4. Thermogravimetric coupling in absorbent liquids

While diffusive forces can generate volumetric flows in turbid media, there is another way to optically induce such flows. When a liquid layer is heated locally by the absorption of a continuous laser wave, its density $\rho \left(T\right)$ decreases in the heated area $\left(\left(\partial \rho \mathrm{/}\partial T\right)<0\right)$ . This radial decrease induces a pressure gradient which, in turn, sets the liquid in motion—a phenomenon known as the thermogravitational effect, or forced convection. By the law of conservation...