Search results

1 – 3 of 3
Per page
102050
Citations:
Loading...
Access Restricted. View access options
Article
Publication date: 4 September 2017

Santiago Francisco Corzo, Damian Enrique Ramajo and Norberto Marcelo Nigro

The purpose of this paper is to assess the Boussinesq approach for a wide range of Ra (10 × 6 to 10 × 11) in two-dimensional (square cavity) and three-dimensional (cubic cavity…

134

Abstract

Purpose

The purpose of this paper is to assess the Boussinesq approach for a wide range of Ra (10 × 6 to 10 × 11) in two-dimensional (square cavity) and three-dimensional (cubic cavity) problems for air- and liquid-filled domains.

Design/methodology/approach

The thermal behavior in “differentially heated cavities” filled with air (low and medium Rayleigh) and water (high Rayleigh) is solved using computational fluid dynamics (CFDs) (OpenFOAM) with a non-compressible (Boussinesq) and compressible approach (real water properties from the IAPWS database).

Findings

The results from the wide range of Rayleigh numbers allowed for the establishment of the limitation of the Boussinesq approach in problems where the fluid has significant density changes within the operation temperature range and especially when the dependence of density with temperature is not linear. For these cases, the symmetry behavior predicted by Boussinesq is far from the compressible results, thus inducing a transient heat imbalance and leading to a higher mean temperature.

Research limitations/implications

The main limitation of the present research can be found in the shortage of experimental data for very high Rayleigh problems.

Practical implications

Practical implications of the current research could be use of the Boussinesq approach by carefully observing its limitations, especially for sensible problems such as the study of pressure vessels, nuclear reactors, etc.

Originality/value

The originality of this paper lies in addressing the limitations of the Boussinesq approach for high Rayleigh water systems. This fluid is commonly used in numerous industrial equipment. This work presents valuable conclusions about the limitations of the currently used models to carry out industrial simulations.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 27 no. 9
Type: Research Article
ISSN: 0961-5539

Keywords

Access Restricted. View access options
Article
Publication date: 6 November 2007

Damian Ramajo, Angel Zanotti and Norberto Nigro

The purpose of this paper is to assess a phenomenological zero‐dimensional model (0‐D model) in order to evaluate both the in‐cylinder tumble motion and turbulence in…

612

Abstract

Purpose

The purpose of this paper is to assess a phenomenological zero‐dimensional model (0‐D model) in order to evaluate both the in‐cylinder tumble motion and turbulence in high‐performance engine, focusing on the capability and sensitivity of the model.

Design/methodology/approach

The study was performed using a four‐valve pentroof engine, testing two different intake ports. The first one was a conventional port and the second one was design in such a way to promote tumble. CFD simulations for admission and compression strokes under different engine conditions were carried out. Then, the in‐cylinder entrance mass and mean velocities from CFD were imposed as boundary conditions in the 0‐D model.

Findings

Marked discrepancies between 0‐D model and CFD results were found. As expected, for the original port, CFD results displayed a poor tumble generation during the admission period. It was followed by a fast degradation of the tumble momentum along the compression stroke due to it was not dominant over the other two momentum components. 0‐D model overestimated the entrance‐tumble but underestimated the vortex degradation along the compression stroke, resulting in higher tumble predictions, thereby it is not recommended for low‐tumble engines. As for the modified port, 0‐D model assumptions were closer to the in‐cylinder flow field from CFD, but results underestimated the entrance‐tumble during the intake stroke and predicted excessive tumble at the end of the compression stroke. Summarizing, 0‐D model neither showed sensitivity to changes in the intake port because of the scarce information about the entrance‐flow field nor it was not suitable to evaluate the tumble degradation.

Originality/value

The limitations of the current model were highlighted, given possible guidelines in order to improve it.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 17 no. 8
Type: Research Article
ISSN: 0961-5539

Keywords

Access Restricted. View access options
Article
Publication date: 22 February 2013

Sergio Rodolfo Idelsohn, Norberto Marcelo Nigro, Juan Marcelo Gimenez, Riccardo Rossi and Julio Marcelo Marti

The purpose of this paper is to highlight the possibilities of a novel Lagrangian formulation in dealing with the solution of the incompressible Navier‐Stokes equations with very…

2444

Abstract

Purpose

The purpose of this paper is to highlight the possibilities of a novel Lagrangian formulation in dealing with the solution of the incompressible Navier‐Stokes equations with very large time steps.

Design/methodology/approach

The design of the paper is based on introducing the origin of this novel numerical method, originally inspired on the Particle Finite Element Method (PFEM), summarizing the previously published theory in its moving mesh version. Afterwards its extension to fixed mesh version is introduced, showing some details about the implementation.

Findings

The authors have found that even though this method was originally designed to deal with heterogeneous or free‐surface flows, it can be competitive with Eulerian alternatives, even in their range of optimal application in terms of accuracy, with an interesting robustness allowing to use large time steps in a stable way.

Originality/value

With this objective in mind, the authors have chosen a number of benchmark examples and have proved that the proposed algorithm provides results which compare favourably, both in terms of solution time and accuracy achieved, with alternative approaches, implemented in in‐house and commercial codes.

1 – 3 of 3
Per page
102050