Aerodynamic Process Research Articles

Innovative aerodynamic grain separation system for plant harvesting in sloped areas: problems, research and optimization of parameters

This article presents the main problems associated with cereal harvesting in sloping areas. The presented innovative aerodynamic system supporting the separating unit of combine harvester can be one of the ways to counteract the negative effects of harvesting machines work on slopes. The Monte Carlo numerical method, presented in this article, was applied in the optimization of an aerodynamic sieve separation process on an inclined terrain. The given variables are the transverse slope of separator α (of the sieve), longitudinal slope β and the output of the main and side fans. The Monte Carlo method makes it possible to determine an optimized set of parameters (α = 10°, β = 2.8°, δ = 9°), the output of the main fan (0.67 m3 s−1) and the output of the side fan (1.86 m3 s−1), allowing to obtain the best indicator values of 2.1% grain loss and 97.5% grain purity.

An Evolving Understanding of Enigmatic Large Ripples on Mars

AbstractTwo scales of ripples form in fine sand on Mars. The larger ripples were proposed to have an equilibrium size set by an aerodynamic process, making them larger under thinner atmospheres and distinct from smaller impact ripples. Sullivan et al. (2020, https://doi.org/10.1029/2020JE006485) show that large ripples can develop in a numerical model due to Mars’ low atmospheric pressure. Although their proposed growth‐limiting mechanism is consistent with an aerodynamic process, they argue that the ripples in their model are simply large versions of impact ripples, not a separate class of ripples. Here, we explore this debate by synthesizing recent advances in large‐ripple formation (including initiation and subsequent evolution to equilibrium). Although significant knowledge gaps remain, it is clear that large Martian ripples in well sorted sand are larger under thinner atmospheres, and thus remain a powerful paleoclimate indicator.

Multi-criteria optimization of wind power plant parameters

The use of renewable energy sources to generate electricity is a hot topic. The author has developed a mathematical model of the aerodynamic process of a wind power plant with the solution of a multi-criteria optimization problem. The optimal range of controlled parameters affecting the aerodynamic process with a minimum amount of blown surface and maximum electrical energy production is determined. Regularities of aerodynamic process are established. The convergence of the results of the study in the calculation on the basis of theoretical dependencies and the solution of the mathematical model is determined. To find the optimal controlled parameters of the aerodynamic installation, a complex research method developed by the author is applied, based on multi-criteria optimization of parameters with the introduction of empirically obtained data. The preliminary procedure of IOSO NM 3.8 consists in the formation of an initial plan of the experiment, which can be implemented both in a passive way (using information about various parameters, optimization criteria and constraints obtained earlier) and in an active way, when too much is generated in the initial search area in accordance with a given distribution law. For each vector of variable parameters, the values of optimization criteria and constraints are determined by direct reference to the mathematical model of the object under study. The number of points that make up the initial plan of the experiment depends on the dimension of the problem and the chosen approximation functions. The solution results in a Pareto (optimal) set of solutions.

RESEARCH PROGRESS IN AERODYNAMIC OPTIMIZATION OF HIGH-SPEED TRAINS

With the increase of running speed, high-speed trains have higher requirement for aerodynamic shape. The pursuit of excellent performance and beautiful aerodynamic shape tends to be an important direction in the development of new high-speed trains. Based on the current aerodynamic study of high-speed trains, aerodynamic shape optimization can be divided into two categories: shape modification optimization based on flow mechanism and shape optimization based on optimization algorithms. After a brief review of the current domestic and foreign work on these two optimization approaches, this paper focuses on a series of aerodynamic shape optimization work done by the author's team in recent years. In terms of the modification optimization based on the flow field mechanism, this paper focuses on the research and development of the appearance of the two main models, namely CRH and Fuxing , to discuss the idea of the modification optimization. It mainly discusses the optimization design of air conditioning cover, pantograph installation platform, windshield and bogie apron, which have obvious influence on the train resistance, and introduces the improvement of aerodynamic performance of these components compared with the previous models. In the shape optimization method based on an optimization algorithm, according to the aerodynamic shape optimization process, taking the streamline of high-speed train head as the main optimization object, we introduce our series of work from three aspects: high-speed train parameterization method, surrogate model development and the improvement of the optimization algorithm. Among them, high-speed train parameterization methods mainly include local function method, modified vehicle modeling function method, and category/shape function method; in the development of the alternative model, the optimization alternative model and Kriging model based on cross-validation are introduced; on the improvement of the optimization algorithm, the improved non-inferior classification multi-objective particle swarm optimization algorithm and continuous domain chaotic ant colony algorithm are introduced. Based on the improvement of the above three aspects, the application cases of the developed aerodynamic shape optimization strategy in typical engineering are further introduced.

Study of the Aerodynamic Process and Its Impact on Cotton Transportation Process through the Cotton Pipeline

The article provides a theoretical analysis of the velocity distribution and distribution in the cross section of the pipe during the transportation of cotton. It studied the factors that move air and transport material in a pneumatic pipeline, developed a mathematical model and built graphs. The effect of pressure on the ease of construction of pipes for air transportation of raw cotton and the speed distribution in the process of transporting cotton, as well as the factors that cause pressure loss in the shells of pipes were studied. So, if the expansion after the air pipe is expanded (5), we will introduce K1 = 0 and the beating coefficient . If the current narrows before burdening, then we enter K1 = 1 and the input soften rate from the formula . The air flow is moving upwards below the slope and the longer the pipe is the air flow is so significant (strong). The flow of air is divided into laminar and turbulent streams according to leakage. The procedure for transportation of raw cotton using air will move the turbulent the sidelines, interacts with the layers. If the turbulent passes in a well-round smooth passenger-pipes, the number of critical Reynolds can be delivered to 200,000. The process of transporting cotton in pnevmotransport is far from the laminary regime in far away and stronger mode.

Study of possibility of using axisymmetric body as heat sink for cooling machine parts

The paper presents the results of the study of possibility using a body with an optimized shape with a minimum aerodynamic drag force as a heat sink in a convective gas flow for cooling machine parts. The relevance of cooling or heat sink systems for mechanical engineering is not in doubt. Maintaining the optimum thermal state of machine parts within the specified limits is necessary to prevent heating, which can cause violations of normal operating conditions, and, as a result, increased wear, jamming and breakage of parts. To ensure the normal operation of the system, it is necessary to cool the parts contacting the hot gases, removing heat from them to the atmosphere directly, or using an intermediate body (water, low-freezing liquid). Heat sink is an aerodynamic process, a process of heat mass transfer of a substance, and aerodynamic characteristics and, in particular, the nature of streamlining of bodies of the simplest forms are of great scientific and practical interest. Bodies of complex shape can always be represented as a combination of simpler ones, for which it is easy to explore and calculate the flow paths, on the basis of which analytical methods for calculating aerodynamic characteristics are compiled. A computational experiment was conducted in the software product Ansys Fluent. The conditions of the experiment (comparison of heat removal bodies) during numerical modeling are the preservation of constants: the volume and shape of the working zone; distances from the sources, drains and centers of bodies; aerodynamic flow rates; masses of compared bodies; thermal power of the source and other parameters in addition to the shape of the surface. The resulting optimized shape of the body coincides with the current lines, which is the main advantage, since no separation from the surface is observed when streamlining the flow. Thus, the entire surface area will be the effective surface area of the heatsink as opposed to other known shapes of bodies, whereby the temperature of the heat loaded element placed in the center of the heatsink will decrease.

An aerodynamic variable-fidelity modelling framework for a low-observable UCAV

The extensive amount of aerodynamic data needed for the creation of a Stability & Control data set requires efficient and reliable tools. For this reason, the task of producing a large and dense data set in general relies on ground-facility testing and is conducted after the product definition phase, where, nevertheless, already plenty of aerodynamic data is generated by use of simple low-fidelity aerodynamic methods. However, these methods are not capable of predicting complex non-linear aerodynamic phenomena, which complicates a reliable assessment of new designs and demands more accurate predictions early in the design process. Variable-fidelity surrogate modelling offers an opportunity to include high-fidelity simulation tools at affordable effort by enriching a low-fidelity data set with just a few selected highly accurate results. In this paper, an automated aerodynamic variable-fidelity modelling process is proposed to create such an aerodynamic data set at product definition phase. It is demonstrated on an industrial-relevant, agile, low-observable unmanned combat aerial vehicle. An adaptive sampling strategy is applied which proves to be both efficient and accurate. This is supplemented by a model selection algorithm. Moreover, a comparison with a single-fidelity surrogate modelling process shows the variable-fidelity modelling strategy to be superior.

Acceleration of vortex-particle simulations using a pseudo-particle method

Vortex methods like vortex-lattice or vortex-panel methods are particularly promising to enhance the industrial aerodynamic design process of modern wind turbines. However, despite their advantages over low order methods, like the blade-element-momentum theory, vortex methods share an essential disadvantage. Their computational cost rapidly increases, which is due to their n-body problem characteristics. To overcome this issue, a method that neither relies on multipole expansions nor on a multi-grid approach is presented. Based on the aerodynamic simulation of the MEXICO rotor, it is shown that the proposed vortex pseudo-particle method (VPPM) is able to reduce the computational cost related to the n-body problem of vortex methods to O(n × log(n)). However, its application is not only advantageous in terms of the reduction of the computational cost. Since vortex-and pseudo-particles share the same properties, the VPPM’s implementation is quite simple compared to that of fast multipole methods. Furthermore, no method specific boundary-conditions need to be imposed as in the case of multi-grid methods. Therefore, the presented pseudo-particle approach is an attractive alternative to fast multipole or multi-grid methods.

A novel reduced-order guidance and control scheme for hypersonic gliding vehicles

A novel analytical model between roll, pitch rates and components of acceleration of the hypersonic vehicle is established, and a reduced-order gliding guidance and control (G&C) design approach for the hypersonic vehicle is proposed in this paper. The six-degree-of-freedom (6DOF) dynamical and kinematic equations of the hypersonic vehicle in the gliding phase are described. An analytical model suitable for the bank to turn (BTT) control strategy is derived by connecting body rates with components of acceleration in the ballistic coordinate system. A novel reduced-order guidance and control design model with respect to quasi-equilibrium gliding flight is deduced and converted into the strict feedback form. The three channel body rates are treated as pseudo-inputs for tracking errors of flight path angle and heading angle of the hypersonic vehicle. Then, the commanded control surface fin deflections of the hypersonic vehicle are obtained by controlling tracking errors of the flight path angle, heading angle, and the body rates by adopting the block dynamic surface control method. In this paper, the aerodynamic coefficient interpolation process for obtaining the commanded angle of attack and bank angle based on expectant guidance overload is avoided. Meanwhile, the control loop of tracking Euler angles for getting the desired body rates is also elided. Finally, effectiveness and robustness of the novel G&C design method are verified and investigated. Moreover, the feasibility of entering quasi-equilibrium gliding phase only depending on the aerodynamic control mechanism is discussed.

The Development and Applications of a Loading Distribution Based Tip Leakage Loss Model for Unshrouded Gas Turbines

Abstract The prediction of tip leakage flow aerothermal loss plays a crucial role in turbine preliminary design, which strongly affects the turbine performance. A new tip leakage loss model for unshrouded turbine is developed in this paper, considering the compressible flow aerothermal process inside the clearance. By coupling with a parameterized loading distribution model proposed in this work, in which the blade loading can be described by four independent parameters, Zweifel coefficient (Zw), diffusion factor (DF), peak velocity location (PVL), and leading edge acceleration (LEA), the loss model can evaluate the tip leakage loss in aerodynamic design process conveniently and accurately. The proposed models are validated by numerical simulations and the results show that, compared with the other acknowledged loss models, the loss model can reduce the deviations by more than 50%. Based on the models, the effects of blade loading design parameters on tip leakage losses are discussed via analysis of variance (ANOVA). The results show that Zw has the most significant influence. As Zw decreases from 1.0 to 0.7, tip leakage losses can be reduced by about 16%. Under lower Zw conditions, the joint effect of PVL and LEA is remarkable. However, under higher Zw conditions, the joint effect of the DF and PVL is more important.

AeroVR: An immersive visualisation system for aerospace design and digital twinning in virtual reality

ABSTRACTOne of today’s most propitious immersive technologies isvirtual reality(VR). This term is colloquially associated with headsets that transport users to a bespoke, built-for-purpose immersive 3D virtual environment. It has given rise to the field of immersive analytics—a new field of research that aims to use immersive technologies for enhancing and empowering data analytics. However, in developing such a new set of tools, one has to ask whether the move from standard hardware setup to a fully immersive 3D environment is justified—both in terms of efficiency and development costs. To this end, in this paper, we presentAeroVR—an immersive aerospace design environment with the objective of aiding the component aerodynamic design process by interactively visualizing performance and geometry. We decompose the design of such an environment into function structures, identify the primary and secondary tasks, present an implementation of the system, and verify the interface in terms of usability and expressiveness. We deploy AeroVR on a prototypical design study of a compressor blade for an engine.

Advantage of multi-step vibrational excitation in laser assisted aerodynamic separation of sulfur isotopes and a novel method of estimating the separation efficiency of the process

The advantage of a red-shifted laser source in furthering the obtainable enrichment factor by laser assisted aerodynamic separation process has been reported. The enhancement owes its origin to the efficient multi-photon excitation possible here due to the red-shifted nature of the incident radiation. This has been experimentally validated in sulfur wherein the emission of a line tunable CW-CO2 laser interacted with SF6-Ar binary jet. Anharmonic splitting of the vibrational levels coupled with Coriolis rotational splitting facilitates such multi-photon up-pumping. Further, a novel spectroscopic method for estimation of relative concentration of isotopes following the above route is reported for the first time. The method exploits the resonant nature of the absorption on 10P(36) and 10P(20) lines of the CO2 laser by 34SF6 and 32SF6 isotopomers respectively. This method renders knowledge of absorption cross-sections irrelevant and facilitates precise measurement of separation factor. The details of the methodology are discussed in appendix section.

Generation of a reduced-order model of an Unmanned Combat Air Vehicle using indicial response functions

Within the NATO STO AVT-251 Task Group, a generic Unmanned Combat Air Vehicle (UCAV) planform was redesigned based on requirements derived from parts of the flight envelope of the defined mission. Because of the lambda-shape planform and associated flow phenomena including shocks and vortices, the aerodynamic design process relies heavily on high-fidelity predictions from computational fluid dynamics (CFD). These simulations enable accurate flight dynamics predictions, allowing for the identification of any potential performance issues early in the design process. Potentially, a complete flight dynamics model can be derived from CFD calculations provided that the underlying reduced order model (ROM) captures the underlying physics contained within the CFD results. This work investigates the creation of a nonlinear ROM using indicial response functions. The response functions are obtained using a grid motion approach that separates the effects of angle of attack and pitch rate. This approach is demonstrated using three different CFD codes from various organizations: ENSOLV at Royal Netherlands Aerospace Centre, USM3D at NASA Langley Research Center, and Kestrel at the United States Air Force Academy. ROM predictions were generated for a manoeuver resembling a low-speed pull-up. The predictions are found to be sensitive to the quality of the steady-state solutions from which step-response calculations were started, as well as the convergence of the step responses themselves. Nevertheless, the indicial response method is shown to provide aerodynamic predictions with acceptable accuracy including transient effects, and as such is a promising method for computationally efficient flight dynamics predictions.

CFD study of aerodynamic sensitivity to air deviation angle for a hatchback vehicle

Movement is the base of most nowadays activities. For this purpose, vehicles that have specific characteristics for various needs were developed. The current legislation enforces an aerodynamic homologation process to assess a vehicle’s CO2 footprint. This process has to be done in specific conditions, with airflow at 0 degree deviation. The increasing concerns toward pollution will soon lead to the introduction of new rules meant to closely simulate real life vehicle usage, like the RDE test. The current paper has the purpose to analyse, using the CFD method, the influence of the directionality of the airflow (i.e. front-at 0 degree deviation and at various deviation angles) on the aerodynamic performance of a vehicle. The paper studies the airflow behaviour of a hatchback body type vehicle for airflow direction angles between 0 and 20 degrees, through Cd parameter. The focus of the analysis was on air direction (± angles) and simulating time. Due to vehicle asymmetry, the results were different in case of positive and negative values of the airflow angle. The simulation time leads to slightly different Cd due to different averaging periods. Obtained results indicate the necessity of future investigations towards the optimisation of aerodynamic elements in crosswind conditions.

Numerical investigation on impingement dynamics and freezing performance of micrometer-sized water droplet on dry flat surface in supercooled environment

In-flight icing usually occurs when supercooled droplets impact on the cold surface of an aircraft, which should be concerned for its adverse effects on aerodynamic performance. To fundamentally elucidate the detailed mechanism of aircraft icing, a mathematical model on the impingement dynamics and solidification of a supercooled water droplet was developed and further validated with previous experimental results. Considering the effects of surface tension, wall adhesion and contact line dynamics, the coupled volume of fluid and level-set method was used to track the air–water interface, with the solidification issue solved by the enthalpy-porosity method. The temporal evolutions of the water phase, flow velocity, temperature and heat flux distributions were tracked and analyzed after the phase transition of supercooled water occurred. High impact velocities and millimeter-sized droplets were considered in this study to make the results more applicable to in-flight icing. As concluded, the spreading ratios of the droplets mainly distribute in the range of 0.8 ± 0.1 corresponding to LWC = 1.0 g/m3. Besides, the transient heat transfer between the solid surface and droplets could be fitted by a logarithmic function after appropriate dimensionless processing, which was proportional to the 1.5th power of the liquid fraction. Contributions of this work could be an effort to understand the microphysical phenomenon in the aerodynamic icing process.

Learning Output Reference Model Tracking for Higher-Order Nonlinear Systems with Unknown Dynamics

This work suggests a solution for the output reference model (ORM) tracking control problem, based on approximate dynamic programming. General nonlinear systems are included in a control system (CS) and subjected to state feedback. By linear ORM selection, indirect CS feedback linearization is obtained, leading to favorable linear behavior of the CS. The Value Iteration (VI) algorithm ensures model-free nonlinear state feedback controller learning, without relying on the process dynamics. From linear to nonlinear parameterizations, a reliable approximate VI implementation in continuous state-action spaces depends on several key parameters such as problem dimension, exploration of the state-action space, the state-transitions dataset size, and a suitable selection of the function approximators. Herein, we find that, given a transition sample dataset and a general linear parameterization of the Q-function, the ORM tracking performance obtained with an approximate VI scheme can reach the performance level of a more general implementation using neural networks (NNs). Although the NN-based implementation takes more time to learn due to its higher complexity (more parameters), it is less sensitive to exploration settings, number of transition samples, and to the selected hyper-parameters, hence it is recommending as the de facto practical implementation. Contributions of this work include the following: VI convergence is guaranteed under general function approximators; a case study for a low-order linear system in order to generalize the more complex ORM tracking validation on a real-world nonlinear multivariable aerodynamic process; comparisons with an offline deep deterministic policy gradient solution; implementation details and further discussions on the obtained results.

Development of a Novel Textile Process for the Production of Highly Oriented Nonwovens Made from Recycled Carbon Fibres

Carbon fibre reinforced plastics (CRFP) are high performance materials with an outstanding lightweight potential. Recycling applications for production waste though, are still scarce and not fully established. In the CaroLIn (carbon fibre nonwovens optimised for aircraft interior components) research project a novel aerodynamic textile process is developed, in order to produce highly orientated non-wovens form recycled carbon fibres. In the first stage of the project a laboratory plant for the orientation of fibres has been constructed and implemented. Afterwards a process window has been defined and a number of process parameters identified. The influence of those parameters was then investigated, using the statistical design of experiment (DOE) method.

Design of Control Law of Post Stall Maneuver under Unsteady Aerodynamics Based on Improved Dynamic Inverse Method

In this paper, a practical improved dynamic inverse control method is proposed to solve the large control error and control hysteresis of post stall maneuver under unsteady aerodynamics. Firstly, depending on the wind tunnel experimental data of the advanced fighter aircraft model under biaxial coupled large oscillation, an accurate unsteady aerodynamic model is established by using the improved extreme learning machine (ELM) method. Secondly, in terms of the time scale separation, the control error caused by unsteady aerodynamic is reduced by adding integral in the fast loop, and the control delay caused by unsteady aerodynamic is eliminated by applying the lag correction link in the slower loop. The deflections of conventional aerodynamic surface and thrust vector are allocated by the daisy chain method. Finally, the formula of the reduced frequency, which is the key factor in the unsteady aerodynamic modelling process, is derived by analyzing the wind tunnel data. The effectiveness of the present method for the scaled model is verified by herbst post stall maneuver. The present work provides a practical and reliable way for the flight test of post stall maneuver.

Numerical investigation on the aerothermoelastic deformation of the hypersonic wing

This paper numerically investigated the aerothermoelastic deformation of the hypersonic wing. An aerothermoelastic analysis framework is developed by using an in-house code and an open source code CalculiX. Aerodynamic load and aerodynamic heat are obtained by employing the in-house code to solve the Reynolds-averaged Navier-Stokes equations. Structural heat transfer analysis and structural static analysis are conducted by adopting the CalculiX module based on the finite element method. The radial basis function interpolation scheme is utilized as a unified method to handle the two-way data transfer and the mesh deformation. The aerothermoelastic analysis framework is validated by several experimental cases. Based on this framework, the aerodynamic heating process, the effects of aerodynamic heating on the characteristics of deformation, and the effects of aerothermoelastic deformation on the aerodynamic performance are investigated in detail. The results indicate that the aerodynamic heating changes the characteristics of the aeroelastic torsion angle. Without aerodynamic heating, the torsion angle increases monotonously along the span direction. With aerodynamic heating, the torsion angle increases at first and then decreases along the span direction. This is mainly due to the severe aerodynamic heating at the leading edge, which causes a larger deformation at the leading edge. In addition, when the aerothermoelastic deformation is taken into consideration, the pressure at the lower surface decreases significantly, and the lift, the drag, the lift-drag ratio and the moment also decrease, especially the moment. The main reason is that the aerothermoelastic deformation reduces the effective angle of attack.

Ambiguous temperature difference in aerodynamic levitation process: Modelling, solving and application

The aerodynamic levitation provides an efficient technique for the research on thermophysical properties and solidification behavior of refractory materials. However, there is a nonnegligible temperature differences across sample, causing unexpected uncertainty of measurement, such as, thermal expansivity and undercooling limit. We establish thermal filed model with properly simplified boundary condition, and derive quantitative expressions of this ambiguous temperature difference. Here we show that the temperature difference not only related to the average temperature, relative size and thermal conductivity of sample, but significantly influenced by the rotation pattern of sample. A huge temperature differences is almost inevitable when the sample with low thermal conductivity and high melting point is smelted in stationary suspension pattern, however, a drastically reduction of temperature difference can be fulfilled by simply making the sample rotation in up to down pattern. The thermal filed simulation was used to confirm the validity of these theoretical expressions. This work shed light on temperature difference in aerodynamic levitation. Based on this work, one can simply estimate the extent of temperature difference across the sample, and regulated that conveniently if needed, which benefit for novel material preparation and solidification mechanism study based on this technique.