Alternative approach for modeling transients in smooth pipe with low turbulent flow

Significance Statement

A new method for modelling and simulating pressure transients from the rapid acceleration/deceleration of turbulent flow in smooth-walled fluid lines is reported. As opposed to the previous methods for modelling turbulence by altering the terms of the head loss in the momentum partial differential equation, this method is realized by coupling the frequency domain solution to the laminar flow version of partial differential equations in series with a lumped resistance sized so that the steady flow resistance for the line is equal to an empirical turbulent steady flow resistance.

Professor David A. Hullender from the University of Texas at Arlington proposed an alternative approach for modelling transients in smooth pipe with low turbulent flow. The motivation for this research was pegged on the need to have a practical means to model, simulate, and/or analyze the effects of fluid transients in lines which are internal components in an engineering system without having to infer the different properties of unsteady turbulence one-and-two-dimensional friction models. The work is now published in the Journal of Fluids Engineering.

The effects of pressure transients, for instance water hammer, that result from acceleration/deceleration of flow in lines in fluid power systems or industrial fluid systems, could be detrimental. For laminar flow, the frequency domain analytical solution to the viscous and compressible flow partial differential equations has been tested and confirmed. There are various methods for converting the frequency domain solutions to time domain solutions depending on the frequency range of concern.

The author presented a method for obtaining the time response of fluid transients in lines with pretransient turbulent flow. To validate the modelling approach, the author compared water hammer simulations to classical turbulence models and simulation methods and also, to experimental data for relatively low Reynolds numbers out to 15,800. Good agreement was demonstrated, and in some instances, the proposed approach provided better agreement with experimental data than some of the classical models.

The modelling approach presented in this research utilized a preprogramed inverse frequency algorithm that generated equivalent high order normalized linear ordinary differential equations that could be coupled with models for other fluid power components and easily solved in the time domain using preprogramed numerical algorithms for ordinary differential equations.

About The Author

Dr. Hullender has BS and MS degrees from Oklahoma State University and a PhD from MIT, all in Mechanical Engineering.  He has worked in fluid power research laboratories and consulted with industry since 1964.  He has been modeling and simulating pressure transients in fluid lines in industrial and aerospace systems since 1980.

Reference

David A. Hullender. Alternative approach for modeling transients in smooth pipe with low turbulent flow. Journal of Fluid Engineering, volume 138 (2016), 121202 (10 pages).

Department of Mechanical and Aerospace Engineering, The University of Texas at Arlington, P.O. Box 19023, Arlington, TX 76019.

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