A Comparison of Turbulence Generated by 3DS Sparse Grids with Different Blockage Ratios and Different Co-frame Arrangements

A new type of grid turbulence generator, the 3D sparse (3DS), is a co-planar arrangement co-frames each containing different length scale elements [Malik, N. A. US Patent No. 9,599,269 B2 (2017)] and possessing much bigger parameter space than flat 2D fractal square (2DF). Using DNS we compare characteristics (mean flow, intensity, energy spectrum) generated by types 3DS grids. The peak intensities can exceed peaks 2DF 80\%; observe that with blockage ratio 24\% produces similar to 32\% implying lower input for same turbulence.