A High-Order HDG Method with Dubiner Basis for Elliptic Flow Problems

We propose a standard hybridizable discontinuous Galerkin (HDG) method to solve a classic problem in fluids mechanics: Darcy’s law. This model describes the behavior of a fluid trough a porous medium and it is relevant to the flow patterns on the macro scale. Here we present the theoretical results of existence and uniqueness of the weak and discontinuous solution of the second order elliptic equation, as well as the predicted convergence order of the HDG method. We highlight the use and implementation of Dubiner polynomial basis functions that allow us to develop a general and efficient high order numerical approximation. We also show some numerical examples that validate the theoretical results.

Large Scale, Multidisciplinary Laboratory Teaching of Fluid Mechanics

The nature of fluid mechanics makes experimentation an important part of a course taught in the subject. Presented here is the application of a novel, large scale multidisciplinary model of practical education in a fluids engineering laboratory. Advantages of this approach include efficiencies through economy of scale leading to better pedagogy for students. The scale justifies dedicated academic resources to focus on developing laboratory classes and giving specific attention to designing activities that meet learning outcomes. Four examples of applying this approach to fluids mechanics experiments are discussed, illustrating tactics that have been developed and honed through many repeated instances of delivery. “The measurement lab” uses a flow measurement context to teach identifying and managing general experimental uncertainty. New students, unfamiliar with fluid mechanics are guided through a process to gain understanding that can be applied to all future experimental activities. The “pressure loss in pipes” lab discusses the advantage and process for sharing equipment and teaching resources between multiple cohorts. The provision for students is adapted for context, such as the degree program or year of study. The “weirs big and small” lab provides a methodology to teach the power of dimensional analysis to mechanical engineers using a field of fluid mechanics that is outside their usual theoretical studies. Finally, the “spillway design” lab discusses mechanisms to deliver student independent, open ended experiments at scale, without excessive staff resource requirement.

FLUCTUACIONES INDUCIDAS DEL FLUJO DE AIRE EN UN DUCTO CON PAREDES DENTADAS

Estudios experimentales y numéricos han centrado el interés en el campo de flujo con superficies de paredes dentadas y cavidades, donde la turbulencia del flujo son captadas en imágenes con la técnica Schlieren y recreadas con códigos computacionales. En el presente trabajo, se realiza un estudio numérico para el flujo de aire en un ducto recto con paredes dentadas para seis casos de presión. El flujo se simuló para un dominio computacional 2D con el código ANSYS-Fluent, para lo cual se empleó el modelo RANS en conjunto con el modelo de turbulencia de Menter. Se obtuvieron los campos de número de Mach, velocidad, presión y temperatura con presencia de remolinos y ondas de choque. En ciertas regiones el flujo presentó desviaciones al chocar con las esquinas de los dientes, por lo cual originó fluctuaciones inducidas de los parámetros termodinámicos aguas abajo y hacia la región del centro; en los espacios entre dientes se presentó remolinos; al final del último diente se presentó ondas de choque oblicuas. Se concluye que la sección dentada incrementa la turbulencia e influye a que la velocidad del flujo tenga un incremento escalonado en régimen transónico. Palabras Clave: ducto, flujo de aire, fluctuación, onda de choque, pared dentada, simulación. Referencias [1]J. Blazek, Computational fluid dynamics: principles and applications. Butterworth- Heinemann, 2015. [2]B. Andersson, R. Andersson, L. Håkansson, M. Mortensen, R. Sudiyo, B. van Wachem, y L. Hellström, Computational Fluid Dynamics Engineers. Cambridge University Press, 2012. [3]T. V. Karman, “The fundamentals of the statistical theory of turbulence,” Journal of the Aeronautical Sciences, vol. 4, no. 4, pp. 131–138, 1937. doi: 10.2514/8.350. [4]F. White, Viscous fluid flow. McGraw-Hill Education, 2005. [5]H. Schlichting, Boundary-layer theory. McGraw-Hill classic textbook reissue series, 2016. [6]J. D. Anderson, Fundamentals of aerodynamics. McGraw-Hill series in aeronautical and aerospace engineering, 2017. [7]D. C. Wilcox, Turbulence modeling for CFD. DCW Industries, 2006. [8]P. Krehl y S. Engemann, “August toepler — the first who visualized shock waves,” Shock Waves, vol. 5, no. 1, pp. 1–18, Jun 1995. doi: 10.1007/BF02425031. [9]G. S. Settles, “Toma ultrarrápida de imágenes de ondas de choque, explosiones y disparos,” Revista Investigación y Ciencia, pp. 74-83, May. 2006. https://www.investigacionyciencia.es [10]H. Hirahara, M. Kawahashi, M. U, Khan y K. Hourigan, “Experimental investigation of fluid dynamic instability in a transonic cavity flow,” Experimental Thermal and Fluid Science, 31, pp. 333–347, 2007. doi: 10.1016/j.expthermflusci.2006.05.007. [11]S. L. Tolentino, S. Caraballo, J. Toledo, J. Mírez y C. Torres, “Oscilaciones de la velocidad del flujo en un ducto recto con cavidades rectangulares,” XVI Jornadas de Investigación 2018, UNEXPO Puerto Ordaz, Venezuela, pp. 34-39, 2018. [12]S. Jeyakumar, K. A. Yuvaraj, K. Jayaraman, F. Cardona y M. T. Sultan, “Effect of cavity fore wall modifications in supersonic flow,” Conference, Materials Science and Engineering, 152, pp. 1-7, 2016. doi: 10.1088/1757-899X/152/1/012002. [13]S. L. Tolentino and S. Caraballo, “Estudio del flujo de aire en un conducto recto con pared dentada,” XIV Jornadas de Investigación 2016, UNEXPO Puerto Ordaz, Venezuela, pp. 203-210, 2016. [14]F. White, Fluids Mechanics. McGraw-Hill Education, 2016. [15]F. R. Menter, “Two equation eddy-viscosity turbulence models for engineering applications,” AIAA Journal, vol. 32, no. 8, pp. 1598-1605, 1994. doi: 10.2514/3.12149. [16]S. L. B. Tolentino Masgo, “Evaluación de modelos de turbulencia para el flujo de aire en una tobera plana,” Revista Ingenius, no. 22, pp. 25-37, Julio-Diciembre 2019. doi: 10.17163/ings.n22.2019.03. [17]S. L. B. Tolentino Masgo, “Evaluación de modelos de turbulencia para el flujo de aire en un difusor transónico,” Revista Politécnica, vol. 45, no. 1, pp. 25-38, 2020. doi: 10.3333/rp.vol45n1.03.

Technics, science and management related to the evolution of water supply network of La Rochelle city, France, from 1864 to 1913.

<p><span>The water issue, as vital element to be protected, is central in all societies, including those where water may seem plentiful. With the conscience of the fragility of this resource, the need to question the evolution of the perception of water over time, of the various means used to exploit and preserve it, of scientific knowledge, currently appears as an essential aid to the decision for its preservation.</span></p><p><span>In many countries, XIXs century was the time of major progress in the construction of water supply networks of cities. Particularly in France, this progress was spured by an hygienist discourse in a context of increase city population, inducing a social demand whose national and local governments seized.The autority of the engineers of the « corps des Ponts et Chaussées » who were in charge of the technical realisation of the cities water network was also an important support in this progress, especially because they also participated at the great evolution of the scientific formulation of fluids mechanics applied to groundwater hydraulic like Henry Darcy (1803-1858) or Jules Dupuit (1804-1866). <span>The latter is also well known as an economist. One of his th</span><span>oughts</span><span> is to relate the progress of science to an economic perspective. According to him, « The only difference between the [Roman water ] distributions and those which would be made according to a sound theory and with the best practical procedures is entirely in the expenditure.”</span></span></p><p><span>In this study, technical, scientific and management aspects of the evolution of the water supply network of La Rochelle (France ) during the XIXs century are investigated from archives documents. The survey of the conditions for setting up the network of a particular city is a gateway to address all the points cited above. This coastal town, which has a long history and whose port is famous, experienced three stages of improvement of its water network, in 1864, 1883 and 1913. The first step coincides with the development of water supply network of many french towns, the second with the discovery of a new aquifer useable for water supply of the city, and the third one, remained at the state of a project due to the first World War, had been planned in response of the increase of water consumption linked both to the growing of the population and to the new ease of access to water.</span></p><p><span>This historical knowledge is necessary to understand the spatial and time evolution of the customary practice of water and could be used to draw one’s inspiration from the past efficient solutions that have sometimes be forgotten and that could be reemployed.</span></p>

Performance of Heat Transfer and Friction Factor of Heat Exchanger with Al2o3/ Water Nano Fluids

This paper summary of heat transfer characteristics and nano fluids mechanics by using single phase convection techniques. Gas having less thermal conductivity compare than the liquids having high thermal conductivity. The heat transfer enhancement improved by using nano fluids Al2O3 compared with base water. The heat transfer enhancement was analysed with plain tube and twisted tape inserts with nano fluids. The experimental investigation was analysed and reading was taken to improve the heat transfer and friction flow characteristics. The Reynolds number varies from different ranges with plain water and Nano fluids. The experimental record of nano fluid heat transfer value was increased with 2.89 percentage compare with the experimental record of plain water. The nano fluids has more concentration than the plain water.