TS EN ISO 80000-11

TS EN ISO 80000-11 is the part of the quantities and units series concerned with characteristic numbers. Its focus is the common naming and symbol approach used for dimensionless quantities in physics, chemistry, and engineering, especially where flows, transfer processes, and similar phenomena are described. These numbers express the character of a physical situation through ratios of relevant quantities rather than through a single unit-bearing quantity.

What characteristic numbers do in practice

In general technical use, characteristic numbers help show which physical effects dominate a system. They are used to describe the relative importance of inertia, viscosity, heat transfer, surface tension, diffusion, and related mechanisms. This makes it easier to compare systems at different scales, interpret experimental results, and discuss similar behavior within one consistent conceptual framework.

The published purpose of this part is to harmonize the terms and symbols used in this field; the provided scope does not specify test methods, numerical limits, or equipment requirements. It should therefore be understood primarily as a terminology standard rather than a performance test document. In that role, it supports consistent usage in engineering calculations, textbooks, data sheets, and technical reports.

• Focuses on naming and symbolisation of dimensionless quantities.
• Supports terminology for characteristic ratios used in transport and flow problems.
• Helps express physical quantities in a comparable and consistent way.
• Promotes clarity and consistency in technical communication.