Strange density variations at cascade inlet.
 

Hi everybody! Actually i'm using Numeca solver for my thesis about compressor cascade. Basically i am running 2D simulations on different profile. The bi-dimensional mesh (70000 grid points )is extracted as a slice from the 3D mesh at midspan. I noticed, especially at high mach number some strange behavior at the inlet boundary. If i plot the gradient of density (schlieren image) i noticed some huge density variations at the inlet, near the boundary of inlet block where the periodicity conditions are imposed. Seems that these variations are not caused by shocks. I also tried different meshes, different inlet boundaries (different distances) but nothing seems changed. Any ideads? Thank you so much for the help!
Federico

hi,
These spots come from periodic boundaries that mimic the impact of adjacent blades.
As seen in the attached pictures shock waves exists at both TE and LE of the airfoil the effects of wich extends to periodic boundaries. in fact what you see at the inlet of the airfoil, is the impacts of shock waves that pass though the periodic patches next to inlet boundary.