Numerical Simulation of Thermo-Pneumatic Effects for Gas-Liquid Flows in Heated Microchannels

Numerical simulations of an air bubble flowing in a micro-channel filled with liquid water and heated on the walls are presented. Due to the small channel size, pressure changes may be induced by a heat supply on the walls. The aim is to quantify these pressure changes. A numerical model, allowing for the description of an incompressible liquid and a compressible gas bubble is presented. Air in the bubble is modeled as a perfect gas, under the low Mach approximation while the liquid is modeled as an incompressible fluid. The Navier Stokes equations and the energy equation are solved. The interface description is performed combining front tracking techniques and a Heaviside step function. A first validation test-case is presented. Then, various heating conditions are examined including uniform and non uniform heating conditions, constant and time dependent heating conditions. It is shown that pressure oscillations in the bubble may be induced by an appropriate thermal actuation.