What is the difference between convection and diffusion?
Convection is the process of heat transfer through the bulk movement of molecules within fluids. Diffusion is the movement of molecules from a region of high concentration to a low concentration via a concentration gradient.
What is the difference between molecular diffusion and turbulent diffusion?
This is fundamentally different from the processes which determine molecular diffusion—in turbulent diffusion, it is the random motion of the fluid that does the mixing, while in molecular diffusion it is the random motion of the pollutant molecules that is important.
What is the meaning of eddy diffusion?
Eddy diffusion, eddy dispersion, multipath, or turbulent diffusion is any diffusion process by which substances are mixed in the atmosphere or in any fluid system due to eddy motion. The concept of turbulence or turbulent flow causes eddy diffusion to occur.
What is turbulent flow diffusion?
Turbulent diffusion is the transport of mass, heat, or momentum within a system due to random and chaotic time dependent motions. In turbulent flow, this is a result of several characteristics such as unpredictability, rapid diffusivity, high levels of fluctuating vorticity, and dissipation of kinetic energy.
What is convective mass transfer?
Convective mass transfer is the movement of material by the action of a fluid. Mass transfer – such as drying, evaporation or dissolution. Heat transfer – heat and mass transfer processes are analogous, and a mass transfer model may be more convenient to use.
Is convective transport slower than diffusion?
Summary. Convection is mass transport due to bulk fluid motion. Except for microfluidic devices, convection is necessary to achieve effective mass transport because diffusion over human length scales is a very slow process.
What is the value of eddy diffusion?
Turbulence, or eddy diffusion, differs fundamentally from molecular diffusion in that all properties (e.g., heat, salt, nutrients, and dissolved gases) have the same eddy diffusion coefficient; a typical value for horizontal eddy diffusivity in the ocean is ∼500 m2 s−1, a value that is 109 times greater than molecular …
What causes eddy diffusion?
What is eddy viscosity in fluid mechanics?
Eddy viscosity is the proportionality factor describing the turbulent transfer of energy as a result of moving eddies, giving rise to tangential stresses.