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[en] Proceeding from the features of on-line retrieval from the INIS data base, a description is given of the technical and organizational conditions established by the national INIS Centre of the GDR in using the INIS direct access service. Data are presented on the structure of search queries, retrieval precision, and connect time to the computer. Experience has shown that efficient dialogue searching necessitates the searcher's skill and familiarity with the system. (author)
[en] This work investigates the influence of water compressibility on pressure pulsations induced by rotor-stator interaction (RSI) in hydraulic machinery, using the commercial CFD solver ANSYS-CFX. A pipe flow example with harmonic velocity excitation at the inlet plane is simulated using different grid densities and time step sizes. Results are compared with a validated code for hydraulic networks (SIMSEN). Subsequently, the solution procedure is applied to a simplified 2.5-dimensional pump-turbine configuration in model scale with an adapted speed of sound. Pressure fluctuations are compared with numerical and experimental data based on prototype scale. The good agreement indicates that the scaling of acoustic effects with an adapted speed of sound works well. Finally, the procedure is applied to a 3-dimensional pump configuration in model scale. Pressure fluctuations are compared with results from prototype measurements. Compared to incompressible computations, compressible simulations provide similar pressure fluctuations in vaneless space, but pressure fluctuations in spiral case and penstock may be much higher. With respect to pressure fluctuation amplitudes along the centerline of runner channels, incompressible solutions exhibit a linear decrease while compressible solutions exhibit sinusoidal distributions with maximum values at half the channel length, coinciding with analytical solutions of one-dimensional acoustics.
[en] In hydro turbine design, fluid-structure interaction (FSI) may play an important role. Examples are flow induced inertia and damping effects, vortex induced vibrations in the lock-in vicinity, or hydroelastic instabilities of flows in deforming gaps (e.g. labyrinth seals). In contrast to aeroelasticity, hydroelastic systems require strongly (iteratively) coupled or even monolithic solution procedures, since the fluid mass which is moving with the structure (added-mass effect) is much higher and changes the dynamic behavior of submerged structures considerably. Depending on the mode shape, natural frequencies of a turbine runner in water may be reduced to less than 50% of the corresponding frequencies in air, and flow induced damping effects may become one or two orders of magnitude higher than structural damping. In order to reduce modeling effort and calculation time, the solution strategy has to be adapted precisely to a given application. Hence, depending on the problem to solve, different approximations may apply. Examples are the calculation of natural frequencies and response spectra in water using an acoustic fluid formulation, the determination of flow induced damping effects by means of partitioned FSI including complex turbulent flows, and the identification of hydroelastic instabilities using monolithic coupling of non-linear structural dynamics and water flow.
[en] An array consisting of scintillating fibers embedded in a lead matrix was tested for use as a calorimeter for showers induced by energetic photons (50 MeV≤Eγ<1 GeV). Experimentally, its efficiency was found to equal 100% for photon energies in excess of 100 MeV, the energy resolution is (σ/E)∼10%/(Eγ/GeV)-1/2 over the full energy range. Extensive Monte Carlo studies show that the efficiency drops rapidly around Eγ=40 MeV. The suitability of cosmic radiation for calibration purposes is demonstrated. Based on these studies design criteria for future arrays can be matched to experimental requirements. (orig.)