Richardson roughness

The Monin-Obukhov length L is not a parameter that is routinely measured. Colder (1972), however, established a relation between the stability classes of Pasquill, the roughness height zo (see Section VII,B), and L. The results of his investigation are shown in Fig. 4. Alternatively, the local wind speed and cloud cover measurements are used to estimate the Pasquill stability class (Table IV). In addition, Colder developed a nonogram for relating the gradient Richardson number R-, to the more easily determined bulk Richardson number / (, ... 

Simons, D.B., Richardson, E.V. (1963). Forms of bed roughness in alluvial channels. Trans. ASCE 128 284-323. Simons, D.B., Senturk, F. (1992). Sediment transport technology Water and sediment dynamics. Water Resources Publications Fort Collins CO. 

Thermal electron emission from a solid (dark current in a photocathode) can be modeled in various degrees of complexity and full models for either classical or NEA emitters [5.139,140] require a fair amount of detail. In simplified form we can consider initially the limit of treating the substance as a perfect electron source (an electron black body ). Here all electrons which are thermally excited to energy greater than the surface barrier (work function or electron affinity) are emitted, and each emitted electron is assumed to be instantly replaced by an electron from the bulk. This is roughly the Richardson model, which applies fairly well to a metal. The dark current computed from this model is an upper limit to emission of a real device. 

Khan and Richardson (1996) pointed out that the concept of an equivalent sand roughness is very speculative as the transition between one layer and the other. By subsequent iterations, the friction factor and velocity for each of the two layers are obtained from the shear stress as the product of the friction factor and the dynamic pressure ... 

In the previous equation. A [A m K ] is the Richardson constant (A = 4nqm k /hp, where m is the effective mass of the charge-carrier). PAN/PEO nanofiber-diodes exhibit good rectifying behavior, and in forward conditions they roughly behave as predicted by the thermoionic emission model, especially at... 

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