The forces data can be accessed trough the menu options View results>Forces on Boundaries and View results>Forces Graph or by using the corresponding icons of the Tdyn toolbar (see Figure 65).
Figure 65. Forces on boundaries and Forces graph icons. |
The resulting data can be compared with the resistance values of the model, using the standard decomposition given by:
CT = Cv + Cw = (1+k)·Cf + Cw
Being CT the total resistance coeficient, Cv = 0.5·VFx/(r·S·ν2) the viscous drag coefficient and Cw = 0.5·PFx/(r·S· ν2) the wave resistance coefficient. Where r is the fluid density, S is the wetted area and ν the velocity of the analysis.
We can obtain the viscous drag coefficient by,
Cv = (1+k)*0.075/(log10(Re)-2)2
Experimentally a value of k» 0.09 is obtained, and since Re = ρ·ν·L/μ = 1.45·107,
we can es
The experimental data of the wave drag Cw» 1.5·10-3, can be compared1 with the pressure force obtained in the simulation Cw = 1.40·10-3.
As can be seen both values are very similar to the experimental ones.
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