An airfoil includes an outer surface having a leading edge, a trailing edge downstream from the leading edge, and a convex surface between the leading and trailing edges. A cavity is inside the outer surface, and a platform is connected to the outer surface and defines a top surface around at least a portion of the outer surface. A first plurality of trenches is beneath the top surface of the platform upstream from the leading edge, wherein each trench in the first plurality of trenches is in fluid communication with the cavity inside the outer surface. A first plurality of cooling passages provide fluid communication from the first plurality of trenches through the top surface of the platform.