Supersonic Gas Flow Research Articles

Shock polar investigation in supersonic rarefied gas flows over a circular cylinder

Well-known polars in classical shock wave theory, that is, flow deflection angle-shock angle (θ-β), hodograph (u*,v*), and pressure deflection (θ-P*) diagrams, are investigated for the rarefied gas flows using a recently proposed shock wave detection technique by Akhlaghi and coworkers. The agreement between the obtained polars with the analytical relations in classical shock wave theory has been shown in the continuum limit for the cases of supersonic flow over the wedge and cylinder geometries. Investigations are performed using the RGS2D direct simulation Monte Carlo solver for supersonic gas flows over a circular cylinder at continuum limit and Kn = 10−4, 10−3, 0.01, 0.03, 0.07, and 0.10. Two species of nitrogen and argon at various Mach numbers of 1.5, 3.0, and 10.0 are considered. The shock polars are investigated along bow shock waves in front of the cylinder. The results indicate that rarefaction significantly affects the shock polars. As Knudsen number increases, shock angle, maximum flow deflection angle, and aft shock pressure increase. However, velocity components after the shock wave decrease as the flow becomes more rarefied. These effects are stronger for θ-β polar under the weak shock condition. Meanwhile, they are stronger for θ-P* and hodograph polars in strong shock situations.

Thermomechanical Stress–Strain State of Retention Compartment

AbstractA retention compartment is an isotropic cylindrical shell with load-bearing structures. When a rocket is launched, this structure is streamed by supersonic high-temperature exhaust gas flow...

The influence of a supersonic flow of gas at glow discharge

Experiments have been carried out to study the effect of a supersonic gas flow on a transverse glow discharge in the case when the supersonic gas outflow enters the region of Faraday dark space, i.e. the positive column ends before reaching the supersonic jet. And also in the case when the supersonic outflow of gas falls into the region of the positive column. It is established that the organization of the supersonic flow changes the glow pattern of the glow discharge, creating a spatial inhomogeneity in the interelectrode space.

Two semi-analytical approaches for solving condensation shocks in supersonic nozzle flows

The paper describes two methods for solving condensation shocks in steady-state quasi-one- dimensional flows. A single-fluid-model has been implemented by solving the algebraic form of compressible flow conservation equations, in conjunction with nucleation and droplet growth laws from gas-kinetic theory. The second method assumes the condensation shock problem as a flow discontinuity, the downstream state of the shock being defined as a weak-detonation, and determined from intersections on the Rayleigh and Hugoniot curves. Both approximations have been implemented with complex multi-parameter equations-of-state based on the Helmholtz free energy, taking into account the non-ideal gas flow behavior of steam and carbon dioxide. In order to reproduce operating conditions of engineering applications, where non-equilibrium condensation occurs such as steam turbines, injectors, supercritical carbon dioxide compressors and supersonic gas flow separators. Both gas-kinetic and flow discontinuity approaches have been tested for several nozzle geometries and results have been compared with low- and high-pressure experimental data of steam and carbon dioxide. The results show that both models are able to model properly the pressure recovery that occurs in supersonic condensing flows. It has been found a low deviation 4% from experimental data of steam, and deviations within 8 % were found for the carbon dioxide case. The average droplet radius size distribution obtained from the droplet growth model is in the same order of magnitude of that of reported by experimental data available in open literature. Finally both methods were implemented in a converging-diverging nozzle of a carbon dioxide ejector in order to explore the effects of the stagnation temperature and to determine conditions free of condensation.

Heat flux in supersonic flow past ballistic model at various angles of attack and wall temperatures

Supersonic flow of viscous heat-conducting gas around the ballistic model HB-2 and the resulting heat flux for M=3, angles of attack α=0°,8°,16°and various model surface temperatures were numerically studied using the compact version of the hyperbolic system of quasi-gasdynamic equations (CHQGD).Three-dimensional features of the flow structure and heat flux's dependence on the angle of attack and wall temperature were investigated. Longitudinal vortices on the model's leeward side near the symmetry plane were observed for α=16°. These flow separation regions significantly affect heat flux distribution on the model's leeward surface.

Measurement of Essentially Nonstationary Heat Fluxes by a Bismuth-Based Gradient Sensor

The gradient heat flux sensor made of a bismuth single crystal is calibrated. The volt–watt sensitivity of the sensor is determined and the method of data processing based on the 1D heat conduction equation for a thin plate is proposed. This method is tested on experimental data obtained for the initiation of a laser discharge in a calm atmosphere and in a supersonic gas flow.

The large clusters influence on the supersonic flows gas dynamics in a rarefied medium

The processes of Van der Waals clusters formation in supersonic gas flows expanding into a rarefied medium are discussed in this report. The necessary conditions for cluster formation, methods for measuring the average size and size distribution of clusters in a rarefied gas flow are considered. The problems associated with electron-beam ionization of clusters during mass spectrometry of clustered flows are analyzed. The process of intracluster energy exchange in mixtures, that leads to the possibility of inverse pumping of electronic levels of atoms, is illustrated. The problems arising during optical measurements of density in cluster flows are demonstrated. The effect of large clusters formation on the shape and structure of supersonic flows is shown.

Pitot probe response for pulsed supersonic gas flow characterization in beam profile monitor.

For beam profile measurement of high-intensity proton beams in the low-energy high-intensity proton accelerator at Bhabha Atomic Research Centre, a recent noninvasive technique based on gas sheets will be explored. The gas sheet for this instrument needs to be characterized for calibration and fine tuning of the sheet properties to provide better profile measurements. Pulsed sheet generators for similar applications have been characterized using movable vacuum chambers with a small slit and a gauge mounted inside. Pitot probes are more compact instruments and have been used to measure gas jet profiles in molecular beam applications where the jet was not pulsed. The performance of Pitot probes in the measurement of pulsed supersonic gas flow in vacuum was, therefore, investigated in this work. A test system was developed to generate a pulsed supersonic gas jet in vacuum, and a Pitot probe was inserted into the flow at various axial locations with respect to the nozzle. Measurements taken along the nozzle axis using this probe, as well as the axial Mach number and impact pressure computed using computational fluid dynamics and direct simulation Monte Carlo algorithms, were compared with fitting formulas. Schlieren images of the jet with and without the Pitot tube were also taken under different vacuum conditions.

Численное исследование нестационарного течения газа в камере сгорания прямоточного воздушно-реактивного двигателя с учетом процесса теплообмена

Проведено численное исследование нестационарного турбулентного сверхзвукового течения в камере сгорания прямоточного воздушно-реактивного двигателя. Описана методика экспериментального измерения температуры на стенке осесимметричного канала в камере сгорания двигателя. Математическое моделирование обтекания исследуемой модели двигателя проводилось для скоростей набегающего потока M = 5 ... 7. Начальные и граничные условия задачи соответствовали реальному аэродинамическому эксперименту. Проанализированы результаты численного расчета. Рассмотрено изменение распределения температуры вдоль стенки канала с течением времени. Проведена оценка согласованности полученных экспериментальных данных с результатами математического моделирования. Purpose. The aim of this study is a numerical simulation of unsteady supersonic gas flow in a working path of ramjet engine under conditions identical to aerodynamic tests. Free stream velocity corresponding to Mach numbers M=5 ... 7 are considered. Methodology. Presented study addresses the methods of physical and numerical simulation. The probing device for thermometric that allows to recording the temperature values along the wall of internal duct was proposed. To describe the motion of a viscous heat-conducting gas the unsteady Reynolds averaged Navier - Stokes equations are considered. The flow turbulence is accounted by the modified SST model. The problem was solved in ANSYS Fluent using finite-volume method. The initial and boundary conditions for unsteady calculation are set according to conditions of real aerodynamic tests. The coupled heat transfer for supersonic flow and elements of ramjet engine model are realized by setting of thermophysical properties of materials. The reliability testing of numerical simulation has been made to compare the results of calculations and the data of thermometric experimental tests. Findings. Numerical simulation of aerodynamic tests for ramjet engine was carried out. The agreement between the results of numerical calculations and experimental measurements for the velocity in the channel under consideration was obtained; the error was shown to be 2%. The temperature values were obtained in the area of contact of the supersonic flow with the surface of the measuring device for the external incident flow velocities for Mach numbers M = 5 ... 7. The process of heating the material in the channel that simulated the section of the engine combustion chamber was analyzed. The temperature distribution was studied depending on the position of the material layer under consideration relative to the contact zone with the flow. Value. In the course of the work, the fields of flow around the model of a ramjet engine were obtained, including the region of supersonic flow in the inner part of axisymmetric channel. The analysis of the temperature fields showed that to improve the quality of the results, it is necessary to take into account the depth of the calorimetric sensor. The obtained results will be used to estimate the time of interaction of the supersonic flow with the fuel surface required to reach the combustion temperature.

Динамічна втрата стійкості складеною нанокомпозитною оболонкою

Free oscillations and dynamic instability due to supersonic airflow pressure are investigated in a functional-gradient compound composite conical-cylindrical shell made of a carbon nanotubes-reinforced material. Nanocomposite materials with a linear distribution of the volumetric fraction of nanotubes over the thickness are considered. Extended mixture rule is used to estimate nanocomposite’s mechanical characteristics. A high-order shear deformation theory is used to represent the shell deformation. The assumed-mode technique, along with a Rayleigh-Ritz method, is applied to obtain the equations of the structure motion. To analyze the compound structure dynamics, a new system of piecewise basic functions is suggested. The pressure of a supersonic flow on the shell is obtained by using the piston theory. An example of the dynamic analysis of a nanocomposite conical-cylindrical shell in the supersonic gas flow is considered. The results of its modal analysis using the Rayleigh-Ritz technique are close to the natural frequencies of the shell obtained by finite element analysis. In this case, finite element analysis can only be used for shells made of material with a uniform distribution of nanotubes over the thickness. The dependence of the natural frequencies of a compound shell on the ratio of the lengths of the conical and cylindrical parts is studied. The dependence of the critical pressure of a supersonic flow on the Mach numbers and the type of carbon nanotubes reinforcement is investigated. Shells with a concentration of nanotubes predominantly near the outer and inner surfaces are characterized by higher values of natural frequencies and critical pressure than the shells with a uniform distribution of nanotubes or with a predominant concentration of nanotubes inside the shell.

Experimental Study on the Diagnostics of Internal Compressible Flows using Outer Surface Nozzle Temperature

Cold spray (CS) is one of the thermal spraying methods which make coatings by spraying melted minute particles on substrate surfaces. Solid particles are sprayed onto a substrate at high speed to form a coating accelerated by a supersonic gas flow using a convergent-divergent nozzle. Therefore, it is important to understand the gas flow condition inside the nozzle that accelerated the gas flow. However, diagnosing internal gas flow is almost impossible for commercial CS nozzles because the nozzle is fabricated with hard metal alloy to prevent abrasions of the nozzle. Therefore, it is impractical to drill pressure taps to the CS nozzle to diagnose the gas flow. To solve this problem, authors propose non-intrusive flow-diagnostic methods which uses outer surface temperature of the CS nozzle and temperature recovery factor of the working gas. This research shows that the accuracy of this method is improved by measuring the outer surface temperature of the entire axial direction of the nozzle, and that the temperature recovery factor of the internal flow depends on the stagnation pressure. Therefore, the temperature recovery factor of the internal flow should be treated as a function of stagnation pressure.

Reynolds analogy for the fluid flow past a flat plate at different regimes

The Reynolds analogy for the fluid flow past a flat plate at zero incidence is considered. For viscous incompressible fluid, we show that at any positive Eckert number, the Reynolds analogy as a function of the Prandtl number has a maximum. For a rarefied gas flow, we investigate the extended Reynolds analogy, i.e., the relation between the shear stress and the energy flux transferred to the plate using the direct simulation Monte Carlo method. We find that the extended Reynolds analogy for a supersonic monatomic rarefied gas flow with the temperature of the undisturbed gas equal to the surface temperature depends weakly on the Knudsen number, it is close to 0.5. We show that the extended Reynolds analogy for supersonic gas flow depends on the plate velocity and temperature and undisturbed gas temperature mainly via the Knudsen and Eckert numbers. We generalize the extended Reynolds analogy. The generalized Reynolds analogy depends on the Knudsen number much more than on the Eckert number.

Управление колебаниями бесконечной мембранной ленты с подвижным краем в сверхзвуковом потоке газа

Управление колебаниями бесконечной мембранной ленты с подвижным краем в сверхзвуковом потоке газа

Meshless algorithm for supersonic inviscid gas flows calculating

Meshless algorithm for supersonic inviscid gas flows calculating

Meshless algorithm for calculating supersonic viscous gas flows

Meshless algorithm for calculating supersonic viscous gas flows

Analysis of the interaction of a supersonic gas flow with a solid low melting polymer as a ramjet engine propellant

The performance of ramjet engines with a supersonic combustion is one of the main directions of hypersonic aircraft development research is studied. Researchers around the world create special experimental facilities for testing engine models, investigate fuels for ramjet engines and classify new scientific data. Since the ambient temperature and the oxidizer flow temperature in engine air duct are low at the flight altitude of a hypersonic aircraft, low melting materials can be used as a fuel agent in a solid propellant. The main purpose of this work is analysis of heat and mass exchange processes associated with the motion of a supersonic gas flow in an axisymmetric duct described as a combustion chamber of a ramjet engine with a solid polymer. The mathematical model of the problem consists of the unsteady Reynolds-averaged Navier-Stokes equations and the equations of a semiempirical turbulence model. The stated problem was solved by the finite volume method. Initial and boundary conditions are identical to experimental conditions and this makes it possible to verify the results of the numerical solution directly during aerodynamic tests. Gas dynamic parameters for the gas flow in an air duct of a ramjet engine are described, pressure profiles at the gas-solid interface are plotted, and a transient pressure behavior is considered. The results of the solution of a coupled heat transfer problem allow analyzing a dynamic heat exchange pattern in a solid polymeric material (caprolone, polyethylene and polyoxymethylene). It has been found that the effect of a supersonic flow on the surface of a low melting material within one second leads to temperature changes in a solid to a depth of 20% of its total thickness.

Self-excited periodic oscillations in a supersonic laminar flow past a blunt-fin body mounted on a plate

Results of numerical simulation of supersonic gas flow past a blunt fin mounted on a flat plate with developing laminar boundary layer are presented. The calculations cover flow cases with the freestream Mach number of 6.7 and three different Reynolds numbers. A detailed analysis of flow characteristics such as temperature and surface heat flux are presented. In the smaller Reynolds number case, solution is steady-state and agrees very well with known numerical and experimental data. In case of larger Re values, the flow becomes periodic. These regimes are characterized by self-excited non-linear oscillations with almost the same fundamental frequency.

Investigation of the cascade mechanism of energy exchange in swirling gas flows based on the effect of secondary swirling

The article presents the results of studies of the secondary swirling effect in supersonic rotating gas and plasma flows. It is shown that the secondary twist of the jets of gas flowing from the nozzle apparatus generates a cascade structure of vortices that separate energy in the field of azimuthal and radial pressure gradients. As shown by the calculations, the effect of energy separation is more significant the higher the level of secondary twisting of the nozzle jets, which, in turn, is determined by the level of energy dissipation. Experimental confirmations of the revealed cascade mechanism of energy separation in supersonic swirling gas flows are discussed.

Gas Flow in Microchannels and Nanochannels With Variable Cross Section for All Knudsen and All Mach Number Values

AbstractThe analytical solution for steady viscous pressure-driven compressible isothermal gas flow through micro- and nanochannels with variable cross section for all Knudsen and all Mach number values is presented in this paper. The continuum one-dimensional governing equations are solved using the friction factor that is established in a special way to provide solutions for mass flow rate, pressure, and velocity distribution through the microchannels and nanochannels in the entire rarefaction regime. The friction factor, defined by the general boundary condition and generalized diffusion coefficient proposed by Beskok and Karniadakis (1999, “A Model for Flows in Channels, Pipes, and Ducts at Micro and Nano Scales,” J. Microscale Thermophys. Eng., 3, pp. 43–77), spreads the solution application to all rarefaction regimes from continuum to free molecular flow. The correlation between the product of friction factor and Reynolds number (Poiseuille number) and Knudsen number is established explicitly in the paper. Moreover, the obtained solution includes the inertia effect, which allows the application of the solution to both subsonic and supersonic gas flows, which was not shown earlier. The presented solution confirms the existence of the Knudsen minimum in the diverging, converging, and microchannels and nanochannels with constant cross section. The proposed solution is verified by comparison with experimental, analytical, and numerical results available in literature.

The effect of the cone rotation in the supersonic gas flow on the velocity propagation of perturbations in the boundary layer

The paper aimed at studying the peculiarities of boundary layer on a rotating body. Rotation of axisymmetric bodies is often used for their stabilization at a high velocity motion in the atmosphere. Presented are calculation of boundary layer flow on a rotating cone at zero angle of attack. Longitudinal and full enthalpy profiles in the laminar boundary layer obtained as a result of calculations were used to determine upstream disturbances propagation velocity. New integral relation was determined to find out disturbances propagation velocity for the regime of weak hypersonic viscous-inviscid interaction. Effects of surface rotation velocity along with the temperature factor influence were investigated.