A data-driven wall-shear stress model for LES using gradient boosted decision trees

With the recent advances in machine learning, data-driven strategies could augment wall modeling in large eddy simulation (LES). In this work, a wall model based on gradient boosted decision trees is presented. The model is trained to learn the boundary layer of a turbulent channel flow so that it can be used to make predictions for significantly different flows where the equilibrium assumptions are valid. The methodology of building the model is presented in detail. The experiment conducted to choose the data for training is described. The trained model is tested a posteriori on a turbulent channel flow and the flow over a wall-mounted hump. The results from the tests are compared with that of an algebraic equilibrium wall model, and the performance is evaluated. The results show that the model has succeeded in learning the boundary layer, proving the effectiveness of our methodology of data-driven model development, which is extendable to complex flows.This work was funded as part of the European Project HiFi-TURB which has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 814837. Sarath Radhakrishnan acknowledges the financial support by the Ministerio de Ciencia y Innovación y Universidades, for the grant, Ayudas para contratos predoctorales para la formación de doctores (Ref: BES-2017-081982). Oriol Lehmkuhl has been partially supported by a Ramon y Cajal postdoctoral contract (Ref: RYC2018-025949- I). We also acknowledge the Barcelona Supercomputing Center for awarding us access to the MareNostrum IV machine based in Barcelona, Spain.Peer ReviewedPostprint (author's final draft