Foi avaliada a capacidade do modelo WRF-ARW (versão 3.2.1) em prever o vento na região do Centro de Lançamento de Alcântara, visando aplicá-lo operacionalmente em ocasiões de lançamentos naquela base. Foram realizadas análises sazonais ao comportamento do modelo a partir de dois conjuntos de dados de radiossondagens representativos das estações seca (vento forte) e chuvosa (vento fraco). Previsões de 72 horas foram feitas a partir de condições iniciais fornecidas pelo Global Forecasting System (GFS/NCEP). Simulações configuradas para três domínios aninhados, resolução horizontal máxima de 1 km e vertical de 42 níveis foram comparadas com observações a cada 6 horas através do índice de concordância de Willmott (d). Foram realizados testes iniciais de sensibilidade para comparação e ajuste de diferentes parâmetros dinâmicos e físicos, como tamanhos de domínios, número de níveis verticais, spin-up time e parametrizações de Camada Limite Planetária. O modelo se mostrou razoável para representar o perfil vertical do vento, dentro de suas limitações, não mostrando diferença em seu desempenho entre as estações seca ou chuvosa e alcançando valores máximos de d na ordem de 0,90. Em geral, o modelo superestimou as componentes do vento (U e V) médias na camada em até 3,0 m/s com relação às observações.
Users may download and print one copy of any publication from the public portal for the purpose of private study or research. You may not further distribute the material or use it for any profit-making activity or commercial gain You may freely distribute the URL identifying the publication in the public portal If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.
Turbulent impingement jet heat transfer on concave surfaces has been employed in different engineering applications, e.g., aviation industry. In the aircraft anti-icing systems, hot air from the engine compressor impinges on the inside surface of the leading edge through small drilled holes, configuring the so-called piccolo tube system. A critical aspect in the design of such system is the prediction of heat transfer impinging jets from the piccolo tube. The correct evaluation of the heat transfer rate in such devices is of great interest to optimize both the anti-icing performance and the hot-air bleeding from the high-pressure compressor. Therefore, the present study develops a parametric study of the impingement jet flow on concave surfaces employing the CFD tool. The main goal is to determine the effect of the jet Mach number on this heat transfer mechanism. The present results also showed that at lower H/d conditions, i.e., lower jet-to-impinging surface distances, the temperature field exhibits a more efficient heating process inside the domain, resulting in greater Nusselt number values. A correlation taking into account geometric parameters such as the jet-to-jet spacing and the jet-to-impinging surface distance and jet Mach number is also proposed. Keywords Hot-air anti-icing system • Heat transfer • Turbulent impingement jet • Mach number List of symbols c Sound velocity d Jet diameter H Jet-to-impinging surface distance h(x,y) Local convection heat coefficient h ave Average convection heat coefficient k Air thermal conductivity Ma Mach number = V/c Nu(x,y) Nusselt number = h(x,y)d/k Nu ave Average Nusselt number p Pressure q w Impinging surface local heat flux T w Impinging surface wall temperature T jet Jet inlet static temperature V Jet velocity at the exit of the piccolo tube W Jet-to-jet spanwise distance x x coordinate y y coordinate ρ Air density μ Air dynamic viscosity
This work focuses on a numerical study of compressible subsonic flow in gas turbine annular diffusers. A diffuser is a diverging passage in which the flow is decelerated and the reduction in velocity head is converted to a rise in static pressure. Usually, for aircraft engines, and also many industrial engines, the length is a crucial restriction, resulting that diffuser shape should be the shortest possible distance. However, with an increase in divergence angle, stall losses arising from boundary-layer separation become more significant and the pressure recovery coefficient is affected. Hence, it is important to study the divergence angle as a function of the airflow behavior. In the numerical solution, mass, momentum and energy equations are discretized and solved employing the finite volume method, and the turbulence effects are taken into account using the realizable k- model with an enhanced wall treatment. Results showed that the annular diffuser performance is insensitive to Mach number for the divergence angle equal to 9°. On the other hand, the pressure recovery coefficient elevates as the Mach number increases for the divergence angle equal to 6°. The opposite phenomenon occurred for 12° diffuser due to the intense recirculation zones as the divergence angle increases.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.