To explain the puzzling situation in the observed bulk flows on scales \sim 150 h ^ { -1 } Mpc ( H _ { 0 } = 100 h ^ { -1 } km sec ^ { -1 } Mpc ^ { -1 } ) , we consider the observational behavior of spherically symmetric inhomogeneous cosmological models , which consist of inner and outer homogeneous regions connected by a shell or an intermediate self-similar region .
It is assumed that the present matter density parameter in the inner region is smaller than that in the outer region , and the present Hubble parameter in the inner region is larger than that in the outer region .
Then galaxies in the inner void-like region can be seen to have a bulk motion relative to matter in the outer region , when we observe them at a point O deviated from the center C of the inner region .
Their velocity v _ { p } in the CD direction is equal to the difference of two Hubble parameters multiplied by the distance between C and O .
It is found also that the velocity v _ { d } corresponding to CMB dipole anisotropy observed at O is by a factor \approx 10 small compared with v _ { p } .
This behavior of v _ { d } and v _ { p } is consistent with the observed cosmic flow of cluster galaxies , when the radius of the inner region and the distance CD are about 200 h ^ { -1 } Mpc and 40 h ^ { -1 } Mpc , respectively , and when the gaps of density and Hubble parameters are \approx 0.5 and 18 \% , respectively .
Moreover , the [ m,z ] relation in these models is discussed in connection with SNIa data .