Myoungkyu Lee

Petascale direct numerical simulation of turbulent channel flow on up to 786K cores

We present results of performance optimization for direct numerical simulation (DNS) of wall bounded turbulent flow (channel flow). DNS is a technique in which the fluid flow equations are solved without subgrid modeling. Of particular interest are high Reynolds number (Re) turbulent flows over walls, because of their importance in technological applications. Simulating high Re turbulence is a challenging computational problem, due to the high spatial and temporal resolution requirements.

A Web services accessible database of turbulent channel flow and its use for testing a new integral wall model for LES

abstract The output from a direct numerical simulation (DNS) of turbulent channel flow at Reτ ≈ 1000 is used to construct a publicly and Web services accessible, spatio-temporal database for this flow. The simulated channel has a size of 8πh × 2h × 3πh, where h is the channel half-height. Data are stored at 2048 × 512 × 1536 spatial grid points for a total of 4000 time samples every 5 time steps of the DNS. These cover an entire channel flow-through time, i.e. the time it takes to traverse the entire channel length 8πh at the mean velocity of the bulk flow. Users can access the database through an interface that is based on the Web services model and perform numerical experiments on the slightly over 100 terabytes (TB) DNS data on their remote platforms, such as laptops or local desktops. Additional technical details about the pressure calculation, database interpolation, and differentiation tools are provided in several appendices. As a sample application of the channel flow database, we use it to conduct an a-priori test of a recently introduced integral wall model for large eddy simulation of wall-bounded turbulent flow. The results are compared with those of the equilibrium wall model, showing the strengths of the integral wall model as compared to the equilibrium model.

Experiences from Leadership Computing in Simulations of Turbulent Fluid Flows

We performed a direct numerical simulation (DNS) of high Reynolds number turbulent channel flow to expand our understanding of wall-bounded turbulence. The resolution requirements inherent to realistic turbulent flows necessitate leadership computing systems. Using Mira at Argonne Leadership Computing Facility, Argonne National Laboratory, we were able to achieve DNS at Re_tau = 5,200, and generated approximately 140 Tbytes of data. To use Mira efficiently, we developed a new DNS code, PoongBack, including a new parallel 3D FFT kernel. The new code shows excellent scalability up to 786,432 cores. Here, we summarize our code development and production simulation efforts, including parallel I/O.

Extreme-scale motions in turbulent plane Couette flows

We study the size of large-scale motions in turbulent plane Couette flows at moderate Reynolds number up to

Direct numerical simulation of turbulent channel flow up to Reτ ≈ 5200

Re_\tau

Direct numerical simulation of turbulent channel flow up to

= 500. Direct numerical simulation domains were as large as

Thermal Analysis of Gold Nanorods Heated with Femtosecond Laser Pulses.

100\pi\delta\times2\delta\times5\pi\delta

Correlation of pressure fluctuations in turbulent wall layers

, where

Spectral analysis of the budget equation in turbulent channel flows at high Re.

\delta

Experiences Porting Scientific Applications to the Intel (KNL) Xeon Phi Platform

is half the distance between the walls. The results indicate that there are structures with streamwise extent, as measured by the wavelength, as long as 78