Dunkirk: Where History Happened. We visit 10 places connected with the remarkable evacuation of the British Expeditionary Force from northern France in 1940. This feature was first published in the April 2010 edition of BBC History Magazine. Tuesday 25th May 2010.
The seepage velocity is less than the actual flow rate of the liquid or gas in the pores because the fluid moves only through the portion of the cross-sectional area S that is occupied by the pores.
To most people, the word velocity means how fast something is traveling. Those people are not wrong. Velocity does, indeed, refer to the quickness or slowness of something, and by that simplified definition, instantaneous velocity is the velocity reading (how fast or slow you're going) at a particular point in time.