Mach wave Mach wave In fluid dynamics, a Mach wave is a pressure wave traveling with the speed of sound caused by a slight change of pressure added to a compressible flow. These weak waves can combine in supersonic flow to become a shock wave if sufficient Mach waves are present at any location. Such a shock wave is called a Mach stem or Mach front. Thus, it is possible to have shockless compression or expansion in a supersonic flow by having the production of Mach waves sufficiently spaced ("cf." isentropic compression in supersonic flows). A Mach wave is the weak limit
Mach (kernel) system would be implemented by starting with the existing BSD code, and re-implementing it bit by bit as inter-process communication-based (IPC-based) programs. Thus Mach would begin as a monolithic system similar to existing UNIX systems, and evolve more towards the microkernel concept over time. Mach started largely as an effort to produce a cleanly defined, UNIX-based, highly portable Accent. The result was a short list of generic concepts: Mach developed on Accent's IPC concepts, but made the system much more UNIX-like in nature, even able to run UNIX programs with little or no modification. To do this, Mach introduced the