Ultrasound is frequently applied in crystallization to enhance nucleation and achieve crystal sizes within a narrow range. In this work, a mathematical model is developed, which couples the acoustic effect of ultrasound on the antisolvent crystallization of aspirin with the flow hydrodynamics and associated micromixing. In the first step, a qualitatively validated three-dimensional (3D) acoustic simulation of the crystallizer is used to understand the acoustic field in the reactor. Following this, an assessment of various flow and micromixing models is carried out using a 3D computational fluid dynamics (CFD) model, which is compared to a previously validated one-dimensional (1D) model. The identified models successfully capture the acoustic field and predict the crystal size and the crystals' coefficient of variation in experimental studies. The proposed model offers a practical platform that can be applied to experiments for improving the design of continuous crystallizers, as the model has the ability to predict the crystal production at larger scales to optimize the antisolvent crystallization of aspirin.