Blockage Corrections for Different Geometries in Enclosed Free-Jet Test Section of High Altitude Test System

Abstract

High altitude simulation tests are of great importance for missile systems to be tested on the ground in their working altitude pressure environment. These altitude simulation tests of tactical missile systems particularly at supersonic speeds need ‘High Altitude Test System’. The missile systems can be tested in two different ways of external flow over the missile systems using the free-jet nozzle at different Mach numbers and the nozzle of the missile system itself. The ‘HATS’ consists of a test chamber that isolates the test article from the outside atmosphere and simulates the high altitude environment. Typically, the test article is installed inside the test chamber through appropriate support systems. This thesis focused on the effects of blockage of the test articles that have different area ratios for determination of the working characteristics of the ‘HATS’. The blockage ratios were chosen as 8%, 15% and 25% according to the exit area for two different free-jet nozzles, ‘Mach 2 and Mach 2.5’. Vacuum test chamber for different blockage area ratios has been studied for cold flow conditions with experimental and CFD analyses. Within the framework of the cold flow tests, Schlieren images were recorded with high speed camera and static pressures and temperatures of the test chamber were also be collected. Results from experimental tests and numerical analyses have been compared in terms of both test chamber pressure and Schlieren images. In the first case, the CFD analyses have been performed to simulate the flow conditions inside the modified ‘HATS’ facility without any test article in the test section and in the second case, the CFD analyses have been performed for the test articles inside the test chamber with different blockage areas. The working characteristics of the ‘HATS’ have been determined according to the different blockage ratios by using experimental results and experimental results have been used both as inputs to the CFD analyses and CFD analyses corrections.