Verification of FDS results in high-speed flow

[MK]

Hi,

Has anyone used FDS to model wind speeds in the 100m/s range? The
verification and validation guides mention that the model involves
numerical algortihms intended for use in high-speed flow applications
and that the program has been validated for applications involving low-
speed flow within enclosures. But the mathematical model (technical
guide) states that the low speed flow assumption rules out using the
model for any scenarios involving flow speeds approaching the speed of
sound (approx. 300 m/s). Does this mean I cannot rely on FDS to yield
valid results involving wind speeds exceeding 2.5 m/s? Where is that
cut off for validity and applicability of the program?

I appreciate any input from you guys.
Thank you!

[dr_jfloyd]

FDS uses a low Mach number formulation. Low Mach number for FDS means
approximately M < 0.3 or about 100 m/s.

[MK]

Thank you very much for the prompt response dr_jfloyd!

[shostikk]

Can we say anything about the magnitude of error when dealing with
speeds like 100 m/s or 200 m/s?

S

[dr_jfloyd]

Isentropic compressibility gives density changes of:

rho_0/rho = (1+(gamma-1)/2 M^2)^(1/(gamma-1))

For air this gives density changes (could roughly consider as error)
of
M,%
0.1,0.5
0.2,2
0.3,5
0.4,8
0.5,13
0.6,19
0.7,26
0.8,35
0.9,36
1.0,58

[shostikk]

Nice!