Supersonic Zone Research Articles

Optimization of Process Parameters for Flow Nozzle with Different Geometry using Computational Fluid Dynamics Method

A nozzle is a tubular structure designed to facilitate the flow of hot gases. Rocket nozzle designs typically consist of a stationary convergent section and a stationary divergent section. The term "CD" is an abbreviation for "convergent-divergent" and is used to refer to this specific nozzle type. Upgrades are being made to nozzles and other engine components in order to enhance performance and optimise thrust delivery. Application-specific improvements will be made to rocket nozzles and other current combustion expansion systems. An instance of such progress is the implementation of the bell and twin bell nozzle. This study conducted a comparative analysis of two kinds of nozzles, namely bell and conical, at different Mach speeds to ascertain which one yields the most optimal flow. Subsequently, the flow parameters were modelled with computational fluid dynamics (CFD). Ensuring optimal pressure thrust integral throughout the supersonic zone of the nozzle surface while taking the base pressure into account was the aim of the problem formulation. The research focused on irrotational flow, taking into consideration the impacts of boundary layers.

The Amount of Circulation when Forming the Aerodynamic Appearance of a Main Aircraft

The work proposed by the authors describes the mechanism for the formation of induced drag for a wing of finite span, as well as a possible option for taking into account the circulation value as a control parameter in the process of preliminary design of a mainline aircraft wing equipped with additional aerodynamic surfaces (wing tips, winglets).Providing the least frictional resistance is achieved by the smoothness of the wing surface in combination with laminar profiles (with the greatest length of the laminar section of the boundary layer), when critical values of the M number are reached, supersonic zones appear on the wing, therefore it is necessary to delay the occurrence of the wave crisis as much as possible - apply the sliding effect for the swept wing of the final scope. A reduction in inductive drag can be achieved by using a high aspect ratio wing or various types of wing tips, which make it possible to control the amount of circulation and localize the process of pressure flow near the end part of a wing of finite span by increasing the effective span. The study of the flow around an aerodynamic model of a mainline aircraft formed the basis of the conceptual model and mathematical support that implements the methodology for selecting the composition of rational design parameters. The identified experimental data and functional dependencies made it possible to form a vector of parameters for a formal aerodynamic model, connecting the geometry of the aircraft model (shape) and its aerodynamic characteristics through dimensionless coefficients for various operating characteristics. Analysis of the results and subsequent processing in order to synthesize a design solution on a validation basis involves the use of a formalized multi-parameter approach, i.e. machine (computer) processing is required. The implementation of a multi-parameter approach in application software in the C++ programming language will allow us to explore and establish connections between parameters and obtain a new version of the design alternative using a smaller amount of data.

Mathematical model of thermophysical loading of a small-caliber artillery barrel with variant discretization of half-integer layers of the computational domain

In the conditions of continuous financing of the programs of the Ministry of defense of the Russian Federation, the question of finding the most effective ways to modernize weapons and military (special) equipment, the developments in which are maximum and the processes of their improvement can take no more than a few years, is particularly acute. Such products, in particular, include aviation artillery weapons (AAO), the prospects for the use of which remain for the entire period of the army's existence with conventional weapons. The main factor influencing the quality of the AAO functioning is considered to be the thermophysical loading of a small-caliber artillery barrel (hereinafter referred to as the barrel) during firing. The problem of increasing the accuracy of determining the temperature field of the barrel is again updated by tightening the conditions for striking targets. Issues closely related to the intensification of AAO application regimes have come to the fore. These are issues of heating, cooling, thermal strength, wear, barrel survivability, issues of safety and firing efficiency. Despite the methodological evidence of analytical and numerical approaches to formalizing heat transfer in the wellbore, their practical implementation is rather complicated. The physical and mathematical meaning of this reason is as follows: possible instability of solutions; manifestation of oscillations in areas of large gradients; simultaneous presence in the solution regions of supersonic, sonic and subsonic zones; the existence of laminar, turbulent flows and other non-linear formations; non-triviality of setting boundary conditions; the presence of thermal resistance of surfaces, etc. However, the practical needs of ensuring safety and increasing the efficiency of fire operation of AAO dictate the need to obtain a close approximation of the problem under consideration to its possibly existing exact analytical solution. The aim of the work is to improve the mathematical apparatus that simulates the temperature field of the shaft based on a combination of heat transfer methods and mathematical physics. By verifying the reliability of the developed mathematical model (hereinafter referred to as the model, if from the context of the presentation of the material it is clear that we are talking about the proposed tools), the facts of the absence of methodological errors in the formation of the constituent blocks of the model and the increase in the accuracy of determining the thermal loading of the wellbore by 9.4% were established. Based on the accents of the stated problem, the directions for improving the model are argued.

Modeling of convective heat transfer processes between inhomogeneous gas mixtures and surfaces of a small-caliber artillery barrel

Modern models of aviation artillery weapons are pulsed heat engines that convert the energy of a powder charge into the energy of highly compressed and heated powder gases (hereinafter referred to as gases), which, when expanding, perform work on communicating kinetic energy to the projectile. In the context of artillery science, aviation artillery weapons and ammunition are structured as a system that interacts with heat sources and the environment, sequentially completing thermodynamic cycles. The main element that is most intensively subjected to thermophysical loads and has a significant impact on the combat qualities and cost of aviation artillery weapons is a small-caliber artillery barrel (hereinafter referred to as the barrel). As a result, the problem of determining the temperature field of the barrel is one of the central problems of designing aviation artillery weapons and optimizing firing modes. The successful solution of this problem largely depends on the accuracy of modeling the processes of heat transfer to the channel and from the outer wall of the barrel during firing. At the same time, an adequate synthesis and calculation of the relations describing the phenomenon of convection accompanying the shot is difficult, which is due to the presence of phase transformations in the state of gases; the simultaneous presence of supersonic and subsonic zones in the solution regions; the existence of laminar, turbulent flows and other non-linear formations. The aim of the work is to develop a relatively simple and acceptable for engineering practice mathematical model of heat transfer inside and around the wellbore with near-wall coolant flows (hereinafter referred to as the model). Achieving the goal of the work is carried out by a concentrated choice of criterial equations of the apparatus of thermodynamic similarity, corresponding to the geometric and physical conditions for the uniqueness of the processes of loading the shaft. The introduction of functions that take into account the dependence of the thermophysical properties of gases on temperature made it possible to increase the accuracy of determining the parameters of heat transfer during a shot by 19% in comparison with the known results. The developed model can be used in applied calculations related to determining the thermal state of the wellbore. The specialization of the object of study does not exclude the possibility of refining the model for the purpose of mathematical representation of thermal effects in thermally stressed structures of complex shape.

On a nonlocal boundary value problem of periodic type for the three-dimensional mixed-type equations of the second kind in an infinite parallelepiped

Как известно, в работе А.В. Бицадзе показано, что задача Дирихле для уравнения смешанного типа некорректна. Естественно возникает вопрос: нельзя ли заменить условия задачи Дирихле другими условиями, охватывающими всю границу, которые обеспечивают корректность задачи? Впервые такие краевые задачи (нелокальные краевые задачи) для уравнения смешанного типа были предложены и изучены в работах Ф.И. Франкля при решении газодинамической задачи об обтекании профилей потоком дозвуковой скорости со сверхзвуковой зоной, оканчивающейся прямым скачком уплотнения. Близкие по постановке задачи для уравнения смешанного типа второго рода второго порядка, имеются в работах А.Н. Терехова, С.Н. Глазатова, М.Г. Каратопраклиевой и С.З. Джамалова. В этих работах для уравнения смешанного типа второго рода второго порядка изучены нелокальные краевые задачи в ограниченных областях. Такие задачи для уравнения смешанного типа первого рода в трехмерном случае (в частости, для уравнения Трикоми) в неограниченных областях изучены в работах С.З. Джамалова и Х. Туракулова. Для уравнений смешанного типа второго рода в неограниченных областях нелокальные краевые задачи в многомерном случае практически не исследованы. С этой целью в данной работе в неограниченном параллелепипеде формулируется и изучается нелокальная краевая задача периодического типа для трехмерного уравнения смешанного типа второго рода второго порядка. Для доказательства единственности обобщённого решения используется метод интегралов энергии. Для доказательства существования обобщённого решения сначала используется преобразование Фурье и в результате получается новая задача на плоскости, а для разрешимости этой задачи используется методы «ε-регуляризации»и априорных оценок. Используя эти методы, и равенство Парсеваля, докажем единственность, существование и гладкость обобщённого решения одной нелокальной краевой задачи периодического типа для трехмерного уравнения смешанного типа второго рода второго порядка. As is known, A.V. Bitsadze in his studies pointed out that the Dirichlet problem for a mixed-type equation, in particular for a degenerate hyperbolic-parabolic equation, is ill-posed. The question naturally arises: is it possible to replace the conditions of the Dirichlet problem with other conditions covering the entire boundary, which will ensure the well-posedness of the problem? For the first time, such boundary value problems (nonlocal boundary value problems) for a mixed-type equation were proposed and studied in the works of F.I. Frankl when solving the gas-dynamic problem of subsonic flow around airfoils with a supersonic zone ending in a direct shock wave. Problems close in formulation to a mixed-type equation of the second order were considered in the studies by A.N. Terekhov, S.N. Glazatov, M.G. Karatopraklieva and S.Z. Dzhamalov. In these papers, nonlocal boundary value problems in bounded domains are studied for a mixed-type equation of the second kind of the second order. Such problems for a mixed-type equation of the first kind in the three-dimensional case (in particular, for the Tricomi equation) in unbounded domains are studied in the works of S.Z. Dzhamalov and H. Turakulov. For mixed-type equations of the second kind in unbounded domains, nonlocal boundary value problems in the multidimensional case are practically not studied. In this article, nonlocal boundary value problem of periodic type for a mixed-type equation of the second kind of the second order, is formulated and studied in an unbounded parallelepiped. To prove the uniqueness of the generalized solution, the method of energy integrals is used. To prove the existence of a generalized solution, the Fourier transforms is used and as a result, a new problem is obtained on the plane. And for the solvability of this problem, the methods of “ε-regularization”and a priori estimates are used. The uniqueness, existence, and smoothness of a generalized solution of a nonlocal boundary value problem of periodic type for a three-dimensional mixed-type equation of the second kind of the second order are proved using above-mentioned methods and Parseval equality.

Condensation of subsonic and supersonic gas flows on a flat surface

Intense heat-mass transfer in a gas flow to a condensation surface is studied with the consistent atomistic and kinetic theory methods. The simple moment method is utilized for solving the Boltzmann kinetic equation (BKE) for the nonequilibrium gas flow and its condensation on the surface, while molecular dynamics (MD) simulation of a similar flow is used for verification of BKE results and boundary conditions applied at the surface. We demonstrate that BKE can provide the flow profiles close to those obtained from MD simulations in both subsonic and supersonic regimes of steady gas flows. In particular MD confirms that the surface at a particular temperature condenses completely a steady supersonic flow with a shock front standing in reference to this surface. Hence it can be interpreted as a permeable condensating piston, which compresses and absorbs completely the incoming gas in contrast to a common nonabsorbing impermeable piston. The shock front divides the vapor flow on the supersonic and subsonic zones, and condensation of shocked gas happens in a subsonic regime. Conditions required for the complete, partial, and ceased condensation regimes are determined. It is shown that a runaway shock front can stop an inflow gas and condensation is ceased if the surface temperature is above some critical threshold determined by a saturation line of gas and its shock Hugoniot. We also demonstrate that the elementary theory of condensation has a good accuracy in a surprisingly wide range of flow parameters.

Numerical simulations of vapor kerosene/air rotating detonation engines with different slot inlet configurations

To investigate the effects of slot inlet configurations on premixed vapor kerosene/air rotating detonation engines, a series of cases with different injection patterns, including baseline inlet, outer slot inlet, middle slot inlet, and inner slot inlet, are simulated by solving three-dimensional reactive Euler equations. Stable rotating detonation waves were obtained in the baseline and the outer slot inlet cases. Instead, an unsteady triple-wave mode was obtained in the middle slot inlet case and a decoupled detonation was observed in the inner slot inlet case. A long supersonic injection zone was observed in the outer slot inlet case and the main total pressure loss was found in the buffer zone. The propagation mechanism analysis demonstrates the crucial role of the outer wall in the propagation of rotating detonation waves, where the detonation waves near the outer wall tend to be over-driven and contributes to the stable propagation of detonations. A positive mass average total pressure gain of 48.0% was obtained in the baseline, confirming the total pressure gain ability of the kerosene/air rotating detonation engines. The simulation results indicate the area ratio between the outlet and the inlet is of great importance for obtaining the positive total pressure gain.

Subsonic and Supersonic Gas Flows to Condensation Surface

Intense heat-mass transfer in a gas flow to a condensation surface is studied with the consistent atomistic and kinetic theory methods. The simple moment method is utilized for solving the Boltzmann kinetic equation (BKE) for the nonequilibrium gas flow and its condensation, while molecular dynamics (MD) simulation of a similar flow is used for verification of BKE results. We demonstrate that BKE can provide the steady flow profiles close to those obtained from MD simulations in both subsonic and supersonic regimes of steady gas flows. Surprisingly, the elementary theory of condensation is shown with BKE results to have a good accuracy in a wide range of gas flow parameters. MD confirms that a steady supersonic gas flow condensates on a surface at the distinctive temperature after formation of a standing shock front in reference to this surface, which can be interpreted as a permeable condensating piston. The last produces the shock compression but completely absorbs incoming gas flow in contrast to a common impermeable piston. The shock front divides the vapor flow on the supersonic and subsonic zones, and condensation of compressed gas happens in the subsonic regime. The complete and partial condensation regimes are discussed. It is shown that above the certain surface temperatures determined by the shock Hugoniot the runaway shock front stops an inflow gas and condensation is ceased.

Investigating the influence of compressibility on the second mode flutter instability of a clamped–free cylinder in axial flow using fluid–structure interaction simulations with the Chimera technique

In this research a numerical framework is presented and validated to investigate the influence of compressibility on the flutter instability of a clamped–free cylinder in axial flow by means of fluid–structure interaction (FSI) simulations. The FSI simulations consist of a computational fluid dynamics (CFD) model coupled with a finite-element model. In the CFD model the large deformation of the cylinder is handled by employing a Chimera technique in which the background mesh remained fixed.The framework was first validated by performing simulations in water flow and comparing these to experimental data from literature. Afterwards, the framework was applied to air flow simulations. The inlet velocity and structural parameters were adapted to investigate the effect of compressibility at different Mach numbers. The dimensionless velocity is kept constant in order to remain in the same working point with second mode flutter.The simulations showed that for a low Mach number there is negligible influence of compressibility on the established flutter regime. At higher Mach numbers the compressibility triggers a more violent flutter regime in which the contact between the cylinder and the channel wall extends over a larger length. In the simulations the flutter motion starts out planar and, given sufficient time, usually develops into a rotational motion. It was also observed that supersonic zones and, consequently, shocks are created in the flow while the inlet is subsonic.

Theoretical analysis of quasi-one-dimensional compressible magnetohydrodynamic channel flow

A theoretical analysis of quasi-one-dimensional, steady, inviscid, compressible channel flow at a low magnetic Reynolds number with variable cross-section is performed in this paper. A second-order nonlinear dynamical system describing the variation of physical parameters is investigated in the phase plane. The characteristics of all possible channel flow with a constant electromagnetic field are obtained by the phase plane and the isomorphism of labeled graphs. It is revealed that the magnetic interaction number novelly derived from the variation rate of the cross-sectional area could significantly affect the phase trajectory in the phase plane of dimensionless velocity and Mach number. Meanwhile, the phase trajectory is only dependent on this magnetic interaction number. Further analysis of the second-order dynamical system discovers five critical values in the range of the magnetic interaction number. These five critical values can divide the whole range into eight subsets under the isomorphism of labeled graphs, forming eight equivalence classes of the phase plane. The study of such eight equivalence classes reveals that the variable cross-section flow in the phase plane can be viewed as a linear superposition of constant cross-section magnetohydrodynamic flow and isentropic flow, the weight ratio being exactly the magnetic interaction number. Consequently, for the divergent channel, the acceleration region in the supersonic zone is larger than that of the constant cross-section flow, while for the convergent channel, only the acceleration region in the subsonic zone is larger than that of the constant cross-section flow.

Experimental study on flow oscillating mechanism of non-condensable gas jet through one- or multi-hole sparger in quiescent water

Submerged gas jet plays a very important role in many industries occasion. It often causes load of pool structure induced by flow oscillation. Exploring the mechanism and key influencing factors of submerged non-condensable gas jet oscillation characteristics is of great significance to ensure the safe operation of the equipment. In the present work, the phenomenon of flow oscillation for non-condensable gas jet through a horizontal one- or multi-hole sparger from sonic to supersonic zone is studied experimentally. The steady and unsteady characteristic of flow process and flow structure are visualized by using high-speed camera, and pressure oscillation is obtained by simultaneous pressure measurement. Experimental results show that gas Froude number and sparger structure have great influence on the gas flow pattern. With Froude number increasing, gas flow pattern is obviously reinforced. Multi-hole sparger significantly weakens the gas jet behavior at horizontal direction away from holes comparing with one-hole sparger under the same Froude number. The spectrogram approaches of pressure oscillation indicates the dynamic pressure data contains two principal frequency components. First dominant frequency is identical with that of transient interfacial fluctuation, which is related to gas jet periodic expansion feedback and independent on Froude number and position. And second dominant frequency is not changed with the position, but decreases significantly with the increase of Froude number. Intensity of pressure oscillation increases with Froude number increasing and the distance from sparger decreasing. In addition, the multi-hole sparger can significantly reduce intensity of pressure oscillation under the same Froude number. Dimensionless relation is developed to evaluate the Froude number and sparger structure on the second dominant frequency and intensity of pressure oscillation. This study can be applied to well understanding of flow oscillation mechanism and provide technical support for looking for mitigation measures to reduce oscillation in the future.

Mathematical modeling of theim pulse bubbling process of bulk mass by the coolant flow

The main directions of pneumodynamic system usage for storage of bulk agricultural products are bubbling and pneumatic mixing; loading and unloading of technological masses. During pneumodynamic impulse wave formation with alternation of supersonic and subsonic zones, which are limited by shock waves, sound force increasing on the technological mediumabout 150…170 dB, pressure increasing on the product mass due to compression-stretching at the pulse limits to amplitudes of 6…15 barare caused, that promotes implementation of loosening processes during the grain material storage. The developed scheme of the studied process involves the opposite arrangement of pneumatic impulse generators, which allows the formation of a stationary wave, that spreads the pulse energy in both longitudinal and transverse directions, covering the maximum space of the free flowing technological medium. Using the method of D’Alembert for solving the equations, methods of mathematical analysis and their processing in the MathCAD mathematical environment graphical and analytical dependences of force parameters of oscillatory system have been obtained. Choosing an effective mode of pneumodynamic loosening, the force pulse magnitude and the regularities of its change under conditions of the highest mechanical resistance of the free-flow mass have been used as the evaluation criteria the standing wave energy.

Experimental Study of a New Method for Reducing Airfoil Wave Drag at Transonic Speeds

This work proposes a new method for reducing the wave drag of an airfoil at transonic speeds, which consists in creating a section of a microwaved upper surface in the local supersonic zone. Weighted and physical studies are carried out for the initial and modified airfoils. It was experimentally established that the proposed new approach results in a system of weak compression waves, a gradual deceleration of the supersonic flow, and a decrease in the Mach number before the rear shock wave—and, as a result, a decrease in its intensity weakening and a decrease in wave drag.

Экспериментальное исследование нового способа уменьшения волнового сопротивления профиля при трансзвуковых скоростях

A new method is proposed for wave drag reducing of a supercritical airfoil at transonic speeds, which is associated with the organization of a microwave section in a local supersonic zone on the upper surface. Simultaneously with optical studies, aerodynamic loads acting on a model were obtained. It is experimentally established that the proposed approach leads to the formation of a system of weak compression waves, to consecutive deceleration of the supersonic flow, to decrease of the Mach number in front of the shock wave, and, as a consequence, to weakening of its intensity and to reducing of the airfoil wave drag

NUMERICAL SIMULATION OF TRANSONIC FLOW OVER SPACE VEHICLES

In this study peculiarities of transonic flow over a space vehicle similar to that of the ExoMars project are studied numerically. Dependencies of axial force coefficients on Mach number are obtained. Flow field transformation is shown when Mach number changes from subsonic to supersonic values. Critical Mach number, at which local supersonic zones disappear, is found.

Various approaches to determine active regions in an unstable global mode: application to transonic buffet

The transonic flow field around a supercritical airfoil is investigated. The objective of the present paper is to enhance the understanding of the physical mechanics behind two-dimensional transonic buffet. The paper is composed of two parts. In the first part, a global stability analysis based on the linearized Reynolds-averaged Navier–Stokes equations is performed. A recently developed technique, based on the direct and adjoint unstable global modes, is used to compute the local contribution of the flow to the growth rate and angular frequency of the unstable global mode. The results allow us to identify which zones are directly responsible for the existence of the instability. The technique is firstly used for the vortex-shedding cylinder mode, as a validating case. In the second part, in order to confirm the results of the first part, a selective frequency damping method is locally used in some regions of the flow field. This method consists of applying a low-pass filter on selected zones of the computational domain in order to damp the fluctuations. It allows us to identify which zones are necessary for the persistence of the instability. The two different approaches give the same results: the shock foot is identified as the core of the instability; the shock and the boundary layer downstream of the shock are also necessary zones while damping the fluctuations on the lower surface of the airfoil; and outside the boundary layer between the shock and the trailing edge or above the supersonic zone does not suppress the shock oscillation. A discussion on the several physical models, proposed until now for the buffet phenomenon, and a new model are finally offered in the last section.

Redchyts Evaluation of aerodynamic and thermal loads on the HYPERLOOP capsule fuselage in a partly evacuated tube

Aerodynamics occupies an important place in the design of high-speed ground transportation systems. When a vehicle is moving at a speed above 500 km/h under atmospheric pressure, the main energy is spent to overcome the aerodynamic drag. Creating a rarefied atmosphere inside a sealed pipe in order to significantly reduce energy loss is one of the key ideas of the HYPERLOOP project [1].The paper assesses the aerodynamic and thermal loads on the HYPERLOOP capsule fuselage in a partly evacuated tube based on the numerical solution of the Navier-Stokes equations of compressible flow closed by a differential turbulence model [2-4]. Numerical modeling was carried out with the help of the computational fluid dynamics software developed by the scientific researchers of the Institute of Transport Systems and Technologies of the National Academy of Sciences of Ukraine [5].It was shown that even under conditions of low air pressure in a partly evacuated tube the high-speed movement of the HYPERLOOP capsule will be accompanied by the formation of local supersonic zones, shock waves and non-stationary vortex systems. The structure of the flow essentially depends on geometry of the streamlined capsule and the speed of its movement.It was found that the flow structure and the values of aerodynamic dimensionless coefficients weakly depend on the pressure in the partly evacuated tube. Thus, the aerodynamic forces acting on the HYPERLOOP capsule at the same speeds are almost directly proportional to the pressure value in the tube.A certain problem in the design of the HYPERLOOP type high-speed vehicles will be the aerodynamic heating of the capsule fuselage. When the capsule moves at transonic speed the temperature of the outer surface of the capsule will be 60÷900 C. This heat load can have a negative impact on the performance of onboard power supply and control systems, as well as on the ensuring of the passengers’ comfort on the way.

Effect of Side Gust on Performance of External Compression Supersonic Inlet

This Paper reports a computational investigation on the effects of side gust on the performance of a double-cone external compression supersonic inlet at Mach 1.8. The supersonic inlet geometry comprises three zones: a supersonic zone, a transit zone, and a subsonic zone. The supersonic zone is designed numerically using the Taylor–Maccoll method, while the transit and subsonic zones are designed using a methodology from literature. A three-dimensional structured mesh is generated by using the ICEM computational fluid dynamics software. Detailed three-dimensional simulations are performed using the ANSYS Fluent 18.2 code. The grid independency tests are performed by using local grid refinements and varying the number of grid points from 2.5 to 9.5 million. Further, the Fluent code is validated by comparing predictions with those using the SUPIN and Wind-US codes. The effects of side gust on the flowfield and oblique and normal shocks are analyzed by examining the Mach number and pressure distributions in the three zones. The inlet performance is characterized in terms of total pressure loss, flow distortion, and mass flow ratio parameters for a side gust of and gust angles of 30, 60, and 90 deg. Results indicate that the inlet performance is significantly affected by the side gust, especially at small gust angles.

Research on forebody active disturbed flow characteristics of slender body in supersonic field

Instantaneous turn rate plays an extremely important role in the generic missile configuration with an appropriate angle of attack in supersonic air flows. Under these special supersonic flow conditions, the dominant aerodynamic coefficient of the generic missile, which was simplified to a slender baseline geometry with a blunt-cone nose, was the side force coefficient. Active disturbed flow control technology on a supersonic missile body referred to the design of micro-flow effectors and controlled the flow around the missile by actively regulating the height of the micro-flow effectors around the missile surface, which allows for active control of the missile flight attitude. This paper used the small perturbation assumptions to calculate the side force model affected by the flow effectors and used Ansys Fluent® to analyze the separated vortex around the slender body, as well as the effects of regularity of the parameters for the micro-flow effector to the side force coefficient. In this paper, we also developed methods to analyze the supersonic complex air flow zones and analyzed the air flows around the body and the side force coefficient of the slender body by changing the parameters of the micro-flow effector structure, air flow field conditions and body structural parameters. The projects concluded that the simulation analysis method and analysis of the results can be used to guide active disturbed flow control systems and actuation device designs for compact and lightweight missiles to provide the necessary reference basis.

The complexity and mechanism of transonic aeroelastic problems

In high-speed flight, transonic aeroelasticity commonly exists, leading to various problems such as transonic flutter, buffeting and buzz. To solve these problems, a good understanding of the underlying physical mechanisms is critical. Unfortunately, the nonlinearity and unsteadiness of airflows complicate this process and consequently impede the development of aircraft design. Here using the numerical simulation and modeling of complex transonic flows, we developed a unified analytical method for aeroelastic stability and response problems. We then explored the mechanisms of three complex aeroelastic phenomena and unveiled their relationships. (1) Transonic buzz is in essence a single degree of freedom (SDOF) flutter caused by the coupling between the most unstable fluid mode and structural mode. SDOF flutter of this kind is possible only when the fluid exhibits sufficiently low damping; that is, the freestream flow is near the buffet boundary or in the low supersonic zone. Besides, the unstable frequency boundaries are determined by zero and pole of the open loop system. (2) The frequency lock-in phenomenon in the transonic buffeting flow is caused by the SDOF flutter in the unstably separated flow rather than resonance. In this process, the response undergoes a transition from the forced vibration to the self-excited flutter, which results in a deviation of the lock-in region from the resonance point. By contrast, the traditional uncoupled method misestimates the risk range and underestimates the amplitude of a vibration. (3) When the pitching degree of freedom is released, transonic buffet will be induced at a lower angle of attack, indicative of the drawbacks of predicting buffet onset by a rigid model. Actually, the elastic characteristic plays a key role in predicting buffet onset in aircraft design. Collectively, the large-amplitude structural vibration in the transonic flow is closely related to aeroelastic instability. The dynamic linear model can correctly predict the boundary of some complex dynamic phenomena. The complexity of transonic aeroelasticity mainly arises from the stability reduction of airflows. Different from classical aeroelastic problems, the new fluid mode is derived from the reduction of fluid stability. The coupling between such a fluid mode and structural mode often leads to complex phenomena in transonic flows.