Aerodynamic Stability Analysis Research Articles

Coupled Kernel Extreme Learning Machine and Cuckoo Search for Aerodynamic Modeling and Stability Analysis of Spinning Projectiles

Coupled Kernel Extreme Learning Machine and Cuckoo Search for Aerodynamic Modeling and Stability Analysis of Spinning Projectiles

Aerodynamic stability analysis of the concrete ceiling reinforced with advanced functionally graded nano-materials: A sustainable approach for construction materials

Proper consideration should be given to the stability of new concrete in order to assure the quality of building engineering, while also demanding its excellent flowability. The inadequate initial state stability negatively impacts the long-term durability of reinforced concrete structures, although this issue has not been well addressed. This work focuses on assessing the aerodynamic response of concrete ceilings reinforced with advanced functionally graded nano-materials. As the reinforcement of the current concrete structure, graphene oxide powders (GOPs) are used with improved material properties than other types of reinforcement. For mathematical modeling of the current structure, Reddy’s Higher-order Shear Deformation Theory is used to model the current work’s displacement fields. Also, the perturbation aerodynamic force is mathematically described using the Bernoulli equation for potential flow. After that using a method that involves separating variables, we may get the answer for the aerodynamic pressure in its ultimate form. Haber-Schaim foundation made of auxetic material in the Cartesian coordinate system is used to model the foundation of the current work with high accuracy. After obtaining the governing equations and associated boundary conditions, a meshless approach with weighted orthogonal basis and Kronecker delta-based shape functions are used to solve the equations. Finally, some suggestions for improving the aerodynamics and flutter velocity of airflow of the presented concrete plate reinforced by GOPs are presented for related aerodynamics industries.

Aerodynamic and thermo-acoustic stability analysis in a super-steady reactive flow

Aerodynamic and thermo-acoustic stability were systematically analyzed to reveal the underlying cause of the super-steady performance found in a strong rotating reactive flow, which is achieved using a stratified vortex-tube combustor (SVC) employing methanol as fuel. Results show that the SVC possesses a wide stability limit and weak pressure fluctuation with a uniform flame. The lean stability limit is always smaller than 0.2 and the amplitude of pressure fluctuation is generally within 2 kPa, indicating a super-steady combustion process. The large tangential velocity produces a large centrifugal force that suppresses the turbulent motion to promote aero-dynamic stability, yielding a small Froude number. The delay in the mixing process is the crucial reason for the generation of the stratified distribution of species and the triple-flame structure. The large transport fluxes of the species and enthalpy promote the reaction and ignition processes to intensify the combustion, which produces a large density gradient to promote thermo-acoustic stability. The large tangential velocity and density gradient result in a large Richardson number, suggesting the laminarization of the fluid. The momentum flux and its fluctuation decrease distinctly downstream of the vortex-flow because of the strong momentum exchange and transfer in the vortex flow, which weakens the pressure fluctuation in the post-flame zone. The intensified combustion can also increase the burning velocity, and promotes its matching with the flow field. The reduced momentum flux and the increased burning velocity are responsible for good thermo-acoustic stability.

AERODYNAMIC CHARACTERISTIC AND AIRPLANE STABILITY AT THE PLERIMENARY DESIGN STAGE

<p>Preliminary Design is the second stage in aircraft design after knowing the needs and specifications at the Conceptual Design stage. This Preliminary Design includes the conceptual design evaluation of aircraft performance in several fields, such as aerodynamics, engine power, and aircraft structure. This Job Training Report illustrates how is taken to conduct aerodynamic and aircraft stability analysis at the plerimenary design stage using NASA's open source software, Open Vehicle Simulation Program (OpenVsp). The aircraft model is simulated until aerodynamic and stability data are obtained which later can be processed for aircraft control design. </p>

Actuator 기법을 이용한 프로펠러 3축 성분 힘/모멘트 해석

For aerodynamic performance and stability analysis of distributed propulsion aircraft which adopt many propellers/rotors, all the 3-axial components forces and moments must be properly taken into account. In this study, two actuator methods have been established to be capable of numerical simulations including all the force and moment components produced by rotor/propeller. A procedure in which the 3-axial components are transformed from the aerodynamic force and moment of blade elements has been added to actuator disk method(ADM) and actuator surface method(ASM). The numerical analyses are carried out for a single propeller of quad tilt propeller(QTP) at various flight conditions including the variation of side slip angle. The results are compared with wind tunnel test data and full CFD simulation with overset grid. All the force and moment components are found to agree very well in terms of engineering purposes and the present methods are identified to be numerically very efficient compared to full CFD. Power-on effect and longitudinal stability of the full configuration of QTP is further analyzed by carrying out the additional numerical simulations. The results indicate that the present methods is practically very useful to investigate the aerodynamic performance of distributed propulsion aircraft.

Low speed lateral-directional aerodynamic and static stability analysis of a hypersonic waverider

Hypersonic waveriders have the potential to significantly reduce travel times on long haul civilian transport routes. The design of hypersonic aircraft is heavily influenced by the aerodynamic efficiency at the cruise Mach number, resulting in less than ideal geometries for subsonic flight. Waverider aerodynamics and stability in the low speed regime is rarely investigated and not well understood, but is crucial for horizontal take-offs and landings. This paper presents a combination of numerical simulation results and experimental data for the low speed propelled variant of the Mach 8 HEXAFLY-INT waverider. Aerodynamic, control and stability testing for lateral-directional cases was conducted in the University of Sydney 4 foot by 3 foot low speed facility. Computational fluid dynamics simulations are compared with wind tunnel tests for angles of attack between -5 and 15 degrees and angles of sideslip between -8 and 8 degrees. Throughout these ranges, aileron and rudder deflections up to 10 degrees are investigated. Results show that the vehicle aerodynamics are dominated by asymmetric wing and fin vortices, resulting in non-linear aerodynamic forces. At a centre of gravity location of 44.4% of the vehicle length the aircraft is stable directionally, but has lateral instability at angles of attack below -2 degrees. This is attributed to the low mounted wings with anhedral. The instability is minor and is not expected to result in an uncontrollable condition. Lowering the centre of gravity by approximately 2 centimetres, or 17% of the local fuselage height, can correct the instability. Lateral-directional dynamic stability was predicted using static derivatives and was found to be stable through the entire AoA range tested, with no dependence on mass moments of inertia. Both aileron and rudder controls are found to provide sufficient control authority, but the aircraft may benefit from increased rudder size. The results from this study, along with previous work on longitudinal stability and performance show the feasibility of moving to the flight test program, but aircraft dynamic stability must first be investigated.

Conceptual design of an aircraft for Mars mission

PurposeThe purpose of this paper is to present the results of a conceptual design of Martian aircraft. This study focuses on the aerodynamic and longitudinal dynamic stability analysis. The main research questions are as follows: Does a tailless aircraft configuration can be used for Martian aircraft? How to the short period characteristic can be improved by side plates modification?Design/methodology/approachBecause of a conceptual design stage of this Martian aircraft, aerodynamic characterises were computed by the Panukl package by using the potential flow model. The longitudinal dynamic stability was computed by MATLAB code, and the derivatives computed by the SDSA software were used as the input data. Different aircraft configurations have been studied, including different wing’s aerofoils and configurations of the side plate.FindingsThis paper presents results of aerodynamic characteristics computations and longitudinal dynamic stability analysis. This paper shows that tailless aircraft configuration has potential to be used as Martian aircraft. Moreover, the study of the impact of side plates’ configurations on the longitudinal dynamic stability is presented. This investigation reveals that the most effective method to improve the short period damping ratio is to change the height of the bottom plate.Practical implicationsThe presented result might be useful in case of further design of the aircrafts for the Mars mission and designing the aircrafts in a tailless configuration.Social implicationsIt is considered by the human expedition that Mars is the most probable planet to explore. This paper presents the conceptual study of aircraft which can be used to take the high-resolution pictures of the surface of Mars, which can be crucial to find the right place to establish a potential Martian base.Originality/valueMost of aircrafts proposed for the Mars mission are designed in a configuration with a classic tail; this paper shows a preliminary calculation of the tailless Martian aircraft. Moreover, this paper shows the results of a dynamic stability analysis, where similar papers about aircrafts for the Mars mission do not show such outcomes, especially in the case of the tailless configuration. Moreover, this paper presents the results of the dynamic stability analysis of tailless aircraft with different configurations of the side plates.

The aerodynamic stability of a new type of Multi-tower cable-stayed bridge with rhombic stiffening cables

Aerodynamic stability is an important problem in the design and research of long-span multi-tower cable-stayed Bridges. The three-dimensional nonlinear aerodynamic stability analysis method is used to qualitatively analyze the aerodynamic stability of a new type of rhombic stiffened cable-stayed bridge in this paper, and compared with conventional cable-stayed bridges. The results show that the new rhombus stiffener can greatly increase the longitudinal stiffness of the structure and reduce the vibration period of the structure. The maximum lateral displacement, vertical displacement and torsion Angle of the structure under wind load are reduced, and the critical unstable wind speed of the structure is increased. It can be seen that the aerodynamic stability of the new type of rhombus cable-stayed bridge is better than conventional cable-stayed bridge.

Aerodynamic stability analysis of geometrically nonlinear orthotropic membrane structure with hyperbolic paraboloid in sag direction

This paper studies the aerodynamic stability of a tensioned, geometrically nonlinear orthotropic membrane structure with hyperbolic paraboloid in sag direction. Considering flow separation, the wind field around membrane structure is simulated as the superposition of a uniform flow and a continuous vortex layer. By the potential flow theory in fluid mechanics and the thin airfoil theory in aerodynamics, aerodynamic pressure acting on membrane surface can be determined. And based on the large amplitude theory of membrane and D\'Alembert\'s principle, interaction governing equations of wind-structure are established. Then, under the circumstance of single-mode response, the Bubnov-Galerkin approximate method is applied to transform the complicated interaction governing equations into a system of second-order nonlinear differential equation with constant coefficients. Through judging the frequency characteristic of the system characteristic equation, the critical velocity of divergence instability is determined. Different parameter analysis shows that the orthotropy, geometrical nonlinearity and scantling of structure is significant for preventing destructive aerodynamic instability in membrane structures. Compared to the model without considering flow separation, it\'s basically consistent about the divergence instability regularities in the flow separation model.

Aeroelastic reliability and sensitivity analysis of a plate interacting with stochastic axial airflow

The aeroelastic reliability and sensitivity of a simply supported isotropic plate interacting with upper axial airflow are investigated. Based on the assumed mode method and the linear potential flow theory, the equation of motion of the plate interacting with axial airflow is established using the Hamilton’s principle. The limit state function representing the aeroelastic failure mode is obtained from aerodynamic stability analysis of the plate. The mean value first order second moment method is adopted to analyze the aeroelastic reliability and sensitivity of the plate. The effects of the stochastic properties of the flow velocity, flow density, and the plate geometry dimensions on the aeroelastic reliability are analyzed. From the results, it can be seen that the aeroelastic reliability decreases with increasing velocity and mass density of the airflow. The flow mass density has more significant effects on the reliability sensitivity than the flow velocity. The reliability decreases with increasing length and width, and increases with increasing thickness of the plate. The standard deviation of the thickness of the plate has more significant effects on the aeroelastic reliability than the length and width. This study provides a new perspective on understanding the instability behaviors of the plate in airflow.

Vehicle Aerodynamic Stability Analysis under High Crosswinds

In a strong crosswind, wind direction change may result in vehicle stability loss. This paper presents a numerical study of vehicle aerodynamic stability in a high crosswind situation. We start with a model explanation and introduce the complete computational fluid dynamics (CFD) framework used in the study. Important CFD parameters such as mesh type, turbulence model, and boundary conditions are exposed and discussed in detail. We demonstrate and discuss the flow structure around a simplified truck model. Results of the CFD analysis are compared to experimental data, showing an almost perfect match. The final CFD outcomes are functions of aerodynamic coefficients that depend on the apparent wind angle. Then, CFD results are used in the application of an aerodynamic stability analysis for the truck model. Finally, the critical stability bounds are calculated, showing the marginal crosswind driving properties of the vehicles.

Aerodynamic Stability Analysis of Two Heterogeneous UAVs in Close Formation Flight System

The close formation flight of UAVs has many significant advantages over single vehicle flight. The aerodynamic stability analysis of two heterogeneous UAVs in close formation flight is detailed in the present paper. The issues of altitude changes and the associated shifts or changes in centre of gravity or moments, the equivalent actuator control surface deflections etc. are explained with the help of simulations. The short period frequency variations with these changes are also correlated with the help of pole-zero diagrams.

Aero-thermo-dynamic analysis of a low ballistic coefficient deployable capsule in Earth re-entry

The paper deals with a microsatellite and the related deployable recovery capsule. The aero-brake is folded at launch and deployed in space and is able to perform a de-orbiting controlled re-entry. This kind of capsule, with a flexible, high temperature resistant fabric, thanks to its lightness and modulating capability, can be an alternative to the current “conventional” recovery capsules. The present authors already analyzed the trajectory and the aerodynamic behavior of low ballistic coefficient capsules during Earth re-entry and Mars entry. In previous studies, aerodynamic longitudinal stability analysis and evaluation of thermal and aerodynamic loads for a possible suborbital re-entry demonstrator were carried out in both continuum and rarefied regimes. The present study is aimed at providing preliminary information about thermal and aerodynamic loads and longitudinal stability for a similar deployable capsule, as well as information about the electronic composition of the plasma sheet and its possible influence on radio communications at the altitudes where GPS black-out could occur. Since the computer tests were carried out at high altitudes, therefore in rarefied flow fields, use of Direct Simulation Monte Carlo codes was mandatory. The computations involved both global aerodynamic quantities (drag and longitudinal moment coefficients) and local aerodynamic quantities (heat flux and pressure distributions along the capsule surface). The results verified that the capsule at high altitude (150km) is self-stabilizing; it is stable around the nominal attitude or at zero angle of attack and unstable around the reverse attitude or at 180° angle of attack. The analysis also pointed out the presence of extra statically stable equilibrium trim points.

Numerical Prediction of the Influence of Thrust Reverser on Aeroengine’s Aerodynamic Stability

AbstractA numerical method was developed to predict the aerodynamic stability of a high bypass ratio turbofan engine, at the landing stage of a large transport aircraft, when the thrust reverser was deployed. 3D CFD simulation and 2D aeroengine aerodynamic stability analysis code were performed in this work, the former is to achieve distortion coefficient for the analysis of engine stability. The 3D CFD simulation was divided into two steps, the single engine calculation and the integrated aircraft and engine calculation. Results of the CFD simulation show that with the decreasing of relative wind Mach number, the engine inlet will suffer more severe flow distortion. The total pressure and total temperature distortion coefficients at the inlet of the engines were obtained from the results of the numerical simulation. Then an aeroengine aerodynamic stability analysis program was used to quantitatively analyze the aerodynamic stability of the high bypass ratio turbofan engine. The results of the stability analysis show that the engine can work stably, when the reverser flow is re-ingested. But the anti-distortion ability of the booster is weaker than that of the fan and high pressure compressor. It is a weak link of engine stability.

Preliminary aerodynamic and static stability analysis for hybrid buoyant aerial vehicles at low speeds using digital DATCOM

It is well-known that air transportation of passengers and goods is a large market in the world of aviation. Hybrid buoyant aerial vehicles have the potential to be candidates for such applications. This paper addresses the preliminary static stability analysis for hybrid buoyant aerial vehicles in which a novel concept of ballonet arrangement is applied. A study was performed to assess the suitability of commercial off-the-shelf software for this task. A generic geometric model was created to obtain the lift and drag characteristics of the aircraft and provide geometric parameters. These parameters were input into DATCOM, which was used to model the aerodynamic characteristics and to determine the stability and control derivatives for static analysis and airship performance enhancement. This study demonstrates that the aerodynamic and stability trends for low-speed airships can be obtained and analyzed using DATCOM.

Longitudinal stability analysis of a suborbital re-entry demonstrator for a deployable capsule

In the field of atmospheric re-entry technology several research and industrial projects are based on the design of deployable, umbrella-like Thermal Protection Systems (TPSs) and aero-brakes. These systems are made of flexible, high temperature resistant fabrics, folded at launch and deployed in space for de-orbit and re-entry operations.This technology is very promising for low cost research and industrial applications, but requires to be validated by experimental flight tests. The University of Naples “Federico II” is currently working on the development of different down-scaled technological demonstrators for this kind of capsule to be launched by different classes of sounding rockets.In the present work an aerodynamic longitudinal stability analysis for a possible, suborbital re-entry demonstrator, has been performed in continuum and rarefied regimes.The longitudinal stability behavior of the capsule, along the entire re-entry path, has been investigated in the whole range of angle of attack and, in particular, around the nominal and the reverse equilibrium re-entry attitudes (i.e. around 0° and 180°, respectively) to implement a proper re-entry strategy able not to compromise the effectiveness of the flying system.

Design, performance evaluation and optimization of a UAV

Following current trends towards UAV innovative designs, a small size light UAV was designed, constructed and tested in flight. The purpose of this light UAV aircraft is to serve as a reconnaissance plane capable of carrying state-of-the-art photography and video equipment. The UAV is also equipped with first person view (FPV) systems for easier and more accurate control by a remote user. For the initial configuration, apart from classical conceptual design procedures, some new relations were developed and used. For the preliminary design, linear aerodynamic performance and stability analysis was carried out first. Next, the aerodynamic characteristics and efficiency of the airfoil section, the wing, and the full configuration were evaluated using CFD. Finally, further improvements of the aerodynamic efficiency of the full configuration were carried out through computational optimization.

Aerodynamic modeling and stability analysis of a high-speed train under strong rain and crosswind conditions

With the development of high-speed train, it is considerably concerned about the aerodynamic characteristics and operation safety issues of the high-speed train under extreme weather conditions. The aerodynamic performance of a high-speed train under heavy rain and strong crosswind conditions are modeled using the Eulerian two-phase model in this paper. The impact of heavy rainfall on train aerodynamics is investigated, coupling heavy rain and a strong crosswind. Results show that the lift force, side force, and rolling moment of the train increase significantly with wind speed up to 40 m/s under a rainfall rate of 60 mm/h. when considering the rain and wind conditions. The increases of the lift force, side force, and rolling moment may deteriorate the train operating safety and cause the train to overturn. A quasi-static stability analysis based on the moment balance is used to determine the limit safety speed of a train under different rain and wind levels. The results can provide a frame of reference for the train safe operation under strong rain and crosswind conditions.

Aerodynamic Stability Analysis of Geometrically Nonlinear Orthotropic Membrane Structure with Hyperbolic Paraboloid

This paper studies the aerodynamic stability of a tensioned, geometrically nonlinear orthotropic membrane structure with hyperbolic paraboloid. The aerodynamic force acting on the membrane surface is determined by the potential flow theory in fluid mechanics and the thin airfoil theory in aerodynamics. The interaction governing the equation of wind-structure is established on the basis of large-amplitude theory and the D’Alembert principle. Then, under the circumstance of single-mode response, the Bubnov-Galerkin approximate method is applied to transform the complicated interaction equation into a system of second-order nonlinear differential equations with constant coefficients. Through judging the stability of the system characteristic equation, the critical velocity of divergence instability is determined. Different parameter analysis shows that the orthotropy and geometrical nonlinearity is significant for preventing destructive aerodynamic instability in membrane structures. Compared to the planar model, there is a little inconsistency about the divergence instability regularities in the hyperbolic paraboloid model.

Nonlinear aerodynamic stability analysis of orthotropic membrane structures with large amplitude

The aerodynamic stability of orthotropic tensioned membrane structures with rectangular plane is theoretically studied under the uniform ideal potential flow. The aerodynamic force acting on the membrane surface is determined by the potential flow theory in fluid mechanics and the thin airfoil theory in aerodynamics. Then, based on the large amplitude theory and the D'Alembert's principle, the interaction governing equation of wind-structure is established. Under the circumstances of single mode response, the Bubnov-Galerkin approximate method is applied to transform the complicated interaction equation into a system of second order nonlinear differential equation with constant coefficients. Through judging the stability of the system characteristic equation, the critical divergence instability wind velocity is determined. Finally, from different parametric analysis, we can conclude that it has positive significance to consider the characteristics of orthotropic and large amplitude for preventing the instability destruction of structures.