With the growth of the demand for electric power in China,power transmission capacity is increasing continuously,resulting in ever wider application of the technology for large size overhead conductors.

Considering the friction of duct wall to gas-particle flow and choking phenomena, a mathemati cal model is developed describing the behavior of gas-particle flow passing through constant area duct with friction,with a critical duct length determined by Mach checkout method.

Study on the equivalent circuit of non-uniform cross section acoustic waveguide;