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On Isothermal Flow of Air Into a Partially Cased Rectangular Snow Trench
In a previous paper, Yen and Fisher (PB-167 436) 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 (K sub 1'/2 K sub 1) (K/mu) (rho sub avg) (P sub s - P sub w), where Q is the mass flow rate per unit length of the trench, K sub 1'/2 K sub 1 is a configuration factor; k is permeability, mu is viscosity of air; rho sub avg is the average density at mean pressure; and p sub s and p sub w 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 sub l, depth of the trench, d sub t, and depth of the trench casing, d sub c. In the present study, however, values of K sub 1'/2 K sub 1 were determined which included the effect of half trench width b as well as d sub l, d sub t and d sub c. It is found that in any practical analysis the effect of trench width is not negligible and should be considered. (Author).
EPA Newsletter
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Water Spectrum
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Feasibility of Using an Acoustic Velocity Meter to Measure Flow in the Chipps Island Channel, Suisun Bay, California
Tests were conducted in 1978 to determine the feasibility of using an acoustic velocity meter to measure the Sacramento-San Joaquin Delta outflow in the Chipps Island Channel, Suisun Bay, Calif. Three parts of transducers with frequencies of 100, 40, and 24 kilohertz were installed on a cross-channel test path and operated at three elevations, 15.5, 8.0, and 4.0 feet below mean lower low water, to test signal transmission at varying depths. Transmission was most reliable at the lowest depth, and the 24-kilohertz transducers at the 7-millivolt threshold of signal strength met the study 's criterion of no persistent signal loss of more than one hour 's duration in any phase of the tidal cycle....
Water Resources
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