scholarly journals Roll waves and their generation criteria

RBRH ◽  
2021 ◽  
Vol 26 ◽  
Author(s):  
Fabiana de Oliveira Ferreira ◽  
Geraldo de Freitas Maciel ◽  
João Batista Pereira
Keyword(s):  
Free Surface ◽  
Froude Number ◽  
Technical Note ◽  
Flowing Fluid ◽  
Roll Waves ◽  
Simulation Based ◽  
Fluent Software ◽  
New Generation ◽  
Averaged Model

ABSTRACT Pulsating waves (also known as roll waves) might occur on the free surface of extreme events like mud and debris flows, among others, usually intensifying the caused damage. This technical note aims to inform about the roll wave phenomenon developing in a free-surface laminar flow, and analyze its generation criteria, centered on the concepts of Froude number and disturbance frequency. The complete linear stability analysis of the new depth-averaged model was proven a useful theoretical tool in determining new generation criteria for roll waves developing in non-Newtonian fluids. The results showed that the roll wave generation depends on two criteria: the first is associated to the minimum Froude number, and the second is related to the cut-off frequency. In addition, we have confirmed that the new generation criteria can be verified via numerical simulation based on a second model with full equations (Fluent software). Globally, the emergence of roll waves is favored by the non-Newtonian properties of the flowing fluid and the fact that the cut-off frequency decreases along with the minimum Froude number. Lastly, both generation criteria were tested in order to examine a case study involving the occurrence of roll waves in a watershed.

DARCY RIBEIRO UNIVERSITY CAMPUS MAP – 2017- TECHNICAL NOTE

2018 ◽  
Vol 7 (2) ◽  
Author(s):  
Rafael Sanzio Araújo dos Anjos ◽  
Jose Leandro de Araujo Conceição ◽  
Jõao Emanuel ◽  
Matheus Nunes
Keyword(s):  
Spatial Data ◽  
Spatial Information ◽  
Technical Note ◽  
University Campus ◽  
Communication Tool ◽  
Sources Of Information ◽  
Data Manipulation ◽  
Geographic Space ◽  
The Many ◽  
New Generation

The spatial information regarding the use of territory is one of the many strategies used to answer and to inform about what happened, what is happening and what may happen in geographic space. Therefore, the mapping of land use as a communication tool for the spatial data made significant progress in improving sources of information, especially over the last few decades, with new generation remote sensing products for data manipulation.

Ethnic Enterprises, Class Resources and Market Conditions: Indian owned SMEs in Malaysia

2018 ◽  
Vol 35 (2) ◽  
pp. 5-29
Author(s):  
JESRINA ANN XAVIER ◽  
EDMUND TERENCE GOMEZ
Keyword(s):  
Food Industry ◽  
Case Study Method ◽  
Market Conditions ◽  
New Generation ◽  
Insight Into

This article investigates changes in the conduct of ethnic enterprises followingthe emergence of a new generation of owners with varying class resources andas market conditions transform. The case study method is used to examinethe impact of changing class resources and market conditions on ethnicallybasedenterprises, exploring the effects of generational transitions among smallIndian owned companies in the food industry in Malaysia. The results providean insight into key changes in the evolution of Indian owned enterprises. Theyindicate that changes in class resources and market conditions have enabledIndian owned food-based companies to alter their products to fit a largermarket, while responding to the demands of a rapidly modernizing society.

A note on the instabilities of a horizontal shear flow with a free surface

2000 ◽  
Vol 406 ◽  
pp. 337-346 ◽  
Author(s):  
L. ENGEVIK
Keyword(s):  
Surface Tension ◽  
Free Surface ◽  
Shear Flow ◽  
Velocity Profile ◽  
Froude Number ◽  
The Other ◽  
Algebraic Equations ◽  
Horizontal Shear ◽  
Analytical Treatment ◽  
Unstable Region

The instabilities of a free surface shear flow are considered, with special emphasis on the shear flow with the velocity profile U* = U*0sech2 (by*). This velocity profile, which is found to model very well the shear flow in the wake of a hydrofoil, has been focused on in previous studies, for instance by Dimas & Triantyfallou who made a purely numerical investigation of this problem, and by Longuet-Higgins who simplified the problem by approximating the velocity profile with a piecewise-linear profile to make it amenable to an analytical treatment. However, none has so far recognized that this problem in fact has a very simple solution which can be found analytically; that is, the stability boundaries, i.e. the boundaries between the stable and the unstable regions in the wavenumber (k)–Froude number (F)-plane, are given by simple algebraic equations in k and F. This applies also when surface tension is included. With no surface tension present there exist two distinct regimes of unstable waves for all values of the Froude number F > 0. If 0 < F [Lt ] 1, then one of the regimes is given by 0 < k < (1 − F2/6), the other by F−2 < k < 9F−2, which is a very extended region on the k-axis. When F [Gt ] 1 there is one small unstable region close to k = 0, i.e. 0 < k < 9/(4F2), the other unstable region being (3/2)1/2F−1 < k < 2 + 27/(8F2). When surface tension is included there may be one, two or even three distinct regimes of unstable modes depending on the value of the Froude number. For small F there is only one instability region, for intermediate values of F there are two regimes of unstable modes, and when F is large enough there are three distinct instability regions.

Dynamic Simulation-Based Case Study of Fusion on Small-Scale Electrical Grids

2015 ◽  
Vol 68 (2) ◽  
pp. 341-345 ◽  
Author(s):  
Shutaro Takeda ◽  
Satoshi Konishi ◽  
Yasushi Yamamoto ◽  
Ryuta Kasada ◽  
Shigeki Sakurai
Keyword(s):  
Dynamic Simulation ◽  
Small Scale ◽  
Electrical Grids ◽  
Simulation Based
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