RheoCube .18 latest features
RheoCube .18 latest features
13 October 2021
The latest release notes from RheoCube highlight several new features for users. There are improvements for everything from basic user functionality to better modeling features such as surfactant physics, an experimental feature in microscale, and some touch ups in Data Visualization and Analysis. Let’s take a look at RheoCube Version 0.18.
Improvements to RheoCube overall target a better user experience with improved error messages and new tabs.
In Fig. 1, you can see that the left panel has been organized into Specification, Process, and Preview (where applicable). The Process tab allows you to control the processing of the object (previously handled within the Specification tab), and will display messages from the simulation engine.
Moving on, now we have simplified specifications for homogenous States by hiding the domains and the button to create additional domains in the specification form and pre-filling the volume fractions with the values from Formulation and disabling the inputs. (Check Fig. 2)
Improved Surfactant Physics
Surfactant physics have been largely improved. Strong fluid interfaces are nanoscale in width, which are often smaller than the size of SPH blobs (the basic volume element used in the mesoscale SPH model). We use the local mixing thermodynamics to infer the presence of sharp interfaces and feed this into the surfactant physics model. In RheoCube 0.18, we enhanced the interface detection in the cases where interfaces are strongly curved. For example, you can see this in colloidal droplets.
Who’s up for some experimentation? These next few features described are experimental. The behavior of these new features is expected to change as refinements are made during the next release cycle(s).
Monovalent salt (e.g. sodium chloride, NaCl) can now be included when creating a fluid by specifying that fluid’s dissolved monovalent salt concentration. The salt undergoes thermodynamic transport during the simulation. The presence of salt in the mesoscale simulation leads to a concentration-dependent screening of electrostatic interactions (higher salt concentration leads to weakening of electrostatic interactions). The relative permittivity also has to be added to the Fluid. Check Fig. 3 below.
Electrostatics-based interactions between particles
One common technique for stabilizing particulate suspensions is through electrostatic interactions. Particles with the appropriate surface chemistry develop surface charges in certain solvents. Since like particles develop like charges, particles are repelled from each other. When the repulsion is sufficiently strong to overcome the innate tendency for aggregation, the outcome is a stable suspension. In the movies below we can see 2 suspensions under shear. On the left, without electrostatics, we see that clusters are formed when particles come in contact. On the right, with electrostatics turned on, we see that no clusters are formed.
Interactions between particles carrying surface charges were developed based on Gouy-Chapman theory. The level of charge is controlled by a user-specified zeta potential, which can often be determined experimentally. The electrostatic interaction is screened by the presence of salt. The zeta potential (Fig 4.) for a fluid-particle pair can be defined in Composition under Fluid-Particle interactions and has units of volts. The electrostatics model is enabled by checking the Enable electrostatic interactions toggle in Experiment. It requires all Fluids in the experiment to have a Relative permittivity.
Random initialization procedure
The microscale simulation is now initialized in a random configuration, as opposed to the previous lattice configuration. The new initialization allows for a more efficient route to obtaining a properly equilibrated simulation.
Non-equilibrium shear simulations (Experimental feature)
Non-zero shear rates can now be specified in the experiment card for microscale simulations. This will trigger a sheared non-equilibrium molecular dynamics simulation, where the equilibrium “Production” stage of the simulation is replaced with a non-equilibrium “Shear” stage. Other settings such as run time are kept the same.
Data Visualization and Analysis
Two or more mesoscale experiments can now be merged if the latter is derived from the former using the ‘state from snapshot‘ feature. Merged experiments are seamlessly combined and can be treated as a singular experiment in all other widgets, except for the ‘versus parameter‘ tab of the Material Properties widget and the Oscillatory Shear Viscosity widget.
Microscale modeling clustering analysis
Micro data is now accepted by the clustering widget, giving the ability to cluster droplet or micelle structures and get information on size distributions, cluster shapes and spatial distribution.
Per-component isosurface creation
We’ve added the ability to quickly generate isosurfaces for any component in the simulation, as well as the ability to quickly hide fluid and/or particle blobs.
Volume fraction for color mixing
The color mixing of blobs in the visualization is now based on the volume fractions of the different components, instead of their mass fractions.
Fixer Uppers and Solved Issues
Data Visualization and Analysis sessions leading to 400 error: Opening a session might lead to a page with a 400 error. This can be solved by clearing the site data in browser settings or working in an incognito browser. If you need assistance with this please contact your Scientific Consultant.
Applying widget presets during calculation may cause issues: Applying a previously saved widget preset while a widget is performing a calculation may result in an error. To prevent this, only apply a preset when the widget is performing a calculation. Widgets that are stuck can be refreshed from the preset menu.
Resolved: For now, we’ve resolved an issue where the number of periods in the oscillatory shear analysis widget is not automatically updated. When a running oscillatory shear experiment is loaded in the oscillatory shear analysis widget, periods that are completed afterwards are not automatically updated. To get the correct number of periods, deselect and select the experiment.
Again, for users who can still use some help troubleshooting, please contact your scientific consultant.
Find out more
Log into your RheoCube account today to access our fully detailed release notes. Not a RheoCube user yet and curious about our software? Send us a message and we’ll be in touch shortly.