On the application of isogeometric finite volume method in numerical analysis of wet-steam flow through turbine cascades

The isogeometric finite volume analysis is utilized in this research to numerically simulate the two-dimensional viscous wet-steam flow between stationary cascades of a steam turbine for the first time. In this approach, the analysis-suitable computational mesh with ‘‘curved’’ boundaries is generated for the fluid flow by employing a non- uniform rational B-spline (NURBS) surface that describes the cascade geometry, and the governing equations are then discretized by the NURBS representation. Thanks to smooth and accurate geometry representation of the NURBS formulation, the employed isogeometric framework not only resolves issues concerning the conventional mesh generation techniques of the finite volume method in steam turbine problems, but also, as validated against well-established experiments, significantly improves the accuracy of the numerical solution. In addition, the shock location in the cascade is predicted and tracked with a sufficient accuracy

Institute for Computational Mechanics in Propulsion (ICOMP)

The Institute for Computational Mechanics in Propulsion (ICOMP) is a combined activity of Case Western Reserve University, Ohio Aerospace Institute (OAI) and NASA Lewis. The purpose of ICOMP is to develop techniques to improve problem solving capabilities in all aspects of computational mechanics related to propulsion. The activities at ICOMP during 1991 are described

Numerical Investigation of Wet Inflow in Steam Turbine Cascades Using NURBS-based Mesh Generation Method

In this paper, the impact of existence of wetness in the inflow of stationary cascades of steam turbine blades has been numerically investigated. A new mesh generation method based on non-uniform rational B-splines (NURBS) has been adopted to reduce the numerical error of the wet inflow simulation. Moreover, two common meshing scenarios namely blade-to-blade (B-B) and periodic-to-periodic boundary (P-P) are studied and different angle of the grid at the trailing edge have been considered. The classical nucleation theory corrected by Courtney–Kantrowitz model and the Young's droplet growth model are employed to simulate the condensation phenomenon. By validating against experimental data, the results showed that implementing the proposed NURBS-based meshing technique decreased the prediction errors of static pressure distribution and droplet average radius by 35.64% and 78.44%, respectively, in comparison to typical grid generation methods. In addition, it was observed that existence of wetness at inlet significantly decreased the supercooling degree and postponed the nucleation process. Thus, the nucleation rate could be ameliorated in the case when we have a specific amount of wetness fraction in the inflow

Solution of the general dynamic equation along approximate fluid trajectories generated by the method of moments

We consider condensing flow with droplets that nucleate and grow, but do not slip with respect to the surrounding gas phase. To compute the local droplet size distribution, one could solve the general dynamic equation and the fluid dynamics equations simultaneously. To reduce the overall computational effort of this procedure by roughly an order of magnitude, we propose an alternative procedure, in which the general dynamic equation is initially replaced by moment equations complemented with a closure assumption. The key notion is that the flow field obtained from this so-called method of moments, i.e., solving the moment equations and the fluid dynamics equations simultaneously, approximately accommodates the thermodynamic effects of condensation. Instead of estimating the droplet size distribution from the obtained moments by making assumptions about its shape, we subsequently solve the exact general dynamic equation along a number of selected fluid trajectories, keeping the flow field fixed. This alternative procedure leads to fairly accurate size distribution estimates at low cost, and it eliminates the need for assumptions on the distribution shape. Furthermore, it leads to the exact size distribution whenever the closure of the moment equations is exact

Aeronautical engineering: A continuing bibliography with indexes (supplement 303)

This bibliography lists 211 reports, articles, and other documents introduced into the NASA scientific and technical information database. Subject coverage includes: design, construction, and testing of aircraft and aircraft engines; aircraft components, equipment, and systems; ground support systems; and theoretical and applied aspects of aerodynamics and general fluid dynamics

Identification of weakly- to strongly-turbulent three-wave processes in a micro-scale system

We find capillary wave turbulence (WT) to span multiple dynamical regimes and geometries -- from weakly to strongly nonlinear WT (SWT) and from shallow to deep domains -- all within a 40uL volume millifluidic system. This study is made viable with recent advances in ultra-high-speed digital holographic microscopy, providing 10-us time and 10-nm spatial resolutions for images across the entire field of view, and encompassing a complete wave system at speeds sufficient to capture the salient wave phenomena. We provide a set of tractable parameters that identify the four fundamental WT regimes present in this simple system. A proposed nonlinearity measure permits comparative analysis while varying input conditions. This work augments current understanding of WT regimes and behaviors, and directly applies to many fields beyond fluid mechanics. For example, SWT appears upon the fluid interface at powers less than required for atomization, indicating that further study of SWT is needed to properly understand ultrasound-driven fuel spray atomization and drug and agricultural nebulization.Comment: revision: 10 pages, 3 figures, longer format adds theory and supporting citation

Aeronautical engineering: A continuing bibliography with indexes (supplement 214)

This bibliography lists 422 reports, articles and other documents introduced into the NASA scientific and technical information system in May, l987