result, you can imagine if I restrict the flow, then there is a tendency of the flow to go faster that is, the velocity of water what it would have been in open sea would be slightly more if I have the restrictions on the sides and the bottom, which would therefore, give a higher resistance. So, what we will be measuring will have slightly higher value than what it would have been if the tank was larger representing an infinite water domain- we do not want this to happen, that, this particular aspect is called blockage.