1,721,019 research outputs found
Prediction of turbulence and transition in turbomachinery flows using an innovative second moment closure modelling
No full textPrediction of tip-leakage flows in axial flow compressor with Second Moment Closures
No full textAn innovative analysis based on second-moment closure (SMC), incorporating proper modelling of low-Re-number and wall proximity effects is adopted in conjunction with numerical model based on an in-house parallel finite element code for the prediction of a 3D linear compressor cascade How with tip clearance. The strong interaction between the lip leakage vortex, the mainstream, the passage vortex and the other turbulent structures causes important portion of energy losses and it influences the overall performance of the compressors. A systematic comparison of the prediction of the proposed SMC with respect to a linear eddy viscosity closure (standard k-ε) and experiments is carried out. In the tip leakage the turbulent flow is characterized by an high level of anisotropy induced by complex shear effects. The present predictions demonstrates that second moment closures feature a superior capability to reproduce all major phenomenological features and mean flow parameters of turbomachinery flows. Copyright © 2006 by ASME
A study of wall-deposit formation using LES-generated velocity field
No full textWe consider a model of deposition of non reactive, adhesive micro-particles in a turbulent flow around a single short wall-bounded cylinder mimicking a segment of a plate-fin-and-tube heat exchanger. The flow field is provided by a prior LES (Borello et al. 2008) and the particles dispersion is described by the Particle Cloud Tracking of Baxter (1989). The deposition model is based on the balance between the rolling moments by the drag and the adhesion forces on the solid surfaces (Abd-Elhadi et al. 2004)
LES of heat transfer in an asymmetric rib-roughened duct: influence of rotation
No full textWe report on an LES study of effects of destabilising
rotation on heat transfer over a ribbed surface in
a rectangular duct at Re = 15000. The duct bottom
wall, ribbed by flow-normal, equally-spaced squaresectioned
ribs, was uniformly heated (except for the
ribs) by a constant heat flux. The duct was rotated with
angular velocity corresponding to the rotation number
of 0.3, around an axis parallel to the ribs in counterclockwise
direction destabilising the ribbed-wall adjacent
flow.
These well-resolved LES gave some new insight
into the rotation effects on flow and heat transfer providing
information that are not easily accessible to experiments.
An attempt was made to identify the heat
transfer effects due to the rotation-induced modifications
of the secondary motion, and the direct effects on
the turbulence statistics, especially the budgets of the
temperature variance and turbulent heat flux. It turned
out that the former is predominant in the recirculation
zone, whereas the latter prevails just after it
Scrutinizing a seamless hybrid LES/RANS approach for turbomachinery applications (short communication)
No full textURANS and Hybrid LES/RANS Computations of Tip Leakage and Secondary Flows in Axial Compressor Cascade
No full textLarge Eddy Simulation of Periodic Discrete Hole Effusion without and with Rotation
No full textIn order to provide further insight into multiple-hole film cooling of gas turbine blades, large-eddy simulations (LES) was performed for stationary and rotating discrete fluid effusion through periodic inclined cylindrical holes in a flat wall separating two turbulent streams. This generic configuration, investigated earlier using LES by Mendez and Nicoud (2008), was chosen to further study effects of using different computational domains, the corresponding bi-periodic boundary conditions, mesh types and quality, and the influence of rotation. The preliminary simulations in a diamond-shaped domain with a single hole, and a rectangular domain containing two holes, reproduced well the main flow features detected by Mendez and Nicoud (2008). The imposed system rotation - mimicking the real turbo-machinery operation - caused notable alteration of the effusion jet direction and modification of the vortical structures and their wall imprints with consequent effects on the local and average wall friction, expected also to modify the wall heat transfer. Copyright © 2009 Local Organising Committee
- …
