Boltzmann kinetic scheme for Knudsen flow in a micro in-plane radiometric actuator: Shakhov model with heat flux specified walls

A fixed-surface heat flux boundary condition was implemented using the Shakhov–Boltzmann kinetic model. Our approach is tested by simulating a fixed heat flux boundary condition in a Micro In-plane Knudsen Radiometric Actuator (MIKRA) device, across the range of Knudsen number (Kn = 0.3–11.49), designed for extreme, vacuum-like environments. Simulation results, compared with laboratory measurements under identical heat-flux conditions, show strong agreement, confirming the model's ability to accurately predict rarefied gas dynamics. Surface temperatures on both hot and cold MIKRA arms are predicted within 1% error for moderate Knudsen numbers (Kn < 4.64), with accuracy decreasing to 3%–5% at higher Knudsen numbers (Kn > 4.64) due to radiative effects beyond the model's conductive framework. Notably, the overall mean absolute percentage error is 2.07%. Experimental force validation indicates the model's improved performance, especially vs Direct Simulation Monte Carlo, in the sensor-relevant Knudsen regime. Our work lays a strong computational foundation for rarefied microscale gas simulation with direct experimental validation. A thorough parametric study addresses accommodation coefficients and microscale rarefaction effects, including one- and two-dimensional flow profiles, velocity contours, and core phenomena like thermal creep and the Knudsen layer. Also, the variation of accommodation coefficients for both arms is discussed, and a comparison is drawn. Parametric analysis reveals that asymmetric accommodation coefficients on hot and cold sensor arms produce a synergistic effect: increasing the hot arm coefficient while decreasing the cold arm coefficient enhances Knudsen effects. The fixed heat flux boundary condition is also compared with the fixed heat flux boundary condition to see the difference in findings.