Pol Grasland-Mongrain edited The_absorption_of_the_laser__.tex  over 8 years ago

Commit id: 047ad76c88d2e6e1acc5f7f937553894b86fb669

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To verify this physical model, a numerical calculation was performed. The thermal dilatation was modeled as two opposite forces directed along Y direction with a depth of 50 $\mu$m and decreasing linearly from 2.5 to 0 mm (respectively -2.5 to 0 mm), to simulate an approximate Gaussian shape \cite{Davies_1993}. Propagation as a shear wave along Z axis was calculated using Green operators $G_{yz}$ as calculated by Aki Richards \cite{aki1980quantitative}:  \begin{equation}  G_{yz} (r,\theta,z)= \frac{\cos \beta \sin \theta}{4\pi \rho c_p^2 r} \delta_P + \frac{-\sin \theta \cos \theta}{4\pi \rho c_s^2 r} \delta_S + \frac{3\cos \theta \sin \beta}{4\pi \rho r^3} \int_{r/c_p}^{r/c_s}{\tau \delta_{NF}}  \label{eq:akirichards} \label{eq:Gyz}  \end{equation}  where $\theta$ is the angle between the applied force and the considered point (r,$\theta$,z), $c_p$ and $c_s$ the compression and shear wave speed respectively, $\delta_S$ and $\delta_P$ Dirac distribution indicating the position of the compression and shear waves along space and time, $\tau$ the time and $\delta_{NF}$ representing near-field effects. The three terms correspond respectively to the far-field compression wave, the far-field shear wave and the near-field component.  Displacement can then be computed by convoluting $G_yz$ with time and spatial extent of the force:  \begin{equation}  u_z = H_y(x,y,z,t) * G_{yz}  \label{eq:akirichards2} \label{eq:uz}  \end{equation}  where $H_y$ is a 4-D matrix of the applied force (directed along Y) along space and time.