Trailing vortices and downwash phenomenon of an aircraft in flight are seen clearly in this figure. In this situation, a Cessna Citation VI was flown immediately above the fog bank over Lake Tahoe at approximately 313 km/h or 170 knots (B. Budzowski, Director of Flight Operations, Cessna Aircraft Company, private communication, 1993). Aircraft altitude was about 122 m (400 ft) above the lake, and the weight was approximately 8400 kg. As the trailing vortices descended over the fog layer due to the downwash, the flow field in the wake was made visible by the distortion of the fog layer. The aircraft is seen initiating a gentle climb after a level flight, leaving a portion of the fog layer yet unaffected. The wing span measured 16.3 m and the wing area was 29 m^2. The Reynolds number based on the mean aerodynamic chord of 2.1 m was 1.1x10^7. See also Citation 1 and Citation 3.

Text is from the Gallery of Fluid Motion, Physics of Fluids A, Vol. 5, September 1993 (Hiroshi Higuchi, Syracuse University).

The photo was taken by Paul Bowen for the Cessna Aircraft Company from the tail gun- ner's position in a B-25 flying in formation slightly above and ahead of the Cessna. Courtesy of Cessna Aircraft Company.