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Aaron Johnson (Fed)

Dr. Aaron Johnson is the Group Leader of the Fluid Metrology Group within NIST's Sensor Science Division. He oversees the group’s research and calibration efforts in gas and liquid flow, airspeed, and liquid volume. Additionally, he responsible for NIST's gas flow measurement calibration service, which spans a mass flow range across 11 decades, from 2 × 10-9 kg/s to 500 kg/s.

Dr. Johnson has played a pivotal role in designing innovative, low-uncertainty Pressure-Volume-Temperature-time (PVTt) standards and Rate-of-Rise (RoR) gas flow standards. He has leveraged the low uncertainty of these primary gas flow standards to investigate the fundamental physics of various flow meters. Notably, his work on critical flow venturi (CFV) standards focuses on thermal boundary layer effects, gas species effects, and real gas corrections. Dr. Johnson has also made significant contributions to ASME and ISO standards, particularly in CFV applications, principles of operation, and uncertainty analysis.

Dr. Johnson established the U.S. national standard for the custody transfer of pipeline-scale natural gas. He employed a "bootstrap" approach, using calibrated CFVs in a parallel configuration to extend the flow range of NIST's primary standards to pipeline-scale natural gas flows. This work resulted in an eight-fold increase in pressure and a 1,000-fold increase in mass flow, ultimately facilitating the accurate calibration of flow meters used in the buying and selling of natural gas, both domestically and internationally, thereby promoting fair trade.

Dr. Johnson also has experience in liquid flow primary standards and airspeed measurements. His current research interests include:

  • Developing advanced physical models to extend the application of flow meters.
  • Quantifying the uncertainty of flow and velocity measurements in laboratory and field applications.
  • Developing flow standards for semiconductor process gases.
  • Advancing static and dynamic volumetric primary flow standards.

Selected Publications

Relaxation Effects in Small Critical Nozzles

Author(s)
Aaron N. Johnson, C L. Merkle, Michael R. Moldover, John D. Wright
We computed the flow of four gases (He, N 2, CO 2, and SF 6) through a critical nozzle by augmenting traditional computational fluid dynamics (CFD) with a rate

Publications

Calibrating laser Doppler anemometers utilizing an optical chopper

Author(s)
Christopher Crowley, Iosif Isaakovich Shinder, Michael R. Moldover, Joey Boyd, James Filla, Aaron Johnson
Laser Doppler anemometers (LDAs) use scattered light to determine velocity components of a flowing fluid. The operating principal of LDAs is simple conceptually

Non-nulling Protocols for Fast, Accurate, 3-D Velocity Measurements in Stacks

Author(s)
Iosif Isaakovich Shinder, Aaron Johnson, James Filla, Vladimir B. Khromchenko, Michael R. Moldover, Joey Boyd, John D. Wright, John R. Stoup
We present protocols for making fast, accurate, 3-D velocity measurements in the stacks of coal-fired power plants. The measurements are traceable to

Gas Flow Standards and Their Uncertainty

Author(s)
John D. Wright, Aaron Johnson, Michael R. Moldover, Shin-ichi Nakao
We review diverse types of gas flow standards that are used to calibrate other gas flow meters. For each type of standard, we describe the principles of its

Thermal Boundary Layers in Critical Flow Venturis

Author(s)
John D. Wright, Aaron Johnson, Michael R. Moldover, Woong Kang, Liang Zhang, Bodo Mickan
We improve the usefulness of small (diameter 10 mm) critical flow venturis (CFVs) as transfer standards for gas flow by measuring and explaining how their

Patents (2018-Present)

Created April 2, 2019, Updated March 4, 2025