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I have some doubts about this "lamellar grille" business. I do not see any magical mechanism resulting from the airfoil grille sections. Depending on the vehicle speed and the cooling airflow volume rate, a frontal inlet will take different sized "bites" out of the external flow. The area of the streamtube (a 'duct' with a surface formed of streamlines) entering the front grille will be larger than the grille at zero to low vehicle speeds. At higher speeds, the cooling airflow streamtube gets progressively smaller in area, becoming much smaller than the inlet grille area. I have seen this using smoke with my wind tunnel models; at high speeds there is only a small area in front of the cooling inlet opening where the smoke will actually go in. So at high vehicle speeds, most of the airflow in the vicinity of the frontal inlet is actually "spilled" outside the opening. I would imagine that there are some grille configurations that spill with less drag than others.
I remember an anecdote from a Ford aerodynamicist who was shocked by the ignorance of a manager who suggested a car model should have a "lamilar flow grille" rather than using the correct word: laminar.
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