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The role of the spatial resolution of a three-dimensional hydrodynamic model for marine transport risk assessment

Andrejev O., Soomere T., Sokolov A., Myrberg K.

Oceanologia

2011

No. 53 (1-TI)

309-334

The paper addresses the sensitivity of a novel method for quantifying the environmental risks associated with the current-driven transport of adverse impacts released from offshore sources (e.g. ship traffic) with respect to the spatial resolution of the underlying hydrodynamic model. The risk is evaluated as the probability of particles released in different sea areas hitting the coast and in terms of the time after which the hit occurs (particle age) on the basis of a statistical analysis of large sets of 10-day long Lagrangian trajectories calculated for 1987-1991 for the Gulf of Finland, the Baltic Sea. The relevant 2D maps are calculated using the OAAS model with spatial resolutions of 2, 1 and 0.5 nautical miles (nm) and with identical initial, boundary and forcing conditions from the Rossby Centre 3D hydrodynamic model (RCO, Swedish Meteorological and Hydrological Institute). The spatially averaged values of the probability and particle age display hardly any dependence on the resolution. They both reach almost identical stationary levels (0.67-0.69 and ca 5.3 days respectively) after a few years of simulations. Also, the spatial distributions of the relevant fields are qualitatively similar for all resolutions. In contrast, the optimum locations for fairways depend substantially on the resolution, whereas the results for the 2 nm model differ considerably from those obtained using finer-resolution models. It is concluded that eddy-permitting models with a grid step exceeding half the local baroclinic Rossby radius are suitable for a quick check of whether or not any potential gain from this method is feasible, whereas higher-resolution simulations with eddy-resolving models are necessary for detailed planning. The asymptotic values of the average probability and particle age are suggested as an indicator of the potential gain from the method in question and also as a new measure of the vulnerability of the nearshore of water bodies to offshore traffic accidents.

Metodyka określania temperatury spalin na wylocie z komina w obliczeniach propagacji zanieczyszczeń

Mazur M., Buczek A.

Ochrona Powietrza i Problemy Odpadów

1999

Vol. 33 nr 2

54-56

W obliczeniach zasięgu propagacji emisji zanieczyszczeń ze źródeł punktowych jednym z niezbędnych do obliczeń parametrem spalin jest ich temperatura na wylocie z komina. Jej wartość zależy od parametrów termodynamicznych spalin oraz cech konstrukcyjnych komina. W praktyce niezwykle rzadko wykonuje się pomiary temperatury na wylocie komina. najczęściej temperatura jest określana w sposób uproszczony poprzez przyjęcie stałego spadku temperatury wraz z wysokością w zależności od materiału z którego jest wykonany komin. Punktem wyjścia do obliczenia temperatury spalin na wylocie z komina jest bilans energii komina opierający się na założeniu, że strumień entalpii spalin na wylocie z komina jest równy strumieniowi entalpii spalin na wlocie do komina pomniejszonemu o strumień strat ciepła od spalin poprzez ścianę komina do otoczenia. Z kolei wiadomo że, strumień entalpii na wylocie z komina jest zależny od poszukiwanej temperatury, a więc można ją obliczyć poprzez procedurę iteracyjną Przeprowadzone obliczenia dla komina ceramicznego o wysokości wynoszącej 80 m, wykonanego z żelbetu, izolowanego wełną mineralną i określonych parametrach termodynamicznych spalin na wlocie do komina wykazały że, spadek temperatury wyniósł tylko ok. O.6K

One of the needed exhaust gases parameters in calculations of the range of the pollution propagation from point sources is the gases temperature at the chimney outlet. Its value depends on the thermodynamic parameters of the gases and on the chimney construction. In practice, the temperature on the chimney outlet is measured extremely seldom: it is usually calculated a simplified way by assuming its constant decrease rate with the height. depending also on the material the chimney is made of. The starting point to the calculations of the temperature on the chimney outlet is the chimneys energy balance. It is based on the assumption that the l1ux enthalpy on the chimney outlet is the same as the one at the chimney inlet, minus the heat loss l1ux from the exhaust gases through the chimneys wall to the environment. On the other band, the enthalpy l1ux at the outlet depends on the calculated temperature so an iteration procedure can be applied. The calculations conducted for 80-meters high ceramic chimney, made of reinforced concrete insulated with mineral wool. and with the given thermodynamic parameters of the exhaust gases at the chimney inlet showed that the temperature had dropped only by about O.6K.