No abstract

The single-mode equations of Boussinesq thermal convection have been modified to include the vertical component of vorticity, which has led, in certain parameter ranges, to a new family of solutions for stationary convection in the absence of external constraints. The features of these solutions are discussed and a comparison with the family of solutions possessing zero vertical vorticity, which are also solutions of the equations, is presented. Specifically, these new solutions are characterized by a lower vertical velocity and heat flux, nonzero vertical vorticity thereby giving them a helical structure and considerably reduced thermal boundary layers in comparison with the family of solutions with zero vertical vorticity. It is to be stressed that this new family of solutions is not due to externally applied influences such as rotation or a magnetic field, the only driving force present being that due to buoyancy.

Diamond coatings have been deposited by plasma enhanced chemical vapor deposition (PCVD) onto WC-Co cemented carbides by use of specially developed barrier interlayers, well compatible with cemented carbides. The barrier interlayer comprises a Ti-based layer adjacent to the substrate, which completely prevents both substrate decarburization and Co diffusion from the substrate, and a diamond-bonding layer needed to obtain high adhesion to the diamond coating. The diamond-bond layer is obtained by seeding the surface with nanograined diamond particles by laser ablation. Diamond deposition under controlled parameters allows one to obtain fine-grained and uniform diamond coatings. The diamond coating obtained in this way has a high adhesion to the cemented carbide substrate due to the enhanced interaction through the nanograined diamond interlayer.

Vortex generators are passive devices employed to improve the aerodynamic performance of aircraft and wind turbine blades. More concretely, these devices have high potential in improving the power output of wind turbines that are producing less power than expected. Besides, it can improve the aerodynamic performance of the nearest parts to the rotor of turbine blades that usually enter in stall. The main goal of this article is to model the triangular vortex generator effect on a DU97-W-300 airfoil by a source term model. This is aimed by comparing the lift and drag coefficients from experimental studies with the data obtained in the computational fluid dynamics study. Furthermore, the vertical path and the size and strength of the vortex are studied for different angles of attack in order to see how the vortex genertaor behaves in different conditions.