Coarse-Grid Computational Fluid Dynamic (CG-CFD) Error Prediction using Machine Learning

Abstract: Despite the progress in high performance computing, Computational Fluid Dynamics (CFD) simulations are still computationally expensive for many practical engineering applications such as simulating large computational domains and highly turbulent flows. One of the major reasons of the high expense of CFD is the need for a fine grid to resolve phenomena at the relevant scale, and obtain a grid-independent solution. The fine grid requirements often drive the computational time step size down, which makes long transient problems prohibitively expensive. In the research presented, the feasibility of a Coarse Grid CFD (CG-CFD) approach is investigated by utilizing Machine Learning (ML) algorithms. Relying on coarse grids increases the discretization error. Hence, a method is suggested to produce a surrogate model that predicts the CG-CFD local errors to correct the variables of interest. Given high-fidelity data, a surrogate model is trained to predict the CG-CFD local errors as a function of the coarse grid local features. ML regression algorithms are utilized to construct a surrogate model that relates the local error and the coarse grid features. This method is applied to a three-dimensional flow in a lid driven cubic cavity domain. The performance of the method was assessed by training the surrogate model on the flow full field spatial data and tested on new data (from flows of different Reynolds number and/or computed by different grid sizes). The proposed method maximizes the benefit of the available data and shows potential for a good predictive capability.