Thisstudypresentsthenumericalresultsforthethree-dimensionalnaturalgas-airmixinginarectangularsubsonicchannelunderthestandarddatumstate.ThelowerandupperdecompositionmethodwasemployedtoobtainthesolutionsofthefullNavier-Stokesequationscapableofdescribingcompressiblefluidmixing.Gridwasgeneratedbytheareaorthogonaltechnique.Theresultsindicatethatthree-dimensionalmixingbetweenNaturalGas(NG)andairhasmorecomplicatedcompressiblewavesaroundtheinjectionnozzle.Thepresenceofinjectionwithlargespeedcansuppresstheboundaryseparationhappenedoccurringatthetopwallduetothechannelexpansion,butmakesthenear-wakeflowmorecomplicated.Themixingregioncanbewidenedbyincreasingtheinjectionspeed.TherecurrenceofthevortexstructureandthecoherentstructurecanbefoundfromthefullNavier-Stokessimulation.ItcanbeconcludedthattheincreaseintheinjectionvelocitycanimprovetheeffectivenessofmixingofNGandairinthenearwakeoftheinjectors.
