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The mechanism of transition from laminar state to turbulent state inKeplerian disks is still unknown. The most popular version today is generationof turbulence due to magnetorotational instability (MRI). Howevermagnetohydrodynamic simulations give the value of Shakura-Sunyaev parametermore then an order of magnitude smaller rather than that found fromobservations. One way to solve this problem is the existence of an alternativeor additional mechanism for generating turbulence. It can be the bypassmechanism, which is responsible for transition to turbulence in Couette andPoiseuille flows. This mechanism is based on the transient growth of linearperturbations in the flow with the subsequent transition to the nonlinearstage. In order to clarify the role of this mechanism in astrophysical disksfirst of all it is necessary to calculate the maximal possible growth factor oflinear perturbations in the flow. In this paper the results of suchcalculations are presented for perturbations on different scales compared withthe disk thickness. Qualitative description of mechanisms responsible for thegrowth will also be presented. It was found that the most rapidly growing shearharmonics have azimuthal wavelength of the order of the disk thickness. Inaddition, their initial form is always similar to the vortex perturbations withthe same potential vorticity. It was shown that the vortices with azimuthalwavelength more than an order of magnitude in excess of the disc thickness, arestill able to grow by dozens of times.

Transient dynamics of large scale vortices in Keplerian disk