  We analyze the Millennium run semi-analytic galaxy catalog to explore
quantitatively the gravitational pancaking effect on the orientation of galaxy
velocity field. We first calculate the probability density distribution of the
cosine of the angle between the velocity of a field galaxy and the direction
normal to a local pancake plane which is determined using two nearest neighbor
field galaxies. A clear signal of alignment is detected for the case that the
pancake scale is in the range of $5-8h^{-1}$ Mpc. The tendency of the
velocity-pancake alignment is found to still exist when the pancakes are
determined using three neighbor galaxies, indicating that it has a spatial
coherence. The degree of the velocity-pancake alignment is shown to increase
with the velocity magnitude and the local density, while it decreases with the
separation distance from the galaxy to the pancake and disappears when the
pancake has a filamentary shape. A final conclusion is that our work may
provide another clue to understanding the large-scale structure in the
universe.
