[Mohinder Suresh]

Hi@all,
i'm simulating an axial Turbine and I want to calculate the circumferential and radial Forces on the blades. therefore i created expressions (Rotation Axis: Z):

F_tan = sum(-Force X*cos(Theta)-Force Y*sin(Theta))@Blade
F_rad = sum(-Force X*sin(Theta)+Force Y*cos(Theta))@Blade
F_ax = sum(Force Z)@Blade

But when I calculate the Magnitude of this vektor

F_mag = sqrt(F_tan^2+F_rad^2+F_ax^2)

im getting a significantly different result as if I calculate it through

F_mag = sqrt(sum(Force X)@Blade^2+sum(Force Y)@Blade^2+sum(Force Z)@Blade^2)

What is the right solution ?!
PS: I checked the transformation and its definetly correct!

Many thanks in advance!
Mohinder

[Opaque]

I think your algebra is incorrect because it mixes summation, with squares and square roots. In this case order is VERY important.

My suggestion would be

F_tan = -Force X*cos(Theta)-Force Y*sin(Theta)
F_rad = -Force X*sin(Theta)+Force Y*cos(Theta)
F_ax = Force Z

Now, sum over the blade each component

Total F_tan = sum(F_tan)@Blade
...

Now, compute magnitude

[Mohinder Suresh]

Thank u very much for ur reply,
but this gives exact the same results!
Mohinder