below line as a function of the reattachment length and base angle, respectively, are proposed. These equations will illustrate the recirculation zone at the leeward side of the pyramid.The pressure measurement results show that the three investigated parameters (base angle, wind direction and pyramid height) have an important influence to the pressure characteristics (magnitude of pressure, suction and fluctuation) in the surfaces of the pyramids. For practical purposes, this study was able to provide the typical values of pressure and aerodynamic coefficients for pyramidal buildings that can be used for structural calculations. The values that are given in this study can be used to fill in the gap of the unavailable design values for pyramidal buildings in standard tables.

Weitere Ausg.: ISBN 1000003455

Sprache: Englisch

UID:

Umfang: 1 online resource (154 pages)

Inhalt: Zur Bestimmung der Anzahl und Lage von Hubstandorten sowie der Transportmengen auf einzelnen Transportrelationen wird ein Hub-Location-Problem mit Direktverkehrsrelationen und beschränkter Sortierkapazität der potentiellen Hubstandorte als gemischt binäres lineares Optimierungsproblem modelliert. Somit werden bereits in der Planungsphase die Kapazitätsrestriktionen der Hubs berücksichtigt und dadurch mögliche Kapazitätsüberlastungen der Hubs sowie die daraus resultierende Errichtung von Sekundäarhubs vermieden.Zur optimalen Lösung des Hub-Location-Problems wird ein Branch-and-Bound-Verfahren eingesetzt, für das ein effizientes Näherungsverfahren zur Bestimmung von unteren Schranken in den Knoten des Suchbaums entwickelt wird. Zur Bestimmung einer Eröffnungslösung werden die heuristischen Add- und Drop-Verfahren eingesetzt. Für die im Rahmen der Eröffnungsverfahren notwendigen Berechnungen von Allokationslösungen wird ein modifizierter Tripel-Algorithmus entwickelt. Im Verlauf des Branch-and-Bound- Verfahrens werden erstmalig logische Tests bei einem Hub-Location-Problem mit dem Ziel eingesetzt, noch freie Entscheidungsvariablen des Suchbaums vorzeitig zu fixieren.Mit Hilfe der entwickelten Verfahren werden Problemgrößen mit bis zu 100 potentiellen Hubstandorten optimal gelöst. Dies ist auf den Einsatz der logischen Tests sowie die effizient Berechnung der unteren Schranken zurückzuführen. Der Einsatz der logischen Tests bewirkt eine Reduzierung der Rechenzeit um bis zu 80%.

Weitere Ausg.: ISBN 1000003457

Sprache: Deutsch

UID:

Umfang: 1 online resource (154 pages)

Inhalt: Zur Bestimmung der Anzahl und Lage von Hubstandorten sowie der Transportmengen auf einzelnen Transportrelationen wird ein Hub-Location-Problem mit Direktverkehrsrelationen und beschränkter Sortierkapazität der potentiellen Hubstandorte als gemischt binäres lineares Optimierungsproblem modelliert. Somit werden bereits in der Planungsphase die Kapazitätsrestriktionen der Hubs berücksichtigt und dadurch mögliche Kapazitätsüberlastungen der Hubs sowie die daraus resultierende Errichtung von Sekundäarhubs vermieden.Zur optimalen Lösung des Hub-Location-Problems wird ein Branch-and-Bound-Verfahren eingesetzt, für das ein effizientes Näherungsverfahren zur Bestimmung von unteren Schranken in den Knoten des Suchbaums entwickelt wird. Zur Bestimmung einer Eröffnungslösung werden die heuristischen Add- und Drop-Verfahren eingesetzt. Für die im Rahmen der Eröffnungsverfahren notwendigen Berechnungen von Allokationslösungen wird ein modifizierter Tripel-Algorithmus entwickelt. Im Verlauf des Branch-and-Bound- Verfahrens werden erstmalig logische Tests bei einem Hub-Location-Problem mit dem Ziel eingesetzt, noch freie Entscheidungsvariablen des Suchbaums vorzeitig zu fixieren.Mit Hilfe der entwickelten Verfahren werden Problemgrößen mit bis zu 100 potentiellen Hubstandorten optimal gelöst. Dies ist auf den Einsatz der logischen Tests sowie die effizient Berechnung der unteren Schranken zurückzuführen. Der Einsatz der logischen Tests bewirkt eine Reduzierung der Rechenzeit um bis zu 80%.

Weitere Ausg.: ISBN 1000003457

Sprache: Deutsch

UID:

Umfang: 1 online resource (xvi, 138 pages)

Inhalt: Pyramidal buildings are undergoing a renaissance in todays architectural design due to their attractive mystery that has fascinated many architects. From an aerodynamic engineering point of view, structural buildings with the shape of a pyramid have their own interesting and particular aerodynamic characteristics as compared to other usual structural buildings (i.e. cuboidal).However, despite its distinct aerodynamic characteristics compared to other usual structural buildings, the flow and pressure characteristics around pyramidal structures have not yet been investigated completely. Very limited studies about pyramidal buildings can be found in the literature.Consequently, the technical layout with respect to wind load assumption of pyramidal buildings are usually not listed in standard tables which underlines the need of systematic investigations for pyramidal structures.In this study, pyramids with a wide range of base angle variation (theta = 30°, 40°, 45°, 50°, 55°, 60°, 70°) have been investigated intensively through a detailed and accurate laboratory experiments at the Laboratory of Building- and Environmental Aerodynamics, Institute for Hydromechanics, at the University of Karlsruhe. The flow measurements were performed using a 2-D Laser Doppler anemometry (LDA) and The pressure measurements were carried out using a standard pressure tapping technique. The present study focuses on the most important parameters affecting the flow and pressure characteristics that include the influence of base angles, the influence of wind directions and the influence of the pyramid heights with respect to a characteristic length. Besides the experimental investigations, numerical investigations with the aid of a software package called FLOVENT were also additionally performed in order to prove, whether experimental and numerical studies deliver the same results.Based on the flow measurement results, this study was able to distinguish the general characteristics of flow around pyramid building when compared to other type of structures (i.e. cuboidal structure). A set of equations to calculate the reattachment length at the leeward side of the pyramid was generated. In addition, an equation to estimate the zero streamline and an area below line as a function of the reattachment length and base angle, respectively, are proposed. These equations will illustrate the recirculation zone at the leeward side of the pyramid.The pressure measurement results show that the three investigated parameters (base angle, wind direction and pyramid height) have an important influence to the pressure characteristics (magnitude of pressure, suction and fluctuation) in the surfaces of the pyramids. For practical purposes, this study was able to provide the typical values of pressure and aerodynamic coefficients for pyramidal buildings that can be used for structural calculations. The values that are given in this study can be used to fill in the gap of the unavailable design values for pyramidal buildings in standard tables.

Weitere Ausg.: ISBN 1000003455

Sprache: Englisch

UID:

Umfang: 1 online resource (xvi, 138 pages)

Inhalt: Pyramidal buildings are undergoing a renaissance in todays architectural design due to their attractive mystery that has fascinated many architects. From an aerodynamic engineering point of view, structural buildings with the shape of a pyramid have their own interesting and particular aerodynamic characteristics as compared to other usual structural buildings (i.e. cuboidal).However, despite its distinct aerodynamic characteristics compared to other usual structural buildings, the flow and pressure characteristics around pyramidal structures have not yet been investigated completely. Very limited studies about pyramidal buildings can be found in the literature.Consequently, the technical layout with respect to wind load assumption of pyramidal buildings are usually not listed in standard tables which underlines the need of systematic investigations for pyramidal structures.In this study, pyramids with a wide range of base angle variation (theta = 30°, 40°, 45°, 50°, 55°, 60°, 70°) have been investigated intensively through a detailed and accurate laboratory experiments at the Laboratory of Building- and Environmental Aerodynamics, Institute for Hydromechanics, at the University of Karlsruhe. The flow measurements were performed using a 2-D Laser Doppler anemometry (LDA) and The pressure measurements were carried out using a standard pressure tapping technique. The present study focuses on the most important parameters affecting the flow and pressure characteristics that include the influence of base angles, the influence of wind directions and the influence of the pyramid heights with respect to a characteristic length. Besides the experimental investigations, numerical investigations with the aid of a software package called FLOVENT were also additionally performed in order to prove, whether experimental and numerical studies deliver the same results.Based on the flow measurement results, this study was able to distinguish the general characteristics of flow around pyramid building when compared to other type of structures (i.e. cuboidal structure). A set of equations to calculate the reattachment length at the leeward side of the pyramid was generated. In addition, an equation to estimate the zero streamline and an area below line as a function of the reattachment length and base angle, respectively, are proposed. These equations will illustrate the recirculation zone at the leeward side of the pyramid.The pressure measurement results show that the three investigated parameters (base angle, wind direction and pyramid height) have an important influence to the pressure characteristics (magnitude of pressure, suction and fluctuation) in the surfaces of the pyramids. For practical purposes, this study was able to provide the typical values of pressure and aerodynamic coefficients for pyramidal buildings that can be used for structural calculations. The values that are given in this study can be used to fill in the gap of the unavailable design values for pyramidal buildings in standard tables.

Weitere Ausg.: ISBN 1000003455

Sprache: Englisch