Experimental Study On Single?Double Propeller Jet Under Hydrostatic?still Propeller Condition

Xiangjiang is one of the important high-grade inland waterways in the planning of the national high-grade inland waterway network.It is also the key river in the construction of the waterway in Hunan Province.The governance and protection of the Xiangjiang is also a matter of great concern to the provincial government in recent years,on the one hand,the water level in the middle and lower reaches of the Xiangjiang continued to decline,and on the other hand,the tonnage of the ships was increasing.The disturbance of the jet generated by the large tonnage ships on the sediment of the river under the condition of low water level was gradually be concerned about.The propeller jet is one of the important dynamic mechanisms to re-suspend the sediment of the river and release the heavy metal and other pollutants,and its characteristics,velocity distribution and disturbance range need detailed study.In this paper,combined with the existing research results,to carry out single and double propeller jet flow characteristics of experimental study in the still water condition,used the PIV(Particle Image Velocimetry)method to photograph and measure the flow field on the vertical plane of the propeller shaft in the model propeller jet,and the flow field data,the characteristics of the propeller jet,the velocity distribution and the range of disturbance 'are analyzed,and the following conclusions are drawn:1?The value of efflux velocity(the maximum axial velocity on the propeller plane)of propeller jet is independent of the depth of water and the depth of the propeller submerged,only in relation to the rotation speed,pitch and shape of the propeller.To the double propeller jet,one of the jet's efflux velocity's value is not affected by another propeller jet,which is the same as the single jet.2?The position of the efflux velocity of propeller jet is independent of the depth of water,the submerged depth of propeller and the rotation speed of propeller.It is related to the diameter and shape of propeller.Under the same shape of the propeller,the larger the diameter of the propeller,the more the position of the efflux velocity is closer to the axis of the propeller.Under the same propeller diameter,the more the number of blades,the greater the pitch,the position of the efflux velocity is closer to the propeller axis.To twin jet,two propeller jet's efflux velocity do not influence each other,the position is same with single propeller jet.3?Characteristics of the velocity distribution on the axis of propeller jet:single propeller jet,in the efflux plane,due to the influence of the hub,the axis velocity is small,after,the velocity increases rapidly,and in a very short distance(0.5D)increase to the maximum,and then began to decay,the decay rate is from big to small.Twin propeller jet,in the distance near the propeller plane,the characteristics of the velocity on the propeller axis is similar to the single propeller jet,When the distance from the propeller plane is large,the fluctuation rate fluctuates greatly and the decay rate is smaller than that of the single propeller jet.4?The range of jet disturbance:propeller speed and propeller diameter are the main influencing factors of jet disturbance range.Propeller shape characteristics,water depth and propeller submerged depth also have important influence on the disturbance range of jet.The propeller shape features affect the development and diffusion characteristics of the jet,thus affecting the vertical depth and axial length of the jet disturbance range.Deepened water depth,The vertical disturbance depth of the single propeller jet decreases,the axial disturbance length increases.To twin propeller jet,the vertical and axial disturbance distance were all increased.