Optimization of a Wind Tunnel Settling Chamber: Experimental and Computational Analysis

Abstract

Pressure loss reduction by the use of different arrangement of manipulators was studied for an existing wind tunnel. The analysis is concentrated on the settling chamber and the wide angle diffuser which is where the four screens and the honeycomb are located. The analysis is carried out in three phases. The first is to evaluate the current state of the wind tunnel through experimental measurements. The second concerns the numerical study of the zone of interest. The third phase analyzes the optimization of the manipulator arrangement in order to improve the efficiency of the wind tunnel. The simulations are implemented in Ansys CFX with the turbulence model k-$\omega$ SST. A grid with 3 million elements is selected. At the inlet the Dirichlet boundary condition and at the outlet the Neumann boundary condition were imposed. The behavior of the flow through the manipulators is simulated with the porous momentum loss model which is implemented in the software. The measurements show differences in the flow quality of the wind tunnel, which were not predicted by the simulations. Therefore, the simulation is taken as a reference for the optimization phase. The optimization involves ten proposed designs, where the screens and the honeycomb were replaced. It is found that the best compromise between preserved turbulence intensity and reduced pressure losses is observed in case 6 where one of the screens is left out. Therefore, the improvement of the quality of the flow by an additional screen is possible. This configuration reduces the turbulence intensity by 2.81 % and the pressure losses by 13 % in the simulated domain. This corresponds to a decrease of 4.5 % of the pressure loss in the complete wind tunnel.