Simulation of a stirred tank ultrasonic batch reactor containing immobilized enzymes is done. The objective is to predict the particle trajectories resulting from stirring and ultrasound. This information can be used to understand the phenomenon of mas transfer to and from catalyst particles. This information can be used to predict the performance of an ultrasonic reactor. A lab scale glass reactor is taken as example of simulation. The reactor can be agitated using a stirrer and a variable frequency variable power ultrasonic  transducer. Effect of stirring as well as ultrasound is modeled and model equations are solved using COMSOL multiphysics. In order to validate simulation results particle trajectories resulting from agitator and ultrasound are determined experimentally. For this purpose PIV (particle image velocimetry) is used. In PIV pictures of reactor (while its running) are taken using high speed camera (40000 frames/s). These images are evaluated using PIVlab. From evaluation of the recorded images it is not only possible to determine the flow pattern but also the magnitude of particle velocities. Measured velocities are compared with simulated velocities under identical conditions in order to validate model. It is seen that data from simulation and PIVLab are in agreement. This proves that the employed modeling approach is correct. Results of simulation show that ultrasound dispersion pattern in reactor is highly dependent on frequency; on the other hand change in ultrasonic power doesn't affect ultrasonic field. It is also observed that application of ultrasound greatly improves the hydrodynamics of heterogeneous reactor. This improvement in hydrodynamics can be translated into improvement of mass transfer rate resulting from ultrasound.