Improvement of the Thermodynamic Model for a Flux-Difference-Splitting Algorithm for the Computation of High Speed Flows
Abstract
This study modifies the thermodynamic model of a previously existing first-order accurate Flux Difference Splitting (FDS) algorithm for planar, supersonic nozzles. The thermodynamic model is changed from a calorically and thermally perfect gas to a thermally perfect (imperfect) gas, where the flow field is frozen or non-reacting. The frozen flow and imperfect gas assumptions more nearly approximate the real behavior of a fluid in supersonic propulsive nozzles. The modified code can now account for specific heats that vary as a function of temperature. Using curve fittings of JANAF thermochemical data, the code can handle nine gas species, as well, to model combustion products entering the nozzle inlet. The marching scheme is not altered in order to retain the robustness and efficiency of the first-order method. An oblique shock reflection study is done to validate the improved gas model. A low pressure, low temperature case and a high pressure, high temperature case are run. For the first case, the perfect and imperfect models are nearly identical. For the more extreme case, pressure for the perfect gas is 9.4% greater than the exact solution, at the upper boundary, across the shock. An interior flow nozzle is run for the two cases, with air as the working fluid. Again, the two models give identical results for the low pressure case. For the high pressure case, integrated nozzle thrust for the imperfect gas model is 16% higher than that for the original perfect gas model.
Document Details
- Document Type
- Technical Report
- Publication Date
- Dec 01, 1991
- Accession Number
- ADA244285
Entities
People
- Mark E. Schieve
Organizations
- Air Force Institute of Technology