A Study On The Change Of Roughness Coefficient Of Artificial Roughening Channel With Large Slope

Artificial open-channel flow is a common flow with free surfaces and is the most common form of flow in water conservancy projects.Therefore,the hydraulic problems related to artificial open channels have gradually attracted people's attention.There are many hydraulic elements that affect the flow of open channels.Roughness is one of the most important hydraulic parameters.Over the years,previous researchers have studied the relationship between the roughness coefficient of open channels and various hydraulic elements,but the laws between them have not yet been clearly revealed.In order to study this issue,this paper uses a combination of experimental and theoretical research methods to study the regularity and correlation between the roughness coefficient of artificial rough open channel and the hydraulic elements under high gradient.The main research contents and conclusions are as follows:(1)The roughening rate of the channel is changed by artificial roughening,and the slope of the channel is changed by using the slope adjusting device.The average channel depth of artificial channel with different flow rate of different slope under five kinds of roughness is observed.Then use the relevant theoretical formula to calculate the corresponding hydraulic component values.(2)The accuracy of the test data is verified by combining the PPR projection pursuit method and the uniform design table.The test results show that the test data is true and reliable.(3)Obtained by analyzing the test data: ?1 In the case of steep slope,when the absolute roughness is fixed,the influence of the increase of Reynolds number on the roughness coefficient is not obvious.With the change of absolute roughness,the effect of Reynolds number on the roughness is still negligible.?2Under these five kinds of absolute roughness,with the gradual increase of the flow rate,the change of the corresponding roughness coefficient under each absolute roughness is not obvious.It shows that the influence of flow rate Q on roughness coefficient n is very small.?3 Combined with data analysis and theoretical analysis,it is concluded that when Fr<1,the number of Froude is the most important hydraulic factor that affects the roughness coefficient when the slope is large.But when Fr>1,the main hydraulic element that affects the roughness coefficient is the number of Froude and the slope.?4 Non-linear regression analysis of main hydraulic factors related to roughness coefficient in the case of open channel flow for both slow and fast flow.We obtain the two functions of the roughness coefficient and the related hydraulic factor in the case of this test.After verification and analysis of the above formula is true and reliable.