 wake axial compressor wake axial compressor tendenc assum wake non-uniform total head profil fed axial compressor constant static pressur prevail entri variat total head appear variat veloc variat veloc variat incid earli stage blade row rise excit blade vibrat assumpt implicit instanc refer 1 2 common assumpt peopl work field compressor fed duct parallel wall reason length ahead assumpt appear justifi duct air flow test outlet discharg instanc atmospher compressor distribut assum fact survei duct repres fashion object note fact distribut occur compressor expect constant veloc compressor attend static pressur distribut match total head variat ahead intak cours attend curv flow support static pressur gradient 