Effects of trips on the oscillatory flow of an axisymmetric hypersonic inlet with downstream throttle  

作　　者：Wenzhi GAO Zhufei LI Jiming YANG Yishan ZENG 

机构地区：[1]School of Mechanical Engineering, Hefei University of Technology [2]Department of Modern Mechanics, University of Science and Technology of China

出　　处：《Chinese Journal of Aeronautics》2018年第2期225-236,共12页中国航空学报（英文版）

基　　金：co-supported by the China Postdoctoral Science Foundation (No. 2017M612059);the Fundamental Research Funds for the Central Universities of China (JZ2015HGBZ0471);the National Natural Science Foundation of China (Nos. 11402263 and 11132010)

摘　　要：Experimental investigations are conducted on an axisymmetric hypersonic inlet to evaluate the effects of trips on oscillatory flows. The model exit is throttled with a fixed block to generate oscillatory flows at a freestream Mach number of 6 in a conventional wind tunnel and a shock tunnel. Schlieren imaging and pressure measurements are adopted to record unsteady flow features.Results indicate that trips with a 1 mm thickness prominently suppress external separations, shorten oscillatory cycles, and modify pressure magnitudes. Trips can reduce the upstream movement ranges of separated shocks from nose regions to locations axially 142 mm downstream. The oscillatory cycles are shortened from 3.75 ms to 3.25 ms and from 4 ms to 3.13 ms in two facilities.Tripped cases generally exhibit higher pressure magnitudes than those of untripped cases, of which the increment is up to 21 times the freestream static pressure for the farthest downstream transducer in the shock tunnel. The effects of trips are related to the streamwise vortexes in wake flows, in which interactions between external separations modify the separated flow patterns and enhance the sustainment of the forebody boundary layers to backpressure. Flow processes causing increments of oscillatory frequencies and pressure magnitudes are analyzed, while the flow mechanisms dominating the processes still need to be clarified in the future.Experimental investigations are conducted on an axisymmetric hypersonic inlet to evaluate the effects of trips on oscillatory flows. The model exit is throttled with a fixed block to generate oscillatory flows at a freestream Mach number of 6 in a conventional wind tunnel and a shock tunnel. Schlieren imaging and pressure measurements are adopted to record unsteady flow features.Results indicate that trips with a 1 mm thickness prominently suppress external separations, shorten oscillatory cycles, and modify pressure magnitudes. Trips can reduce the upstream movement ranges of separated shocks from nose regions to locations axially 142 mm downstream. The oscillatory cycles are shortened from 3.75 ms to 3.25 ms and from 4 ms to 3.13 ms in two facilities.Tripped cases generally exhibit higher pressure magnitudes than those of untripped cases, of which the increment is up to 21 times the freestream static pressure for the farthest downstream transducer in the shock tunnel. The effects of trips are related to the streamwise vortexes in wake flows, in which interactions between external separations modify the separated flow patterns and enhance the sustainment of the forebody boundary layers to backpressure. Flow processes causing increments of oscillatory frequencies and pressure magnitudes are analyzed, while the flow mechanisms dominating the processes still need to be clarified in the future.

关 键 词：Backpressure Flow separations Hypersonic inlets Inlet unstart Oscillatory flow TRIPS 

分 类 号：V211.48[航空宇航科学与技术—航空宇航推进理论与工程]