In Fall 2001 entered the production state a computing system dedicated to the Direct Numerical Simulation (DNS) of wall turbulence, in particolar turbulent plane channel flows and pipe flows. The system has been designed on top of a related computer code, written in the programming language CPL, developed by Prof. P.Luchini

The system  (codename: dilbert) is a sigle computing machine, designed for running in a very efficient way just our code, and is (as to now) formed by 8 computing nodes. Each of them is a commodity Dual Pentium III Personal Computer, with 2 733MHz CPUs (namely one dilbert and seven dogberts :-)

The nodes are connected each other with two commodity Fast Ethernet cards, without hubs or switch altoghether. On every node runs the operating system Debian/GNU Linux .  Parallel computing does not require message-passing libraries like MPI.

The nodes of the cluster are connected with a simple ring topology, which reflects how data are exchanged between nodes for parallel execution of simulations. In the diagram below the correspondence is shown between the cluster nodes and the slices into which the channel is partitioned, in the wall-normal direction.  Color represent the interface between slices, with the corresponding ethernet cable connecting the two neighbouring nodes.

The computer code solves the incompressible Navier-Stokes equations both in cartesian and cylindrical coordinates, with the highest efficiency. Together with the dilbert system, the DNS of turbulent wall flows at relatively high Reynolds numbers can be afforded easily, without the nedd of resorting to external, cost-uneffective supercomputers.

A synthetic description of the comuting system, the numerical method and a comparison of their performaces with those os some amongs the bleeding-edge researc DNS codes in the world is reported in this paper.