  We present in this technical note an open-source web framework for the
generation and visualization of parametric OpenFOAM simulations from surrogate
models. It consists of a JavaScript module (rom.js) and a web app (cfd.xyz) to
explore fluid dynamics problems efficiently and easily for a wide range of
parameters. rom.js is a JavaScript port of a set of open-source packages
(Eigen, Splinter, VTK/C++ and ITHACA-FV) to solve the online stage of
reduced-order models (ROM) generated by the ITHACA-FV tool. It can be executed
outside a web browser within a backend JavaScript runtime environment, or in a
given web solution. This methodology can also be extended to methods using
machine learning. The rom.js module was used in cfd.xyz, an open-source web
service to deliver a collection of interactive CFD cases in a parametric space.
The framework includes some tutorials, showing the whole process from the
generation of the surrogate model to the web browser. It also includes a
standalone web tool for visualizing users' ROMs by directly dragging and
dropping the output folder of the offline stage. Beyond the current proof of
technology, this enables a collaborative effort for the implementation of
OpenFOAM surrogate models in applications demanding real-time solutions such as
digital twins and other digital transformation technologies.
