{"id":161677,"date":"2023-01-25T07:16:40","date_gmt":"2023-01-25T07:16:40","guid":{"rendered":"\/knowledge\/forums\/topic\/how-to-estimate-the-first-cell-height-y-for-the-mesh-from-the-desired-value-of-y-plus-y\/"},"modified":"2023-07-31T12:35:42","modified_gmt":"2023-07-31T12:35:42","slug":"how-to-estimate-the-first-cell-height-y-for-the-mesh-from-the-desired-value-of-y-plus-y","status":"publish","type":"topic","link":"https:\/\/innovationspace.ansys.com\/knowledge\/forums\/topic\/how-to-estimate-the-first-cell-height-y-for-the-mesh-from-the-desired-value-of-y-plus-y\/","title":{"rendered":"How to estimate the first cell height (y) for the mesh from the desired value of y plus (y+)?"},"content":{"rendered":"

Known Parameters: density (rho), kinetic viscosity (mu), free stream velocity (U_inf), characteristic length scale (L), and the desired y plus (y+). Find: the first cell height (y). The Reynolds number is Re = rho * U_inf * L \/ mu. The skin friction coefficient C_f can be calculated from Re. For example, for flow on a plate, we have the following formula: C_f = 0.058*Re^(-0.2). For internal flows, we have: C_f = 0.079*Re^(-0.25), in which Re is based on pipe diameter. Use C_f to predict the wall shear stress tao_w: tao_w = 0.5*C_f * rho*U_inf^2. From tao_w compute the velocity U_tao: U_tao = sqrt(tao_w\/rho) . Then, the first cell height can be calculated as: y = y+ * mu \/ (U_tao * rho).<\/p>\n","protected":false},"template":"","class_list":["post-161677","topic","type-topic","status-publish","hentry","topic-tag-4424","topic-tag-fluent","topic-tag-fluid-dynamics","topic-tag-general","topic-tag-general-fluent","topic-tag-turbulence"],"aioseo_notices":[],"aioseo_head":"\n\t\t\n\t\n\t\n\t\n\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t