A Reduced Nonlinear Model for the Simulation of Two Phase Flow in a Horizontal Pipe.

In the last 10 years many 3D numerical schemes have been developed for the study the flow of a mixture of liquid and gas in a pipeline (Frank, Numerical simulation of slug flow regime for an air-water two-phase flow in horizontal pipes. In: The 11th international topical meeting on nuclear reactor thermal-hydraulics (NURETH-11), Avignon, 2005; Vallée et al., Nucl Eng Des 238(3):637–646, 2008; Höhne, Experiments and numerical simulations of horizontal two-phase flow regimes. In: Proceeding of the seventh international conference on CFD in the minerals and process industries, Melbourne, 2009; Bartosiewicz et al., Nucl Eng Des 240(9):2375–2381, 2010) but although they offer a very good accuracy, they are rarely fit for modelling a long pipe, due to the high computational costs. Then one is usually led to consider 1D models, see e.g. the works of Issa and his group (Issa and Kempf, Int J Multiphase Flow 29(1):69–95, 2003). Such models offer much faster simulations than 3D schemes, on the other hand they almost completely miss the dynamics in the transversal direction. Here we present a model able of representing the full 3D dynamics, but with the computational cost typical of 1D simulation. The main feature of our model consists in describing the dynamical variables in the direction transversal to the pipe by means of a family of functions depending on a set of parameters. The model is then solved by a standard finite volume scheme

Predictive, miniature co-extrusion of multilayered glass fiber-optic preforms

A miniature co-extrusion technique, to produce a concentric multilayered glass fiber-optic preform of ~3 mm diameter, is modeled and experimentally demonstrated. A three-dimensional, incompressible, noncavitating, and nonisothermal Computational Fluid Dynamics (CFD) model, similar to one developed in our previous work, is used to predict the dimensions of an alternating four-layer glass stack feed required to produce the desired layer dimensions in a multilayered-glass preform extrudate, using a miniaturized and thus more economical co-extrusion. Strong agreement in the cross-sectional geometrical proportions of the simulated and experimentally obtained preform supports the prowess of the predictive modeling. Nevertheless, some small deviations between the simulated and experimentally obtained dimensions indicate topics for future rheological study. Performing the co-extrusion process under vacuum helps to minimize the inter-layer defects in the multi-layered fiber-optic preform. The miniature co-extrusion potentially removes the need for a postextrusion draw-down prior to fiber drawing, avoiding devitrification issues possible in non-oxide novel glass compositions

Acoustic characteristics of a ported shroud turbocompressor operating at design conditions

[EN] In this article, the acoustic characterisation of a turbocharger compressor with ported shroud design is carried out through the numerical simulation of the system operating under design conditions of maximum isentropic efficiency. While ported shroud compressors have been proposed as a way to control the flow near unstable conditions in order to obtain a more stable operation and enhance deep surge margin, it is often assumed that the behaviour under stable design conditions is characterised by a smooth, non-detached flow that matches an equivalent standard compressor. Furthermore, research is scarce regarding the acoustic effects of the ported shroud addition, especially under the design conditions. To analyse the flow field evolution and its relation with the noise generation, spectral signatures using statistical and scale-resolving turbulence modelling methods are obtained after successfully validating the performance and acoustic predictions of the numerical model with experimental measurements. Propagation of the frequency content through the ducts has been estimated with the aid of pressure decomposition methods to enhance the content coming from the compressor. Expected acoustic phenomena such as `buzz-saw¿ tones, blade passing peaks and broadband noise are correctly identified in the modelled spectrum. Analysis of the flow behaviour in the ported shroud shows rotating structures through the slot that may impact the acoustic and vibration response. Further inspection of the pressure field through modal decomposition confirms the influence of the ported shroud cavity in noise generation and propagation, especially at lower frequencies, suggesting that further research should be carried out on the impact these flow enhancement solutions have on the noise emission of the turbocharger.The project was sponsored and supported by BorgWarner Turbo Systems and the Regional Growth Fund (RGF Grant Award 01.09.07.01/1789C). The authors would like to thank BorgWarner Turbo Systems for permission to publish the results presented in this article. The support of the HPC group at the University of Huddersfield is gratefully acknowledged.Sharma, S.; Broatch, A.; Garcia Tiscar, J.; Allport, JM.; Nickson, AK. (2020). Acoustic characteristics of a ported shroud turbocompressor operating at design conditions. International Journal of Engine Research. 21(8):1454-1468. https://doi.org/10.1177/1468087418814635S14541468218Sundström, E., Semlitsch, B., & Mihăescu, M. (2017). Generation Mechanisms of Rotating Stall and Surge in Centrifugal Compressors. Flow, Turbulence and Combustion, 100(3), 705-719. doi:10.1007/s10494-017-9877-zGonzalez, A., Ferrer, M., de Diego, M., Piñero, G., & Garcia-Bonito, J. . (2003). Sound quality of low-frequency and car engine noises after active noise control. Journal of Sound and Vibration, 265(3), 663-679. doi:10.1016/s0022-460x(02)01462-1Brizon, C. J. da S., & Bauzer Medeiros, E. (2012). Combining subjective and objective assessments to improve acoustic comfort evaluation of motor cars. Applied Acoustics, 73(9), 913-920. doi:10.1016/j.apacoust.2012.03.013Teng, C., & Homco, S. (2009). Investigation of Compressor Whoosh Noise in Automotive Turbochargers. SAE International Journal of Passenger Cars - Mechanical Systems, 2(1), 1345-1351. doi:10.4271/2009-01-2053Figurella, N., Dehner, R., Selamet, A., Tallio, K., Miazgowicz, K., & Wade, R. (2014). Noise at the mid to high flow range of a turbocharger compressor. Noise Control Engineering Journal, 62(5), 306-312. doi:10.3397/1/376229Torregrosa, A. J., Broatch, A., Margot, X., García-Tíscar, J., Narvekar, Y., & Cheung, R. (2017). Local flow measurements in a turbocharger compressor inlet. Experimental Thermal and Fluid Science, 88, 542-553. doi:10.1016/j.expthermflusci.2017.07.007Broatch, A., Galindo, J., Navarro, R., García-Tíscar, J., Daglish, A., & Sharma, R. K. (2015). Simulations and measurements of automotive turbocharger compressor whoosh noise. Engineering Applications of Computational Fluid Mechanics, 9(1), 12-20. doi:10.1080/19942060.2015.1004788Raitor, T., & Neise, W. (2008). Sound generation in centrifugal compressors. Journal of Sound and Vibration, 314(3-5), 738-756. doi:10.1016/j.jsv.2008.01.034Galindo, J., Tiseira, A., Navarro, R., & López, M. A. (2015). Influence of tip clearance on flow behavior and noise generation of centrifugal compressors in near-surge conditions. International Journal of Heat and Fluid Flow, 52, 129-139. doi:10.1016/j.ijheatfluidflow.2014.12.004Broatch, A., Galindo, J., Navarro, R., & García-Tíscar, J. (2014). Methodology for experimental validation of a CFD model for predicting noise generation in centrifugal compressors. International Journal of Heat and Fluid Flow, 50, 134-144. doi:10.1016/j.ijheatfluidflow.2014.06.006Semlitsch, B., & Mihăescu, M. (2016). Flow phenomena leading to surge in a centrifugal compressor. Energy, 103, 572-587. doi:10.1016/j.energy.2016.03.032Sundström, E., Semlitsch, B., & Mihăescu, M. (2018). Acoustic signature of flow instabilities in radial compressors. Journal of Sound and Vibration, 434, 221-236. doi:10.1016/j.jsv.2018.07.040Torregrosa, A. J., Broatch, A., Margot, X., & García-Tíscar, J. (2016). Experimental methodology for turbocompressor in-duct noise evaluation based on beamforming wave decomposition. Journal of Sound and Vibration, 376, 60-71. doi:10.1016/j.jsv.2016.04.035Nicoud, F., & Ducros, F. (1999). Flow, Turbulence and Combustion, 62(3), 183-200. doi:10.1023/a:1009995426001Chow, P., Cross, M., & Pericleous, K. (1996). A natural extension of the conventional finite volume method into polygonal unstructured meshes for CFD application. Applied Mathematical Modelling, 20(2), 170-183. doi:10.1016/0307-904x(95)00156-eKaji, S., & Okazaki, T. (1970). Generation of sound by rotor-stator interaction. Journal of Sound and Vibration, 13(3), 281-307. doi:10.1016/s0022-460x(70)80020-7Sivagnanasundaram, S., Spence, S., & Early, J. (2013). Map Width Enhancement Technique for a Turbocharger Compressor. Journal of Turbomachinery, 136(6). doi:10.1115/1.4007895Aubry, N. (1991). On the hidden beauty of the proper orthogonal decomposition. Theoretical and Computational Fluid Dynamics, 2(5-6), 339-352. doi:10.1007/bf00271473Wold, S., Esbensen, K., & Geladi, P. (1987). Principal component analysis. Chemometrics and Intelligent Laboratory Systems, 2(1-3), 37-52. doi:10.1016/0169-7439(87)80084-9LIANG, Y. C., LEE, H. P., LIM, S. P., LIN, W. Z., LEE, K. H., & WU, C. G. (2002). PROPER ORTHOGONAL DECOMPOSITION AND ITS APPLICATIONS—PART I: THEORY. Journal of Sound and Vibration, 252(3), 527-544. doi:10.1006/jsvi.2001.4041Abdi, H., & Williams, L. J. (2010). Principal component analysis. Wiley Interdisciplinary Reviews: Computational Statistics, 2(4), 433-459. doi:10.1002/wics.101Nikiforov, V. (2007). The energy of graphs and matrices. Journal of Mathematical Analysis and Applications, 326(2), 1472-1475. doi:10.1016/j.jmaa.2006.03.07

1 Calculations of Coolant Flow in a VVER-440 Fuel Bundle with the Code

From the aspect of planning the power upgrading of nuclear reactors- including the VVER-440 type reactor – it is essential to get to know the flow field in the fuel assembly. For this purpose we have developed models of the fuel assembly of the VVER-440 reactor using the ANSYS CFX 10.0 CFD code. At first a 240 mm long part of a 60 degrees segment of the fuel pin bundle was modelled. Implementing this model a sensitivity study on the appropriate meshing was performed. Based on the development of the above described model, further models were built: a 960 mm long part of a 60-degree-segment and a full length part (2420 mm) of the fuel pin bundle segment. Calculations were run using the full length model to investigate a fuel assembly. In the calculations constant coolant properties and several turbulence models were applied. The impacts of choosing different turbulence models were in detail studied. For the investigated fuel assembly calculation was performed using the COBRA subchannel code too [2]. The results of the CFX and the COBRA calculations were compared. The results of the above-mentioned investigations are presented in this paper. 1