Hi everyone,

In Star-CD 3.26 Methodology on page 2-25 under LES Models section it is written "The current implementation in STAR-CD is valid for density-varying, non-isothermal, low-speed flows (free stream Mach number less or equal 0.6)".

In case of simulating diesel spray, if a free stream is injected fuel, then it means that LES model in Star-CD is limited to low injection pressures. Because if we calculate Mach number, to get 0.6, the injection velocity must be lower than that in contemporary Common-Rail Injection Systems. If a free stream is ambient gas, then this LES model is perfectly applicable to this kind of problems.

Any help will be really appreciated

I think you're right: LES is applicable only on low speed flows and so you can't use it to study the diesel injection problem of a common rail system, where you get injection velocity with Mach > 0.6.
Bye Usker,
Andrea