Eventos Anais de eventos
COBEM 2021
26th International Congress of Mechanical Engineering
NUMERICAL ANALYSIS OF CONTROLLED PERTURBATION IN THE GENERATION OF ROLL WAVES IN OPEN-CHANNEL FLOWS
Submission Author:
Valdirene Rocho , SC , Brazil
Co-Authors:
Valdirene Rocho, Guilherme Henrique Fiorot, Sergio Viçosa Möller
Presenter: Valdirene Rocho
doi://10.26678/ABCM.COBEM2021.COB2021-0093
Abstract
This article brings a numerical work presenting results of two-phase flow of Newtonian fluids in a laminar, transient regime, evolving in an open channel, in conditions of propagation of roll wave instability. The simulations were performed using the OpenFOAM software, which uses the complete Navier-Stokes equations discretization by the finite volume technique. The fluids used in the numerical tests were glycerin and air for different entry conditions. In this work, more specifically, Euler schemes were employed for the time-derivative (CFL = 0.5), PIMPLE for the coupling of velocity pressure, and VoF technique (fluid of volume) to solve the interface. Firstly, the boundary conditions were specified in order to achieve the permanent and uniform regime for specific set of Froude and Reynolds numbers. Subsequently, a sinusoidal flow, with fixed frequency (3 Hz) and amplitude (15 \% of the uniform regime), was applied. Then, from the information of the fluid dynamic field, the generation and propagation of the roll waves was evaluated based on measurements at the interface of the following variables: position, longitudinal and transverse velocity. Data analysis was performed for different cases depending on the number of Froude. Finally, data was then processed, and the following wave characteristics were identified: length, velocity, amplitude, maximum and minimum height. From the results obtained, it was found that the stabilized waves are presented as long waves $\left(\sfrac{\Delta h}{\lambda} << 1 \right)$, validating mathematical hypotheses used in shallow water modeling for simplifying mathematical models. It was noticed that the greater the number of Froude, the greater the amplitude in meters of the roll wave. In addition, the Froude number shows a proportional relationship with the wave amplitude relative to mean flow height. Likewise, the increase in the length of the wave generated as a function of Froude was also corroborated. For the simulated cases, all roll waves reached stability conditions and maintained their properties after a specific channel length.
Keywords
Roll Waves, Froude Number, Perturbation frequency, Newtonian fluids.
