Simulation and Analysis of Natural Rain in a Wind Tunnel via Digital Image Processing Techniques

Creators: Aaron, K. M.; Hernan, M. A.; Parikh, P.; Sarohia, V.; Gharib, M.

Abstract

It is desired to simulate natural rain in a wind tunnel in order to investigate its influence on the aerodynamic characteristics of aircraft. Rain simulation nozzles have been developed and tested at JPL. Pulsed laser sheet illumination is used to photograph the droplets in the moving airstream. Digital image processing techniques are applied to these photographs for calculation of rain statistics to evaluate the performance of the nozzles. It is found that fixed hypodermic type nozzles inject too much water to simulate natural rain conditions. A modification uses two aerodynamic spinners to flex a tube in a pseudo-random fashion to distribute the water over a larger area.

Additional Information

This paper is declared a work of the U.S. Government and therefore is in the public domain. This work was carried out at the Jet Propulsion Laboratory, California Institute of Technology under Contract NAS7-918, Task Order RE 65/Amendment 459, jointly funded by NASA Langley Research Center and Goddard Space Flight Center - Wallops Flight Facility (505-45-00-04-59). The authors extend their gratitude to Mr. Earl Dunham Jr., NASA Langley Research Center, and Mr. Edward Melson, NASA Wallops Flight Facility for many valuable technical suggestions throughout the program. The assistance of Mr. R. Smither, Mr. W. Bixler and Mr. S. Kikkert in the design and fabrication of the experimental facilities and in acquisition of the data is greatly appreciated.

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