The photo shows a MD-80 with the UDF on each side. GE also had a 727-100 testbed with only one UDF installed.
'twas designed at a time when fuel costs were in decline from 1980 highs. It showed great promise, but no airline wanted to take on the technical risk of much new technology, with cheaper fuel on the (then) horizon. Cabin noise was also an issue.
Alternative translation of UDF