A Numerical Study for Meniscus Vortices Induced by Mold Flow Instabilities

2021 ◽  
Vol 45 (9) ◽  
pp. 479-486
Author(s):  
Seong Bae Pak ◽  
Jong Hui Lee ◽  
Il Seouk Park
2002 ◽  
Vol 124 (2) ◽  
pp. 363-370 ◽  
Author(s):  
Takeshi Sano ◽  
Yoshiki Yoshida ◽  
Yoshinobu Tsujimoto ◽  
Yuki Nakamura ◽  
Tatsuhito Matsushima

This paper treats the flow instabilities in a vaned diffuser by using CFD. A commercial code with the standard κ-ε turbulence model was used for the present work. It was found that the flow instabilities in the vaned diffuser: i.e., rotating stall, alternate blade stall, and asymmetric stall, could be simulated by the present calculations. These instabilities were observed in a range with negative slope of the pressure performance curve of the diffuser. The rotating stall onset flow rate is larger for the case with larger clearance between the impeller and diffuser vanes.


Author(s):  
Clemens Olbricht ◽  
Felix Flemming ◽  
Amsini Sadiki ◽  
Johannes Janicka ◽  
Friedrich Bake ◽  
...  

Due to successful noise reduction strategies concerning fan- and jet-noise in gas turbine configurations, the relevance of combustion noise is increasing. In order to distinguish between turbulent noise and combustion noise a model gas turbine combustor consisting of a swirl burner and an exit nozzle of Laval-shape is investigated. Because of the instationary character of the flow this configuration is analysed by means of Large Eddy Simulation (LES). Numerical results are first validated by comparison with experimental data. Then a numerical study of noise generated by turbulent flow instabilities is carried out. Providing an extensive temporal and spatial analysis of the isothermal flow length- and timescales as well as vorticitiy are investigated with regard to the formation of rotating flow-instabilities in the recirculating swirling flow. Subsequently a link to the acoustic perturbation equations (APE) is provided, from which the Lamb vector represents the essential noise sources. Therfore noise sources are identified and evaluated by means of LES based on the Lamb vector consideration. It results that the noise sources increase with an increasing swirl number.


2021 ◽  
Vol 54 (8) ◽  
pp. 424-430
Author(s):  
Radeesha Laknath ◽  
Agampodi Mendis ◽  
Atsushi Sekimoto ◽  
Yasunori Okano ◽  
Hisashi Minakuchi ◽  
...  

1998 ◽  
Vol 77 (2) ◽  
pp. 473-484 ◽  
Author(s):  
M. Sampoli, P. Benassi, R. Dell'Anna,

2020 ◽  
pp. 57-65
Author(s):  
Eusébio Conceiçã ◽  
João Gomes ◽  
Maria Manuela Lúcio ◽  
Jorge Raposo ◽  
Domingos Xavier Viegas ◽  
...  

This paper refers to a numerical study of the hypo-thermal behaviour of a pine tree in a forest fire environment. The pine tree thermal response numerical model is based on energy balance integral equations for the tree elements and mass balance integral equation for the water in the tree. The simulation performed considers the heat conduction through the tree elements, heat exchanges by convection between the external tree surfaces and the environment, heat exchanges by radiation between the flame and the external tree surfaces and water heat loss by evaporation from the tree to the environment. The virtual three-dimensional tree model has a height of 7.5 m and is constituted by 8863 cylindrical elements representative of its trunks, branches and leaves. The fire front has 10 m long and a 2 m high. The study was conducted taking into account that the pine tree is located 5, 10 or 15 m from the fire front. For these three analyzed distances, the numerical results obtained regarding to the distribution of the view factors, mean radiant temperature and surface temperatures of the pine tree are presented. As main conclusion, it can be stated that the values of the view factor, MRT and surface temperatures of the pine tree decrease with increasing distance from the pine tree in front of fire.


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