Ship's Log

The ability of accurately predicting transitional fluid flow behavior is important to the design of many engineering systems. From a design standpoint, Reynolds Averaged Navier-Stokes based CFD represents a reasonable compromise between accuracy and expense. More recent research efforts for RANS based CFD have focused on models specifically developed to predict transitional behavior.

The k-kl-omega model is a new transitional turbulence model which is described in [1]. However in 2013 it is appeared that this paper has several errors which must be corrected. In OpenFOAM these corrections have been applied with the version 2.4.0 and later.

As today, the Virtual Marine Arsenal directory has been extensively updated. Total of 51 software has been added and one removed. Most of the the new additions went to the Computer Aided Engineering and Specialized Tools categories.

k-kl-omega is a relatively new transition turbulence model. Since the version 2.1.0 this model has been implemented in OpenFOAM.  The model is based on the k-omega with an additional transport equation included to predict low-frequency velocity fluctuations that trigger transition in the boundary layer [1].

According to the notes in OpenFOAM source code, the latest version which is 2.4.0 as today has a significant update for the implementation of this turbulence model. Original note in the "kkLOmega.H (OpenFOAM-2.4.0.tgz)" is as follows:

Prolate spheroids can be considered as simple geometries. On the other hand the flow around a prolate spheroid at incidence offers a complex three-dimensional turbulent shear flows, featuring stagnation flow, a highly three-dimensional boundary layer, cross-flow separation, the formation and evolution of free-vortex sheets and stream-wise vortices etc.

Since these flow features are important in the area of aerodynamic and hydrodynamic design of vehicles, they have been the basis of much research over the years and many experimental studies have provided comprehensive data that reveals the salient physics of these king of flows specially for 3:1 and 6:1 prolate spheroids. The 6:1 case has been most widely researched though.

Construct2D is an open source preprocessor for building the computational structured grids around wing sections. It may also work for other shapes though. Basically it works on 2D but also has a limited 3D capability by extruding the 3D grid on z axis.

The software has no GUI and written in Fortran. Indeed it does not need a GUI and works perfectly and efficiently via the command line. Construct2D can be compiled on different operating systems but I am using it on Linux and my experience is based on that OS only. On Linux the installation procedure is simple and smooth.

The Virtual Marine Arsenal is just a simple directory trying to compile some stuff (mostly software) which may be directly related to the naval architecture and marine engineering interests. The first version had been released in 1997. The active development has been stopped in June 2005.

After almost ten years later (see Picture.1) I decided for an update! It took about eleven weeks to build the new structure which is database driven this time and move the old data to the new site. The work was not that straightforward tough...

Corrosion is either chemical or electrochemical in nature. The distinction between chemical and electrochemical corrosion is based on the corrosion causing mechanism. Chemical corrosion is the direct result of exposure of a material to a chemical and is governed by the kinetics of chemical reactions.

Electrochemical corrosion is the dissolution of a metal through the oxidation process and can be defined as "degradation of a metal by an  electrochemical reaction with its environment". This phomena also known as galvanic corrision.