variavel0=<b>Márcio Staschower</b> - marcio_sta@yahoo.com Escola Politécnica da Universidade de São Paulo
<b>Marcelo Mendes Vieira</b> - mmendes@usp.br xEscola Politécnica da Universidade de São Paulo
<b>José Roberto Simões-Moreira</b> - jrsimoes@usp.br Escola Politécnica da Universidade de São Paulo
<b>Abstract.</b> The  goal  of  this work  is  to  present  an  educational  digital moving  film  for  studying  compressible  flow  of  gases  inside  nozzles. The flow visualization has been obtained from a "Schlieren" system setup. A two-dimensional, convergent-divergent nozzle  was used in the tests working with nitrogen gas discharging into local atmosphere. All of the tests were carried out by varying the  reservoir pressure up to 1000 kPa, which allowed us to observe normal shock waves (inside the nozzle) and oblique shock waves  (outside the nozzle). The images were registered by a CCD camera and then digitalized and stored in a computer. Techniques of  image  processing  were  applied  to  improve  the  quality  of  the  shock  waves,  expansion  waves  and  pressure  gradients.  The  experimental results were compared with the classical one-dimensional, isentropic flow theory in nozzles.
<b>Keywords.</b> compressible flow, schlieren, shock waves, nozzle.