Key themes of the release of FLOW-3D v11.1 are improving users’ workflow control and automation. Notable and exciting new developments include active simulation control, batch post-processing and report generation. Active simulation control lets users control the design stages of their simulations helping them to better understand and fine-tune parameters in their manufacturing processes. Batch post-processing, the ability to request desired output prior to launching a simulation, for automatic generation upon conclusion of the simulation, will save users valuable time. The new report generation function enables users to create HTML-based reports on customizable templates, allowing them to communicate simulation results in a light and portable manner.
Active Simulation Control
Active Simulation Control allows simulation parameters to be automatically changed during run-time based on user-defined conditions at history probes. Flow variables recorded by history probes can be used to control the behavior of time-dependent objects, such as mesh boundary conditions, mass sources and GMO components.
Active simulation control can be applied to a mixing simulation to control filling on/off and mixer motion. This simulation shows dye concentration in the fluid as the container is filled and then mixed. The simulation shows evolution of the flow profile of the fluid volume under circulation. The circulation is induced by a mechanical mixer that rotates inside the fluid volume. Over time the fluid profile attains a partially stable profile (if run longer, a paraboloid profile is expected to be seen).
Batch Postprocessing & Report Generation
Users can now define a series of plots/animations that will be automatically generated when the solver completes. These are generated in FlowSight and use context files to create the desired output. The batch postprocessing option can also be used to generate HTML-based reports.
Raster Data Interface
Bathymetry data can be imported from raster data files containing terrain elevation values at regular intervals. In addition, terrain roughness can be mapped onto the geometry using raster data for land usage, providing the means for more realistic modeling of flood events over complex terrain.
Water & Environmental Applications
The springs and ropes model has been extended to model mooring lines, which are long and heavy ropes or cables used, for example, to attach floating platforms to the seabed. The model accounts for the mooring line’s mass, tension and buoyancy, as well as fluid forces acting on the submerged section of the line.
In this simulation a semi-submersible offshore platform is tethered to the sea bottom using FLOW-3D‘s Mooring Line model. The platform is tethered by twelve high modulus polyethylene (HPME), SK78 EA mooring lines rated at 630 tons minimum breaking load rope. A severe sea state with 10 meter high non-linear propagating waves is defined.
Hydrostatic Mesh Boundary Conditions
A rating curve, relating fluid elevation to flow rate, can now be used to define inlet flow conditions at mesh boundaries, simplifying the definition of such boundary conditions. The user only needs to define a flow rate; fluid elevation will be automatically computed using the rating curve. A rating curve can also be coupled to a hydrostatic pressure boundary condition at outlet boundaries, in which case fluid elevation is automatically determined from the computed flow rate. In the absence of a rating curve at an inlet, the user can define a Natural boundary condition, in which the fluid elevation at the boundary is automatically calculated during simulation.
Subcomponent-specific Surface Roughness
In addition to the ability to define variable surface roughness using external raster data, the definition of surface roughness has been extended from components to subcomponents.
Wave Absorbing Layer
A wave damping algorithm based on the sponge layer approach has been added to help minimize surface wave reflection from mesh boundaries and their interference with the solution. A special type of the geometry component is used to specify the location, shape and orientation of sponge layers.
The existing Meyer-Peter model (1948) for bed load transport has been complemented by two more empirical approximations – from Van Rijn (1984) and Nielsen (1992) – to expand the range of applicability of the sediment transport model.
Metal Casting Applications
Squeeze Pin Model
Squeeze pins can now be simulated to model the behavior of the real die casting machines, where they are used to compensate metal shrinkage during solidification in hard-to-feed areas of the casting.
The use of the PQ2 diagram allows users to better approximate the real-life behavior of the shot sleeve plunger. The new feature is especially useful during the die casting design stage, when the actual process parameters are not yet known.
Thermal Die Cycling Model
The thermal die cycling (TDC) model has been enhanced by the addition of two new stages: the ejection stage, when the die is open but the part is still inside the ejector side, and the preparation stage, when the die is closed just before the filling. In addition, the TDC solver has been optimized to deliver fully converged solution during all thermal die cycles, instead of targeting it towards the last one. This is achieved at no loss to performance.
This simulation is a cross-sectional view of the die components during the entire tenth, and final, cycle. For this thermal die cycling analysis there were 6 stages in each cycle: 1. Solidification, 2. Ejection, 3. Open, 4. Blow Air, 5. Spray lubricant, 6. Closed, and we ran 10 total cycles. On the shop floor this would translate to 10 “shots” in order to develop this temperature profile. Notice the cooling profile at the parting lines, which are the horizontal contours, and how they change with time.
Valves and Vents
External pressure and temperature at valves and vents can now be defined as a tabular function of time, allowing users to define a more realistic behavior of these components of the die casting process during filling. The valve/vent pressure and temperature can also be controlled by probes placed inside the cavity, which is useful during the process design stage.
Cooling channels can now be controlled by the total amount of heat removed or added by each cooling channel to the die.
Mass-Based Air Entrainment Model
A new option has been added to the air entrainment model to take into account the compressibility of the entrained air, which is important in flows with significant variation of fluid pressure, for example, in the high-pressure die casting filling process. The new model uses mass instead of volume to represent the amount of entrained air, which for some applications is preferable, as shown in the following video.
Rapid bottle filling application of a syrup using FLOW-3D v11.1. Results show entrained air mass density, wetted area, velocity contours, dynamic bubble entrainment and streamlines during the filling process.
The cavitation model has been enhanced to better represent the behavior of cavitating fluid in turbulent flows. A new option for cavitation nucleation, based on empirical relations, complements the existing constant rate approach. A new passive model option has been added that tracks the cavitating gas in the fluid, but does not interact with the actual flow.
Combusting Solid Components
Solid fuel combustion is a traditional method of extracting energy from solid objects. However, an important relatively new application of solid fuel combustion is in rocket propulsion. The development of the new Combustible objects model in FLOW-3D v11.1 was motivated by solid propellant combustion in rockets. The model describes the conversion of solid rocket propellant to gas with a heat source, mimicking the combustion process in solid-fuel rockets.
Deformation of the combustible component (in red) of a rocket part. The combustible object gets converted into gas creating pressure inside the combustion chamber. Pressure evolution is shown at the right in the simulation.
Two-fluid Phase Change Model
Super-cooling has been added to the two-fluid, liquid and gas, phase change model. It is handled by defining a constant super-cooling temperature, allowing the gas temperature to descend below the saturation point before condensation takes place.
Fluid/wall Contact Time
A new spatial quantity has been added to the solution output that stores the time that fluid spent in contact with each geometric components, as well as the time spent by each component with fluid.
A new property has been added to flux surfaces which, when activated, resets certain spatial variables, such as surface defect and fluid residence time, to zero when fluid passes through the surface, allowing users to refine the evaluation of these properties in specific regions of the flow.
Results File Editor
A utility to edit FLOW-3D v11.1.0 results files allows users to merge results files and remove edits.
flsgrf.* files from restart simulations can be linked to the files from restart source simulation to display the results in a single, continuous animation in FlowSight.
Performance and Usability
Performance of the structural analysis model has been enhanced through improved parallelization and optimization of the solver for simulations with partial coupling. Additionally, the built-in finite element mesh generator has been extended to work in cylindrical coordinate systems so the user no longer needs to do the extra step of generating an FE mesh in a Cartesian system and importing it into the simulation with the cylindrical system.
Improved Runtime – GMRES pressure solver
The speed of the GMRES pressure solver has been improved by up to a factor of two by optimization of data structures used in the solver. The gain in performance comes at a modest increase in memory usage of less than 20%.
The sampling volume tool has been overhauled by adding the definition of sampling volumes using a special type of components of arbitrary shape thus allowing users to better fit the sampling volumes to their computational requirements. The list of output quantities calculated for each sampling volume has been expanded to include all the same quantities computed for the whole computational domain, such as fluid volume, min/max temperatures and particle counts.
Portfolios can now be imported from previous installations of FLOW-3D.
Other Usability Improvements
Expanded Simulation Pre-check
Simulation pre-check now includes the preprocessor checks and links an issue to where the problem is occurring.
The depth-peeling option now gives better representations of transparent geometries and is 10x faster than before.
Interactive Tools in the Model Setup
There are new, interactive creation tools for baffles, history probes, void/fluid pointers, valves, mass-momentum sources, and squeeze pins. Additionally, the interactive tools for probing and clipping are improved.
All objects can now be enabled/disabled.
Images can now be overlaid on geometry in the model setup to help orient structures and give more realistic views during setup.
Components can now be reordered using a “drag and drop” method.
An option has been added to the mass/momentum source model to define the flow using the flow velocity, instead of the flow rate. Also, STL objects can now be used to define the geometry of mass/momentum sources.
Estimated Remaining Time
The estimated remaining simulation time has been added to the short-print output to the solver message file.
A ruler was added to the Meshing & Geometry window to aid in simulation setup.
The most important change in the FORTRAN source code is the way directional indices, i, j and k, are extracted for a given mesh cell. Given the cell’s structured index ijk_str, the directional indices are
In previous versions the fluid sub-domain index ijk was used, instead of ijk_str.