| In actual projects such as reservoir dredging,the slurry transported through the pipeline is often accompanied by a large number of pebble particles,which can cause pipeline blockage,reduce pipeline transport efficiency and increase the friction loss of the pipe wall,and the pipeline transport process not only needs to provide more power,but also often causes damage to the pipeline.The pebbles in the pipeline and the movement of the water flow into a reciprocal feedback effect,the transport mode of the pipeline and the flow pattern and flow field of the sand-containing water flow feedback each other,forming a complex transport system,the study of the fluctuation pressure characteristics of the pipeline coarse particle transport can provide theoretical support for the safe operation of the pipeline,the search for the lowest energy consumption transport operating conditions,to ensure the safety and stability of the pipeline,but also to prevent the accumulation and blockage of pebbles in the pipeline,and provide theoretical support for the study of coarse particle transportation in other engineering fields,which has important scientific research value.The project adopts research methods such as control variates,particle image velocimetry and mathematical statistics,and combines basic theories such as fluid mechanics and sediment dynamics to conduct in-depth research on the transportation status of coarse particles in the model test and the distribution law of pipeline pressure characteristics under different pipeline transportation conditions in the pipeline The internal relationship between the combined effect of pipeline flow velocity and inclination angle,as well as the time averaged pressure loss along the pipeline,the probability distribution of fluctuation pressure amplitude,and the power spectrum distribution,has been drawn.The following main conclusions have been drawn:(1)When horizontal clear water is conveyed by flow,the movement state of coarse particles in the pipe is divided into three different conveying states with the change of pipe flow velocity.With the increase of the flow velocity,the trend of the fluctuation of the measured pressure and fluctuation pressure in the pipeline is related to the transport state of the coarse particles,when the pipeline flow velocity increases to the state of motion of coarse particles in the second and third transport state transition state,the fluctuation of the fluctuation pressure in the pipeline is the smallest at this time,and the transport efficiency of the pipeline reaches the highest,the thickness of the particle mass accumulated in the coarse particles in the pipeline before this state is the main factor affecting the fluctuation of the pipeline,with the increase of the pipeline flow rate,the flow rate gradually becomes the main factor affecting the fluctuation of the pipeline.As the motion state of coarse particles gradually develops from the first to the third conveying state,the fluctuation pressure amplitude probability distribution also develops from a bimodal distribution to a single-peaked distribution that conforms to the Gaussian distribution characteristics.The power spectrum of the fluctuation pressure is mainly concentrated in the range of 0～25 Hz,and the variation of the fluctuation pressure power spectrum components in the frequency band of 10～15 Hz is most obvious with the flow velocity,and its trend is consistent with the volatility of the pipe.(2)The variation trend in horizontal turbid water-carrying transport is basically consistent with that in horizontal clear water-carrying transport.However,the existence of suspicious quality sediment in the pipeline increases the volatility of the pipeline,and also increases the energy consumption in the pipeline conveying process transient clear water-carrying conveying conditions of various changes in the law more significant.(3)When inclined pipeline conveying,the movement of coarse particles is slightly different from that of horizontal pipeline.In the process of inclined pipeline conveying,there is a situation that the pipe outlet cannot be full in a large range of flow rate.Coarse particles are also transported with a large starting pressure.At the beginning of the movement of coarse particles,there is a large starting pressure inside the pipeline.During the initial starting stage,the pressure first maintains a small increase with the increase of flow velocity,and then gradually decreases with the increase of flow velocity.When the pipe is exactly at full pipe,the pressure of the pipe reaches the minimum value.Then,as the flow velocity of the pipeline continues to increase,the pressure inside the pipeline gradually increases again.Under different inclination angles,the closer the feeding port of the reverse slope pipeline is,the greater the inclination angle of the pipeline,the greater the measured pressure and pulsating pressure;the closer the pipeline outlet is,the greater the inclination angle of the pipeline,the smaller the measured pressure.The larger the inclination angle of the pipeline,the greater the energy loss along the transportation process,and the greater the required starting pressure.(4)When studying the joint effects of pipeline flow velocity and inclination angle on pulsating pressure,the pipeline flow velocity during the pressure conveying stage is selected for research;the measured pressure and pulsating pressure measured at different tilt angles increase with the increase of pipeline flow velocity.The greater the inclination of the pipe,the greater the fluctuation with the flow velocity,and the greater the energy loss along the way.The fluctuation trend of the inclined pipeline with a 10° inclination angle decreases first and then increases,and the fluctuation pressure amplitude also decreases first and then increases;While the volatility and fluctuation pressure amplitude of 20° and 30°inclination increase gradually with the increase of flow velocity.The fluctuation pressure power spectrum at each inclination angle is distributed in the range of 0～25 Hz,and the larger the inclination angle is,the more obvious is the variation pattern of the power spectrum components in this range with the change of flow velocity. |
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