| With the construction and operation of the Jinsha River and Minjiang River hydropower projects,the unsteady flow will cause the downstream channel to have faster and larger amplitude than the natural condition when the peak load is generated.Syria Lu waterway is the most upstream high-grade waterway of the Yangtze River.The daily regulation of these two rivers converging in Yibin will generate newly unsteady flow,which will have a significant influence on this stream way.In this thesis,the author will discuss the propagation properties of unsteady flow in the Syria Lu River.The mathematical model of unsteady flow and measured data will be used.Besides,the variation of propagation velocity,wavelength,flow rate and water level of typical unsteady flow and the difference with constant flow conditions in the process of unsteady flow in Yibin are analyzed.The main conclusions are as follows:(1)When the wave heights of common unsteady flow in Yibin are 0.8~1.5m,the time to spread from the water level peak to the Guanyinbei dowmstream is between 12~14 hours,and the wave heights attenuation to the original 1/2;the larger the flow base value of the unsteady flow is,the less obvious the attenuation effect of the wave is.The minimum water level along the path is only influenced by the flow base value,but has nothing to do with the peak value of the flow rate,and the maximum diurnal variation along the water level along the path decreases with the increase of the propagation distance.(2)The typical unsteady flow period is about 26 h,the wavelength is about 217.4km,the average propagation speed is 8.4km/h,and the internal wave velocity decreases along the half wavelength.Under the condition of unsteady flow,the magnitude of the amplitude of the flow along the flow is only related to the initial flow amplitude and period,but not related to the initial flow peak value and the absolute value of the base value.Cycle is an important factor affecting the attenuation of flow amplitude.The shorter the cycle,the faster the attenuation rate is,and the larger the attenuation is.With the increase of the propagation distance,the attenuation trend of the flow amplitude decays and attenuates to 54.2% to 64.5% of the initial flow amplitude after the half wavelength,and the variation of the water level along the path is basically similar to that of the flow variation.With the increase of the distance,the wave peak falls along the range and the wave valley rises along the range,but the variation amplitude decreases gradually,but the total period is maintained.Unchanged;(3)Compared with the constant flow condition,the flow rate gradually decreases from the Yibin flow peak,and the flow rate increases gradually from the wave valley.With the increase of distance,the flow rate is narrowed and the average value is close to the average,but the flow rate outside the distance is related to the stage and distance,and the water level change is similar to the flow variation.The maximum water level difference of Luzhou reach reaches 2m when the constant flow and constant flow condition.(4)In the straight channel unsteady flow high decreases gradually from top to bottom,the wave height attenuation rate increased gradually,the decay rate of wave speed.The unsteady flow waves in the relaxed channel decrease rapidly and promote the attenuation of the wave.The decrease of the water level along the narrow channel and the attenuation rate of wave height decrease along the path,and the waveform is inhibited.In the unsteady flow of river channel changes associated with high specific Tan and bending radius;(5)With the increase of flow rate and the increase of water surface ratio and peak,the decrease of flow rate decreases with the decrease of valley.The maximum value of additional drop occurs during the period of rising or falling.The velocity is directly proportional to the flow rate.The velocity of the same flow is higher than the corresponding velocity of precipitation,and the velocity distribution along the flow is also related to the shape of the cross section.When the additional flow rate is generated by the unsteady flow,there is an additional velocity at the same time.The value of the ascending section is positive and the value of the descending section is negative. |
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