Air Force Propulsion Team Continues Flow Visualization Study

July 7, 2022

A nozzle is connected to a testing apparatus in SL-2, a sea level turbine engine test cell at Arnold Air Force Base. A team with the 717th Test Squadron, 804th Test Group, Arnold Engineering Development Complex, was investigating ways to study the acoustic properties of the nozzle. (U.S. Air Force photo by Jill Pickett)

Team members with the 717th Test Squadron, 804th Test Group, Arnold Engineering Development Complex at Arnold Air Force Base are continuing to collect shadowgraph measurements of high sound pressure level nozzle acoustic events to validate computational fluid dynamics (CFD) prediction methods.

To assist with this effort, the team received funding through the AEDC Spark Tank, an event that invited AEDC personnel to submit their innovative ideas that would positively impact the mission of the complex.

Capt. Brian Gatzke, a test engineer, and Steve Arnold, technical adviser for the 717 TS, are heading up the project for the flow visualization and CFD within one of the AEDC engine test facilities at Arnold. Gatzke explained why the studies are important to future engine tests.

“Future configurations may be more complex, so we are trying to determine the possible test cell interactions,” he said. “This non-proprietary data is needed from the exhaust plumes in order to validate the CFD for robust test installations.”

To do this, various nozzles are 3D printed and installed in the test cell. Air is then blown through the nozzles and shadowgraph measurements are collected.

“The data collected from this testing enables us to clearly identify the nozzle acoustics of different nozzle geometries and we utilize the shadowgraph measurements to validate the CFD computational acoustic field,” Arnold said. “This better prepares us when customers with the same or similar engine nozzles come to test with AEDC because we know what we’re looking at and what we need to do to resolve any acoustic disturbances that might be created from the particular nozzle.”

Much of the equipment needed to conduct the nozzle testing was previously installed at the University of Tennessee Space Institute as part of a Small Business Technology Transfer, or STTR, and the air supply hardware was already available in the engine test cell.

“This STTR project was really a part of a combined effort of our AEDC organizations,” Arnold said. “The Test Operations and Sustainment contractor team conducted the testing during an 8-hour test day, and members with Technical Management Advisory Services [contract]-obtained CFD predictions. From there the DOD test analysts compared shadowgraph measurements to CFD predictions using UTSI’s optical support software.”

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