Lecture

Dimensionless Number

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Description

This lecture covers the concept of dimensionless numbers in the context of nanoscience for sustainable cement and concrete, focusing on Reynolds, Weber, and Capillary numbers. It explains the relationship between inertial, viscous, and surface forces, and their impact on sorption and transport in cementitious materials. Additionally, it discusses other important dimensionless numbers like Grashof, Bond, and Peclet numbers.

In MOOC

Sorption and transport in cementitious materials

In the MOOC: “Cement chemistry and sustainable cementitious materials”; you learned how to create more sustainable cementitious materials. But concrete is not an inert rock. It is a dynamic porous material, which can exchange water, gas and ions with its environment. Through physical and chemical interactions, these exchanges can have dramatic consequences: cracks due to shrinkage, reinforcement bars corrosion, spalling, … For a true sustainability, the durability of cementitious materials should not be f

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Related concepts (9)

Reynolds number

In fluid mechanics, the Reynolds number (Re) is a dimensionless quantity that helps predict fluid flow patterns in different situations by measuring the ratio between inertial and viscous forces. At low Reynolds numbers, flows tend to be dominated by laminar (sheet-like) flow, while at high Reynolds numbers, flows tend to be turbulent. The turbulence results from differences in the fluid's speed and direction, which may sometimes intersect or even move counter to the overall direction of the flow (eddy currents).

Dimensionless quantity

A dimensionless quantity (also known as a bare quantity, pure quantity as well as quantity of dimension one) is a quantity to which no physical dimension is assigned. Dimensionless quantities are widely used in many fields, such as mathematics, physics, chemistry, engineering, and economics. Dimensionless quantities are distinct from quantities that have associated dimensions, such as time (measured in seconds). The corresponding unit of measurement is one (symbol 1), which is not explicitly shown.

Dimensionless physical constant

In physics, a dimensionless physical constant is a physical constant that is dimensionless, i.e. a pure number having no units attached and having a numerical value that is independent of whatever system of units may be used. In aerodynamics for example, if one considers one particular airfoil, the Reynolds number value of the laminar–turbulent transition is one relevant dimensionless physical constant of the problem. However, it is strictly related to the particular problem: for example, it is related to the airfoil being considered and also to the type of fluid in which it moves.

Viscous stress tensor

The viscous stress tensor is a tensor used in continuum mechanics to model the part of the stress at a point within some material that can be attributed to the strain rate, the rate at which it is deforming around that point. The viscous stress tensor is formally similar to the elastic stress tensor (Cauchy tensor) that describes internal forces in an elastic material due to its deformation. Both tensors map the normal vector of a surface element to the density and direction of the stress acting on that surface element.

Surface tension

Surface tension is the tendency of liquid surfaces at rest to shrink into the minimum surface area possible. Surface tension is what allows objects with a higher density than water such as razor blades and insects (e.g. water striders) to float on a water surface without becoming even partly submerged. At liquid–air interfaces, surface tension results from the greater attraction of liquid molecules to each other (due to cohesion) than to the molecules in the air (due to adhesion). There are two primary mechanisms in play.

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