Abstract
Velocity gradients traditionally have been used to predict the performance of freestanding exhaust inlets along their centerline axes. The study investigated velocity gradients for inlets near an external boundary surface, as predicted by two computer modeling approaches: finite-element method (FEM) and (2) graphical approximation (GA). Comparison was made with experimental data obtained for high velocity/low volume exhaust inlets. Two situations were examined: (1) surface velocity gradients for an inlet at different orientations near a boundad surface and (2) centerline velocity gradients for inlets of different shape facing a boundary surface. The FEM model is limited two-dimensional (2-D) airflow characteristics and cannot predict 3-D effects, such as result from variations in inlet end shape. The GA mode overall, predicts velocity gradients which are closer than FEM to experimental data. Velocities predicted by the GA model may 1 significantly affected by using different empirical data (from studies of freestanding inlets) provided by different investigators. Characteristic associated with velocity gradients, however, are not sufficient to confirm preference of GA over FEM. Further studies should focus upon additional experimental data and the development of opportunities offered by FEM modeling to represent complex 2-D configuration (beyond GA capabilities) and the feasibility of 3-D FEM models.