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Showing papers by "Leibniz University of Hanover published in 1972"


Journal ArticleDOI
TL;DR: In this article, the effects of surface roughness and profile changes on turbine performance were measured on a four-stage air turbine with artificially roughened blade surfaces and thinned and thickened profiles.
Abstract: During operation the blading of turbines undergoes certain changes. Corrosion, erosion, and contamination cause deterioration of the surface quality and blade profile changes. As a result, the performance characteristics of the turbine, especially the efficiency, change during operation. Through measurements on a four-stage air turbine with artificially roughened blade surfaces and thinned and thickened profiles which simulate the effects of corrosion and pollution respectively, it has been possible to ascertain the influence of these profile changes on the flow conditions in the turbine. This paper shows the measuring results which are representative of the effects of surface roughness and profile changes.

27 citations


Proceedings ArticleDOI
26 Mar 1972
TL;DR: In this paper, the effect of axial flow compressors roughened by corrosion or erosion on the boundary layers of the blades has been investigated with an enlarged cascade and the results enabled to develop new formulas for a modified friction coefficient and for the laminar-turbulent transition and separation points of the boundary layer.
Abstract: Blades of axial flow compressors are often roughened by corrosion or erosion. There is only scant information about the influence of this roughening on the boundary layers of the blades and thereby on the compressor efficiency. To obtain detailed information for calculating the efficiency drop due to the roughness, experimental investigations with an enlarged cascade have been executed. The results enabled to develop new formulas for a modified friction coefficient in the laminar region and for the laminar-turbulent transition and the separation points of the boundary layer. Thus, together with the Truckenbrodt theory, it was possible, to get a good reproduction of the experimental results.Copyright © 1972 by ASME

17 citations


Book ChapterDOI
TL;DR: It is concluded from the observations that mechanisms involved in the regulation of the local blood flow are virtually the same at all levels in the CNS.
Abstract: Publisher Summary The blood flow of the spinal cord, forebrain, cerebellum, and brain-stem are measured on anaesthetized cats using the particle distribution technique. With normal arterial blood pressure, normal CO2 partial pressure and O2 partial pressure, and with normal pH, the mean blood flow value of the total spinal cord is 19.28 m1/100 g - min. These correspondents to 0.68% of the cardiac output under resting conditions. The blood flow value of the particular segments of the spinal cord differs; for the cervical cord there was a value of 19.92, for the thoracic cord 16.79 and for the lumbosacral cord 22.05 ml/l00 g - min. The blood flow values determined in the same experiment for the fore-brain, cerebellum and brain-stem were 47.15,55.92, and 37.33 m1/100 g. min respectively. The effects of Pao2, Paco2, and arterial blood pressure on blood flow through the different segments of the spinal cord and the different parts of the brain are studied comparatively. Spinal cord vascular resistance is closely correlated to arterial carbon dioxide tension however there are quantitative differences in the CO2 response at different levels on the CNS. No significant correlation between arterial oxygen tension and spinal cord blood flow was observed when Pao2, varied between 60-146 torr and Paco2 is kept in the normal range. The existence of autoregulation of spinal cord blood flow is demonstrated here. It is concluded from the observations that mechanisms involved in the regulation of the local blood flow are virtually the same at all levels in the CNS.

9 citations



Journal ArticleDOI
29 Jan 1972
TL;DR: In this article, the velocity potential of a damped co-oscillating tides is derived from the potential method, and the wave amplitude is taken into account compared with the water depth.
Abstract: Several mathematical models have been lately presented which describe the tidal wave propagation within an estuary. The existing models derived from the method for damped co-oscillating tides are based on sinusoidal wave profile. Meanwhile a tidal wave which moves upstream, generally exhibits a progressive deformation which tends to unbalance the length of time between flood and ebb tides. The actual profile is therefore no longer sinusoidal. Our investigation uses the potential method, and takes into account the wave amplitude which is usually neglected compared with the water depth. Finally, the velocity potential is obtained explicitely, using a double iterative method. Tidal elevation, particle velocities and trajectories are given by the same computer programmed algorithm. Our study shows that l) the phenomenon can be clearly visualized on the theoretical curves and 2) the magnitude of this deformation is inversely proportional to the water depth, becoming significant when the ratio f|/h reaches the critical value of 1/10. Damping and geometrical effects are also considered and the theory was applied to the St.Lawrence Estuary. A partial positive reflection of the incoming tidal wave is assumed at the narrow section near Quebec, whereas a complete negative reflection is assumed at the entrance to Lake St.Peter. The calculated and observed wave profiles, velocity distributions, and phase shifts are in good agreement.

1 citations