Computational fluid dynamics (CFD) can be classified into three categories: direct numerical simulation (DNS), large eddy simulation (LES), and Reynolds-averaged Navier-Stokes (RANS) simulation.  DNS numerically solves the Navier–Stokes equations without any modeling. LES directly calculates the larger 3-D unsteady turbulent motion, but the smaller scale motion is represented by subgrid-scale models. RANS simulations calculate the time average of the Navier-Stokes equations, and employ turbulence models.
CFD can be utilized for various applications, as it can provide physical insight to complex flow and thermal phenomena. It can be also used to design products and predict performance. Our laboratory utilizes commercial RANS and LES codes (such as Ansys), and in-house LES codes. In the upper right figure, the vorticity contour on the downstream of the film cooling hole exit and the velocity contour in the film cooling hole of gas turbine blade are shown using commercial RANS simulation . In the lower left figure, the streamline and normalized velocity contour are plotted to see the cooling effect of turbulence generated by the ribs on the trailing edge of the gas turbine blade . In the lower right figure, we analyzed the flow and convective heat transfer around a heated cylinder known as a conjugate heat transfer problem by simultaneously solving the heat conduction in the solid and the convection in the fluid domain . Both of the figures below are results of LES analysis using in-house code.
 Comparison of a DNS, LES and RANS. (2006). Italian National Agency for New Energy Technologies, Energy and Sustainable Economic Development. Retrieved from https://www.researchgate.net/figure/Left-Comparison-of-a-DNS-a-LES-b-and-RANS-c-simulation-of-a-jet-flow-Italian_fig1_330765625
 Lee, S., Hwang, W., & Yee, K. (2018). Robust design optimization of a turbine blade film cooling hole affected by roughness and blockage. International Journal of Thermal Sciences, 133, 216.
 Baek, S., Lee, S., Hwang, W., & Park, J. (2019). Experimental and numerical investigation of the flow in a trailing edge ribbed internal cooling passage. Journal of Turbomachinery, 141(1), 011012.
 Lee, S., & Hwang, W. (2019). Development of an efficient immersed-boundary method with subgrid-scale models for conjugate heat transfer analysis using large eddy simulation. International Journal of Heat and Mass Transfer, 134, 198.