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Results: Potential loads |
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Results: Potential loads |
These quantities are reported on the potential loads (direct) and potential loads (indirect) sheets of the results tables. All potential loads are reported in body coordinates $\Bxyz$.
The potential load is one of the contributions to the second-order load on a body. It is the load arising from the second-order potential, $\phi\so$. When added to the quadratic load, it gives the full QTF. OrcaWave evaluates potential loads if the solve type is full QTF.
Analogous to load RAOs at first order, the potential load can be evaluated by two different methods known as direct and indirect.
| Note: | The two forms are mathematically equivalent; they differ only because the integral equations have been solved using a discrete mesh (at both first order and second order). The difference between them can be a useful metric for the level of the discretisation errors in your results. Discretisation errors can be reduced by refining the body mesh and refining the representation of the free surface in the QTF data. |
The potential load is obtained from direct integration of the pressure due to the second-order potential \begin{equation} \vec{F}^{\pm}_{p,ij} = -\textrm{i}(\omega_i \pm \omega_j)\rho \int_{\SB} \left(\phi_I^{\pm} + \phi_S^{\pm}\right)\vec{n}_{\textrm{vel}} \ud S \end{equation}
The indirect potential load is a second-order analogue of the Haskind load RAO. It is equivalent to the direct load, but written in terms of the incident wave field, $\phi^{\pm}_I$, and the radiation potentials, $\phi^{\pm}_k$, at the second-order frequency (i.e. $\omega=\omega_i \pm \omega_j$) \begin{equation} \left(\vec{F}^{\pm}_{p,ij}\right)_k = -\textrm{i}(\omega_i \pm \omega_j)\rho \left[ \int_{\SB}\left\{ \left(\vec{n}_{\textrm{vel}}\right)_k \phi_I^{\pm} + q_B^{\pm}\phi_k^{\pm} \right\}\ud S + \frac{1}{g}\int_{\SF} q_F^{\pm} \phi_k^{\pm} \ud S \right] \end{equation} where $q_B^{\pm}$ and $q_F^{\pm}$ are the forcing functions on $\phi_S^{\pm}$.