Lattice-Boltzmann Method (LBM)
The Lattice-Boltzmann method (LBM) is a pseudo-statistical technique for simulating fluids. It mimics the Navier-Stokes equation up to second order accuracy and provides good results for many fluid dynamical situations.
The group uses a Beowulf cluster of PCs with eight 1Ghz Intel PIII CPUs to perform simulations. Parallelisation of the code is achieved using the MPI standard and the LAM-MPI implementation.
Research by Mark Neal using LBM has simulated the air flow travelling from the mouth of a brass player into brass instrument mouthpiece. A number of static models of the lips where used for these simulations, with the different lip shapes based on measurements taken from real players lips at different stages of the oscillation cycle.
The upper two animations show the formation and breakdown of a jet passing between the lips and into the mouthpiece for two different lip profiles created when there is the same steady mouth overpressure. The colours indicate the strength of the vorticity in the flow, red areas having high vorticity and blue/green areas having low vorticity.
The bottom animation shows the results of a two-dimensional simulation using the LBM to study the development of turbulence in oscillatory channel flow. The animation shows the velocity of the fluid in the stream-wise (z-axis) and span-wise (x-y plane) directions. The velocity magnitude is also illustrated in the contour colours.
