"CFD can be exact but CFD does not have to be exact to drive product development decisions"
This is a great article, from Informative Design Partners, that is also the topic of a linked in discussion. The article addresses a question that is probably ancient. But with the advent of CFD, I think it's importance is certainly strengthening, and a lot more businesses are concerned about the answer. The URL's to the blog article and the Linked In discussion are in the adjacent column.
I believe that a thorough knowledge of the limitations of a technique and assumptions made in formulating it, are critical factors contributing to the accuracy/ reliability of a CFD analysis. That's also an area where experience comes in. I should probably say, a lot of experiences.
I've faced such a situation myself, with an overwhelming amount of simulation data : case studies with very minute observable differences; where the question arises, how much of the data should be plodded through. Especially considering the stranglehold placed on the Time you can dedicate to achieving 'perfection', the ultimate objective of exact scientific application. It takes a certain amount of common sense, and intuition to pick and choose the data that makes the biggest impact relevant to the focus of your study. Intuition/Hunches are not infallible. That's where common sense and a scientific perspective of thorough but selective evaluation comes into the picture.
Does CFD then fall into the category of an exact science ? Being a CFD man myself, I'm more inclined to give in to my bias and label it's current status as the art of Refined Engineering Application. But make no mistake, the ultimate objective of CFD is to become an Exact Science. I believe several relatively simple case studies do exist which quantify the assumptions made while performing a CFD analysis. More on this later.