Abstract
For long-distance water transfer projects, the residual air mass in the pipeline will not only reduce the efficiency, but also be detrimental to the safety of the system. In order to study the influence of the water flow velocity of the pressurized water pipeline and the pipeline angle of the hump on the motion characteristics of the residual air mass, an experimental platform with Particle Image Velocimetry (PIV) measuring system was constructed to analyse the flow field. The RSM turbulence model was combined with the VOF multiphase flow model to construct a local high-point gas-liquid two-phase fluid dynamics model for numerical simulation. The results showed that with the increase of water flow velocity, the local hump residual air mass would go through three states, namely, no bubble generation, air bubble was generated and partial discharged, and air mass discharge at one time. If the gas was greater than a certain volume, the increase in the water flow rate required to carry the air mass out of the hump at one time would slow down; the larger the local hump angle was, the greater the water flow rate was required to carry the gas out of the local hump part.
Highlights
Long-distance water transfer pipeline projects are limited by terrain and construction conditions, and local humps will occur in pipeline layout
It has been confirmed in a large number of projects that due to the change of slope, roughness and diameter of long-distance water pipelines, the air mass existing in the pipeline disperses and aggregates when flowing with water, which causes a drastic change in the pressure inside the pipeline
The flow field at a local hump was measured with Particle Image Velocimetry (PIV) system to study the effects of the water flow velocity in the pipeline, the volume of the retained air mass in the pipeline, and the downward angle of the hump pipeline on the motion characteristics of the retained air mass
Summary
Long-distance water transfer pipeline projects are limited by terrain and construction conditions, and local humps will occur in pipeline layout. In the long-distance water supply pipeline, if the water delivery flow rate is small, the gas will stay in the local hump in the pipeline, the valve plate position in the pipeline, the reducer, the throttle Orifice plate, relatively flat reverse slope pipe section and other positions. It has been confirmed in a large number of projects that due to the change of slope, roughness and diameter of long-distance water pipelines, the air mass existing in the pipeline disperses and aggregates when flowing with water, which causes a drastic change in the pressure inside the pipeline. It is of great significance to study the motion characteristics of air mass in the pipeline to prevent water hammer damage
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