Research Report 167 ON ISOTHERMAL FLOW OF AIR INTO A PARTIALLY CASED RECTANGULAR SNOW TRENCH

摘要

In a previous paper, Yen and Fisher (1963) developed an expression for evaluating the quantity of air flowing into a partly cased rectangular porous trench of constant permeability. The flow was assumed to be isothermal, steady and two-dimensional. The formula is Q = 2(K1’I’2K1) (k/μ) ( pave) (Ps * Pw)' where Q is the mass flow rate per unit length of the trench, K1/2K1 is a configuration factor; k is permeability, μ. is viscosity of air; pang is the average density at mean pressure; and ps and pw are the air pressures at the trench top and the uncased trench walls respectively. The configuration factor in this earlier work was arrived at by considering the effects of depth to the impermeable layer, d , depth of the trench, do, and depth of the trench casing, dc. In the present study, however, values of K1/2K1 were determined which included the effect of half trench width _b as well as d., dt and dc. It is found that in any practical analysis the effect of trench width is not negligible and should be considered.