Does turbulence increase mixing?
As the flow Reynolds number is increased from small values to values approaching some minimum Reynolds number for fully-developed turbulence, the flow is able to generate ever-increasing interfacial area between the mixing species, increasing mixing thereby and, in the case of chemically-reacting flow, chemical-product …
What do you understand by Prandtl’s mixing length theory?
Prandtl’s mixing length theory is a 2-Dimensional model attempting to describe the momentum transfer within a turbulent fluid flow. OR simply It can be defined as the average distance that a small mass of fluid will travel before it exchanges its momentum with another mass of fluid.
What is turbulent mixing?
Turbulent mixing describes the transversal exchange resulted by the turbulent fluctuation of thermal-hydraulic parameters such as velocity and temperature or enthalpy, as schematically indicated in Fig. 5.10.
What is laminar mixing?
Laminar mixing processes are based on the repeated separation of the flow into layers, followed by redistribution and recombination parallel to the flow direction. The number of layers, and hence the homogeneity, increases with each additional mixing element.
Is turbulent flow good for transport?
Turbulent flow is all around us. It can be beneficial in some cases and not in others. When the airflow around a vehicle becomes turbulent, air resistance increases. When the flow of a liquid transported in a tube such as a water pipe is turbulent, more force (energy) is required to transport the liquid.
What is mixing length parameter?
The mixing-length parameter, \alpha, is a key factor for the near-surface structure. In the convection formulations used in evolution codes, the \alpha is a free parameter that needs to be properly specified. The structure below the photosphere depends on the convection model.
What is meant by mixing length?
The mixing length is a distance that a fluid parcel will keep its original characteristics before dispersing them into the surrounding fluid.
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.
What is turbulent flow give examples?
Common examples of turbulent flow are blood flow in arteries, oil transport in pipelines, lava flow, atmosphere and ocean currents, the flow through pumps and turbines, and the flow in boat wakes and around aircraft-wing tips.
How does a high shear mixer work?
A high shear mixer uses a rotor, rotating at high speeds, to direct material outwards towards a stationary stator and thus shear the material. Variable rotor speeds provide the ability to uniquely tailor the amount of shear energy for each application.
Is laminar a flow?
laminar flow, type of fluid (gas or liquid) flow in which the fluid travels smoothly or in regular paths, in contrast to turbulent flow, in which the fluid undergoes irregular fluctuations and mixing. The fluid in contact with the horizontal surface is stationary, but all the other layers slide over each other.
It is a considerable experimental, theoretical, modeling, and computational challenge to capture and represent turbulent mixing which, for high Reynolds number ( Re) flows, occurs across a spectrum of scales of considerable span.
How much does Dimotakis amount of chemical product by?
74 P. E. Dimotakis amount of chemical product by, roughly, a factor of two, as con\frmed in chemically- reacting experiments which measured the chemical product volume fraction directly (KD86).
Can turbulent flows mix entrained fluids to a molecular scale?
▪ Abstract The ability of turbulent flows to effectively mix entrained fluids to a molecular scale is a vital part of the dynamics of such flows, with wide-ranging consequences in nature and engineering.
What is the scale of mixing transition in turbulent materials?
The mixing transition in turbulent ﬂows 89 scale that can be generated directly from the outer scale. Such a scale would be estimated on the basis of an outer laminar-layer thickness,, that can be generated by a single-size sweep across the whole transverse extent of the turbulent region, for example.