UFR 4-16 Best Practice Advice: Difference between revisions
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flow direction — induced by the Reynolds stress anisotropy. | flow direction — induced by the Reynolds stress anisotropy. | ||
== Numerical | == Numerical Issues == | ||
== Physical Modelling == | == Physical Modelling == | ||
{{Demo_UFR_BPA3}} | {{Demo_UFR_BPA3}} | ||
Revision as of 11:04, 26 July 2012
Flow in a 3D diffuser
Confined flows
Underlying Flow Regime 4-16
Best Practice Advice
Key Physics
The flow in the present three-dimensional diffuser configurations is extremely complex, despite a simple geometry: namely a "through flow" in a duct — with the cross-section of its "central part" exhibiting a certain expansion and having one clearly defined inlet and one clearly defined outlet. The basic feature of the flow is a complex three-dimensional separation pattern being the consequence of an adverse pressure gradient imposed on the flow through a duct expansion. Two diffuser configurations characterized by slightly different expansion geometry but leading to completely different recirculation zone topology have been investigated. The differences are with respect to the separation onset and reattachment (form and position of the 3D separation/reattachment line) — multiple corner separation and corner reattachment — as well as with the shape and size (length, thickness, fraction of the cross-sectional area occupied by separation) of the recirculation pattern. An important prerequisite for a successful reproduction of the separating flow structure in the diffuser section is the correct capturing of the flow in the inlet duct characterized by intensive secondary currents — being normal to the main flow direction — induced by the Reynolds stress anisotropy.
Numerical Issues
Physical Modelling
- Turbulence modelling
- Transition modelling
- Near-wall modelling
- Other modelling
Application Uncertainties
Summarise any aspects of the UFR model set-up which are subject to uncertainty and to which the assessment parameters are particularly sensitive (e.g location and nature of transition to turbulence; specification of turbulence quantities at inlet; flow leakage through gaps etc.)
Recommendations for Future Work
Propose further studies which will improve the
quality or scope of the BPA and perhaps bring it up to date. For example,
perhaps further calculations of the test-case should be performed
employing more recent, highly promising models of turbulence (e.g Spalart
and Allmaras, Durbin's v2f, etc.). Or perhaps new experiments should be
undertaken for which the values of key parameters (e.g. pressure gradient
or streamline curvature) are much closer to those encountered in real
application challenges.
Contributed by: Suad Jakirlić, Gisa John-Puthenveettil — Technische Universität Darmstadt
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