Local resistance coefficient, combined

Some of the structural factors, such as the changes in cross section area of flow passage and flow direction etc., may also cause pressure losses. Obviously, these factors depend on the specific structure of the device under consideration and vary from device to device. For convenience, and for more generalization, the resistance resulting from all the structural factors is represented in terms of the combined local resistance coefficient, 1s, which is also related to the velocity of the gas flow in the accelerating tube, i.e., the impinging velocity, utl. i.e.. 

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