  A parametric, hybrid reduced order model approach based on the Proper
Orthogonal Decomposition with both Galerkin projection and interpolation based
on Radial Basis Functions method is presented. This method is tested against a
case of turbulent non-isothermal mixing in a T-junction pipe, a common ow
arrangement found in nuclear reactor cooling systems. The reduced order model
is derived from the 3D unsteady, incompressible Navier-Stokes equations weakly
coupled with the energy equation. For high Reynolds numbers, the eddy viscosity
and eddy diffusivity are incorporated into the reduced order model with a
Proper Orthogonal Decomposition (nested and standard) with Interpolation
(PODI), where the interpolation is performed using Radial Basis Functions. The
reduced order solver, obtained using a k-{\omega} SST URANS full order model,
is tested against the full order solver in a 3D T-junction pipe with parametric
velocity inlet boundary conditions.
