Inside the Safety Injection Tanks (SIT) of APR1400s, fluidic devices (FD) are installed to passively control the mass flow discharged from the SIT, thus, eliminating the need for low pressure safety injection pumps. As passive safety mechanisms are emphasized more and more nowadays, it has become more important to understand the flow structure and the loss mechanism within the fluidic device. However, current computational fluid dynamics (CFD) calculations have had limited success in predicting the fluid flow accurately. This study proposes to find a more exact result using CFD and more realistic modeling. Preliminary CFD results match quite well with the experiment data. Comprehensive CFD results also match well with the experiment results and show interesting patterns which was analyzed using Fast Fourier Transform(FFT). Calculation is still in progress but current status shows promising results