Speed-accuracy tradeoffs, velocity profiles, and physiological tremor are fundamental characteristics of human movement. The principles underlying these phenomena have long attracted major interest and controversy. Each is well established experimentally but as yet they have no common theoretical basis. It is proposed that these three phenomena occur as the direct consequence of a movement response planning system that acts as an intermittent optimal controller operating at discrete intervals of ~100 ms. The BUMP model of response planning describes such a system. It forms the kernel of adaptive model theory which defines, in computational terms, a basic unit of motor production or BUMP. Each BUMP consists of three processes: (i) analysing sensory information, (ii) planning a desired optimal response, and (iii) executing that response. These processes operate in parallel across successive sequential BUMPs. The response planning process requires a discrete time interval in which to generate a minimum acceleration trajectory of variable duration, or horizon, to connect the actual response with the predicted future state of the target and compensate for executional error. BUMP model simulation studies show that intermittent adaptive optimal control employing two extremes of variable horizon predictive control reproduces almost exactly findings from several authoritative human experiments. On the one extreme, simulating spatially-constrained movements, a receding horizon strategy results in a logarithmic speed-accuracy tradeoff and accompanying asymmetrical velocity profiles. On the other extreme, simulating temporally-constrained movements, a fixed horizon strategy results in a linear speed-accuracy tradeoff and accompanying symmetrical velocity profiles. Furthermore, simulating ramp movements, a receding horizon strategy closely reproduces experimental observations of 10 Hz physiological tremor. A 100 ms planning interval yields waveforms and power spectra equivalent to those of joint-angle, angular velocity and electromyogram signals recorded for several speeds, directions, and skill levels of finger movement. While other models of response planning account for one or other set of experimentally observed features of speed-accuracy tradeoffs, velocity profiles, and physiological tremor, none accounts for all three. The BUMP model succeeds in explaining these disparate movement phenomena within a single framework, strengthening this approach as the foundation for a unified theory of motor control and planning.

The development flow region of stepped chutes was studied experimentally. Three configuration of chute bed slopes 3.5H:1V, 5H:1V, and 10H:1V were used to study the flow characteristics. Each model had five horizontal steps and with constant step height of 15 cm. Constant temperature anemometry was used to investigate the velocity field characteristics as well as local void fraction. Pressure transducers were used to examine the pressure distribution. The conditions of aerated and non-aerated cavity were studied. It was found that the temperature anemometry is a valuable tool in the study of water flow problems due to its good spatial and temporal resolution. It is recommended that the constant overheat ratio procedure should be used in dealing with non-isothermal water flows. Flow conditions along the development flow region were found to be quite complex with abrupt changes between steps depending whether or not the flow jet has disintegrated. The flow on this region does not resemble a drop structure and after the first step, the step cavity condition does not affect the flow parameters. Pressure distribution was also found to be complex. It was found that there are no conclusive pressure profiles either on the step treads nor on step risers. No correlation was observed with the values of pool depth. The instantaneous characteristics of the velocity field along the jet of a drop structure were also studied. It was concluded that the cavity condition does not affect the velocity field of the sliding jet. The shear stress layer at the jet/pool interface was quantified. / May 2006

Mit dieser Arbeit liegt eine ausführliche Studie zu den Integralverfahren der Grenzschichttheorie vor. Der Schwerpunkt liegt dabei auf den Dissipationsintegralverfahren. Im Vergleich zu anderen Grenzschichtverfahren bestehen die generellen Vorteile der Integralverfahren in ihrer Robustheit, ihrer hohen Praktikabilität sowie den im Sinne der aufzuwendenden Computerkapazität geringen Kosten. Ein spezieller Vorteil der Dissipationsintegralverfahren ist es zudem, das komplette Schubspannungsprofil der Grenzschicht zu berücksichtigen. Über eine entsprechende Ableitung der Dissipationsintegrale kann die Vorgeschichte der Grenzschicht erfassen werden. Ausgangspunkt der Arbeit ist eine Literaturanalyse, welche aufzeigt, dass Integralverfahren weit verbreitet sind und für vielfältige Typen von Grenzschichten Anwendung finden. Ausgehend von den Navier-Stokes-Gleichungen wird über die Grenzschichtgleichungen die allgemeine Form der Dissipationsintegralgleichungen hergeleitet. Auf der Basis dieser Gleichungen werden Berechnungsalgorithmen für zwei- und dreidimensionale Grenzschichten entworfen und ausführlich diskutiert. Die zur Komplettierung der Berechnungsalgorithmen benötigten Parameterzusammenhänge werden aus expliziten Geschwindigkeitsprofilen hergeleitet. Hierzu werden beruhend auf dem Zweischichtenmodell turbulenter Grenzschichten Geschwindigkeitsprofile turbulenter Grenzschichten diskutiert. Drei Kombinationen von Haupt- und Querströmungsprofil werden für den dreidimensionalen Fall ausgewählt und algorithmisch umgesetzt. Die Algorithmen für zweidimensionale Grenzschichten beruhen auf einem Geschwindigkeitsprofil. Dem Aufbau der Algorithmen schließen sich ausführliche Testrechnungen sowie eine Bewertung der Verfahren an. Es wird festgestellt, dass Dissipationsintegralverfahren für zwei- und dreidimensionale Grenzschichten mit gutem Erfolg angewandt werden können. Vergleiche der Rechenergebnisse für zweidimensionale Grenzschichten zeigen die zumindest Gleichwertigkeit mit Zweigleichungsmodellen an. / Calculation and prediction of turbulent boundary layers are among the most challenging tasks of present fluid mechanics. A strong demand exists for robust, easy-to-handle and in terms of computing effort cheap algorithms which can be used for technical applications. From an engineering point of view zonal methods and RANS are the most useful tools for solution of fluid mechanical problems. It is known that zonal methods which use integral approaches for the description of the boundary layer can be used successfully in manifold forms. One way to improve zonal methods further is the Basically three different types of integral algorithms - entrainment, momentum of momentum and dissipation integral method - can be derived from the three-dimensional boundary layer equations. If one compares the usual entrainment integral method with the dissipation integral method it turns out that the latter has the following physical advantages. While the entrainment method considers information about the shear stress distribution only at the outer edge of the boundary layer, the dissipation integral method uses the whole distribution. This work gives an overview over dissipation integral method and extends them to three-dimensional boundary layers. The general integral equations for the three-dimensional case are derived. Using two different sets of mean velocity profiles the hyperbolical character of a dissipation integral method is shown. Apart from the integral momentum balance, the dissipation integral method satisfies a second major balance with the integral balance of mechanical energy. It is found that for a practical calculation the integral momentum equation and the integral energy equation are most useful. Sixteen two-dimensional experimental test cases with none-zero pressure gradients were computed. It was found that the averaged relative deviation between measured and computed values for the skin friction coefficient is about 5 % and about 3 % for the shape parameter. Two three-dimensional fully turbulent boundary layers approaching an obstacle where computed. The agreement between experimental results and the calculation is reasonably good. The calculation allows the prediction of the velocity distributions. Flow angle and flow gradient angle distributions being additional results.

No description available.

The development flow region of stepped chutes was studied experimentally. Three configuration of chute bed slopes 3.5H:1V, 5H:1V, and 10H:1V were used to study the flow characteristics. Each model had five horizontal steps and with constant step height of 15 cm. Constant temperature anemometry was used to investigate the velocity field characteristics as well as local void fraction. Pressure transducers were used to examine the pressure distribution. The conditions of aerated and non-aerated cavity were studied. It was found that the temperature anemometry is a valuable tool in the study of water flow problems due to its good spatial and temporal resolution. It is recommended that the constant overheat ratio procedure should be used in dealing with non-isothermal water flows. Flow conditions along the development flow region were found to be quite complex with abrupt changes between steps depending whether or not the flow jet has disintegrated. The flow on this region does not resemble a drop structure and after the first step, the step cavity condition does not affect the flow parameters. Pressure distribution was also found to be complex. It was found that there are no conclusive pressure profiles either on the step treads nor on step risers. No correlation was observed with the values of pool depth. The instantaneous characteristics of the velocity field along the jet of a drop structure were also studied. It was concluded that the cavity condition does not affect the velocity field of the sliding jet. The shear stress layer at the jet/pool interface was quantified.

An isolated wing-tip vortex from a square-tipped NACA 0012 wing at an angle of attack of 5 degrees was studied in a water tunnel at a chord based Reynolds number of approximately 24000. Measurements were taken using stereo particle image velocimetry at three measurement planes downstream of the wing under each of three freestream turbulence conditions. The amplitude of wandering of the vortex axis increased with increasing distance downstream of the wing and with increasing freestream turbulence intensity. The magnitude of the peak azimuthal velocity decreased with increasing distance from the wing as well as with increases in the freestream turbulence intensity. The streamwise velocity in the vortex core was less than the freestream velocity in all cases. Time resolved histories of the instantaneous waveform shape and location of the vortex axis were determined from sequences of images of fluorescent dye released from the wing.

The development flow region of stepped chutes was studied experimentally. Three configuration of chute bed slopes 3.5H:1V, 5H:1V, and 10H:1V were used to study the flow characteristics. Each model had five horizontal steps and with constant step height of 15 cm. Constant temperature anemometry was used to investigate the velocity field characteristics as well as local void fraction. Pressure transducers were used to examine the pressure distribution. The conditions of aerated and non-aerated cavity were studied. It was found that the temperature anemometry is a valuable tool in the study of water flow problems due to its good spatial and temporal resolution. It is recommended that the constant overheat ratio procedure should be used in dealing with non-isothermal water flows. Flow conditions along the development flow region were found to be quite complex with abrupt changes between steps depending whether or not the flow jet has disintegrated. The flow on this region does not resemble a drop structure and after the first step, the step cavity condition does not affect the flow parameters. Pressure distribution was also found to be complex. It was found that there are no conclusive pressure profiles either on the step treads nor on step risers. No correlation was observed with the values of pool depth. The instantaneous characteristics of the velocity field along the jet of a drop structure were also studied. It was concluded that the cavity condition does not affect the velocity field of the sliding jet. The shear stress layer at the jet/pool interface was quantified.

Speed-accuracy tradeoffs, velocity profiles, and physiological tremor are fundamental characteristics of human movement. The principles underlying these phenomena have long attracted major interest and controversy. Each is well established experimentally but as yet they have no common theoretical basis. It is proposed that these three phenomena occur as the direct consequence of a movement response planning system that acts as an intermittent optimal controller operating at discrete intervals of ~100 ms. The BUMP model of response planning describes such a system. It forms the kernel of adaptive model theory which defines, in computational terms, a basic unit of motor production or BUMP. Each BUMP consists of three processes: (i) analysing sensory information, (ii) planning a desired optimal response, and (iii) executing that response. These processes operate in parallel across successive sequential BUMPs. The response planning process requires a discrete time interval in which to generate a minimum acceleration trajectory of variable duration, or horizon, to connect the actual response with the predicted future state of the target and compensate for executional error. BUMP model simulation studies show that intermittent adaptive optimal control employing two extremes of variable horizon predictive control reproduces almost exactly findings from several authoritative human experiments. On the one extreme, simulating spatially-constrained movements, a receding horizon strategy results in a logarithmic speed-accuracy tradeoff and accompanying asymmetrical velocity profiles. On the other extreme, simulating temporally-constrained movements, a fixed horizon strategy results in a linear speed-accuracy tradeoff and accompanying symmetrical velocity profiles. Furthermore, simulating ramp movements, a receding horizon strategy closely reproduces experimental observations of 10 Hz physiological tremor. A 100 ms planning interval yields waveforms and power spectra equivalent to those of joint-angle, angular velocity and electromyogram signals recorded for several speeds, directions, and skill levels of finger movement. While other models of response planning account for one or other set of experimentally observed features of speed-accuracy tradeoffs, velocity profiles, and physiological tremor, none accounts for all three. The BUMP model succeeds in explaining these disparate movement phenomena within a single framework, strengthening this approach as the foundation for a unified theory of motor control and planning.

An isolated wing-tip vortex from a square-tipped NACA 0012 wing at an angle of attack of 5 degrees was studied in a water tunnel at a chord based Reynolds number of approximately 24000. Measurements were taken using stereo particle image velocimetry at three measurement planes downstream of the wing under each of three freestream turbulence conditions. The amplitude of wandering of the vortex axis increased with increasing distance downstream of the wing and with increasing freestream turbulence intensity. The magnitude of the peak azimuthal velocity decreased with increasing distance from the wing as well as with increases in the freestream turbulence intensity. The streamwise velocity in the vortex core was less than the freestream velocity in all cases. Time resolved histories of the instantaneous waveform shape and location of the vortex axis were determined from sequences of images of fluorescent dye released from the wing.

The thesis deals with the description of the unstable flow of non-Newtonian fluid in a slit-flow rheometer, which negatively affects its behaviour. The initiators of unstable fluid flow are the roughness of the rheometer slit walls, the slip on the rheometer walls, and the influence of the inlet and outlet region geometry of the rheometer slit. The work contains methodical procedures for mathematical consideration of individual unstable fluid flow initiators and design of change of slit geometry of slit-flow rheometer. Part of the work is also a comparison of the most commonly used rheological models, derivation of general relations for the creation of the velocity profile of individual rheological models and their subsequent implementation in the rheological application, which significantly simplifies the process of evaluation of measured data when measured on slit-flow rheometer. This application can be used to determine basic parameters in CFD simulations or as a teaching aid.