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Hydraulic Flows: Overview
Published in Marian (Editor-in-Chief) Muste, Dennis A. Lyn, David M. Admiraal, Robert Ettema, Vladimir Nikora, Marcelo H. Garcia, Experimental Hydraulics: Methods, Instrumentation, Data Processing and Management, 2017
Marian (Editor-in-Chief) Muste, Dennis A. Lyn, David M. Admiraal, Robert Ettema, Vladimir Nikora, Marcelo H. Garcia
Although many equations in hydraulic research (Figure 2.3.1) stem from Equation (2.3.1), it is rarely employed in its original form. Indeed, Equation (2.3.1) operates with instantaneous variables which in turbulent flows are highly fluctuating and thus Equation (2.3.1) is impracticable. This inconvenience of Equation (2.3.1) for engineering applications has been highlighted by Reynolds (1895) who introduced two important procedures: (1) decomposition of hydrodynamic fields into slow (or mean) and fast (or turbulent) components (known as the Reynolds decomposition); and (2) averaging (or filtering) of instantaneous variables and corresponding hydrodynamic equations.
The Physics of Natural Ventilation
Published in Cristian Ghiaus, Francis Allard, Natural Ventilation in the Urban Environment, 2012
Cristian Ghiaus, Francis Allard
where τ0 is the friction stress at the ground. τ0 is usually equal to Δu*2, u* being a velocity scale called the ‘friction velocity’. Reynolds decomposition enables us to introduce turbulence effects into the mean airflow equations. Reynolds stresses should, nevertheless, be expressed in terms of mean velocity in order to close the system of equations.
Hydrodynamic performance and the power production of the tidal turbine by new profiles at the leading-edge tubercles
Published in Ships and Offshore Structures, 2023
Mohamad Amin Ghazi, Hassan Ghassemi, Hamid Reza Ghafari
The components of the Navier-Stokes equations in the Reynolds averaging by presenting the Reynolds decomposition can be divided into mean and fluctuating components. Concerning the Reynolds-averaged Navier-Stokes (RANS) method, the hydrodynamics of the tidal turbine can be solved by the incompressible Navier-Stocks equations. Reynolds-averaged Navier-Stokes equations (RANS equations) can be approximated using a two-equation the turbulence model. This model has a modified ability to solve streamwise pressure gradients as well as the viscous near-wall region. is used to create a more robust and accurate flow model based on wall effects. The free-stream vorticity values strongly impact the results of this turbulence model outside the shear layer. The (shear stress transport) turbulence model has been used in the present study. More details of the governing equations, turbulence model and numerical implementation can be found in ref. Ghafari et al. (2022).
Inertial Effects and Anisotropy for the Flow in a Domain of Close Packed Spheres with a Bounding Wall
Published in Nuclear Technology, 2022
Lambert H. Fick, Elia Merzari, Yassin A. Hassan
Here, standard Reynolds decomposition is used to obtain the fluctuating velocity components. Departing from this approach, an ensemble-averaging method was used to generate the turbulence statistics in this work. The ensemble-averaged data are calculated from independent solutions of for the time-dependent problem in Eqs. (1) and (2). This procedure delivers statistics of the form