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.
The âAreaâ (in square feet) for each size is the âAKâ number listed under each diameter. For instance, to find the face velocity of the 10-inch at our stated 120 CFM requirement, divide 120 by the area: CFM/Area = Face Velocity or 120/.345 = 348 FPM face velocity. Engineering Data for a Hart & Cooley #16 Round Ceiling Diffuser