Large-Eddy Simulation of the Flow Developing in Static and Rotating Ribbed Channels

In the present work, the turbulent flow fields in a static and rotating ribbed channel representative of an aeronautical gas turbine are investigated by the means of wall-resolved compressible large-Eddy simulation (LES). This approach has been previously validated in a squared ribbed channel based on an experimental database from the Von Karman Institute (Reynolds and rotation numbers of about 15,000 and ±0.38, respectively). LES results prove to reproduce differences induced by buoyancy in the near rib region and resulting from adiabatic or anisothermal flows under rotation. The model also manages to predict the turbulence increase (decrease) around the rib in destabilizing (stabilizing) rotation of the ribbed channels. On this basis, this paper investigates in more detail the spatial development of the flow along the channel and its potential impact on secondary flow structures. More specifically and for all simulations, results of the adiabatic static case exhibit two contra-rotating structures that are close to the lateral walls of the channel induced by transversal pressure difference created by the ribs. These structures are generated after the first ribs and appear behind all inter-rib sections, their relative position is partly affected by rotation. When considering the stabilizing rotating case, two additional contra-rotating structures also develop along the channel from the entrance close to the low-pressure wall (rib-mounted side). These vortices are due to the confinement of the configuration, inflow profile and are the result of Coriolis forces induced by rotation. Görtler vortices also appear on the pressure wall (opposite to the rib-mounted side). In the destabilizing rotating case, these two types of secondary structures are found to co-exist, and their migration in the channel is significantly different due to the presence of the ribs on the pressure side. Finally, it is shown that heat transfer affects only marginally the static and stabilized cases while it changes more significantly the flow organization in the destabilizing case mainly because of enhanced heat transfer and increased buoyancy force effects.

Large Eddy Simulation of the Flow Developing in Static and Rotating Ribbed Channels

In the present work, the turbulent flow fields in a static and rotating ribbed channel representative of an aeronautical gas turbine are investigated by mean of wall-resolved compressible Large Eddy Simulation (LES). This approach has been previously validated in a squared ribbed channel based on an experimental database from Von Karman Institute (Reynolds and rotation numbers of about 15000 and +/− 0.38 respectively). LES results prove to reproduce differences induced by buoyancy in the near rib region and resulting from adiabatic or anisothermal flows under rotation. The model also manages to predict the turbulence increase (decrease) around the rib in destabilizing (stabilizing) rotation of the ribbed channels. On this basis, this paper investigates in more details the spatial development of the flow along the channel and its potential impact on secondary flow structures. More specifically and for all simulations, results on the adiabatic static case exhibits two contra-rotating structures close to the lateral walls of the channel induced by transversal pressure difference created by the ribs. These structures are generated after the first ribs and appear behind all inter rib sections, their relative position being partly affected by rotation. When considering the stabilizing rotating case, two additional contra-rotating structures also develop along the channel from the entrance close to the low-pressure wall (rib-mounted side). These vortices are due to the confinement of the configuration, inflow profile and are the result of Coriolis forces induced by rotation. Görtler vortices also appear on the pressure wall (opposite to the rib-mounted side). In the destabilizing rotating case, these two types of secondary structures are found to co-exist and their migration in the channel is significantly different due to the presence of the ribs on the pressure side. Finally, it is shown that heat transfer affects only marginally the static and stabilized cases while it changes more significantly the flow organization in the destabilizing case mainly because of enhanced heat transfer and increased buoyancy force effects.

Transversal Pressure Effect in Circulative Separators

Progressive urban development of the human environment requires new methods of rain water treatment. Recently, there has been a growing interest in the improvement of gravitational suspension separation, and especially in the application of the centrifugal force. This important factor can be induced in two ways; by the circulation of the reservoir containing the fluid (centrifugal separators), or by a tangent supply of this reservoir (circulative separators). In addition to the centrifugal force, another essential transversal force is at work in this case, resulting from the local variability of the pressure. In the literature, this force is derived for centrifuge conditions, but applied also to circulative separators, which is questionable, as in the latter devices velocity and pressure fields are clearly different. The paper is devoted to the determination of the transversal pressure effect in circulative separators. First, a model of tangent and radial velocity profiles is introduced. The radial pressure distribution, calculated on this basis and verified experimentally, leads to the final result, that is, a technical formula describing the force in question

Modelling of Unilateral Contact of Metal and Fiberglass Shells

In this work the variant of calculation of two coaxial shells of rotation in the form of sphere from a material is offered, corresponding which surfaces are located from each other on the set distance. At action of internal pressure on local sites between shells there is a unilateral contact. Distribution of contact pressure on length of sites of contact is with the account transversal pressure considered shells on a thickness.