Abstract

Abstract

The algorithm introduced in Part I of this paper is applied in its explicit form to a variety of problems in order to demonstrate its wide range of applicability and excellent performance. Examples range from nearly incompressible, viscous, flows through transonic applications to high speed flows with shocks. In most examples linear triangular elements are used in the finite element approximation, but some use of quadratic approximation, again in triangles, indicates satisfactory performance even in the case of severe shocks.

Abstract

This work presents a numerical analysis of the ability of the high lift airfoil profile Selig S1223 for working as hydrofoil under water conditions. The geometry of the hydrofoil blade is designed through a suitable airfoil profile and then studied carefully by means of Computational Fluid Dynamics (CFD) in order to check its hydrodynamic behavior, i.e., including lift and drag analysis, and determinations of streamlines velocities and pressures fields. Finally conclusions on the use of this profile in a possible application for hydrokinetic turbine blades are detailed.

Abstract

The main objective of this article is to achieve a very high lift rotor to take the maximum advantage of the kinetic energy of a slow velocity water flow, which belongs to a lowland river type. Low speed flux and lack of depth are the main obstacles in hydrokinetic operation. The use of a high lift aerodynamic profile and the gain of the rotor number of blades serve to accomplish the task. This work presents the fluid dynamic design for an axial hydrokinetic turbine rotor, studied in a three-dimensional (3D) numerical simulation by means of Computational Fluid Dynamics (CFD). The use of CFD techniques avoids some physical model assays. For the hydrokinetic turbine rotor design, first a one-dimensional (1D) theoretical design was carried out, starting with the selection of a suitable airfoil profile to create the hydrofoil blade. Then, the 3D rotor geometry was defined and studied carefully by means of CFD, to check its hydrodynamic behavior, that is, lift and drag, streamline velocities and pressure fields. The CFD results were obtained using an open CFD code (Kratos) This is the peer reviewed version of the following article: [Oller, S. A., Nallim, L. G. and Oller, S. (2016), Fluid dynamic design of an axial rotor for hydrokinetic riverbed turbine-improvement introduced by a high lift foil profile

Abstract

The finite element solution of the turbulent Navier–Stokes equations developed via (k–ϵ) turbulence models was addressed in previous publications [1–4], where a (k–L)‐predictor/(ϵ)‐corrector iterative algorithm was developed. It was shown that the developed algorithm is robust and converges for the analyses of different flows without requiring the implementation of ad hoc numerical procedures. The turbulent convection–diffusion transport equations are solved by using the velocity distributions determined from the solution of the turbulent Navier–Stokes equations. The dispersion of a die in a turbulent flow can therefore be modelled and the obtained dispersion patterns are validated via flow visualizations in water models. In the present paper, the developed analysis capability is applied to the analysis of continuous casting processes.

Abstract

A summary is given of the mechanical characteristics of virus contaminants and the transmission via droplets and aerosols. The ordinary and partial differential equations describing the physics of these processes with high fidelity are presented, as well as appropriate numerical schemes to solve them. Several examples taken from recent evaluations of the built environment are shown, as well as the optimal placement of sensors.

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Abstract

Abstract

In the present work, an investigation on the Characteristic Based Split (CBS) method applied to the analysis of incompressible, transient and turbulent flows is proposed aiming at the evaluation of computational efficiency and accuracy of the present formulation considering problems typically found in Computational Wind Engineering (CWE). The flow fundamental equations are discretized here using the CBS method in the context of the Finite Element Method (FEM), where triangular and linear tetrahedral elements are employed. A fully explicit scheme is obtained applying the artificial compressibility method and a semi-implicit scheme is also tested, where the momentum equations are solved explicitly while the mass equation is solved implicitly through a Poisson equation. For the analysis of turbulent flows Large Eddy Simulation (LES) is adopted with the classic Smagorinsky’s model for sub-grid scales. Some classical Computational Fluid Dynamics (CDF) problems are analyzed first for code verification and evaluation. Subsequently, the numerical model is validated considering typical CWE applications, such as the wind action on a large-span bridge deck and the boundary-layer flow over a hill model. It is concluded that the proposed numerical tool is able to obtain results consistent with the phenomena involved and more efficiently than other stabilization methods available.

Abstract