Yes. Two central studies have tested the Coupled Vortex Effect.

In 2010, Dr. John Dabiri and his researchers at CalTech University studied the increased efficiency and synergistic effect of fish swimming in school formation. They wondered if closely spaced and counter-rotating H-type wind turbines might exhibit similar efficiency-boosting capabilities. Subsequent field testing of small turbines corroborated their hypotheses.

In 2014, a French and Belgian team studied the effect of closely spaced H-type turbines. They conducted a series of wind tunnel experiments coupled with measurements of flow field effects. They concluded that the spacing, rotor rotational direction, and synchronization of two-bladed turbines could increase efficiency by 10% to 20% for each turbine in the pair.