Fig. 1: Schematics of the double-layer and triple-layer model.
From: Amplifying time-harmonic thermal signal in spinning lock-in thermography
The base of the bottom layer provides continuous sinusoidal thermal wave, while the first layer acts as a convective medium whose angular velocity modulates the temperature amplitude on its top surface. a Diagrammatic figure. b Side view of the double-layer structure. For the triple-layer model, the top (corresponding to the second layer in (c)) layer can be seen as a device under test, in this model, where the combined angular velocities of both the first and second layers simultaneously modulate the sample’s thermal response. c Diagrammatic figure and d Side view of the triple-layer structure. e temperature profile by flattening the circumference. Letters \(b\), \(d\) and \(R\) are geometric parameters: \(b\) = 0.005 m, \(d\) = 0.022 m, \(R\) = 0.055 m. \(z=0\) represents the coordinate origin. \(\omega\) is the thermal frequency. \(\Omega\) and \({\Omega }_{i}(i=1,\,2)\) denote corresponding angular velocities. When viewed from the origin towards the negative direction of the z-axis, a clockwise rotation corresponds to a positive value.
