Eventos Anais de eventos
ENCIT 2016
16th Brazilian Congress of Thermal Sciences and Engineering
NUMERICAL COMPARISON OF ONE AND TWO-DIMENSIONAL MODELS FOR NON-NEWTONIAN FLUID HAMMER
Submission Author:
Tainan Gabardo , PR
Co-Authors:
Gabriel Merhy de Oliveira, Cezar Otaviano Ribeiro Negrao
Presenter: Tainan Gabardo
doi://10.26678/ABCM.ENCIT2016.CIT2016-0587
Abstract
The study of fluid transients is essential when designing pipelines. Transients may be caused by sudden changes in boundary conditions such as the closure of a valve in a fluid hammer problem. The closure causes over pressure and wave propagations that can damage the pipeline causing accidents and leakage. Most works use water or Newtonian oils to study the problem. Nevertheless, non-Newtonian fluids, such as slurries, pastes, swages and suspensions, are also transported. Therefore, this work aims to study the non-Newtonian fluid hammer problem through the numerical simulation of two mathematical models. In these models the flow is considered laminar, weakly compressible, isothermal and the fluid is assumed to behave as a Power Law fluid. The mass and momentum balance equation are solved by the method of the characteristics (MOC). The first model is one-dimensional (1D) and the second is two-dimensional (2D). A comparison is realized in order to evaluate in which conditions the solution of both models converges or diverges. The results show that the 1D model is less dissipative and predicts a lower pressure overshoot when compared to the 2D model. When the fluid is more dissipative, the solution of these models is closer. The effect of the power law index is also studied. As the fluid becomes more pseudoplastic (lower values of the power law index) the dissipation increases and equilibrium is reached with shorter times. The Richardson annular effect (the presence of a local maximum for the axial velocity near the wall) is more pronounced for shear-thickening fluids.
Keywords
power-law model, fluid hammer, mathematical models, fluid transients
