Hi,
This tool is really amazing!
Do you have any plan to include the feature that simulates thermoelastic deformation of the sample when illuminated by a nanosecond laser pulse?
The thermoelastic deformation occurs due to the nonuniform temperature distribution and can be described by thermoelastic wave equation.
Thank you.
Best regards,
Seongjun Park
Hi Seongjun,
Glad you're enjoying it! Are you referring to the (photo)acoustic pulse that would be emitted following the absorption of a nanosecond pulse, or the propagation of the thermal wave that accompanies it (that will obey the heat diffusion equation), or changes in the positions of boundaries between different materials as the heat flows because of differences in thermal expansion coefficients? Or something else?
The acoustic pulse can be modelled in k-Wave using an initial pressure distribution (assuming the physical dimensions are such that the acoustic timescale is much longer than the optical timescale) but I think you know that! We haven't implemented heat diffusion or any heat modelling yet in k-Wave.
Hope that helps,
Ben
Hi Ben,
Thank you for the response.
When the sample is illuminated by a laser impulse, the sample surface is displaced via thermoelastic expansion. In this case, the effects of the thermal diffusion were neglected because of the time scale for stress relaxationis much more rapid compared to the time scale for thermal diffusion. The trace of the sample displacement can be functions of the optical/mechenical properties of the sample. The corresponding wave equation is expressed as:
diff(u,z,2) - 1/c^2*diff(u,t,2) = -(B*K*T0)/(rho*c^2*D)*exp(-z/D)
where
(1) diff(u,z,2) is double partial derivative of u with respect to z
(2) u displacement of the sample surface
(3) c longitudinal speed of sound
(4) B thermal expansion coef.
(5) T0 relative surface temperature at z=0
(6) rho density
(7) D effectilve optical attenuation depth
(8) K bulk modulus
initial B.C. when the semi-infinite sample is surrounded by air environment.
u=0 at t=0, diff(u,t)=0 at t=0, stress=0 at z=0, u=0 at z->infinite
I think this belongs to photoacoustic regime.
Thank you.
Seongjun Park.
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