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Fluid Metrology Group

Develops models, standards, reference data, methods, and uncertainty analyses for metering liquid and gas flows, airspeed, liquid density, and volume. We measure micro-flows (e.g., pharmaceuticals) and mega-flows (e.g., natural gas in major pipelines, pollutants from power plants).

The Fluid Metrology Group maintains the national standards for flow quantities, including gas and liquid flow, airspeed, liquid volume, and liquid density. For instance, the group maintains six flow calibration systems to measure gas flows from 0.1 cm3/min to 105 m3/min (an eleven decade flow range) and five primary liquid flow standards to cover five decades of flow range. The group’s unique and often best in the world facilities are used to conduct collaborative research on flow measurement, to perform calibrations of reference meters that meter manufacturers use to calibrate their products, and to perform proficiency tests for commercial laboratories seeking accreditation. 

NIST flow measurements contribute to nearly every US economic sector including defense, energy, transportation, pollution control, and the manufacture of pharmaceuticals and semi-conductors. The group’s volume and gas flow standards ensure equitable trade of trillions of dollars' worth of petroleum and natural gas each year. Our research is focused on improving primary standards that realize flow units and improving the physical models of flow meters so that their calibrations can be extrapolated to real applications with the required accuracy. The group works closely with leading US meter manufacturers and users, government agencies, and academic research institutes to provide new measurement solutions for emerging needs. We participate in national and international documentary standards efforts that ensure product quality and advance US trade. 


  • Documentary Standards
    The group’s staff are active in the development of Documentary Standards on various Standards Developing Organizations (SDOs) by providing the necessary expertise, fundamental measurement science, and testing. We engage with the following SDOs: ASME, ASTM, API, and ISO.


The Fluid Metrology Group welcomes opportunities to collaborate on joint research, technology, and standards development projects to advance flow metrology. The group provides multiple opportunities for students, scientists, industry, academia, and other R&D laboratories to collaborate. Specific opportunities depend on current areas of interest within the group, but may include undergraduate research fellowships, postdoctoral fellowships, visiting scientists, and guest researchers as well as various cooperative research arrangements ranging from formal agreements, such as CRADAs, Consortia, and interagency agreements, to informal collaborations. For more details, see Employment and Internship Opportunities and Collaboration Opportunities.

Projects and Programs

Atomic Standard for Pressure

NIST scientists are developing a highly accurate primary standard for pressure in the range 2 MPa to 7 MPa based on fundamental physical properties of helium

Smoke Stack Flow Measurement

Presently used methods to measure CO2 and other emissions from smoke stacks have errors of 20 % or more depending on the level of swirl in the flow. The

Transient Flow Facility

Today, demonstration vehicles are refueled with hydrogen from dispensers within 3 to 5 minutes using sequential gas releases from a bank of pressurized

Tools and Instruments

Transient Gas Flow Facility

A compressor is used to pressurize up to twenty-five 40 L gas cylinders to 35 MPa. The cylinders can then be used as a source of rapidly changing gas flow by

Gas Flow Standards

NIST uses pressure, volume, temperature, and time (PVTt) standards to calibrate gas flow meters. PVTt flow standards generate selected, steady gas flows through

Wind Tunnel

NIST’s wind tunnel can produce air speeds between 0.15 m/s and 40 m/s. The air speed reference is a Laser Doppler Anemometer (LDA) with an uncertainty of 2.5 %

News and Updates

Better Flowmeters with the Big Blue Ball

Last year, upwards of 25 trillion cubic feet of natural gas were delivered to customers in the United States, and when it changed hands, nearly every cubic foot


Modeling Temperature Effects on a Coriolis Mass Flowmeter

Fabio O. Costa, Jodie G. Pope, Keith A. Gillis
Coriolis mass flowmeters are known to be stable, have low uncertainty (± 0.1 %), and are insensitive to fluid properties. This meter type is used for many

Faster, More Accurate, Stack-Flow Measurements

Aaron N. Johnson, Iosif I. Shinder, Bernard J. Filla, Joey T. Boyd, Rodney A. Bryant, Michael R. Moldover, Thomaa D. Martz, Matthew Gentry
Exhaust flows from coal-fired electricity-generating-plants are determined by measuring the flue gas velocity at prescribed points in the stack cross section



Group Leader

Office Manager