Numerical simulation of the solution dynamics (natural and forced convection) above the surface of growing aqueous-soluble KDP crystals is carried out. A flow of supersaturated solution falling on the crystal surface through the multi-nozzle feeder is considered. An effective method based on time-dependent Navier-Stokes and energy equations in Boussinesq approximation has been developed for numerical investigation. Parametrical calculations of different regimes of hydrodynamics and mass transfer in a crystallization chamber are performed. Some important quantitative characteristics for high-rate growth technology development are obtained.