5E-5 Numerical Simulation and Schlieren Visualization of the Ultrasonic Field Generated by a Piston Transducer in Gas

Numerically simulated ultrasonic density and pressure fields are compared with the schlieren pictures of the same field. The validation of the schlieren visualization is presented. From the experiment in which the gas jets through the nozzle against the piston surface, it can be concluded that in the case without ultrasound application, the gas flow leaving the nozzle does not significantly diverge and forms a boundary layer along the piston surface. In the presence of an ultrasonic field, the gas flow pattern is changed in a very similar way to the simulated ultrasonic pressure maximum gradient distribution. The results are used to explain the interaction of the gas flow with the ultrasonic field generated by the piston. Knowledge of these density distributions is required for the description of more complex processes, which take place if an electrical discharge is formed between the nozzle and the ultrasonic transducer. Such combined electrical and aerodynamic phenomena are presented in environmental applications such as production of ozone, VOC decomposition and de-NO_x processes enhancement.