Experimental observation of Faraday waves in soft gels

We report the experimental observation of Faraday waves on soft gels. These were obtained using agarose in a mechanically vibrated cylindrical container. Low driving frequencies induce subharmonic standing waves with spatial structure that conforms to the geometry of the container. We report the experimental observation of the first 15 resonant Faraday wave modes that can be defined by the mode number $(n,\ell )$ pair. We also characterize the shape of the instability tongue and show the complex dependence upon material properties can be understood as an elastocapillary effect.

Figure 1

Experimentally observed surface modes with mode number pair ($n,\ell$) on a gel with $G=3.9\mathrm{Pa}$.

Figure 2

Schematic of (a) experimental setup and (b) optical system.

Figure 3

Frequency sweep plotting acceleration $A$ against driving frequency $f_d$ for $G=3.9\mathrm{Pa}$ reveals instability tongues for modes $(n,\ell )$.

Figure 4

Table of experimentally observed Faraday wave mode shapes on a gel with $G=5.9\mathrm{Pa}$ defined by the mode number pair ($n,\ell$) with a corresponding frequency range.

Figure 5

Instability tongue for the (1,2) mode in the acceleration $A$ versus frequency $f_d$ space as it depends upon shear modulus $G$.