Turbulent Compressible Flow in a Slender Tube

K.O. Lund[1], C.M. Lord[2]
[1]Kurt Lund Consulting, Del Mar, CA, USA
[2]Lord Engineering Corp., Encinitas, CA, USA

Pressure-drop experiments were conducted for the turbulent, compressible flow of air in a small, slender tube, and modeled with COMSOL heat transfer module, and analytically. A scalar integration variable is introduced which integrates the mass velocity [kg/m²s] over the inlet area and iteratively equates this to the input mass flow [kg/s]. For computation, the temperature specification is related to the local, calculated pressure through the isentropic relationships. Additionally, based on the numerical results, an analytical 1-D model is derived. The results show significant density variations along the tube, and indicate choking at the outlet (Ma ~ 1) for the highest flow. For the adiabatic conditions, there is excellent agreement with the experimental data for a wide range of flows, though excluding near-choking conditions at the outlet.