[MBDyn-users] aerodynamic body element
pierangelo.masarati at polimi.it
Tue Mar 21 21:16:06 CET 2017
The local Mach number is computed according to the formula
Mach = V_tot * sqrt(cos(Gamma))
where V_tot is the norm of the local velocity
sqrt(V(1)*V(1)+V(2)*V(2)+V(3)*V(3)), and Gamma is the sweep angle,
defined as atan2(-V(3), |V(1)).
This should be in accordance with Harris et al., "Rotor High Speed
Performance, Theory vs. Test", J. of the Am. Hel. Soc., 1970, which is
not the perpendicular Mach number.
On 03/21/2017 08:30 PM, Edoardo Codispoti wrote:
> Hi Mbdyn community,
> I have a problem with the aerodynamic body element.
> I don't understand how the local mach number is defined.
> I wrote a simple problem to check the behavior.
> I defined an aerodynamic body attached to a node.
> The panel has a sweep angle of 45° with respect to the asymptotic speed.
> The asymptotic mach number is 0.294. So the perpendicular mach of the
> panel should be M_pan = M_inf * cos(45°) = 0.2079 ?
> As suggested in the input manual, the 4th column(standard output) of
> the .aer file is the local mach number of the aero element, the value
> printed is 0.2473.
> I misunderstood the manual?
> Thank you.
> MBDyn-users mailing list
> MBDyn-users at mbdyn.org
Dipartimento di Scienze e Tecnologie Aerospaziali
Politecnico di Milano
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