V. I. Zapryagaev

Flow structure formed due to interaction of a supersonic jet with a porous obstacle

Results of studying impingement of a supersonic underexpanded air jet onto a finite-thickness porous metal obstacle whose frontal plane is normal to the jet axis and whose side surface is impermeable for the gas flow are reported. The case of a non-porous obstacle of the same diameter is considered for determining the effect of porosity on gas-dynamic characteristics of jet–obstacle interaction.

Impingement of a supersonic underexpanded jet onto obstacles with different permeabilities

Results of an experimental study of the flow structure and characteristics of flow oscillations induced by impinging of a supersonic underexpanded jet onto obstacles made of permeable and impermeable materials are presented. Spectral characteristics of the acoustic field in the regime of unsteady interaction between the jet and the obstacle are determined. The influence of permeability of porous obstacles on these characteristics is identified.

THE STRUCTURE OF THE SUPERSONIC OVEREXPANDED JET IMPINGING ON AN INCLINED FLAT PLATE

Представлены результаты экспериментального исследования газодинамической структуры течения при взаимодействии сверхзвуковой перерасширенной струи с плоской преградой при различных углах наклона. Эксперименты проведены на специальном газодинамическом стенде – вертикальной струйной установке, оборудованной автоматизированной системой сбора данных и позволяющей контролировать газодинамические параметры эксперимента в реальном времени. Для проведения экспериментов использовалось специальное осесимметричное сверхзвуковое сопло с упрощенной внутренней геометрией, облегчающей его точное изготовление. Число Маха на срезе сопла Ma = 3, относительное полное давление сверхзвуковой струи Npr = 21,4. Расстояние от среза до поверхности преграды H/Da = 2. Модель преграды оснащена сеткой дренажных отверстий для измерения распределения давления. Визуализация течения представлена осредненными и мгновенными шлирен-фотографиями течения. По результатам дренажных измерений построены поля пристенного давления на поверхности преграды. Получены новые данные о структуре течения импактных перерасширенных струй, которые могут быть использованы для верификации численных расчетов. Для рассматриваемых режимов взаимодействия зарегистрировано наличие периферийного максимума пристенного давления на преграде. Выявлен сверхзвуковой характер веерной пристенной струи, приведены основные особенности ударноволновой структуры течения для различных углов наклона преграды. Ключевые слова: ударно-волновая структура, сверхзвуковая перерасширенная струя, преграда, сопло, эксперимент, шлирен-визуализация.

Gasdynamic structure of an axisymmetric supersonic underexpanded jet

The steady-state structure of supersonic underexpanded jet flow at Ma = 1 is experimentally investigated. The measured total pressure distributions are presented in different cross sections and along the jet axis. Certain distinctive features of the supersonic jet flow are revealed. Among these are considerable fluctuations of the density distribution in the mixing layer formed behind the triple point on the normal shock in the jet. They are due to the presence of vortex structures in the internal mixing layer. The data obtained are used in testing the results of numerical calculations.

High-pressure layer generation in a compression corner at a supersonic flow velocity

The results of an experimental and numerical investigation of a three-dimensional laminar separated flow in a compression corner are presented. The freestream Mach number M∞ =6. The model under study is a plate with a sharp leading edge on which a step with a 30° inclination angle is mounted. The model width is equal to the plate length from the leading edge to the step. A thin high-pressure layer located above the boundary layer, downstream of the reattachment line is shown to exist.

Effect of distributed gas injection on aerodynamic characteristics of a body of revolution in a supersonic flow

Results of experimental and numerical investigations of the effect of gas injection through a permeable porous surface on the drag coefficient of a cone-cylinder body of revolution in a supersonic flow with the Mach number range Mh = 3–6 are presented. It is demonstrated that gas injection through a porous nose cone with gas flow rates being 6–8% of the free-stream flow rate in the mid-section leads to a decrease in the drag coefficient approximately by 5–7%. The contributions of the decrease in the drag force acting on the model forebody and of the increase in the base pressure to the total drag reduction are approximately identical. Gas injection through a porous base surface with the flow rate approximately equal to 1% leads to a threefold increase in the base pressure and to a decrease in the drag coefficient. Gas injection through a porous base surface with the flow rate approximately equal to 5% gives rise to a supersonic flow zone in the base region.