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COBEM 2021
26th International Congress of Mechanical Engineering
AN EFFICIENT UNSTEADY TRANSIENT FRICTION MODELLING FOR LIQUID-FILLED PIPE FLOWS
Submission Author:
DOUGLAS MONTEIRO ANDRADE , RJ , Brazil
Co-Authors:
DOUGLAS MONTEIRO ANDRADE, Felipe Bastos de Freitas Rachid
Presenter: DOUGLAS MONTEIRO ANDRADE
doi://10.26678/ABCM.COBEM2021.COB2021-0538
Abstract
This work presents a one-dimensional unsteady friction model to predict the transient responses of a Newtonian fluid under turbulent regimes. Yet the simplicity of the one-dimensional mathematical frame is maintained, the continuum theory of mixtures, which the model is based on, enables the model to access the fluid transient internal structure. In the present approach, the fluid flow is interpreted as a pseudo-mixture formed by constituents of invariant volume-fraction that are geometrically arranged inside the pipe as concentric shells. They all have the same equation of state and their kinematics allow each of them to slide upon their neighbors in the direction of the pipe centerline. The governing equations form a quasi-linear hyperbolic system of partial differential equations whose solution in the context of initial-boundary-value problems are approximated by using the method of characteristics. In the present model, the radius and thickness of each constituent is an arbitrary constitutive choice in such a way that their arrangement appraises how much the internal structure of the flow is accessed. To identify the spatial distribution of the constituents inside the mixture capable to promote the best cost-effective solution, with just a small number of them well-placed and few spatial grid nodes, a numerical study is carried out taking as reference 2D numerical solutions and experimental data available in the literature. The ideal grid allows the one-dimensional proposed model to present responses quite similar to those found in 2D models (k-ω, five-region) in terms of head and rate of energy dissipation with CPU times that beholds its use when real-time applications are sought.
Keywords
unsteady friction, Pipe Flows, turbulent regime, Theory of Mixtures
