APPROXIMATE TRANSFER FUNCTION RELATING TO VARIABLES IN AN UNSTEADY PIPE FLOW.

For fluid control and measurement in an unsteady pipe flow, it is useful to estimate one variable precisely from others. This is done using the transformation calculus. In laminar and axially symmetrical flow, transfer functions which relate pressure gradient, mean flow velocity and local velocity at a specified point on the same cross section of the pipe contain the Bessel function. Approximate functions of the transfer functions are obtained in simple form of linear combination of the proportional element, the first order lag element and the element based on the second order lag element. By use of approximate transfer functions, and efficient transformation calculus of the variables in unsteady pipe flow can be realized.