"rain deflection by jet blast appears feasible for flight speeds"
From NACA-RM-E55E17a.
Introduction
Five of these publications are from the "Jet Penetration" section, and one is from the "Windshield Ice Protection" section of The Historical Selected Bibliography of NACA-NASA Icing Publications.
The first five publications determine by test the characteristics of air jets entering a moving airstream. The final publication applies this technology to windshield rain removal.
Windshield rain removal is often designed in the same group as ice protection. SAE AIR-1168/4 is titled “Ice, Frost, and Rain Protection” [SAE Aerospace Applied Thermodynamics Manual, 1969 (regularly updated, currently document sae.org)]. A design group I worked in was named "Ice and Rain Protection".
That was historically where the knowledge of water drops, air flow control, and mechanical systems resided.
So, it is not surprising that a rain-removal publication is in the "Selected Bibliography of NACA-NASA Aircraft Icing Publications".
Air jets are also of interest for hot gas ice protection. While not detailed in these publications, the "piccolo" spray tubes commonly used for wing anti-ice is one, specialized application. Also, analyzing the hot air exhaust, and if adjacent structure might get too hot, is another application.
Reviews
NACA-TN-1947 "Investigation of Flow Coefficient of Circular, Square, and Elliptical Orifices at High Pressure Ratios"
- "Excellent correlation was obtained between the results for a jet discharging into still air and ... into a moving air stream"
NACA-TN-1615 "Investigation of the Penetration of an Air Jet Directed Perpendicularly to an Air Stream"
- "it was necessary to define the penetration as the point at which the temperature is 1° F above the free-stream total temperature"
NACA-TN-2019 "Investigation of Flow Coefficient of Circular, Square, and Elliptical Orifices at High Pressure Ratios"
- "square orifices ... provided that a jet dimension equal to the diameter of the equivalent area circle was used"
NACA-TN-2466 "A General Correlation of Temperature Profiles Downstream of a Heated-Air Jet Directed Perpendicularly to an Airstream"
- "a reasonably simple means of obtaining the approximate temperature profile downstream of a heated-air jet"
NACA-TN-2855 "General Correlation of Temperature Profiles Downstream of Heated Air Jet Directed at Various Angles to Airstream"
- "For practical application ... the discharging of heated jets into an air stream requires knowledge of the temperature profiles downstream of the heated jet and of the depth of penetration"
NACA-RM-E55E17a "Preliminary Data on Rain Deflection from Aircraft Windshields by Means of High Velocity Jet-Air Blast"
- "rain deflection by jet blast appears feasible for flight speeds"