The present work deals with the flow characteristics induced by a two-dimensional textured surface. The texture consists of identical and equally spaced rectangles with characteristic lengths at least one order of magnitude larger than the clearance of the thin film. Periodic boundary conditions enable the analysis of a single groove and the complete Navier–Stokes analysis is carried on for turbulent flow Reynolds numbers. The analysis is performed for shear driven flows (Couette), pressure driven flows (Poiseuille), and combined Couette–Poiseuille flows. First, the presence of inertial forces generated by the groove is emphasized by the momentum balance performed for the computational cell. The peculiar effect of the groove is also shown by the rotor and the stator shear stresses variations. Finally, it is shown that despite the presence of fluid inertia forces, cell-averaged rotor, and stator shear stresses obtained for pure Couette or Poiseuille flows can be added or subtracted to obtain with good accuracy the characteristics of combined shear and pressure driven flows.
The present work presents a theoretical approach for the analysis of textured annular “damper” seals. The data for the seal were extracted from the work of Childs and Fayolle (ASME J. Tribol. 121(1), pp. 42–49). The texture of the stator consists of equally spaced cylindrical holes of an order of magnitude larger than the seal clearance. The main idea of the present work is that the static and dynamic characteristics of the textured annular seal can be predicted by using a slightly modified bulk-flow model. The modifications are introduced by considering the textured seal as being geometrically similar to a straight seal with the same clearance. The presence of the texture is taken into account by considering modified friction laws for the rotor and for the stator, separately. An additional inertia effect due to the texture is also added as a source term to the momentum equations. The modified friction laws and the inertia effect are deduced from a three-dimensional Navier-Stokes analysis of the flow in the textured seal. This computational analysis is carried on for a single texture element extracted from the round-hole pattern of stator by using periodicity boundary conditions. The stiffness and the damping of the annular seal were calculated by using the modified bulk-flow model and results were compared with the experimental data from Childs and Fayolle. The use of the present model shows a net improvement of the predictions for the direct and cross-coupling stiffness and for the cross-coupling damping. The results obtained for the direct damping are still under discussion.
The present work deals with the flow characteristics induced by a two-dimensional roughness pattern. The roughness pattern consists of identical and equally spaced rectangles with characteristic lengths at least one order of magnitude larger than the clearance of the thin film. Periodic boundary conditions enable the analysis of a single groove and the complete Navier-Stokes analysis is carried on for turbulent Reynolds numbers. The analysis is performed for shear driven flows (Couette), pressure driven flows (Poiseuille) and combined Couette-Poiseuille flows. First, the presence of inertial forces generated by the groove is underlined by the momentum balance performed for the computational cell. The peculiar effect of the groove is also depicted by the rotor and the stator shear stresses variations. Finally, it is shown that despite the presence of inertial forces, cell-averaged rotor and stator shear stresses obtained for pure Couette or Poiseuille flows can be added or subtracted for approximately obtaining the characteristics of combined shear and pressure driven flows.
Abstract-Color Doppler is routinely used for visualisation of intra cardiac flows and quantification of valvular heart disease. Nevertheless the 2D visualisation of a complex 3D phenomenon is the major limitation of this technique. In particular, in clinical setting, the flow rate calculation upstream a regurgitant orifice (i.e. mitral valve insufficiency), assumes that the velocity field in the convergent region have hemispheric shapes and introduce miscalculation specially in case of prolaps regurgitant orifices. The main objective of this study was to characterize the dynamic 3D velocity field of the convergent region upstream a prolaps model of regurgitant orifice based on 2D time dependent PIV reconstruction.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.