I am currently reading up on fluid mechanics and was reading up on the drag force equation, and it come to my attention I am not sure how one can find the coefficient of drag of and object without knowing the drag force. But my understanding is so far that the drag force equation is a purely experimentally derived one, thus this is causing me confusion as I can find the necessary information on what experiment were carried out to to find this equation.
An example in one of my text book give a square plate oscillating up and down in what I assume to be water, and I was wondering how can one find the drag force on this square plate, if the coefficient is not known? Which I believe you cannot.
I have look on various book ect but with fluid mechanics I seem to feel like I am going around in circles, every-time I research drag coefficient I keep getting the rearrangement of the the drag equation.
I was just wondering if maybe could someone could expand on how, it possible to find the drag coefficient of a square plate, if the drag force is not known.