Pressure-sensitive Paint - Where IT Is Used

Where It Is Used

Due to the high cost of constructing airplanes, the first designs of proposed aircraft are usually subjected to aerodynamic testing in wind tunnels. In these tunnels, models (usually subscale) are subjected to airflows to simulate an actual airplane in free flight. The aerodynamic forces acting on the model are measured, and are used to predict the response of an airplane when subjected to equivalent airflows.

Automobiles are also subjected to aerodynamic testing in wind tunnels. Automobile companies use data collected in these tests to measure areas of high and low pressure. This data helps engineers improve designs to increase performance for the vehicles. By changing these designs, engineers can help improve gas mileage and reduce noise.

In order to measure the aerodynamic forces on the whole model, beam balances are connected to the model. However, it is also imperative to also understand how those forces are distributed across the aerodynamic surfaces of the aircraft, and this understanding is more difficult to obtain. The classic approach has been to use an array of pressure taps to measure surface pressure distributions on a model. Pressure taps provide limited spatial resolution and are often limited by model geometry and can be very expensive to integrate into complex geometries.

PSP provides a low-cost alternative that is less invasive than pressure tap arrays. PSP also offers superior spatial resolution, with each pixel of the imaging camera acting as a pressure tap. PSP can achieve accuracy within 150 Pa of pressure tap measurements with good setup and experience.

Time-resolved PSP applications involve pulsed excitation and delay and gating of the imaging devices. One can thus determine pressure differentials as a function of time. In this case, the imaging devices must be synchronized to the excitation. Multi-channel digital delay/pulse generators provide that synchronization.