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Aaron Johnson (Fed)

Dr. Aaron Johnson is a mechanical engineer with expertise in fluid dynamics and flow measurement. His interests include measuring flue gas flows, measuring pipeline-scale natural gas flows, designing primary flow standards, analyzing the uncertainty of flow measurements, computational fluid dynamics, and modeling flow meters (e.g., critical flow venture meters, turbine meters, ultrasonic meters).

Dr. Johnson has leadership roles in three projects:

  1. developing a scale-model smokestack simulator. The simulator's diameter (1.2 m) is approximately 1/10th the diameter of the stack of a typical, coal-fired power plant. The simulator will (a) quantify the accuracy of flow meters used in smokestacks, (b) quantify uncertainties of stack-flow measurement protocols, and (c) test alternative, low-uncertainty flow-measurement technologies (e.g., long-wavelength acoustic meters, multipath ultrasonic techniques). By facilitating accurate stack flow measurements with quantified uncertainties, the simulator supports programs that place a price on the emissions of coal-burning power plants.
  2. developing and maintaining NIST's internationally-recognized, natural gas flow calibration service that provides industry low-uncertainty (0.22 % to 0.4 %) flow measurements. These measurements are traceable to primary flow standards developed and maintained by NIST. Flow meters serve as "cash registers" during custody transfers of natural gas; they determining the money exchanged between buyers and sellers. NIST's natural gas calibration service facilitates equitable custody transfer within the U.S. and in international commerce.
  3. improving gas flow meter calibrations performed under non-ideal flow conditions including (a) swirling, asymmetric flows typical of smokestacks, and (b) transient and quasi-stable flows typical of blow-down methods. Blow-down methods are used to calibrate meters with flows that are too large (> 10 kg/s) to maintain in a steady state laboratories. To facilitate calibrations under these non-ideal circumstances, Johnson is "taking the lab to the field;" thereby making NIST's calibrations more useful to its customers.

Selected Publications

Relaxation Effects in Small Critical Nozzles

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


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

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

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


Jodie Gail Pope, Aaron Johnson, James Filla, Vern E. Bean, Michael R. Moldover, Joey Boyd, Christopher J. Crowley, Iosif Isaakovich Shinder, Keith A. Gillis, John D. Wright
We describe the 15 kg/s water flow calibration standard operated by the Fluid Metrology Group of the National Institute of Standards and Technology (NIST) to

Patents (2018-Present)

Created April 2, 2019, Updated December 8, 2022