Experimental Study On Turbulence Characteristics Of Double-Row Cylinder Pier Circular

The research on turbulence characteristics of open channel flow as an important part of turbulence mechanics have been drawing attention of the turbulence mechanics researchers. The research on turbulence characteristics around the bridge piers is good for the research of local scour on the bridge pier. Local scour on bridge pier caused by the sand movement is based on turbulence, understanding the turbulence characteristics in-depth can better raise awareness of local scour on bridge piers.Many domestic and foreign scholars and scientists conducted a large number of indoor open channel flume model experiments, field measurement and numerical calculation, measured turbulence velocity and analyzed the distribution of turbulence characteristics in their research areas, that made a certain contribution for the research of the turbulence in two-dimensional and three-dimensional flow. However, because the turbulence situation is rather complex and there are many affecting factors, so far the research on turbulence characteristics in theory is not perfect and is still needed to be continued.This paper was based on indoor bridge hydraulic model experiment, designed three kinds of two-row non-downstream bridge site programs and made experiment under different flow conditions. We measured the three-dimensional instantaneous velocity of all the measuring points by using Vectrino and calculated the turbulence velocity, time average velocity, turbulence intensity of all the measuring points by using turbulence mechanical knowledge and statistical knowledge, found out their distributions and the relationship between the maximum depth of local scour and flow characteristics.This paper is based on statistical theory, describes the statistical average and time average of the turbulence. "Traverse hypothesis" provides a theoretical basis for the statistical turbulence experiment research using time average, also makes the experiment achievable in reality. In addition, the paper also describes the statistical characteristics of the turbulence volume-the mean and variance, autocorrelation function, turbulence scale and so on, analyses and calculates the characteristic scale of the turbulence. For the turbulence velocity, we calculates and compares the difference between the experiences probability curve and the theoretical normal calculation probability curve, describes the method-goodness of fit test in theory which can calculate the difference.The velocity pulsing process observation data of all the measuring points indicate that the velocity pulsing process of all the measuring points is almost similar and have different quasi-periodic. To the certain measuring point, the average velocity that long duration observed appears the shortest time interval, the time interval that the average velocity increase or decrease the same velocity are equally increased, and increased significantly closer. The experiences probability curve from the measured data and the theoretical normal calculation probability curve is closer in the free zones than in the shear cutting zone near the wall. In addition, this paper calculated and analyzed distribution of the time average velocity, the turbulence intensity along the cross-section in a particular experimental group, the conditions of fixed angle changed flow and the conditions of fixed flow changed angle. Finally, we obtained distribution of the maximum depth of local scour under each experimental group by analysing and comparing the maximum depth data of local scour maximum.