Experimental study of flow straightening and turbulence reduction characteristics for porosity honeycomb

The honeycomb is an important device which is installed in wind tunnel settling chamber to improve the flow uniformity and decrease the flow angle as well as the turbulence intensity in the wind tunnel test section. For a regular honeycomb, in order to improve the flow straightening and turbulence reduction characteristics, a large length-diameter ratio must be used in the design of the honeycomb which results in the increase of total pressure loss of the honeycomb. A new type of honeycomb with a group of small holes on the wall of honeycomb cells is designed. This type of porosity honeycomb can achieve the exchange of the vortices and pressure between different cells to significantly improve the flow quality downstream the honeycomb. In the solid wall test section of the 0.55m×0.40m low noise aeronautic acoustic wind tunnel, the 2D hot wire is used to measure the turbulence intensity and velocity distribution downstream the porosity honeycomb and the regular one respectively with different flow velocities. The experimental results indicate that the honeycomb with 50% transverse porosity can reduce the turbulence intensity by 13.8% compared against the regular one. The velocity distribution downstream the honeycomb becomes smoother and the flow angle is also reduced. The design of the flow straightening and turbulence reduction system for the wind tunnel with the optimized porosity honeycomb can reduce the number of screens or the constriction ratio of the wind tunnel, and therefore, reduce the power consumption and the construction budget of wind tunnels.