It has been found that proper timing of cavity opening and collapse has an influence on the numerical results. The simulation results show that adjustment of the timing of the cavity collapse has a greater influence on pressure pulses than the time adjustment for cavity opening. Results without time adjustments for cavity opening and collapse are presented as a baseline solution. This is an important finding for developers and users of cavitaional models applied to hydropower.
COBISS.SI-ID: 10361371
Half a century ago Richard Skalak developed fluid-structure interaction equations. The paper considers the propagation of pressure waves in liquid-filled pipes and the coupled radial/axial response of the pipe walls. In a tribute to Skalak's work, his results are used herein to assess the dispersion of wave fronts in long cross-country pipelines, as observed in field measurements. Long pipelines are common in hydropower plants (HPP). Results are presented in dimensionless form. Flow control in HPP is dependent on wave dynamics.
COBISS.SI-ID: 10356763
A guard-gate can be installed at the inlet of the pressure tunnel, at the downstream end of the surge tank or in the draft tube of the water turbine. A hydraulic shape of the gate and characteristics of the hydropower plant system govern the magnitude of pressure forces acting on the gate structure. Numerical analysis of hydraulic characteristics has been performed for a vertical leaf gate at different gate openings. The analysis has been performed with CFD code using finite volume method. Computational results are compared with results of measurements carried out in a model test rig.
COBISS.SI-ID: 10416667
Simplified water hammer equations are presented in standard literature. This paper investigates parameters that may significantly affect water hammer wave attenuation, shape and timing. Possible sources that may affect the waveform predicted by the classic water hammer theory include unsteady friction, cavitation, a number of FSI effects, viscoelastic behaviour of the pipe-wall material, leakage and blockage. The discrepancies originate from assumptions in the development of the classic water hammer equations. These findings are important for developers and users of theoretical models.
COBISS.SI-ID: 10588187
Trapped gas pockets may cause severe operational problems in liquid piping systems. Experimental investigations of beat phenomena have been carried out in a laboratory apparatus. The transient event is initiated by rapid closure of a side-discharge solenoid valve. Predicted and measured results are compared and discussed. It is shown that the fully-developed beat is strongly attenuated by unsteady friction and not so by steady friction. This finding is important for safety analysis of hydropower plant. Air release is strongly recommended.
COBISS.SI-ID: 11272731