Computational Fluid Dynamics Software

New Split Lagrangian VOF Advection model

A new VOF advection model has been added to track sharp and diffuse fluid interfaces. Compared to other VOF methods in FLOW-3D, the new method has superior accuracy in tracking sharp fluid interfaces and in conserving fluid volume. It is applicable to one and two-fluid, sharp and diffuse interface problems, but tracking sharp interfaces is where its real strength lies. This new model was featured in an article in the Fall 2005 FLOW-3D Newsletter.

Additions to General Moving Objects model

Components defined as general moving objects (GMOs) will now be able to have the same heat transfer and mass source capabilities as non-moving components. These changes were featured in an article in the Spring 2005 FLOW-3D Newsletter. Other additions to the GMO model include the ability to attach a moving history probe to a GMO component and the ability of marker and mass particles to stick to the surface of a moving object. Read more about modeling fluid-solid interaction using FLOW-3D here.

New Electric Conductivity model

An extended “leaky dielectric” model has been added to the code. It works in conjunction with the electric potential, electric charge and dielectric models, and requires a positive electrical conductivity of the fluid. Electrical charge is generated at free surfaces and walls due to the differences in dielectric properties of the fluid, void and solid components. The existence of the charge changes the electric field and results in additional forces on the fluid. This new model was covered in an article in the Winter 2005 FLOW-3D Newsletter.

Additions to Air Entrainment model

Several important enhancements have been made to this model:

A turbulence model is no longer required to use the air entrainment model. Also, the entrained air is now allowed to escape back into the atmosphere. Finally, air entrained from or released into a confined adiabatic bubble will appropriately influence the pressure and volume of the bubble.

The model for the escape of rising gas bubbles at free surfaces, which is a part of the drift-flux model, has been improved to include a rate for their escape. This, in particular, improves the air entrainment model, where both the entrainment and escape of air occur at the free surface, and the resulting air concentration is determined by the rates of these processes.

These changes were featured in an article in the Summer 2005 FLOW-3D Newsletter.

Additions to Two-fluid Phase Change model

The two-fluid (liquid and compressible gas) evaporation/condensation model has been extended to allow condensation in pure gas and evaporation in pure liquid for both sharp and diffuse interface cases, and to enable preferential vapor nucleation (boiling) at walls.

Two-fluid Interface Slip model

When the two-fluid, sharp interface model is used, and the ratio of the densities of the two fluids is large (fluid #1 is heavier than fluid #2, like water and air), then velocities of the fluids at the interface can differ significantly. The newly-added interface slip model takes this into account improving accuracy and stability of the flow solution.

New Cavitation Potential model

This new model is designed to predict die erosion due to cavitation during filling in high pressure die casting. Metal pressure can drop several atmospheres below the metal vapor pressure in areas of very fast flow, possibly causing cavitation and erosion.

Surface Tension model enhancement

The accuracy of free surface curvature evaluation has been improved by including more fluid cells in the calculation. Additional improvements in free surface normal evaluation result in reduced noise in surface tension pressure. These enhancements, combined with the Split Lagrangian VOF method, improve the accuracy of the surface tension model in general.

Heat transfer solver improvement

The speed of the implicit solver for the heat transfer model has been increased by up to a factor of two. Convergence has also been improved. The explicit solver for the thermal conduction in fluids has also been optimized for speed.

Post-Processing

Numerous enhancements have been implemented for both improving display options and for improving rendering speed and efficiency. For example, the mesh used to create a simulation will be able to be displayed in 3-D plots, users will be able to apply transparency individually to each STL object imported into the Display window, vectors and streamlines can be displayed together with isosurfaces in 3-D plots, and dynamic memory allocation has been fully implemented in the post-processor to improve post-processing efficiency in terms of memory use and speed and remove limitations on the size of the results file.

Graphical User Interface

The redesigned GUI introduced with Version 9.0 has undergone further advances for Version 9.1. For example, rubber-band mesh creation has been added for cylindrical coordinate; features have been added to enable users to copy, move split and slice mesh blocks; icons for many frequently-used GUI functions have been added to Meshing & Geometry and Display tool bars for faster setup; and subcomponents that are defined as a complement are automatically shown in a semi-transparent mode to reveal any geometric features inside. Even though some variables must still be defined directly in the prepin file using the Text Editor, access to input variables and models has been expanded in the model builder.

Go here to view the featured highlights in Version 9.3.

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