Study On The Velocity Characteristics Of Annular Slit Spiral Flow Of Double Piped Cars Under Different Spacing

The tube-contained material pipeline hydraulic transportation is a new type of material transport mode in the development of modern green logistics industry.It has the advantages of less environmental pollution,low energy consumption and good safety performance.To a certain extent,this transportation mode overcomes the disadvantage of high energy consumption and serious pollution in the traditional transportation industry.Through theoretical analysis and experimental research,the spiral flow velocity characteristics of double piped cars under different inter-vehicle distances have been studied.The main conclusions are as follows:(1)Under the different spacing,the axial velocity contour map of the test section in the front car annular slit region presents the same rule,and there are three vortex areas with a 120 degrees distribution at each test section,and the mean,range,standard deviation and the non-uniform coefficient of axial velocity.The spacing has little effect on the axial velocity of the water flow in the annular slit of the pipeline.(2)Under the same spacing,the axial velocity gradient in the annular slit of the front car gradually descends along the path,the axial velocity distribution is gradually flat along the path,and there are three obvious areas with lower speed.The range,standard deviation and the non-uniform coefficient of axial velocity are greatly reduced in the test section.From the perspective of local characteristics,the axial velocity of the measuring points on the same polar is basically flat,and the axial velocity fluctuation gradually decreases on the same ring along the path.(3)Under the same spacing,the circumferential velocity contour of the annular slit region of the front car has a "dense-sparse-dense" variation pattern.The circumferential velocity gradient decreases first and then increases,and the circumferential velocity is 1 order of magnitude smaller than the axial velocity.The circumferential velocity increased gradually along the path with an increase of 80%.The proportion of the number of measurement points in the circumferential velocity to the counterclockwise direction gradually increased from 68% to 92% in the same test section.The circumferential velocity distribution is relatively smooth,but the interval width of circumferential velocity distribution has increased along the path.From the perspective of local characteristics,the distribution of circumferential velocity on the same polar is relatively stable,and the distribution of circumferential velocity on the same ring is rather disordered.(4)Under the same spacing,the radial velocity of the annular slit region in the front car is 2 orders of magnitude smaller than that of the axial velocity,and the radial velocity of 5/6 is deviating from the center of the circle,and the radial velocity increases along the path.The standard deviation and non-uniformity coefficient decreased first and then increased,and the minimum value was obtained on the 3# test section.From the perspective of local characteristics,the interval width of radial velocity distribution increases gradually on the same polar,and the radial velocity fluctuation gradually increase on the same ring.(5)With the increase of spacing,the axial velocity of the rear car annulus slit region basically remains unchanged,maintaining at around 2.3m/s.In the axial velocity contour map,the number of vortex regions gradually decreases.When the spacing between the two piped cars is 10 cm,the axial velocity distribution is the most disordered,and there are six vortex regions in the axial velocity contour map.When the spacing is 70 cm and 90 cm,the axial velocity is roughly concentric annular distribution;the axial velocity of the inner wall near the pipe is larger than the axial velocity near the outer wall of the piped car.Along with the increase of spacing,the axial velocity range,standard deviation and non-uniformity coefficient of the test section increase first and then decrease,and then tend to be stable.From the perspective of local characteristics,with the increase of spacing,the difference of axial velocity on each polar gradually decreases.On the same ring,the axial velocity shows a wave-like distribution,with three peaks and three troughs and the crest trough interval are separated by 60 degrees.(6)In the region of the annulus slit of the rear car,the circumferential velocity of the water flow is 1 order of magnitude smaller than that of the axial velocity.With the increase of spacing,the isolines of circumferential velocity gradually become sparse and the curvature decreases;the proportion of the measured point number of the circumferential velocity to the clockwise direction increased from 75% to 90% in the same test section,and the circumferential velocity also increased gradually.When the spacing between cars is 90 cm,the contours begin to show a concentric distribution.From the perspective of local characteristics,the circumferential velocity of the amplitude of fluctuation is not large along the polar,and the velocity values are concentrated in the range of 0m/s to 0.2m/s.The circumferential velocity on the same ring basically shows that alternates with the peak-valley interval of 60°.(7)In the region of the annulus slit of the rear car,the radial velocity of the water flow is 1 order of magnitude smaller than that of the axial velocity.With the increase of spacing,the mean,standard deviation and non-uniformity coefficient of radial velocity are decreased.The ratio of radial velocity to the center of the circle presents a rule that decreases first and then increases.Regardless of the spacing,the radial velocity does not fluctuate in the direction of the polar and is smaller than the circumferential velocity fluctuation.From the viewpoint of local characteristics,the radial velocity near the outer wall of the piped car is smaller,and the radial velocity near the inner wall of the pipe is larger.With the increase of the spacing,the difference of the radial velocity between the measuring rings in the test section has a decreasing trend.(8)Regardless of the spacing,the fluctuation intensity of the axial velocity in the annular slit of the front car is 1 order of magnitude larger than the fluctuation intensity of the vertical velocity and lateral velocity,and the vertical and transverse fluctuation intensity is suddenly increased at the local position.With the increase of spacing,the mean value of axial velocity fluctuation intensity decreases gradually,and the intensity of vertical and transverse fluctuation intensity remains unchanged at about 0.02m/s.The research results of this paper not only enrich and improve the theory of annular slit spiral flow,but also have certain reference value for the industrialization and application of the tube-contained material pipeline hydraulic transportation technology.