Yeah, it is.
But note that the numbers above are related to an isolated plate. May be the arrangement around the ROV part, diverts the flow in such a way that dragg reduction results improved or negligible.
Main term of dragg force can be written as:
Fd= 1/2 x fluid density x Area x velocity(squared) x dragg coefficient.
Fd= 1/2 d A V² Cd
(remember that velocity is a vector)
(Area is measured projecting it on a plane normal to the flow)
Hence, any surface reduction will reduce dragg.
But, the term velocity is related to the "relative" velocity between the submerged body and fluid.
If the flow is distorted before arriving to the involved part, velocity vectors will change.
Two main things will happen:
Flow can not be taken as uniform anymore.(each flow portion will have different direction and speed)
Speed and incidence angles on the "plate", can be so diferent than those corresponding to the "isolated" conditions, that holes could have no practical effect.
From my point of view, the ROV would wellcome a complete hydrodynamic hull cover.
That cover does not have to be watertight, but only "flow friendly".
- Ion -