Progress in hybrid RANS - LES modelling papers contributed to the 7th Symposium on Hybrid RANS - LES Methods, 17-19 September, 2018, Berlin, Germany - Hoarau, Yannick; Peng, Shia-Hui; Schwamborn, Dieter; Revell, Alistair; Mockett, Charles (Springer, 2020)