A Modified Wall Matching Treatment to Account for Local Solid to Fluid Thermal Coupling
The wall-matching methodology of Wilcox is modified to include a solid-wall, thermal-conduction model. This coupled fluid-thermal-structure model is derived assuming that the wall thermal-structure behavior is locally one-dimensional and that structural deformations, due to thermally induced stresses, are not significant. The one-dimensional coupled fluid-thermal-structure model is derived such that the wall temperature is removed as an independent boundary condition variable. The one-dimensional coupled fluid-thermal-structure model is also derived for the general case of an arbitrary mixture of thermally prefect gases and a wall of arbitrary thickness and conductivity by using a compressible, streamwise-pressure-gradient-corrected, wall-matching function and Fourier's law of heat conduction. The resulting model was implemented in the VULCAN CFD code as a new boundary condition type. VULCAN was then used to simulate a two-dimensional Mach 6 wind tunnel facility nozzle flow to demonstrate/validate the one-dimensional coupled fluid-thermal-structure model. The nozzle internal-wall surface temperature and heat transfer distributions computed using the one-dimensional coupled fluid-thermal-structure model are compared to wall temperature and heat transfer distributions from an iterative multi-dimensional analysis obtained by coupling the VULCAN CFD code and the MSC/NASTRAN-thermal code. The one-dimensional coupled fluid-thermal-structure model analysis is shown to be very robust and in excellent agreement with the multi-dimensional iteratively coupled analysis. It is also shown that the one-dimensional analysis can be used as an initial guess for the multi-dimensional iteratively coupled analysis.
Numerical Simulation of Scramjet Combustion in a Shock Tunnel
Computational simulations of reactive flow within a hydrogen-fueled scramjet-like geometry experimentally tested in a free piston shock tunnel are presented. The experimental configuration (Odam and Paull, AIAA Paper 2003-5244) involves injection of hydrogen fuel into the scramjet inlet, followed by mixing, shock-induced ignition, and combustion. Experimental results showed significant heat release due to shock induced supersonic combustion. The present steady-state results, performed using a validated threedimensional Navier-Stokes solver, show generally good agreement with experimental data at fuel-off and fuel-on conditions but display a marked sensitivity to the wall temperature boundary condition. This indicates the possible need to account for transient wall heating in simulations of scramjet experiments conducted in short-duration shock-tunnel facilities. The computational results also provide some support for a “radical farming” hypothesis, advanced to explain the ability of the hydrogen-air mixture to auto-ignite at relatively low inlet contraction ratios.
Liquid state 1H high field NMR in food analysis.
2012 Elsevier B.V. All rights reserved.