Discussion Forum

Hi All,

I am a relatively new user to COMSOL and am trying to model evaporation of a water droplet on a heated substrate. For my model geometry, I have defined three domains- Droplet, Air and Substrate. So far, I have modeled laminar flow and heat transfer in both the air and droplet domain seperately. I have coupled these two physics using Nonisothermal flow and Marangoni convection in the droplet domain and for the air domain I have used the buoyancy term as the Boussinesq approximation used as the volume force in laminar flow in the air domain. Up until this point everything seems alright. My problem is when I use the transport of dilute species to use the temperature profile of the droplet to calculate saturation pressure and hence the saturation concentration. As long as I use a constant concentration boundary condition (c_sat) which is calculated from one particular temeprature, the solution converges. However, when I try to define this boundary as a function of temperature, I consistently get the 'Failed to find consistent initial values, last time step is not converged' error. One thing to note is that when I calculate c_sat as a function of temperature (analytic function), but don't apply it as a concentration boundary condition it still calculates the values. I am attaching my model below for you to take a look. Any help is greatly appreciated.