Reduced-order computational-fluid-dynamics-based analysis of aviation heat exchangers

The goal envisioned for the Reduced-Order Computational Fluid Dynamics and Heat Transfer (ROM-CFDHT) procedure is obtaining fast turnaround in simulation time so that computational fluid dynamics can form a component of a system-level design tool. To accomplish this, a set of finite-element schemes is proposed, including the choice of the quadratic interpolation functions, the penalty approach, an intelligent error-control capability, a continuation method, a restart procedure that restores the integrity of the error-control scheme when the procedure encounters difficulties, and the consistent flux method. It is shown that for a natural convection problem simulation using fewer than 20 elements produces Nusselt number Nu results that agree with models using thousands of elements, with simulation time in seconds rather than hours. Forced convection over an asymmetrically laidout bank oftubes is simulated as another test of the proposed procedure. Three values of the Reynolds number, Re = 10,100,1000 are investigated using two grids with significantly different levels of resolution and quality. The local distributions of Nu show some differences between the grids, but the mean results are comparable. The coarse grid could not calculate the Re = 1000 case due to poor resolution and grid quality. A combination of grid resolution and choice of schemes enables successful simulation.