Modelling and simulation of single and multi-phase impinging jets

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Abstract

Title: “Modelling and simulation of single- and multi-phase impinging jets”Impinging jets are a flow geometry that is of interest in many chemical and processing engineering applications for a wide range of industries. Of particular interest in the current research is their application to particle re-suspension in nuclear reprocessing activities such as the HAS (highly active storage) tanks at Sellafield, UK. The challenging nature of these operations and their environment means that in-situ experimental work is impossible. Therefore, when designing and optimising equipment such as HAS tanks, engineers often turn to computational modelling to help gain an understanding about what effects certain modifications may have on the performance of the jet. The challenge then becomes obtaining physically realistic predictions using the methods available to industry.Impinging jets are complex and complicated flow geometries that have caused a number of problems for computational modellers over the years. Indeed, several turbulence models and approaches have been developed specifically with impinging jets in mind to help overcome some of the more difficult aspects of the flow. The work presented herein compares Reynolds-averaged Navier-Stokes (RANS) commercial codes readily available to industrial users for single- and multi-phase flows with RANS and large eddy simulation (LES) codes developed in an academic research environment. The intention is to contrast and compare and highlight where industrial-based computational models fall short and how these might be improved through implementing schemes with fewer simplified terms.The work conducted for this Engineering Doctorate has modelled a series of impinging jets with varying jet heights and Reynolds numbers using a range of RANS turbulence models within commercial and academic-based codes. This allows not only the discussion of the performance of the applied turbulence models, but also the effects of varying jet height. The predictions are validated against available experimental data for assessment of the performance of the scheme used. The degree of alignment with real, physical data is an indication of the performance of a model and is used to conclude where a particular model has failed or whether it is more suited than another. Different particle sizes have also been considered to determine the ability of different particle tracking schemes to predict particle behaviour based on their response to the continuous phase. Multi-phase data is also validated against limited available experimental data. Finally, LES has been used to demonstrate the next step in complexity in terms of simulation and prediction of continuous phase flows in difficult engineering applications and how these can greatly improve upon predictions from RANS methods.

Keyword(s)

cfd; impinging jet; les; multi-phase; single-phase; turbulence modelling

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