Turbulent Flow Past Two-Body Configurations

Flows Around Bodies

Underlying Flow Regime 2-12

Best Practice Advice

NOTE: the BPA formulated below are overall well in line with conclusions based on the outcome of BANC-I [5] and not yet published results of BANC-II.

Key Physics

The key physical features of this UFR are separation of the turbulent shear layer from the upstream cylinder, free shear layer roll-up and chaotization, interaction of the essentially unsteady wake of the upstream cylinder with the downstream one, and massively separated wake of the downstream cylinder. It is found that it is necessary to capture these challenging features in a simulation claiming a reliable prediction of all the UFR characteristics. Whether this is reached or not in a simulation should be checked by:

Obtaining a visual impression of the unsteadiness of the shear layer separated from the upstream cylinder and of a range of spatial scales present in its wake and in the wake of the downstream cylinder using e.g. a snapshot of isosurface of λ₂ ("swirl") or Q-criterion (see Figure 4 for an example of the former) and vorticity contours (Figure 11).
Confirming a mixed tonal and broadband nature of the pressure signals on the surface of the cylinders by their spectral analysis (Figure 16).

Numerical Modelling

Discretisation method
Grids and grid resolution

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: A. Garbaruk, M. Shur and M. Strelets — New Technologies and Services LLC (NTS) and St.-Petersburg State Polytechnic University