Abstract
During operation of high-head hydraulic spillway systems, cavitation phenomena often occur, leading to destruction of structural elements of their flow conductor portions. The article is devoted to the study of erosion due to cavitation in the circulation flows of eddy hydraulic spillways, including those equipped with counter-vortex flow energy dissipators. Cavitation destructive effects depend on many factors: intensity consisting in the rate of decrease in the volume or mass of a cavitating body per unit of time, the stage of cavitation, geometric configuration of the streamlined body, the content of air in water, the flow rate, the type of material. The objective of the study consisted in determination of cavitation impacts in circulating (swirling) water flows. The studies were conducted by a method of physical modeling using high-head research installations. Distribution of amplitudes of pulses of shock cavitation impact is obtained according to the frequency of their occurrence depending on the flow velocity, the swirl angle, the height of the cavitating drop wall and the stage of cavitation. The impact energy depending on the stage of cavitation and the flow rate is given for different operating modes of the counter-vortex flow energy dissipators of a hydraulic spillway. In the conclusions, it is noted that cavitation impacts in the circulation flows occur mainly inside the flow, which is a fundamental difference from similar processes in axial flows.
Highlights
Reliability and long-term operation of spillway systems of hydraulic structures is one of the main conditions for ensuring the safe operation of waterworks
On these curves: N is the number of pulses of shock cavitation impacts; P is the pressure in kPa on the sensitive element PkD; U is the voltage corresponding to the pressure of the pulse in volts; Q - water discharge; uθ is the azimuthal component of the full velocity M of the circulation-longitudinal flow, u M / cos α ; Kcr is a critical value, at which cavitation occurs, equal to 1
0.5ρM 2 where: p is the absolute pressure at the measured point, psat is the pressure of saturated water vapor at a temperature of 20o C, M is the total vector of the flow velocity at the measured point, ρ – is the density of water
Summary
Reliability and long-term operation of spillway systems of hydraulic structures is one of the main conditions for ensuring the safe operation of waterworks. In some cases, depending on water flow velocity, topography, geological features of the spillway foundation, a stepped surface spillway design is applied or that in the form of various piers located in a certain order [6]. Such designs of the flow conductor system of the spillway serves at the same time a flow energy dissipator at the entire length of the spillway [7]
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