Pol Grasland-Mongrain edited Simu disp maps.tex  about 8 years ago

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Next, we sought to characterize examine the physical characteristics of  the other regim regime  observed in our experiments. Solving the equation \ref{eq:eqChaleurApprox} with the same experimental parameters used previously, but with a laser energy of 200 mJ, we found find  a maximum increase in temperature of 60 K, i.e., a maximum medium temperature of about 360 K assuming a room temperature of about 298 K. While slightly below the vaporization point of our medium, supposed close to 373K (water vaporization temperature), its proximity to the water vaporization temperature (373 K) may be sufficient to vaporize the medium. Indeed, it has been demonstrated that graphite and other small particles can act as nucleation sites to facilitate the vaporization of the medium at temperature lower than the vaporization point \cite{Alimpiev_1995}. A series of reactions then leads to displacements inside the medium, which generate shear waves; this constitutes the \textit{ablative regime}. To estimate the initial displacement amplitude in this regime, we again assumed assume  that the medium was homogeneous and isotropic, and we discarded discard  any boundary effect. The stress, $\sigma_{zz}$, is now defined as the sum of the axial strain component and a term given by the second law of motion caused by the reaction of the particles ejected outside the medium upon reaching the vaporization point \cite{ready1971effects}: \begin{equation}   \sigma_{zz} = (\lambda + 2 \mu) \frac{\partial u_z}{\partial z} - \frac{1}{\rho}\frac{I^2}{(L+C(T_V-T_0))^2}  \label{eq:stressAbla}