In a sand casting process the volume flow rate of metal into a mold is 0.02 m/( the top of the sprue has a diameter of 200 mm and a length of 500 mm. what diameter should be specified at the middle and at the bottom of the sprue to have a continuous flow (avoid aspiration)? if the reynold's number at the bottom of the sprue is greater than 20,000 what changes do you suggest (changes to the material or the mold design) in order to avoid a turbulent flow?