The neutrally buoyant bubble technique was developed by Sage Action under Office of Naval Research funding and published in 1971. It has been used in peer-reviewed research and government testing ever since. These are papers we can point to.
Several Neutrally-Buoyant Bubble Generators for Aerodynamic Flow Visualization
R. W. Hale, P. Tan and D. E. Ordway · Sage Action, Inc., Ithaca, New York
Naval Research Reviews, Office of Naval Research, June 1971
Documents the ONR/SAI bubble generator system.
Tail-Rotor Thrust on a 5.5-Foot Helicopter Model in Ground Effect
R. Wayne Empey and Robert A. Ormiston · Ames Directorate, U.S. Army Air Mobility R&D Laboratory, Moffett Field
30th Annual National Forum of the American Helicopter Society, May 1974
Used the Sage Action Model 3 Bubble Generator. The paper reports that the ground vortex core “is nearly invisible with smoke flow visualization, but it is clearly and easily observed with helium bubbles.”
Using a Helium Bubble Generator to Visualize Airflow Patterns In and Around Building Models
Rashed Al-Shaali (UCLA), Pierre Koenig and Marc Schiler (USC School of Architecture)
UAEU School of Architecture, 2010
Used the SAI Helium Bubble Generator to investigate air speed and pattern inside building models.
Visual Documentation of Air Flow Patterns in a Controlled Atmosphere Storage
Martin L. Hellickson, Ph.D., P.E. (Oregon State University) and Robert A. Baskins (Duckwall-Pooley Fruit Company)
Neutrally buoyant helium-filled bubbles verified non-uniform air circulation in commercial fruit storage rooms.
Measurement of Airflow Patterns in Ventilated Spaces Using Particle Image Velocimetry
Lingying Zhao, Yuanhui Zhang, Xinlei Wang, G. L. Riskowski and L. L. Christianson · University of Illinois at Urbana-Champaign
ASAE Paper No. 994156, 1999 Annual International Meeting
Three helium-filled bubble generators seeded a full-scale room for PIV measurement.
Pollination and Airflow Patterns Around Conifer Ovulate Cones
Karl J. Niklas and Kyaw Tha Paw U
Science, Vol. 217, 30 July 1982, pp. 442–444
Airflow visualization achieved by the bubble-streak method using arc-lamp-illuminated, neutrally buoyant 2 mm helium-filled bubbles.
New Wind Tunnel Lets Undergrads Soar
Engineering News, Rensselaer Polytechnic Institute, Spring/Summer 2006
RPI’s Mechanical, Aerospace and Nuclear Engineering department added a neutrally buoyant helium bubble flow visualization system to its subsonic wind tunnel. Technical manager Eric White: “This, combined with the traverse system and the Rensselaer-designed probes, which allow us to vary the position of the bubble injection, presents an extremely useful device for ‘seeing’ the flow. As such, the new system will be an invaluable instructional tool.”
Therma-Fuser VAV Modules Are Better Than VAV Boxes
Acutherm, Form 2.1/402
Air distribution and Coanda effect documented photographically using neutrally buoyant helium bubbles injected at the diffuser neck and side-illuminated against a black background.