Optimal simulation of gas flows

context

As part of the development and certification of its liquefied gas containment and transport systems, our client GTT must anticipate and control the behavior of its technology during tightness tests or in the event of a leak. The size of containment systems (generally in the order of tens of thousands of cubic meters) and their cost make it difficult to produce prototypes and full-scale experiments. It is therefore crucial to be able to numerically simulate the behavior of technology in different situations.

Large cargo ship sailing on a calm sea under a pink-hued sky at sunset with a blanket of low clouds on the horizon.

These simulations of fluid flow in very complex environments represent a real scientific challenge due to the presence of characteristic lengths of very different orders of magnitude: the size of the system is several tens of meters and the size of the flow ducts a few centimeters. 3D finite element simulation methods are therefore too time-consuming to compute.

approach

The coupling between the reduced model and the 3D solver makes it possible to simulate flows in a complete system with a controlled level of precision while controlling the calculation time. This method combines fast local resolution and regular adjustments made by a finer 3D solver, in order to ensure the reliability of the model over time.

How the coupling works

The reduced model simulates the continuous flow in the complete system by locally solving elementary patterns called VER (Elementary Reference Volumes). At regular intervals and on certain relevant VERs, a 3D solver — more accurate but much more expensive in terms of calculation time — is launched. The 3D results make it possible to monitor the quality of the predictions of the reduced model and to adjust its parameters for the next time step.

An integration challenge between models

Setting up the coupling also represents a software challenge: the reduced model and the 3D solver are not written in the same languages or designed to interact natively. It is crucial to ensure smooth and effective communication between the two in order not to degrade the overall calculation time.

Validation and quality control

The quality of the coupling was evaluated using several test cases provided by the customer. For each one, a complete 3D simulation is used as a reference. The results of the coupling (reduced model + 3D solver) are then compared to this reference in order to validate the performance, robustness and precision of the method.

optimization

Cost function

Build a cost function measuring the differences (flow, concentration, etc.) between the simulations of the reduced model and the reference simulations, in order to assess the quality of the coupling.

Calculation time

Estimate the computation time associated with each coupling strategy to find the best compromise between precision and performance.

Optimization levers

Identify the influential parameters: frequency of calls to the 3D solver, number of WORs requested, spatial location... and understand their impact on cost and precision.

Adjusting the parameters

Optimize these parameters to obtain the best possible precision while respecting the strict constraints of calculation time.

Optimal simulation of gas flows

Physical simulation and optimization algorithms at the service of engineering.

Reduced model and precision control Predictions

The PGAz reduced model makes it possible to simulate flows in a short time, with a constant need for precision control and adjustment to maintain the reliability of the predictions. Are you interested in our solution?