What's New in FLOW-3D 2025R1
FLOW-3D 2025R1 expands the products and processes that can be designed and studied with the addition of a new discrete element method (DEM) model that is fully coupled to the core CFD solver. Users can now leverage the advanced particle-particle interaction capabilities to simulate a wide variety of granular material handling, slurry mixing, separation processes, and other particle-laden flows.
Note: This model requires a separate license token, which can be added at an additional cost. Please contact sales@flow3d.com to request access.
What's New in FLOW-3D 2024R1
FLOW-3D 2024R1 continues to refine our product and process development software with a revision of the bubble and phase change model, which makes it easier to use while avoiding common setup errors, especially when using the heat transfer or liquid-vapor phase change options. A reorganization of the user interface groups the liquid-vapor phase change options with the solid-liquid phase change options.
We replaced the adiabatic bubble and thermal bubble models with a consolidated ideal gas equation of state, consolidated the fluid property inputs, and added options to control which parameters are used to define the equation of state. This development reduces the possibility of an engineering error, simplifies the inputs, and provides a more natural grouping for the phase transition models.
A second development adds support for our fluid-structure interaction and thermal stress evolution models in the new EXODUS II-based output files, providing significant postprocessing performance improvements.
What's New in FLOW-3D 2023R2
New results file format
Turbulence model improvements
Hydrostatic pressure initialization
Compressible flow solver performance
FLOW-3D 2023R2 introduces an optimized pressure solver, giving significant performance gains for compressible flow problems. In this example of a compressible jet flow, the 2023R2 solver was ~4x faster than the 2023R1 version.
What's New in FLOW-3D 2023R1
All products in the FLOW-3D software family received IT-related improvements in 2023R1. FLOW-3D 2023R1 now supports Windows 11 and RHEL 8. Our Linux installer has been improved to report missing dependencies and it no longer requires root-level permissions, which makes installation easier and more secure. And for those of you who have automated your workflows, we added a command-line interface to our input file converter so that you can ensure your workflow is working with updated input files, even in scripted environments.
Expanded PQ2 analysis
Hydraulic systems used in manufacturing can be modeled using PQ2 curves. It is often a convenient simplification to approximate the hydraulic system using a mass-momentum source or a velocity boundary condition to skip the details of the device and include its impact on the flow. We expanded our existing PQ2 analysis model to allow for this type of geometric simplification while still giving realistic results. This translates to a reduction in simulation time and model complexity.
What's New in FLOW-3D 2022R2
With the release of the FLOW-3D 2022R2 product family, Flow Science has unified the workstation and HPC versions of FLOW-3D to deliver a single solver engine capable of taking advantage of any type of hardware architecture, from single node CPU configurations to multi-node parallel high performance computing executions. Additional developments include a new log conformation tensor method for visco-elastic flows, continued solver speed performance improvements, advanced cooling channel and phantom component controls, and improved entrained air functionalities.
Unified solver
We migrated our FLOW-3D products to a single, unified solver to run seamlessly on local workstations or on high performance computing hardware environments.
Many users run their models on laptops or local workstations, but in addition run larger models on high performance computing clusters. With the 2022R2 release, the unified solver allows users to exploit the same benefits of OpenMP/MPI hybrid parallelization from HPC solutions to run on workstations and laptops.
Solver performance improvements
Multi socket workstations
Multi socket workstations are now very common and capable of running large simulations. With the new unified solver, users using this type of hardware will generally see performance gains from being able to run models taking advantage of OpenMP/MPI hybrid parallelization that used to be only available on HPC cluster configurations.
Low level routines improved vectorization and memory access
Performance gains on the order of 10% to 20% have been observed for most test cases, with some cases yielding run-time benefits in excess of 20%.
Refined volumetric convective stability limit
Time step stability limit is a major driver in model runtime, with 2022R2, a new time step stability limit, 3D convective stability limit, is available in the numerics widget. For models that are running and convection limited (cx, cy, or cz limits) the new option has shown typical speed-ups on the order of 30%.
Pressure solver pre-conditioner
In some cases, for challenging flow configurations, run times can be drawn out due to excessive pressure solver iterations. For those difficult cases, with 2022R2, when a model iterates too heavily, FLOW-3D automatically activates a new pre-conditioner to help with pressure convergence. Tests have improvements in runtime anywhere from 1.9 to 335x faster!
Log conformation tensor method for visco-elastic fluids
A new solver option for visco-elastic fluids is available to our users, and is particularly effective for high Weissenberg numbers.
Active simulation control extensions
Active simulation control functionalities have been extended to include phantom objects, commonly used for continuous casting and additive manufacturing applications, as well as for cooling channels, used in casting and in many other thermal management applications.
Improved entrained air functionalities
For diffusers and similar industrial bubble flow applications, mass sources can now be used to introduce air into the water column. In addition, default values for the turbulent diffusion of entrained air and dissolved oxygen have been updated, and model accuracy for very low air concentrations has been improved.
What’s New – FLOW-3D 2022R1
The new 2022R1 versioning of FLOW-3D products reflects Flow Science’s adoption of a synchronized release naming convention for FLOW-3D, FLOW-3D CAST and FLOW-3D HYDRO. 2022R1 represents the transition to a unified code base for FLOW-3D products. This important evolution will allow users access to the latest developments as soon as they are ready, at a more frequent product release pace.
The 2022R1 release features an extension to the FAVOR™ method called the detailed cutcell representation, the introduction of simulation templates with themed solver defaults, moving droplet/bubble sources, a new axial pump model, extensions to Active Simulation Control capabilities, tabular properties that allow users to specify complex property dependencies based on two independent variables, and additional numerics features such as a VOF-to-particle development to improve mass conservation for fluid regions subject to breakup. Streamlined GUI improvements include redesigned physics dialogs, a new initial conditions widget, and redesigned output and geometry widgets for easier, faster and error-free simulation setup.
Detailed Cutcell Representation – An Extension to FAVOR™
The FAVOR™ method represents solid geometry using area and volume fractions on a regular, Cartesian grid. It enables FLOW-3D to efficiently simulate flow through and around complex geometry without resorting to unstructured body-fitted meshes. For all its considerable computational benefits, one challenge for the FAVOR™ method is that the calculation of wall shear stresses along solid surfaces can sometimes be noisy. An extension to FAVOR™, called detailed cutcell representation, greatly improves the calculation of wall shear stresses, resulting in significant improvements in the solution near solid surfaces.
Learn more about the advanced numerics as well as validations of the detailed cutcell representation.
Tabular Properties
Material properties such as viscosity and surface tension can be dependent on flow conditions such as temperature, density, strain rate, or user-defined scalar quantities representing things like a contaminant concentration. Fitting these properties to functional forms can require complex curve-fitting, especially when the properties are dependent on more than one independent variable. The new tabular properties feature in FLOW-3D allows users to define fluid properties in table form with up to two independent variables. For example, surface tension can be tabulated from experimental data to describe complex, non-linear dependencies on contaminant concentration and temperature, or viscosity can be tabulated from experimental data to represent a dependency on strain rate and temperature. Users can input a single variable or two variable dependency in the tabular properties dialog.
Viscosity is defined as a function of both solid content (density) and strain rate. In this example a dense fluid region slides down into a quiescent pool which at time zero is layered with a dense settled fluid region and clear water above.
Expanded Active Simulation Control
Active Simulation Control (ASC) is very useful for controlling simulations based on flow information at probes. In this release, ASC has been expanded to allow additional controls based on flow information from general history data, flux surfaces, and sampling volumes.
One of the advantages of flux surfaces and sampling volumes over point probes is that they can provide information averaged over a surface or a volume rather than point-based. In some situations, surface-based and volume-based information can be more representative of the behavior of interest in simulations.
With this new capability, users can:
- Terminate a simulation when the temperature in a control volume exceeds or falls below a critical value.
- Control the filling rate from a nozzle based on the turbulent energy in a sampling volume.
- Control the output frequency based the average velocity on flux planes.
- Terminate a simulation when fill fraction in a sampling volume reaches the value specified by the user.
In this example, a pump (dark grey rectangle) in a cryogenic tank feed pipe pulls liquid oxygen from a propellant tank at a constant flow rate. As the liquid oxygen drains, a mass/momentum source (grey bar at top) is triggered by Active Simulation Control when the pressure in the ullage drops below a specified value. Pressurization is turned off when the ullage pressure rises above a specified value.
VOF to Particles
The accuracy and robustness of the sharp-interface tracking VOF methods in FLOW-3D have been enhanced by combing them with fluid particles. The new particle species, called VOF particles, are used in place of the VOF function to track small fluid ligaments and droplets in the computational domain, achieving better conservation of fluid volume and momentum. Higher time steps size can also be expected in gravity-controlled processes. The VOF fluid is automatically converted to VOF particles at certain times and locations when certain conditions are met. The particle motion is then calculated using the Lagrangian particle model and the particles are converted back to the VOF representation upon reentering the fluid.
Axial Pump Model
FLOW-3D’s new axial pump model allows users to mimic the net effect of an axial pump in their simulations. There are two options with respect to the pump behavior. The first option is to prescribe either a volumetric flow rate or a flow velocity through the pump so that the fluid is moved at the specified rate. This option is appropriate when an operating flow rate is provided for the pump. The second option provides a more complete definition of the pump operation based on a pump performance curve. In this case, the user can define a linear approximation of the pump’s performance curve so that the flow rate through the pump will depend on the pressure drop across the pump. In this configuration, the typical behavior of a pump is represented, whereby the flow will slow down and eventually stall as a reverse dynamic head builds up and pushes back against the pump operation.
Droplet/Bubble Source Model
Since it was first developed, FLOW-3D has been used to model droplets being ejected from nozzles and other orifice shapes to simulate the resulting fluid shapes evolving under the actions of surface tension. However, there are occasions when simulating the shape of the droplet as it leaves a nozzle is unnecessary, as only the impact of the droplet on a substrate is of interest. Additionally, modeling the transport of a bubble in fluid may be of interest, but not the initiation of the bubble. The new droplet/bubble source model is helpful for cases like these.
The new droplet/bubble source model allows either spherical droplets or bubbles to be emitted at defined intervals from a point source. This source can be either stationary or its motion can be defined in a tabular fashion. The initial velocity of the droplet or bubble can also be defined in three dimensions. All physical models are compatible with this model so that typical applications such as porous media flow, evaporation/solidification, and surface tension can be simulated.
In this example, a droplet source moves in a circular pattern while ejecting droplets downward at a velocity of 10 m/s into a porous medium to create a ring-shaped design.
Simulation Templates
New simulation templates pre-load important parameters based on a given modeling framework, such as one fluid incompressible flow with a free surface or a 2 fluid compressible simulation. When a new simulation is created, a dialog is presented to the user with six templates to choose from that cover most commonly modeled cases in FLOW-3D. A ‘None’ option allows advanced users to start with a blank slate so that they can apply specialized numerical settings. Using templates is a convenient way to expedite the model setup process and helps users avoid making mistakes or forgetting to define parameters.
Additional Solver Features
Additional solver features include a Herschel-Bulkley model for non-Newtonian fluids and gas-to-void conversions to improve mass conservation for fluid regions subject to breakup, and extended mass-momentum source probe events, including support for multiple event actions and event options for volume fraction of entrained air and solute concentration.
GUI Improvements
Streamlined GUI improvements using our WSIWYN design approach include redesigned physics and initial condition dialogs, and re-designed output and geometry widgets for easier, faster and error-free simulation setup.
Initial Conditions Widget
The initial conditions widget improves the setup of initial fluid and gas regions, making it easier and faster. In the new design, global, region, and pointer objects are placed in separate tabs, allowing a much clearer view of the setup.
Output Widget
The redesigned output widget lets the user see exactly which outputs will be available in the simulation results file, clarifying restart and selected data outputs in one concise view.
Interactive Geometry Creation and Editing
Interactive geometry creation and editing is better than ever, and now includes:
- New interactive tool selection including rotate, move and resize
- Enter rotate, move, or resize mode by clicking the action and selecting the geometry to modify
- Clicking the up arrow icon or hitting the ESC key will return the user to a normal select mode
Geometry Widget
The Geometry Widget is now easier and faster to navigate using our WYSIWYN design approach that combines different property groups and places relevant items together.
Easier Access to Help
Access to relevant documentation, tutorials and help diagrams is now an easy click away within physics dialogs.
Streamlined Physics Dialogs
Many of the physics dialogs have been streamlined so that users can set up their simulations more quickly and reduce setup errors.
What’s New – FLOW-3D v12.0
FLOW-3D v12.0 marks an important milestone in the design and functionality of the graphical user interface (GUI), which simplifies model setup and improves user workflows. A state-of-the-art Immersed Boundary Method brings greater accuracy to FLOW-3D v12.0’s solution. Other featured developments include the Sludge Settling Model, the 2-Fluid 2-Temperature Model, and the Steady State Accelerator, which allows users to model their free surface flows even faster.
Physical & Numerical Models
Accurate prediction of forces and energy losses is crucial to the success of modeling many engineering problems involving flows around solid bodies. The release of FLOW-3D v12.0 features a new ghost-cell based Immersed Boundary Method (IBM) designed for such problems. IBM provides a more accurate solution near walls for internal and external flows, improving the calculation of drag and lift forces.
The two-fluid heat transfer model has been extended to separate energy transport equations for each fluid. Each fluid now has its own temperature variables, which improves the accuracy of the heat and mass transfer solutions near the interface. Heat transfer at the interface is now controlled by a user-defined heat transfer coefficient that can be a tabular function of time.
The new sludge settling model, a valuable addition for municipal applications, allows users to model the solid waste dynamics in water treatment tanks and clarifiers. Unlike the drift-flux model, where the settling velocity is a function of the droplet size of the dispersed phase, the settling velocity is a function of sludge concentration and can be input in both functional and tabular form.
As the name implies, the steady-state accelerator quickens the approach to a steady state solution. This is achieved by damping small-amplitude gravity and capillary surface waves, and is applicable only to free surface flows.
Void particles have been added to the bubble and phase change model. Void particles represent collapsed void regions, acting as small bubbles that interact with the fluid via drag and pressure forces. Their size changes in response to the surrounding fluid pressure, and their final location at the end of the simulation indicates a potential for air entrainment.
The sediment transport and erosion model has been overhauled to enhance its accuracy and stability. In particular, the mass conservation for sediment species has been greatly improved.
The fixed-pressure boundary condition now includes an ‘outflow’ option, where all flow quantities except for pressure and fluid fraction reflect the flow conditions upstream of that boundary. The outflow pressure boundary condition is a hybrid of a fixed-pressure and continuity boundary conditions.
Particle sources can now move during a simulation. Time-dependent translational and rotational velocities are defined in a tabular form. The motion of a particle source is added to the initial velocity of the particles emitted at the source.
In the gravity and non-inertial reference frame model, the location of the center of gravity as a function of time can be defined as a table in an external file. This feature is useful when modeling, for example, a rocket that is expending fuel and separating stages.
The simplest volume-based air entrainment model option has been replaced by the existing mass-based model. The mass-based model is more physics-based since, unlike volume, entrained air mass is conserved while its volume changes in response to the surrounding fluid pressure.
Tracers generated at flux surfaces can now diffuse due to molecular and turbulent diffusion processes, mimicking the behavior of real pollutants, for example.
Model Setup
The units system must now be fully defined, including temperature. Standard unit systems are provided. Additionally, the user can define units for mass, time and length from a selection of options, allowing for customized and convenient units. The user must also specify whether pressures are defined in gauge or absolute units. Default simulation units can be set in Preferences. The full definition of the units allows FLOW-3D to define default values for physical quantities as well as set universal constants, thus minimizing the amount of work required by the user.
Manning’s roughness in shallow water model
The Manning’s roughness coefficient has been implemented in the shallow water model for the evaluation of the shear stress at the terrain surface. It complements the existing roughness model based on the size of surface imperfections, and can be used in combination with it. As with the standard roughness, the Manning’s coefficient can be an attribute of a component or subcomponent, or can be imported from a terrain raster data set.
Mesh generation
Mesh setup for the vertical direction has been simplified by requiring only the definition of the bottom and top boundary coordinates.
Users can now apply rotational, translational and scaling transformations to components consisting of multiple subcomponents, simplifying the process of setting up complex geometry assemblies. For a General Moving Object (GMO) component, these transformations can be applied to the body-fitted coordinate system so that it is aligned with the component’s symmetry axes.
The ability to change the number of threads used by the solver during simulation has been added to the Runtime Options dialog, allowing the user to add threads as they become available, or reduce their number if resources are needed for another task.
Active Simulation Control has been extended to heat sources associated with geometry components. The release of heat can now be controlled by history probes.
Fluid temperature at mass and mass/momentum sources can now be defined as a function of time using tabular input.
Emissivity coefficients for radiative heat transfer to voids are now defined directly, instead of requiring the user to specify the product of emissivity and the Stefan-Boltzmann constant. The latter is now automatically set by the solver, based on the units system.
- Flow velocities can now be output to Selected data when using the constant velocity field solver option.
- Torque on geometry components due to wall adhesion is output to General History data as a separate quantity, in addition to the existing output of wall adhesion forces.
- Shear velocity and y+ are automatically output to Selected data along with turbulent energy and dissipation, when turbulence model output is requested.
- Several quantities have been added to the air entrainment model output. The volume flux of entrained air and of escaping air in every cell containing free surface is output to Restart and Selected data, providing the user with detailed information of where and when air is being entrained and detrained. The time- and space-integrated equivalents of those two quantities in the whole computational domain, as well as for each Sampling Volume, are output to the General History
- The final size of the solver’s output file, flsgrf, is reported at the end of the simulation.
- For two-fluid simulations, the existing output quantities fluid residence time and distance traveled by fluid are now computed separately for fluid #1 and #2 and for the mixture of the fluids.
- For mass particles, the total volume and mass of each species are computed and output to General history for the whole computational domain, Sampling Volumes and Flux Surfaces, complementing the current output for the particle species counts.
- The last local gas pressure has been added as an optional output quantity to help the user identify gas entrapment and to assist in designing the venting system in fuel tanks, for example. That quantity records the last void pressure in a cell before it is filled with fluid and is used in combination with the adiabatic bubble model.
In the gravity and non-inertial reference frame model, the location of the center of gravity as a function of time can be defined as a table in an external file. This feature is useful when modeling, for example, a rocket that is expending fuel and separating stages.
New user-customizable source routines have been added and can be accessed in the user’s development environment:
Source routine name | Description |
cav_prod_cal | Cavitation production and dissipation rates |
sldg_uset | Sludge settling velocity |
phchg_mass_flux | Mass flux due to evaporation and condensation |
flhtccl | Heat transfer coefficient between fluid #1 and #2 |
dsize_cal | Coalescence and breakup rates for the dynamic droplet size model in two-phase flows |
elstc_custom | Source terms in the stress equations for viscoelastic fluids |
Brand New User Interface
The FLOW-3D user interface has been completely redesigned, resulting in a modern, flat structure that dramatically streamlines the user’s workflow.
Setup dock widgets
All setup operations, including Physics, Fluids, Mesh, and FAVOR™, have been converted into dock widgets around the geometry window, allowing Model Setup to be condensed into a single tab. With this transition, the crowded collapsible trees from prior versions have been replaced with a much cleaner, more efficient menu presentation, providing users easy access to every parameter without ever leaving the Model Setup tab.
New Model Setup icons
With our new Model Setup design comes new icons, representing each step of the setup process.
New Physics icons
Our Physics icons are designed to be easily differentiated from one another at a glance, while providing clear visual representation of each model’s purpose and use.
RSS feed
The Simulation Manager tab has been revamped for FLOW-3D v12.0, starting with the new RSS Feed. Upon launching FLOW-3D, users are now greeted with the latest news, events, and blog posts from Flow Science.
Configurable simulation monitor
An important task when running simulations is monitoring them. In FLOW-3D v12.0, the Simulation Manager has increased plotting capabilities to help the user better monitor their simulations. The user can select from all available general history data variables to monitor via the simulation runtime graphs and can add multiple variables to each graph. General history data available at runtime now includes:
- Minimum/maximum fluid temperatures
- Temperatures at probe locations
- Flow rates at flux surface locations
- Simulation diagnostics (e.g., time step, stability limits)
Conforming mesh visualization
Users can now visualize conforming mesh blocks via the new FAVOR™ dock widget.
Large raster and STL data
Processing large geometry data can be painstaking, due to the amount of time it takes for the data to be processed. While processing large geometry data can still take a significant amount of time, FLOW-3D now loads these large data sets as background tasks, allowing the user to continue working in a fully responsive, uninterrupted interface while their data is being processed.