Example of free surface captured at each time step for a submarine at the water surface

ReFRESCO successfully coupled to ParaView Catalyst for in-situ analysis

When running complex parallel calculations on thousands of processors, the amount of data generated quickly becomes a bottleneck. To tackle this problem, ReFRESCO has been coupled to ParaView Catalyst.

ReFRESCO is the maritime CFD code used by MARIN to simulate all sorts of maritime problems, from ship resistance and propulsion, propeller performance, wave-, current- and wind loads to fluid structure interaction problems and detailed studies of turbulent flows. However, I/O time and limited capacity for the several terabytes of data generated when deploying ReFRESCO can seriously limit the work of the CFD practitioners.

Menno Deij–van Rijswijk

22 report

To avoid this issue, ReFRESCO has been coupled to ParaView Catalyst, which is an existing open source solution for in-situ analysis that performs analysis of the data while the simulation is running. This has several major advantages: first of all, no time is lost in writing to and reading from storage. Secondly, the storage needed for the analysis results is usually much smaller than that required for storing the complete state of the simulation. For example, storing the computational grid and data of a ship at speed for the analysis of its wave pattern can easily take a few gigabytes at each time step. But analysis of the wave pattern and storing that result takes only a few

megabytes at each time step! Furthermore, the users can quickly see the results visually, leading to a better understanding of the physics being simulated, and time saved when performing exploratory calculations for example.

To create the coupling between ReFRESCO and ParaView Catalyst, ReFRESCO was extended with an adapter that takes the ReFRESCO data, and submits it to Catalyst in the Visualization Toolkit (VTK) data format. The development of the adapter required a careful approach, where all the details of both data models needed to fall into place for it to work. Using the open source ParaView Catalyst enabled the developers to quickly get up to speed with the VTK data model and develop the adapter between the two codes.

Extensive testing shows that the performance of the ReFRESCO code is not affected: the analysis can be performed without a significant slowdown with moderate memory overhead. Initial reactions of the first users were very positive. Comments included: “it is very easy to use” and “this is a game changer!”

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