Aerodynamic Characteristics Of Aircraft Research Articles

ВИЗНАЧЕННЯ АЕРОДИНАМІЧНИХ ХАРАКТЕРИСТИК ЛІТАЛЬНОГО АПАРАТА З НАДЗВУКОВИМ ШВИДКОСТЯМИ ПОЛЬОТУ

The aircraft aerodynamic characteristics at supersonic flight modes can be determined with a high level of accuracy through testing the aircraft in wind tunnels or through time-consuming three-dimensional and analytical computational methods. However, in certain cases when the aircraft aerodynamic characteristics are already known within a given Mach number range for supersonic flight, it is possible to develop a relatively simple mathematical model for the aircraft aerodynamic characteristics at supersonic speeds using the aerodynamic properties of the supersonic wing leading edge for flight speeds Mf ≥ 1.2M. The object of the study is the aircraft aerodynamic characteristics at supersonic flight speeds. The subject of the study is the impact of the aircraft geometric features on the mathematical model, which is used to determine its aerodynamic characteristics in the supersonic flight speed range. The study hypothesizes that to determine the aerodynamic characteristics of an aircraft at Mf ≥ 1.2, it is sufficient to identify the values of the aircraft aerodynamic parameters at a flight speed of Mf =1.2 and then use aerodynamic analytical dependencies for the supersonic wing leading edge to determine these parameters at Mf ≥ 1.2. A mathematical model of the aircraft aerodynamic characteristics in the supersonic flight speed range was developed. Coefficients of drag polar and zero-lift drag for the reference mode Mf = 1.2 have been identified by the developed mathematical model. Then, the Mach number range for the aerodynamic characteristics of the NASA 1044 configuration has been extended to supersonic speeds of Mf = 1.8…4.0. The resultsof the aerodynamic calculations, obtained in the form of dependencies of the drag polar and zero-lift drag coefficients on Mach number, and the aircraft polar plot, have been compared with known NASA data for the 1044 configuration aircraft. The average modeling error of the aircraft aerodynamic characteristics in the supersonic speed range is less than 3%.

Koopman neural operator approach to fast flow prediction of airfoil transonic buffet

Transonic buffet on airfoil is of great importance in the aerodynamic characteristics of aircraft. In the present work, a modified Koopman neural operator (KNO) is applied to predict flow fields during the transonic buffet process of the OAT15A [ONERA (National Office for Aerospace Studies and Research) Aerospatiale Transport aircraft 15 Airfoil] airfoil. Transonic buffet flow with different angles of attack is simulated by Reynolds averaged numerical simulation with the Menter's k−ω shear stress transport (SST) model at Reynolds number Re=3×106. A prediction model is directly constructed between the flow fields at several previous time nodes and that at the future time node by KNO. The predictions of flow fields with single sample and multi samples are performed to demonstrate the prediction accuracy and efficiency of KNO. The prediction of sequence flow fields based on the iterative prediction strategy is achieved for the transonic buffet process. The results indicate that KNO can achieve a fast and accurate prediction of flow physical quantities for the transonic buffet. Compared with other deep learning models including Unet and Fourier neural operator, KNO has a more advanced capability of predicting airfoil transonic buffet flow fields with higher accuracy and efficiency and less hardware requirements.

CFD Study of the Effect of Special Aerodynamic Devices on Saras MK II

In order to study the effect of special devices like spoilers, stabilons etc. on the aircraft aerodynamic characteristics, Computational Fluid Dynamics (CFD) simulations have been carried out for the flow past SARAS Mk II aircraft using an open source SU2 CFD solver with Spalart Allmaras (SA) turbulence model. The reduction in CL and increase in CD due to spoilers has been quantified which in turn reduces the landing distance of the aircraft. The effect of stabilons on the lateral stability of the aircraft has also been studied and the results are explained in terms of flow-field and aerodynamic coefficients. These studies have helped in making decisions on the configuration design.

Uncertainty quantification analysis with arbitrary polynomial chaos method: Application in slipstream effect of propeller aircraft

The slipstream effect of propeller aircraft has a major impact on aircraft aerodynamic characteristics. Predicting the interaction of propeller slipstream on flow field over a complete aircraft has been an important topic in the field of fluid mechanics. In the flight test, we found that parameters in the flight data of propeller aircraft exhibit significant stochastic characteristics, and the mechanism of the influence of these stochastic parameters on aerodynamic characteristics of propeller aircraft needs to be further studied. Therefore, we combine arbitrary Polynomial Chaos method with Computational Fluid Dynamics (CFD) according to the characteristics of stochastic parameter distribution, propose an uncertainty CFD analysis method, and apply it to the aerodynamic uncertainty analysis of propeller aircraft. Results show that the standard deviation (Std) of the pressure coefficient [Formula: see text] on the wing surface will form an extreme region at windward side and separation position, respectively, which will gradually decrease with the flow direction. Furthermore, the slipstream will reduce the local Std on wing surface, and the downwash caused by slipstream will change the Std distribution on the leading edge of the horizontal tail.

Parameterization investigation on distributed electric propulsion aircraft aerodynamic characteristics

Revealing the principle of distributed electric propulsion (DEP) plane aerodynamic design under the effect of strong aerodynamic coupling of distributed power-wing and the change law of total gain is the key to carrying out the design of distributed electric propulsion plane. For the distributed electric propulsion plane aerodynamic layout, the aerodynamic performance of the DEP configuration is studied based on the VLM-ADT aerodynamic characteristics fast solver method. This paper gives a set of fast parametric methods to research the aerodynamic performance of DEP layout, which mainly includes three comprehensive indexes such as lift-to-drag ratio L/D, power loading T/P, and lift loading L/P—focused on; the factor of propeller number, which affects the aerodynamic performance of DEP aerodynamic layout. As the propeller number increases, the lift-to-drag ratio decreases, but the wing’s lift efficiency increases.

Wall-Modeled Large-Eddy Simulation with Second-Order-Accurate Upwind Scheme

In aircraft aerodynamic design, it is essential for certification by analysis to estimate aircraft aerodynamic characteristics with high fidelity across the full flight envelope using computational fluid dynamics. Improving accuracy of the simulation of unsteady flows such as transonic buffet is one of the problems. Wall-modeled large-eddy simulation (WMLES) is expected to improve the accuracy. In this study, three quantitative requirements for the matching points, where LES feeds the wall model with flow variables, are proposed to ensure the accuracy of the WMLES with a second-order-accurate upwind scheme that is often used for engineering codes. These requirements are related to 1) matching point height, 2) the number of cells below the matching point, and 3) grid resolution at the matching point. The proposed requirements are assessed on a flat-plate turbulent boundary layer and a shock/turbulent boundary-layer interaction flow. As a result, it is clarified that all of the requirements are necessary to ensure the accuracy in terms of mean velocity, Reynolds stresses, and skin friction.

An enhanced hybrid deep neural network reduced-order model for transonic buffet flow prediction

In the transonic flight environment, transonic buffet has significant influence on the aerodynamic characteristics of aircraft. In the face of the strong nonlinear characteristics of transonic buffet, the reduced-order model (ROM) technology based on deep learning (DL) is introduced to study the flow field. In this article, an enhanced hybrid deep neural network (eHDNN) consisting of Convolutional Neural Network (CNN) and Convolutional Long Short-Term Memory (ConvLSTM) neural network is constructed as the ROM of unsteady transonic buffet flow field. By mining the spatial-temporal characteristic of buffet flow directly from large-scale flow field data, the eHDNN can predict complex flow characteristics such as shock wave motion in the unsteady buffet flow. Structural similarity information and nonlinear improvement strategies are introduced to improve the nonlinear expression ability of eHDNN. The predicted result is consistent with the numerical simulation and has high degree of prediction accuracy. In addition, the eHDNN has good generalization ability, which can predict the spatial-temporal evolution of buffet flow field at unknown angles of attack. The prediction method has good application prospect of the transonic buffet flow control and prediction, which also provides experience for DL modeling in other complex and strongly nonlinear flows.

A novel FEM-FVM coupled method of evaluating the explosion shock wave of a thermobaric bomb on the internal and external flow characteristics of aircraft

The high-temperature and high-pressure shock waves generated after the explosion of a thermobaric bomb have a considerable impact on the aerodynamic characteristics of aircraft. Taking a typical thermoelastic model as the object, the explosion process was calculated by LS-DYNA software. The obtained pressure–time history curve data were written into a UDF function and coupled with Fluent software. At the same time, the afterburning effect of the combustion agent was considered. The influence of the explosion effect on the flow field characteristics of an M6 wing and the inlet of a turboprop engine was evaluated. Thus, an FEM-FVM co-simulation method was established. The results showed that when affected by the explosion shock wave of a thermobaric bomb, the maximum changes in the lift, drag, and pitch moment of an M6 wing in a very short period of time are 29, 13, and 7 times those of the original, respectively, and the effect is mainly reflected in the first shock wave. For the flow field in the intake duct, the total pressure recovery coefficient of the outlet section is reduced by up to 68%, and the distortion rate is increased by up to 325%. This change may even lead to engine surge and shutdown. Moreover, regardless of internal or external flow, the high-temperature airflow after detonation also affects the thermal protection ability of the wing or the inlet profile. All these factors need to be considered comprehensively in the design phase of the aircraft.

Numerical simulation of wake vortex for the flight near the ground with different boundary conditions

The aerodynamic performances of aircraft change due to the ground effect for flights near the ground. The air cushion generated near the ground will change the development of the aircraft wake vortex. Researchers have compared several different ground boundary conditions with two-dimensional airfoils, while three-dimensional cases have not been studied specifically. In this study, the effects of stationary and moving wall boundary conditions on the aircraft aerodynamic characteristics and wake development were numerically investigated in three dimensions. The results showed that the stationary wall overestimated the viscous effect of the ground, resulting in a reduction of the wingtip vortex (WTV) vorticity magnitude. The difference appeared at (wingspan of the aircraft) where the secondary vortex was induced by the wingtip and horizontal tail vortex (HTV).

New Aerodynamic Studies of an Adaptive Winglet Application on the Regional Jet CRJ700.

This study aims to evaluates how an adaptive winglet during flight can improve aircraft aerodynamic characteristics of the CRJ700. The aircraft geometry was slightly modified to integrate a one-rotation axis adaptive winglet. Aerodynamic characteristics of the new adaptive design were computed using a validated high-fidelity aerodynamic model developed with the open-source code OpenFoam. The aerodynamic model successively uses the two solvers simpleFoam and rhoSimpleFoam based on Reynold Averaged Navier Stokes equations. Characteristics of the adaptive winglet design were studied for 16 flight conditions, representative of climb and cruise usually considered by the CRJ700. The adaptive winglet can increase the lift-to-drag ratio by up to 6.10% and reduce the drag coefficient by up to 2.65%. This study also compared the aerodynamic polar and pitching moment coefficients variations of the Bombardier CRJ700 equipped with an adaptive versus a fixed winglet.

Fixed Boundary transition effect on transport aircraft aerodynamic characteristics under different Reynolds numbers

Scale differences between test models and real aircraft result in Reynolds number effect, which made it impossible to simulate boundary layer conditions and obtain accurate aerodynamic characteristics of vehicles, especially of transport aircraft, by wind tunnel tests. Normally, laminar flow would exit over super critical wing during wind tunnel tests. Fixed transition effect on super critical wing aerodynamics characteristics was investigated in traditional wind tunnels. The relative experiments were conducted in a transonic wind tunnel. Force/moment and surface pressure distribution were measured with a full model and a half model respectively. Test Mach number ranged from 0.7 to 0.86, and Reynolds number ranged from 3.3 million to 16.5 million. Experiment results showed that surface pressure distribution would be changed significantly by fixed transition when shock wave and induced boundary layer separation appeared on upper surface. With the increasing of test Reynolds numbers, its effect became weakened, and the effect was ignorable when test Reynolds number exceeded 15 million. To obtain credible wind tunnel results, fixed boundary layer transition of super critical airfoil were recommended when test Reynolds numbers were less than 15 million.

3D RECONSTRUCTION OF ICE SHAPE USING VISIBLE AND THERMAL RANGE IMAGING FOR AIRCRAFT ICING STUDY

Abstract. Aircraft icing is one of the main factors decreasing the flight safety. Qualitative and quantitative understanding of the icing process is crucially needed for developing anti-icing measures and safety recommendations. Changes in aerodynamic characteristics of aircraft caused by changes in shape of aircraft surfaces due to the ice accretion can lead to significant aerodynamic performance degradation. So the reliable and accurate information of how the shape of the ice accretion influences on aerodynamic characteristics is a key point for predicting the changes in aerodynamic performance.The study addresses to a problem of accurate shape measuring of ice accretion for further experimental study of iced-aircraft aerodynamic in a hydrodynamic tunnel. For this purpose the evaluation of various techniques of ice 3D measurements is performed that include as visible so thermal imaging of ice accretion. The results of evaluation serves for the decision of preferable technique to be used in experimental study. Also the framework is developed for creating physical models of iced aircraft based on result of real ice accretion shape measurement. It allows to produce stereolithography (SLA) copies of of an aircraft under icing condition for different levels of icing. These SLA-models of an aircraft under icing condition are then used for flow behaviour study in order to identify critical flying condition.

Research on the Key Technology of Propulsion Drag System Division and Performance Analysis of Turboprop-powered Aircraft

The remarkable characteristic of turboprop-powered aircraft is that its power system has great influence on the aerodynamic characteristics of the aircraft. Due to the action of turboprop slipstream, the airflow velocity after the propeller is obviously increased compared with the velocity of free flow. The turbulence caused by turboprop slipstream affects the aerodynamics of the aircraft, which in turn affects the performance of turboprop blades. In this paper, the layout characteristic and development trend of turboprop powered aircraft are briefly analysed. According to the characteristics of turboprop aircraft, a thrust/drag system division principle and interference characteristics treatment method for turboprop powered aircraft are introduced. Finally the influence of slipstream on a typical turboprop powered aircraft is analysed, It is very necessary to study the influence of propeller slipstream on aircraft aerodynamic performance in the early stage of developmental the effect of propeller slipstream on the aerodynamic characteristics of the whole aircraft is the strongest in take-off state, the influence of climbing state is weakened the influence of cruise state is the lease and the effect of slipstream effect increases with the increase of thrust.

Determining aircraft aerodynamic characteristics of regular and non-linear airframes and evaluating the efficiency of the applied methods

This paper discusses three methods of determining aerodynamic characteristics and compares the research results. The research cases are two planes selected by the authors, i.e. EM-10 Bielik and YOKOSUKA MXY7 OHKA and investigated as an airframe with the so-called non-linear aerodynamic flow and a classical design. Aerodynamic characteristics was determined by the following methods: aerospace engineering formulas, CAD simulation of the airflow around the object and examining the prototype in a wind tunnel. The last section of the paper compares the obtained results and evaluates the efficiency of all methods to examine both types of the aircraft. The compared parameters are lift and drag versus angles of attack and aircraft polars.

Comparative Study on the Prediction of Aerodynamic Characteristics of Mini - Unmanned Aerial Vehicle with Turbulence Models

When dealing with CFD simulations the turbulent nature is seen on most of the engineering flows and these flows need to be solved. Reliable and applicable CFD outputs can be obtained from the accurate modelling of the turbulence as it is one of the most vital elements of CFD modelling. The RANS equations are extensively employed to analyse the complex flows over aircraft and for this purpose, a turbulence model is needed for turbulent flow analyses. Compatible turbulence must be chosen for the exact predictions of aircraft aerodynamic characteristics. In this report, numerical analyses of Mini-UAV are done to compare the outputs of different types of turbulence models for the prediction of aircraft aerodynamic characteristics for various flight conditions i.e., -4° to 40° at Mach number 0.04. ANSYS software is employed for this aerodynamic analysis. The six turbulence models compared are the Spalart-Allmaras, k-ɛ standard, k-ɛ RNG, k-ɛ Realizable, k-ω standard, and k-ω SST model. The impact of several turbulence models on the Mini-UAV aerodynamic performance is also studied numerically and validated with existing experimental data from reliable sources. The lift and drag coefficients for both numerical and experimental results exhibit an excellent correlation at Mach number 0.04. The recorded maximum variation of the coefficient of lift and the lift-to-drag ratio is determined to be 9.43% at a stall angle of attack (38°) and 7.01% at a 4˚ angle of attack among the six various turbulence models. The summation of deviation of coefficients of lift and drag values i.e., 0.0166 for the Spalart-Allmaras turbulence model is found to be less compared with all the other turbulence models so it can be said that the Spalart-Allmaras turbulence model is the best fit in terms of coefficients of lift and drag for Mini-UAV applications for subsonic flow.

A quantitative study of the aerodynamic characteristics of a low aspect ratio aircraft when flying at near-critical Mach numbers

This paper presents calculations of aerodynamic characteristics for an aircraft of the conventional aerodynamic design, i.e. with a wing module of the X-type and a tail assembly of the cruciform design. The calculations were performed using a numerical simulation method based on Reynolds-averaged Navier – Stokes equations. Integral aerodynamic coefficients were calculated within a wide range of Mach numbers. The obtained aero-dynamic characteristics were compared with those of aircrafts with a rectangular wing and a trapezoidal wing. The contribution of outer wings in the generation of ascensional power was assessed. The determination of the aerodynamic characteristics of an aircraft in the range of near-critical Mach numbers is necessary both for mathematical modelling of control systems and for establishing possible flight modes.

Measurements of Aerodynamic Interference of a Hybrid Aircraft with Multirotor Propulsion.

This article deals with the phenomenon of aerodynamic interference occurring in the innovative hybrid system of multirotor aircraft propulsion. The approach to aerodynamics requires a determination of the impact of active sources of lift and thrust upon the aircraft aerodynamic characteristics. The hybrid propulsion unit, composed of a conventional multirotor source of thrust as well as lift in the form of the main rotor and a pusher, was equipped with an additional propeller drive unit. The tests were conducted in a continuous-flow low speed wind tunnel with an open measuring space, 1.5 m in diameter and 2.0 m long. Force testing made it possible to develop aerodynamic characteristics as well as defining aerodynamic characteristics and defining the field of speed for the considered design configurations. Our investigations enabled us to analyze the results in terms of a mutual impact of particular components of the research object and the area of impact of active elements present in a common flow.

Flexible Formulation of Spatial Integration Constraints in Aerodynamic Shape Optimization

In aircraft design, spatial integration limits aerodynamic and structural performance. While the outer mold line shape determines aircraft aerodynamic characteristics, aircraft systems and passengers or payloads must fit inside. Emerging categories of aircraft, such as electric aircraft, are likely to experience new and critical spatial integration challenges. Existing aerodynamic shape optimization tools use a narrowly defined set of geometric constraints. However, no known aerodynamic optimization framework can handle spatial integration constraints derived directly from three-dimensional (3-D) geometry. A general geometric constraint formulation based on triangulated 3-D geometry is proposed. The constraint consists of two metrics: the length of the intersection curve(s) between any two objects, and the Kreisselmeier–Steinhauser function aggregated minimum distance. The proposed implementation of the intersection and distance computations is fast and analytically differentiable with respect to geometric design variables, making it suitable for efficient gradient-based optimization. The constraint formulation is validated using three Reynolds-averaged Navier–Stokes-based aerodynamic shape optimization problems: a 2-D fairing design problem, a 3-D fairing design problem, and the design of an aeroshell to surround a human avatar. It is shown that this approach is robust and efficient, enabling the aerodynamic optimization of bodies containing objects with arbitrary shapes.

Numerical Study on Aerodynamic Characteristics of Variable-sweep Morphing Aircraft at Transonic Speeds

The variable-sweep morphing aircraft (VMA) has both high speed and low speed flight performance, and can be competent for combat tasks and practical requirements in different flight environments. Aerodynamic characteristics of VMA have a great impact on flight performance. The transonic stage is particularly important in the whole variation process. It is also one of the most difficult problems in aerodynamic layout design of aircraft. In order to explore the aerodynamic characteristics of the VMA at transonic speeds, this paper adopts an efficient engineering algorithm. The aerodynamic characteristics of VMA at different Sweepback Angle, Angle of attack, Mach number and Altitude are analysed. The result demonstrates that: Sweepback Angle has great influence on aerodynamic characteristics of aircraft. For the lift coefficient, at subsonic speeds, small sweep has great influence. When the Angle of attack (AOA) is 12°, the sweepback changes from 45° to 25°, and the lift coefficient increases by 48.9%. At transonic speeds, large sweepback has great influence. When the AOA is 12°, the sweepback changes from 75° to 55°, and the lift coefficient increases by 85.7%. For the drag coefficient, at subsonic speeds, small sweepback has great influence. When the AOA is 12°, the sweepback changes from 45° to 25°, and the drag coefficient increases by 45.5%.All the changes of sweepback have great influence on drag coefficient at transonic speeds. The influence of sweepback on lift-drag ratio is complex. In general, when the Mach number increases, the sweepback corresponding to the maximum lift-drag ratio increases. The altitude factor only has some influence on the drag coefficient at subsonic speeds. These aerodynamic change rules can provide a basis for the shape design and dynamic analysis of VMA.

Cargo container assembly effect on the unmanned carrier aircraft aerodynamic characteristics

The study is devoted to the use of a landing glider. The classic way of landing is by plane, which lands the landing glider at the point of separation using a rope of a certain length. The dissertation proposes the concept of an unmanned aerial vehicle consisting of an unmanned aerial vehicle and an unmanned aerial transport container, which, during take-off and horizontal flight to the point of separation, make up one whole aircraft. All the necessary parameters of the delivery and delivery system, Viconano viglyadі.Using the methods of computational aerodynamics (panel-vortex method), the influence of different variants of layout of the transport container on the value of aerodynamic excellence was simulated , lift coefficient , the maximum range criterion and sustainability carrier-container system.The aerodynamic layout of the unmanned carrier allows for a sufficiently high level of flight performance:- the maximum value of aerodynamic excellence ;- unmanned vehicle balancing happens automatically at the angle of attack, which corresponds to the maximum value of aerodynamic excellence ;- the level of static stability of unmanned carrier layout is , which meets the requirements of airworthiness standards;the maximum load-carrying properties of the carrier aircraft in the balanced state are characterized by value .