The Enigma of Turbulence – Part I

  which description would you choose describe turbulence best: Big whirls have little whirls that feed on their velocity, and little whirls have lesser whirls and so on to viscosity... Lewis Fry Richardson Turbulence is a phenomenon which sets in in a viscous fluid for values of viscosity, hence its purest, limiting form may be interpreted as asymptotic, …

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From Reynolds Transport Theorem to Navier-Cauchy to Navier-Stokes Voyage: Part I

There are certain fundamental principles of conservation that govern the implementation of CFD. These principles are Conservation of mass, momentum & energy. We will see how we can represent these principles evolve in a mathematical form that expresses the dynamics of fluid flow by preserving mass, momentum and energy conservation. The Need of Reynolds Transport …

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SIMPLE Algorithm: Way to solve incompressible NV-Stokes Equation

Introduction Transport equations for each velocity component – momentum equations – can be derived from the general transport equation by replacing the variable φ with u, v and w respectively. The above equations govern a two-dimensional laminar steady flow. The Main Problem! The velocity field obtained from the momentum equation must also satisfy the continuity …

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Eddy Viscosity Concept & Turbulent Kinetic Energy Equation

Turbulence flow exhibits randomness but it is possible to approach them via statistical methods. It fluctuates in time and space. It is possible to do spatial and time averaging. In RANS approach, we time average the turbulent quantities to extract the mean flow properties from the fluctuating ones. Now, we have to find some way …

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Navier-Stokes Equation in Moving Reference Frame (MRF)

Reference: ANSYS Officials Most of the cfd applications consist of stationary objects around/inside which fluid will be flowing. So meshes are stationary. If the flow is incompressible, Incompressible Steady Navier-Stokes equations are solved. Very common applications are – Flow around Aerofoil, Flow inside Pipe. In both cases aerofoil and pipe are stationary hence meshes are …

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