Definition of viscous and pressure forces, computation of force components in CFX Post?
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From theory, shear stress is a symmetric tensor T_xx T_xy T_xz T_yx T_yy T_yz T_zx T_zy T_zz If we have a face normal vector nx ny nz then, in CFX Post, T_xx T_xy T_xz nx T_xx*nx + T_xy*ny + T_xz*nz =: Wall Shear X T_yx T_yy T_yz * ny = T_yx*nx + T_yy*ny + T_yz*nz =: Wall Shear Y T_zx T_zy T_zz nz T_zx*nx + T_zy*ny + T_zz*nz =: Wall Shear Z Wall Shear = sqrt(Wall Shear X^2 + Wall Shear Y^2 + Wall Shear Z^2) force_X = areaInt_X(Pressure) + areaInt(Wall Shear X) Explanation: Pressure is a scalar value, that always exerts a force normal to a surface. To get the force component in a certain direction, the area normal has to be taken into account in the integral, areaInt_X(). Wall Shear is the vector of force density, units [force/area] with components in X,Y,Z directions. The force component is computed by a simple area integral over the vector component, areaInt(). |
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