Flow-Through Transducer for Wind Tunnel Analysis

Langley Research Center, Hampton, VA

A section view depicts the flow path through the transducer. In the design, structural tubes replace the bellows and membranes provide compliance similar to bellows. (Image: NASA)

Existing integral flow-through balances have been limited to five-component force and moment measurements (normal and side force; pitch, yaw, and rolling moment) excluding a sixth desired force measurement: axial force. To enable key aerospace R&D applications, NASA’s Langley Research Center has developed a single-piece flow-through transducer design capable of measuring all six components adding in the Axial force measurement.

Axial force is the dominant component used to measure aircraft drag (for fuel efficiency purposes) and provides important control information (such as vehicle deceleration rate). Integration of axial force measurement into this design enables a direct measure of the drag force, while simultaneously providing a fluid flow path for powered simulation in wind tunnel testing.

Current state-of-the art alternatives (i.e., flow-through balances without axial force) either require investigators to infer the drag force by integrating pressure taps on the test article (which further increases axial force measurement uncertainty) or run a redundant, second wind tunnel entry with a standard six-component balance without the flow-through capability (which is not desirable because they are expensive, time consuming, and impede efficiency).

The upper image shows a prototype of the six-component integral flow-through balance concept manufactured using additive manufacturing; in this prototype, the balance was manufactured out of a transparent plastic so the internal flow paths (painted red for visualization purposes) could be visualized from outside the part. The lower image shows an additive metal prototype, which is expected to be used to enable timely and affordable manufacturing of a functional part. (Image: NASA)

Compared to NASA’s technology, conventional flow-around designs (which require bellows and provide only a structurally parallel flow path around the balance) are typically restricted to low pressure applications; in contrast, NASAs technology can accommodate both high- and low-pressure requirements, while eliminating the employment of bellows. NASA’s rigid and stable integral flow-through balance offers repeatable and high-quality measurements that are significantly less dependent on pressure and flow rate affects.

A key application of this technology is force measurement in wind tunnel testing, which supports tests requiring fluids at high pressure (i.e., enabling direct measurement of supersonic retropropulsion forces), systems tuning (controlling the static and/or dynamic structural response via active stiffness and dampening adjustment), and a range of other applications.

While NASA’s flow-through transducer technology could be manufactured using conventional fabrication methods, additive manufacturing is expected to be preferred as it enables relatively simple incorporation of the flow-through axial element into the design without increasing manufacturing complexity or costs.

NASA is actively seeking licensees to commercialize this technology. Please contact NASA’s Licensing Concierge at This email address is being protected from spambots. You need JavaScript enabled to view it. or call at 202-358-7432 to initiate licensing discussions. For more information, visit https://technology.nasa.gov/patent/LAR-TOPS-344 .