A direct numerical simulation is performed to examine the initial relaxatio
n of spatially,evolving turbulent channel flow subjected to uniform wall bl
owing and suction. Just beyond the entrance section, a uniform blowing is a
pplied at the lower wall and a uniform suction at the upper. The relaxation
processes of the mean velocity, turbulence intensities, Reynolds shear str
esses, and vorticity fluctuations after the sudden wall blowing and suction
are scrutinized. The effect of wall blowing and suction on the location an
d strength of the streamwise vortices is significant. The relaxation associ
ated with suction is much slower than that with blowing. The initial relaxa
tion is evaluated in terms of the turbulent kinetic energy transport. Blowi
ng enhances the intercomponent energy transfer between the Reynolds stresse
s, whereas suction suppresses it.