Based on the cosmic dark matter fluid model, this paper proposes that the visible matter of the cosmic galaxy is formed by various turbulences of the dark matter fluid. This perturbation may be caused by a huge dark matter entity moving faster than the speed of light, which in turn forms Cherenkov radiation of gravitational waves. This paper estimates the size of this dark matter entity, pointing out that this disturbance will form two regions of high and low pressure in the dark matter fluid. The pressure gradient generated around the turbulence can be estimated using the Fujita formula for tropical cyclones. Computational analysis shows that when it reaches the outer periphery of the galaxy, the pressure gradient becomes small, and the effect of the Corio force is not obvious, so the rotation speed of the galaxy material is mainly affected by the speed of the dark matter fluid itself. This can be confirmed by the fact that the peripheral material rotation speed of all galaxies in the local group is basically the same. In addition, because the dark matter entity may have a certain length, just like a jet that produces a sonic boom, a low-pressure region and a high-pressure region will be generated at both ends of the length, which also means that the same dark matter entity may produce multiple galaxies, and there should be at least two galaxies in multiple galaxies with the same structure. This can be confirmed by some observations. Examples include the Milky Way and Andromeda Galaxy (M31), as well as the Hickson Compact Group.