Fabrication and Characterization of 3-D printed Heat Flux Sensors for Advanced Wind Tunnel Models and Improved CFD Validation

Abstract

3-D printing, rapid prototyping, and additive manufacturing (AM) technologies are maturing to the point where direct integration of sensors into Wind Tunnel Models (WTM's) is becoming feasible. Direct integration thru rapid prototyping can enable WTM's having a larger number of enhanced measurements. Such easily integrated and ubiquitous sensor capabilities are critical to improving the correlation between model performance and CFD simulations, especially in the transonic regime where computational predictions are often lacking. Heat flux sensors have been a mainstay of aerodynamic testing due to the sensor's simplicity, conformal application, and ability to infer many phenomena such as flow separation, shock behavior, and boundary layer phenomena. Here we describe our efforts to directly print heat flux sensors onto 3-D printed WTM components. We present data to characterize these sensors in a low-speed wind tunnel and compare results to commercially available heat flux sensors. The effort addresses several challenges to 3-D printed heat flux integration including printed heat flux sensor design, printing onto curved surfaces, printing of electrical traces, and printing of electrical via's such that electrical traces can be routed on the inner surfaces of the WTM. The printed sensor's ability to detect flow separation and vortex shedding phenomena is demonstrated. The printed sensors are also shown to have comparable performance to commercially available sensors fabricated using traditional methods.