Large eddy simulations of pipe bend flows

Oscillatory phenomena in turbulent flows through 90° pipe bends are numerically investigated using large-eddy simulations. Single bends with curvature radii of one and three pipe diameters are considered and an in-plane double bend geometry with a curvature radius of one diameter. The simulations are carried out for Reynolds numbers in the range of 5000-27000. The spatial derivatives of the Navier-Stokes equations are discretized using a mixed central-upwind scheme with low numerical dissipation, and the solution is time advanced using an explicit Runge-Kutta method. The turbulent inflow data are obtained from simultaneously conducted simulations of fully developed straight pipe flows that contain all the space and time modes required for the bend simulations. The numerical method, which is of 2nd-order accuracy, is validated by comparing the simulation data to measurement results with respect to time-averaged velocities, Reynolds stress components, and power spectra of the velocities.