| In this paper,using physical model test and numerical simulation method to study the flow characteristics near spur dike and its influence on current in bending reach.In the part of physical model tests,using the automatic water level measurement system and the velocity measurement system to measure water level and velocity near spur dike and bending reach,and using the measurement results to study law of the changes of water level along the way,velocity distribution,the length of backflow zone and turbulent kinetic energy.In the part of numerical simulation calculations,2D flow mathematical model is set up by MIKE 21 software,which has the same size as the physical model size.The model has been validated with the test results,and using this model to analyze the law of the changes of water level,velocity distribution and the length of backflow zone.The results of physical model tests show that:(1)The water level along the way in the side of spur dike are all higher than the water level along the way in the other side of spur dike under various conditions,and after water flow passed bending reach,the water level both sides begin to recover to normal water level.(2)When the distance between spur dike and import of bending reach is definite,the water discharge is different:(1)The greater the water discharge,the higher the water level along the way,the greater the transverse gradient.When the distance between spur dike and import of bending reach is 45 cm,longitudinal gradient decreases along with the increase of the water discharge;when the distance between spur dike and import of bending reach is 55 cm,longitudinal gradient increases along with the increase of the water discharge.(2)When the distance between spur dike and import of bending reach is larger,the length of relative backflow zone increases along with the increase of water discharge.(3)The distribution area of maximum turbulent kinetic energy from the jetty head to downstream of spur dike increases along with the increase of water discharge.(3)When the water discharge is definite,the distance between spur dike and import of bending reach is different:(1)The closer the distance between spur dike and import of bending reach,the greater the highest water level and the transverse gradient along the way.When the distance between spur dike and import of bending reach is 45 cm,the maximum longitudinal gradient in the side of spur dike higher than the maximum longitudinal gradient in the other side of spur dike;when the distance between spur dike and import of bending reach is 55 cm,the maximum longitudinal gradient in the side of spur dike lower than the maximum longitudinal gradient in the other side of spur dike.(2)When the water discharge is larger,the closer the distance between spur dike and import of bending reach,the maximum and minimum flow velocity along the way is larger.(3)When the water discharge is smaller,the closer the distance between spur dike and import of bending reach,the length of relative backflow zone is longer.(4)Along with the increases of the distance between spur dike and import of bending reach,the distribution area of maximum turbulent kinetic energy in the side of spur dike and the other side of spur dike is decreasing.The results of numerical simulation calculations show that:(1)When the distance between spur dike and import of bending reach is definite,along with the increase of water discharge:(1)The water level rises gradually along the way near spur dike,the increasing degree of water level in front of the dam and the decreasing degree of water level after the dam are all increased,and the decreasing degree of water level after the dam is greater than the increasing degree of water level in front of the dam;the transverse gradient each section along the way near spur dike show an increasing trend.(2)The range of low velocity area dike upstream gradually decreases,the range of high velocity area start from the jetty head to the convex bank in bending reach expand gradually,the area from high velocity to low velocity after the dam decreases continuously,when the water discharge is increased to 35m3/h,the range from high velocity area to low velocity area after the dam shorten to the curved top section.(3)The length of relative backflow zone after the dam increases along with the increase of the water discharge.(2)When the water discharge is definite,along with the increase of the distance between spur dike and import of bending reach:(1)In the other side of spur dike,the water level decreases gradually in the range of section 1 to 5,the water level rises in the range of section 5 to 7 after the dam;in the side of spur dike,the increasing degree of water level in front of the dam and the decreasing degree of water level after the dam are all increased gradually;the transverse gradient increases gradually in local backwater range in front of the dam,and decreases gradually in the range of after the dam to the position of the lowest water level.(2)The high velocity area start from the jetty head to the convex bank and the area from high velocity area to low velocity area on the concave bank expand gradually,the range of backflow zone after the dam is decreasing.(3)The length of relative backflow zone after the dam decreases along with the increase of the distance between spur dike and import of bending reach. |
PDF Full Text Request