Shanjun Liu

Hydraulic characteristics of plug energy dissipater in flood discharge tunnel

The hydraulic characteristics of three types of plugs, namely, the single plug, the stepped plug and the gradually contracted plug were studied by means of experimental and numerical simulations. Main research findings are as follows. For the single plug, the pressure recovery lengths inside and after the plug range from 0.63–1.05 times and 2.02–2.84 times of the tunnel diameter, respectively. For the stepped plug, the lengths are 0.24–0.32 times and 1.62–2.84 times of the tunnel diameter, respectively. The best ratio of the inlet diameter to the outlet diameter of the gradually contracted plug can be expressed by a linear function. The relationship between the head loss coefficient and the area contraction ratio is obtained. The incipient cavitation numbers of different plugs are experimentally and numerically determined, and the incipient cavitation numbers are expressed by a formula. Model experiment with scale of 1:50 was carried out on a pressure tunnel with three-stage gradually contracted plugs. The results show that this type of energy dissipater is suitable for spill tunnels of high head (nearly 200 m) and large flow rate (nearly 2500 m3/s).

Experimental Investigation of Air–Water Flow Properties of Offset Aerators

AbstractAlthough chute aerators have been investigated experimentally by many researchers, only a few studies have been conducted on the comprehensive air–water flow properties of the lower jet dow...

THEORETICAL AND EXPERIMENTAL STUDIES OF HYDRAULIC CHARACTERISTICS OF DISCHARGE TUNNEL WITH VORTEX DROP

The velocities at given points in the volute chamber, the contracted section and the vertical dropshaft of a discharge tunnel with vortex drop were measured by a small specially designed L-shaped tube, as Laser Doppler Velocimetry (LDV) or Particle Image Velocimetry (PIV) would not work there due to the special structure of the discharge tunnel with vortex drop. Hydraulic empirical formulas were proposed to predict the velocities and the angles of the velocities made with the vertical direction θ. The theoretical analysis results were in good agreement with experimental data. Therefore, the method proposed in this paper can be used to analyze related characteristics of discharge tunnels with vortex drop. Additionally, different model scales were considered to predict the cavitation characteristics on the wall of a dropshaft in practical engineering.

Equivalent pipe algorithm for metal spiral casing and its application in hydraulic transient computation based on equiangular spiral model

For the metal spiral casing of water turbines, a new equivalent pipe algorithm is developed based on the idea of equiangular spiral. Prototype tests and computations are carried out to investigate the hydraulic transient characteristics. The computation results by using the new model are in a good agreement with the prototype test data with respect to the maximum speed of the turbine-generator unit, the maximum water hammer pressure in the spiral casing and the maximum vacuum in the draft tube. The proposed method is a significant improvement over the conventional algorithm with the accuracy increased and the error reduced by about 3%.