New ideas on governing equations of fluid dynamics

2021 ◽  
Author(s):  
Chaoqun Liu
Keyword(s):  
Fluid Dynamics ◽  
Governing Equations ◽  
New Ideas

scholarly journals Recurrent flows: the clockwork behind turbulence

2013 ◽  
Vol 726 ◽  
pp. 1-4 ◽  
Author(s):  
Predrag Cvitanović
Keyword(s):  
Fluid Dynamics ◽  
Reynolds Number ◽  
Chaotic Dynamics ◽  
High Dimensional ◽  
Governing Equations ◽  
Infinite Dimensional ◽  
Long Run ◽  
Moderate Reynolds Number ◽  
Dimensional State Space ◽  
Exhaustive Study

AbstractThe understanding of chaotic dynamics in high-dimensional systems that has emerged in the last decade offers a promising dynamical framework to study turbulence. Here turbulence is viewed as a walk through a forest of exact solutions in the infinite-dimensional state space of the governing equations. Recently, Chandler & Kerswell (J. Fluid Mech., vol. 722, 2013, pp. 554–595) carry out the most exhaustive study of this programme undertaken so far in fluid dynamics, a feat that requires every tool in the dynamicist’s toolbox: numerical searches for recurrent flows, computation of their stability, their symmetry classification, and estimating from these solutions statistical averages over the turbulent flow. In the long run this research promises to develop a quantitative, predictive description of moderate-Reynolds-number turbulence, and to use this description to control flows and explain their statistics.

Numerical Modeling of Air Flow in a Cabinet Dryer Equipped by Deflector Plates

2019 ◽  
Vol 15 (10) ◽  
Author(s):  
Omid Reza Roustapour ◽  
Hamid Reza Gazor ◽  
Kazemi Farzin
Keyword(s):  
Fluid Dynamics ◽  
Numerical Modeling ◽  
Air Flow ◽  
Outlet Temperature ◽  
Governing Equations ◽  
Air Velocity ◽  
Drying Time ◽  
Elapsed Time ◽  
Quadrilateral Elements ◽  
Simulation Results

AbstractIn this study, air deflector plates were used in order to increase the air elapsed time in the chamber. The air flow pattern was simulated using computational fluid dynamics. The geometry of the chamber was produced in 2D and meshed by triangular and quadrilateral elements, boundary conditions were defined and the governing equations solved. Modeling of flow without any deflectors depicted the air flowed to the chamber conducted to the outlet without any distortion. Air vortices were generated when the deflectors defined in model. To evaluate the influence of deflectors on drying period, constructed plates installed in the dryer chamber and melon slices were dried when deflectors used or not. Simulation results showed magnitude of the air velocity was increased and temperature uniform distribution developed on the surface of trays. The outlet temperature was also decreased up to 10 % and drying time reduced to 22 % when the deflectors were employed.

Stability of an Evaporating Liquid Film Under Nonequilibrium Conditions With Variable Gravity

2012 ◽  
Author(s):  
Aneet D. Narendranath ◽  
James C. Hermanson ◽  
Allan A. Struthers ◽  
Robert W. Kolkka ◽  
Jeffrey S. Allen
Keyword(s):  
Fluid Dynamics ◽  
Evolution Equation ◽  
Liquid Film ◽  
Evaporation Rate ◽  
Time Dependent ◽  
Lubrication Approximation ◽  
Governing Equations ◽  
Initial Value ◽  
Nonequilibrium Conditions ◽  
Variable Gravity

An evolution equation describing the dynamics of an evaporating liquid film has previously been developed from the governing equations of fluid dynamics after the application of the lubrication approximation and the choice of a viscous time scale. The authors have solved the evaporating liquid film evolution equation with a validated numeric program. Different mechanical boundary conditions were successfully applied and their effect on the film dynamics was examined. The evolution equation has also been modified to include buoyancy driven instabilities. This paper outlines a linear stability analysis that was performed on the time dependent, evaporating liquid film evolution equation. The effect of the evaporation rate, departure from equilibrium at the interface and variable gravity is examined by solving the equation as an initial value problem.

Fundamentals of fluid dynamics with an introduction to the importance of interfaces

2017 ◽  
Author(s):  
H. A. Stone
Keyword(s):  
Fluid Dynamics ◽  
Differential Equations ◽  
Fluid Mechanics ◽  
Scaling Laws ◽  
Fluid Flows ◽  
Governing Equations ◽  
Soft Interfaces ◽  
Physical Intuition ◽  
Basic Fluid ◽  
Wide Range

The topics discussed are all related to basic fluid mechanics. In these introductory notes I highlight some of the main features of fluid flows and their mathematical characterization. There is much physical intuition encapsulated in the differential equations, and one of our goals is to gain more experience (i) understanding the governing equations and various related principles of kinematics, (ii) developing intuition with approximating the equations, (iii) applying the principles to a wide range of problems, which includes (iv) being able to rationalize scaling laws and quantitative trends, often without having a detailed solution in hand. Where possible we provide examples of the ideas with ‘soft interfaces’ in mind.

scholarly journals Use of computational fluid dynamics to study forces exerted on prey by aquatic suction feeders

2009 ◽  
Vol 7 (44) ◽  
pp. 475-484 ◽  
Author(s):  
Tyler Skorczewski ◽  
Angela Cheer ◽  
Samson Cheung ◽  
Peter C. Wainwright
Keyword(s):  
Fluid Dynamics ◽  
Prey Capture ◽  
Maximum Force ◽  
Governing Equations ◽  
Overset Grids ◽  
One Dimensional ◽  
Dimensional Flow ◽  
Prefer Prey ◽  
Aquatic Vertebrates ◽  
Prey Interaction

Suction feeding is the most commonly used mechanism of prey capture among aquatic vertebrates. Most previous models of the fluid flow caused by suction feeders involve making several untested assumptions. In this paper, a Chimera overset grids approach is used to solve the governing equations of fluid dynamics in order to investigate the assumptions that prey do not interact with the flow and that the flow can be modelled as a one-dimensional flow. Results show that, for small prey, both neglecting the prey and considering prey interaction give similar calculated forces exerted on the prey. However, as the prey item increases in size toward the size of the gape, its effect on the flow becomes more pronounced. This in turn affects both the magnitude of the hydrodynamic forces imparted to the prey and the time when maximum force is delivered. Maximum force is delivered most quickly to intermediate sized prey, about one-third of mouth diameter, and most slowly to prey less than 7 per cent or greater than 67 per cent of mouth diameter. This suggests that the effect of prey size on the timing of suction forces may have substantial consequences for the feeding ecology of suction feeders that are known to prefer prey between 25 and 50 per cent of mouth diameter. Moreover, for a 15 cm fish with a 15 mm gape, assuming a radial one-dimensional flow field can result in underestimating the maximum force exerted on a 5 mm diameter spherical prey 1 gape distance from the mouth by up to 28.7 per cent.

Determination of Wake Propagation Downstream of the Wind Turbine Using Computational Fluid Dynamics

2012 ◽  
Author(s):  
Abolfazl Pourrajabian ◽  
Reza Ebrahimi ◽  
Masoud Mirzaei
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Wind Turbine ◽  
Wind Turbines ◽  
Wind Farm ◽  
Turbulence Modeling ◽  
Governing Equations ◽  
Horizontal Axis Wind Turbine ◽  
Velocity Magnitude

A numerical scheme for determination of wake propagation in downstream of a wind turbine was developed by Computational Fluid Dynamics (CFD) and analytical correlation. A 3bladed horizontal axis wind turbine was selected and airflow around the wind turbine was analyzed. The flow was assumed steady state and a pressure based approach was adopted to solve the governing equations in an unstructured grid distribution using parallel processing. In conjunction with governing equations, the kω – SST model was used for turbulence modeling. The formation of the wake behind the wind turbine was estimated and an appropriate equation was derived for velocity magnitude at the downstream of the wind turbine. Moreover, the suitable distances between wind turbines in wind and crosswind directions were estimated. Results show a good agreement between the previous researches and the comparison indicates that the CFD could be considered as a proper tool for determination of wake properties, windward and crosswind distance between wind turbines in a wind farm.

scholarly journals OVERVIEW OF NUMERICAL METHODS FOR SIMULATING RANQUE-HILSCH EFFECT WITHIN VORTEX TUBES / LIETUVOS KARJERŲ UŽPILDŲ POVEIKIO BETONO ŠARMINEI KOROZIJAI TYRIMAI

2016 ◽  
Vol 7 (5) ◽  
pp. 571-576
Author(s):  
Vadim Nikitin ◽  
Paulius Bogdevičius ◽  
Marijonas Bogdevičius
Keyword(s):  
Fluid Dynamics ◽  
Experimental Data ◽  
Vortex Tube ◽  
Geometric Model ◽  
Governing Equations ◽  
Computational Fluid Dynamics Cfd ◽  
The Subject ◽  
Published Research ◽  
Vortex Tubes ◽  
Good Agreement

The main goal of this paper is to present a summarized overview of the methods used for Ranque–Hilsch vortex tube numerical analysis using computational fluid dynamics (CFD). The overview is mainly focused on the most recently conducted studies that are both backed by experimental data and is evaluated by the authors as being in good agreement with experimental results. Generalized tendencies in computational vortex tube analysis are presented while focusing on researchers’ approach towards the geometric model used for the study and the governing equations. A brief introduction to the subject matter is presented followed by a short retrospective of the previous studies and related challenges. The conclusions are formed based on the most recent, as well as previously analysed, published research results. Užpildų šarminė korozija betone vyksta reaguojant cemente esantiems natrio ir kalio hidroksidams (šarmams) su aktyviu SiO2, esančiu kai kuriuose užpilduose. Vykstant šiai reakcijai betone susidaro didelių vidinių įtempių, kurie sukelia betono deformacijas, pleišėjimą ir suirimą. Reakcija vyksta lėtai, betono irimo požymių atsiranda tik po kelių mėnesių ar metų. Tyrimams buvo naudojami dviejų skirtingų karjerų užpildai. Atlikus tyrimus nustatyta, kad Lietuvos žvyro karjerai užteršti reaktyviomis dalelėmis, turinčiomis amorfinio silicio dioksido, reaguojančio su cemente esančiais natrio ir kalio šarmais, ir sukeliančiomis betono šarminę koroziją. Nustatyta, kad pagal AAR 2 stambieji užpildai priskiriami II grupei – galimai reaktyviems užpildams, nes jų plėtra po 14 parų viršija 0,1 %.

scholarly journals New governing equations for fluid dynamics

AIP Advances ◽  
2021 ◽  
Vol 11 (11) ◽  
pp. 115025
Author(s):  
Chaoqun Liu ◽  
Zhining Liu
Keyword(s):  
Fluid Dynamics ◽  
Governing Equations
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