  The birth of the lattice Boltzmann method (LBM) fulfils a dream that simple
arithmetic calculations can simulate complex fluid flows without solving
complicated partial differential flow equations. Its power and potential of
resolving more and more challenging physical problems have been and are being
demonstrated in science and engineering covering a wide range of disciplines
such as physics, chemistry, biology, material science and image analysis. The
method is a highly simplified model for fluid flows using a few limited
fictitious particles that move one grid at a constant time interval and collide
each other at a grid point on uniform lattices, which are the two routine steps
for implementation of the method to simulate fluid flows. As such, a real
complex particle dynamics is approximated as a regular particle model using
three parameters of lattice size, particle speed and collision operator. A
fundamental question is "Are the two steps integral to the method or can the
three parameters be reduced to one for a minimal lattice Boltzmann method?".
Here, I show that the collision step can be removed and the standard LBM can be
reformulated into a simple macroscopic lattice Boltzmann method (MacLAB). This
model relies on macroscopic physical variables only and is completely defined
by one basic parameter of lattice size dx, bringing the LBM into a precise
"Lattice" Boltzmann method. The viscous effect on flows is naturally embedded
through the particle speed, making it an ideal automatic simulator for fluid
flows. The findings have been demonstrated and confirmed with numerical tests
including flows that are independent of and dependent on fluid viscosity, 2D
and 3D cavity flows, and an unsteady Taylor-Green vortex flow. This provides an
efficient and powerful model for resolving physical problems in various
disciplines of science and engineering.
