Aerodynamic System Research Articles

Ground test modeling of cylindrical aero-engine casing under high-temperature and high-pressure aerodynamic load

The aero-engine casing is subjected to high-temperature and high-pressure aerodynamic loads during operation. It is essential to perform the ground strength tests for the casing. To optimize the ground strength test and to improve the accuracy of temperature and pressure loading during the test, a mathematical model of high-temperature and high-pressure aerodynamic loading system for simulating the ground strength test of typical aero-engine casing is established to study the actual temperature and pressure loads on casing during ground test. The temperature and pressure results calculated by the mathematical model under typical loads matched well with the experimental measurements. The verification results show that under the test conditions, the thermal inertia of the heater, the radiation heating of the gas in the test chamber by the heater, and the heat transfer of gas mixing in the pressure process can be ignored. The sensitivity analysis of the parameters affecting the accuracy of pressure and temperature loading is carried out. We show that the pressure can be controlled quantitatively by adjusting the inlet and exhaust pipe parameters, and accurate temperature control can be achieved by designing reasonable heater power and selecting appropriate heating control parameters.

Robust PID control of a two-rotor aerodynamical system with decoupling

Abstract In this work, robust PID design via μ synthesis for controlling a MIMO two-rotor aerodynamic system manufactured by the Polish company Inteco is presented. The controller consists of a decoupling system and two PID controllers. The aim is to demonstrate an approach enabling further fine-tuning based on an already synthesized controller structure. Tools from Robust Control Toolbox in MATLAB are used. The PIDs are constructed as tunablePID objects, and the decoupler is also tunable and has the preset structure of a static gain matrix (tunableGain) or dynamic state-space system with a given number of states (tunableSS). The model contains some parameters with structured uncertainty. Several variants of the controller with a fixed structure have been created, and their performance has been tested by simulation and on the laboratory set-up.

Decay time estimate for LEO spacecraft

The growing concerns posed by orbital debris represent a serious threat to the future of space operations in low Earth orbit. With the goal of limiting the formation of new debris, space agencies are proposing international guidelines that satellites should be able to deorbiting within 25 years of the end of their operational life. Orbital decay is typically caused by atmospheric drag, so estimating the decay time of a satellite subject to drag is critical to assessing whether the guidelines are met. However, such estimate is a very challenging task because of the difficulty of accurately modeling atmospheric properties and because of the coupling of orbital dynamics with spacecraft attitude. In this paper, a simplified algorithm based on the King-Hele formulation is proposed to rapidly estimate the decay time of an orbiting satellite without imposing any assumptions on the spacecraft’s nominal size, mass, geometry or attitude. The algorithm accounts for the effect of solar activity level variations on atmospheric properties and drag coefficient through an iterative procedure and can be applied to any object in orbit. Numerical tests show that the predictions in terms of decay times are very accurate for satellites that are quite different in size and geometry, including the presence of an aerodynamic drag augmentation system such as a drag sail.

Concurrent and sequential coupled optimization design of a transonic compressor blade with axial slot casing treatment

This paper explores the optimization of the interaction between the rotor and axial slot casing treatment (ASCT) to enhance both efficiency and stability margins. Previous studies primarily focused on rotor tip optimization, often compromising flow in non-tip regions and reducing overall rotor performance. To address these limitations, this study introduces a new optimization framework integrating full-span 3D blade design with a semicircular axial slot, utilizing both sequential and concurrent optimization strategies. The sequential approach first optimizes blade geometries, followed by ASCT adjustments, while the concurrent approach treats the blade and ASCT as a unified aerodynamic system. Compared to prior studies focusing exclusively on tip-only 3D shape optimization, results indicate that sequential coupled optimization improves the stall margin by 13.32% and efficiency by 0.05%, whereas the concurrent strategy further enhances performance, shaping the blades into an inverse S form, reducing efficiency losses from 0.12% to 0.02%, and increasing the stall margin increment from 14.88% to 21.83%. These findings demonstrate the significant performance gains achievable through coordinated rotor and ASCT design.

Efficient Forced Response Minimization Using a Full-Viscosity Discrete Adjoint Harmonic Balance Method

A forced response induced by inlet distortion and blade row interactions can lead to high-cycle fatigue failure, especially when the unsteady excitation frequency is close to the natural vibration frequency of a blade. This paper presents the study of forced response sensitivity analysis and minimization using a full-viscosity unsteady discrete adjoint method. The goal is to improve the aeroelastic performances of turbomachinery blades and simultaneously constrain/improve aerodynamic performances. The decoupled modal reduction method is used to compute the forced response, which is considered the objective function in adjoint-based design optimization. To analyze aeroforcing and aerodamping flow and adjoint fields efficiently, the harmonic balance method and its adjoint counterpart developed by an automatic differentiation tool are applied. Two cases—the NASA Rotor 67 with inlet distortion and a three-row configuration with multiple fundamental frequencies in the second row—are used to demonstrate the effectiveness of the aerodynamic and aeroelastic coupled design optimization system developed in this work. For the latter case, the Fourier-transform-based method that first decomposes and then matches the time and space modes at two sides of an interface is used for interface coupling. The almost-periodic Fourier transform method is used to determine the time instances for cases with multiple fundamental frequencies.

Hysteresis behavior and generalized Hopf bifurcation in a three-degrees-of-freedom aeroelastic system with concentrated nonlinearities

A three-degrees-of-freedom aeroelastic system with concentrated structural nonlinearities is considered. The aerodynamic loads in the model are simulated by using unsteady aerodynamic forces. First, we evaluate the linear stability region of the aerodynamic system employing the Lienard–Chipart criterion so that the stability boundaries of the center of gravity position and the uncoupled pitch natural frequency are obtained. Next, we present the distribution of the first Lyapunov coefficient l1 in the parameter space by using the Poincaré projection method to determine the type of Hopf bifurcation (subcritical or supercritical). We identify three types of hysteresis loops associated with Hopf bifurcations: the first type contains one stable equilibrium point and one stable limit cycle, the second type consists of one stable equilibrium point and two stable limit cycles, and the third type comprises two stable limit cycles. Nonlinear analysis shows that the variations in hysteresis loop types are mainly caused by the nonlinear flutter critical points, namely the saddle–node bifurcation points of limit cycles. Furthermore, we determine a degenerate Hopf bifurcation type known as generalized Hopf bifurcation (Bautin bifurcation) and its corresponding second Lyapunov coefficient, l2. Subsequently, we conduct nonlinear flutter analyses for positive and negative values of l2 by using bifurcation diagrams and phase portraits. The results show that when the uncoupled pitch natural frequency is used as the control parameter, the occurring generalized Hopf bifurcations are all supercritical (l2<0). However, when the center of gravity position is used as the control parameter, the generalized Hopf bifurcations that occur have both supercritical and subcritical (l2>0) modes.

AERODYNAMIC HIGH-RISE BUILDING IN STRUCTURAL REVIEW AND DESIGN INTEGRATION

Tall buildings that have aerodynamic characteristics are tall buildings that can respond to wind flow and lateral loads that occur on the upper structure of the building. Obstacles in understanding the structural systems in tall buildings often become obstacles for architecture students so design integration cannot be achieved, especially in tall buildings with aerodynamic shapes. Therefore, it is necessary to analyze how the structural patterns that form aerodynamic buildings can be realized using case studies in Indonesia and abroad. The method used in this research is a literature review and analysis with a review of aerodynamic building designs and structures in three building case studies in Indonesia and abroad. It is hoped that by understanding aerodynamic building structural systems, students will be able to combine creativity with their structural systems. Conversely, understanding the structural system can produce design creativity to create an integration of the design and structural system. From the literature review and analysis, it is found that aerodynamic tall buildings have a structural system obtained from twister-shape processing with a composite structural system and a core system. As well as the diagrid system which usually uses a steel diagrid structure system and a core structure system. The core system is still the main reference because its use is more efficient in terms of costs and work methods.

Robust residual generator design for sensor fault detection in twin rotor aerodynamic system

The twin rotor aerodynamic system (TRAS) reflects the dynamics of vertical take-off rotor systems. TRAS considers the coupling effect and gyroscopic disturbance torque as unwanted signals. For safe and reliable TRAS operation, proper control input is vital, along with fast fault indication. This paper addresses the output sensor fault detection problem in the linear model of TRAS subjected to l2-norm bounded disturbance. A robust design of an observer is formulated as H-/H∞ optimization problem to maximize the sensitivity/robustness criterion. The approach minimizes the disturbance effect on the residual signal, which leads to successful fault detection. Furthermore, a linear quadratic regulator-based state feedback controller is proposed to meet the system's desired transient response requirement. The incorporation of an observer-based residual generator for fault detection along with the state-feedback controller differs the current work from the existing work. Successful fault detection in the output sensor of TRAS depicts the good performance of the proposed observer.

A comparison of the phonation quotient between patients with voice disorders caused by benign vocal fold lesions and normal adults 20-80 years of age

Background: A voice evaluation is an important first step in analyzing voice symptoms and determining appropriate treatment plans. The phonation quotient is a valid aerodynamic parameter in voice evaluations which is an indirect source of information for evaluating the valve function of the vocal folds of patients with voice disorders, especially patients with voice disorders caused by tumors of the vocal folds which is the most common cause in the patients with voice disorders. Objective: The present study aims to determine and compare the phonation quotient between patients with voice disorders caused by benign vocal fold lesions and normal adults between 20-80 years of age. Materials and methods: The participants comprised 40 adults with voice disorders caused by benign vocal fold lesions and 40 with normal voices. All participants’ voices were evaluated in the Speech Clinic at Ramathibodi Hospital, Bangkok. The phonation quotient (PQ) was calculated by the ratio of vital capacity (VC) to the maximum phonation time (MPT). VC and MPT were measured using a phonatory aerodynamic system (PAS). Results: The results of the present study indicated that the mean value of the PQ of adults with normal voices was 122.60 cc/sec (SD=16.36). The mean value of the PQ of adults with voice disorders caused by benign vocal fold lesions was 292.08 cc/ sec (SD=97.14). The mean value of the PQ in the group with voice disorders caused by benign vocal fold lesions was significantly more significant than the mean value of the PQ in the group with normal voice. Conclusion: The significant difference between the phonation quotient of adults with voice disorders caused by benign vocal fold lesions and adults with normal voice was that the PQ might be an indicator for indirect evaluation of the airflow leakage related to the efficiency of vocal fold movement during phonation. The PQ can be the optional voice measurement for monitoring and analyzing the outcomes of voice therapy.

Constructing nonlinear data-driven models from pitching wing experiments using multisine excitation signals

Accurate modelling of unsteady nonlinear aerodynamic loads is crucial for the effective design and control of aerodynamic systems. Data-driven modelling approaches have emerged as powerful tools for capturing intricate system dynamics without prior knowledge of the underlying physical principles. This paper focuses on the construction of nonlinear data-driven models for pitching wing systems using multisine excitation signals and their relative merits compared to swept sine signals. The polynomial nonlinear state-space (PNLSS) modelling framework is used, which has been proven in the system identification community to offer flexibility and richness in representing diverse nonlinear phenomena. Data are gathered with a dedicated experimental wind tunnel setup. A NACA 0018 wing is made to oscillate in pitch according to a swept sine and a multisine with a frequency up to 2 Hz. The experiments are repeated to cover the attached flow, light stall, and deep stall regimes. PNLSS models are trained on multisines and benchmarked against models trained on swept sines to assess their comparative performance. Then, all models are successfully cross-validated using single sine data at different angles of attack. We conclude that one single data-driven model can accurately represent the lift force across different linear (attached flow) and nonlinear (light and deep stall) operating regimes.

Mathematical model for selecting the auxiliary equipment parameters of aerodynamic deorbit systems

The goal of this work is to develop a model for selecting the design parameters of auxiliary equipment for aerodynamic deorbit systems. For normal operation, an aerodynamic deorbit system, according to its class, is equipped with the following support systems: for deployment, inflation, аnd storage onboard the space object to be deorbited. The deployment system consists of two components: a mast deployment system, in which four rolled-up masts are stored and deployed, and an airfoil storage spindle, on which four quadrants of a film material are wound. Aerodynamic systems can be inflated in several ways: using a system of gas storage and supply to the shell, using the residual pressure, or using the sublimation of a powder substance. The characteristics of sublimable substances and inert gases for inflation are given. The paper presents a methodology for determining the inflating gas parameters taking into account the exposure of the aerodynamic system to space debris fragments. The following requirements are imposed on the storage system materials: resistance to space factors, resistance to dynamic loads in orbital injection, and resistance to thermal deformations. A mathematical model for selecting the auxiliary system parameters of aerodynamic deorbit systems is presented. This model includes deployment system mass estimation, relationships for determining the inflation system mass for aerodynamic systems of various configurations, wall thickness estimation for gas cylinders of different configurations, and relationships for determining the storage system mass for aerodynamic deorbit systems of different configurations.

Aerodynamic/control integrated optimization method for unpowered high-speed vehicle configuration design

The unpowered high-speed vehicle experiences a significant coupling between the disciplines of aerodynamics and control due to its characteristics of high flight speed and extensive maneuverability within large airspace. The conventional aircraft conceptual design process follows a sequential design approach, and there is an artificial separation between the disciplines of aerodynamics and control, neglecting the coupling effects arising from their interaction. As a result, this design process often requires extensive iterations over long periods when applied to high-speed vehicles, and may not be able to effectively achieve the desired design objectives. To enhance the overall performance and design efficiency of high-speed vehicles, this study integrates the concept of Active Control Technology (ACT) from modern aircraft into the philosophy of aerodynamic/control integrated optimization. Two integrated optimization strategies, with differences in coupling granularity, have been developed. Subsequently, these strategies are put into action on a biconical vehicle that operates at Mach 5. The results reveal that the comprehensive performance of the synthesis optimal model derived from the aerodynamic/control integrated optimization strategy is improved by 31.76% and 28.29% respectively compared to the base model under high-speed conditions, demonstrating the feasibility and effectiveness of the method and optimization strategies employed. Moreover, in comparison to the single-stage strategy, the multi-stage strategy takes into deeper consideration the impact of control capacity. As a result, the control performance of the synthesis optimal model derived from the multi-stage strategy improves by 13.99%, whereas the single-stage strategy only achieves a 5.79% improvement. This method enables a fruitful interaction between aerodynamic configuration design and control system design, leading to enhanced overall performance and design efficiency. Furthermore, it improves the controllability of high-speed vehicles, mitigating the risk of mission failure resulting from an ineffective control system.

Improved Set-point Tracking Control of an Unmanned Aerodynamic MIMO System Using Hybrid Neural Networks

Artificial neural networks (ANN), an Artificial Intelligence (AI) technique, are both bio-inspired and nature-inspired models that mimic the operations of the human brain and the central nervous system that is capable of learning. This paper is based on a system that optimizes the performance of an uncertain unmanned nonlinear Multi-Input Multi-Output (MIMO) aerodynamic plant called Twin Rotor MIMO System (TRMS). The pitch and yaw angles which are challenging to control and optimize in practice, are being used as the input to the Nonlinear Auto-Regressive with eXogenous (NARX) model, and eventually trained. The training features use the Matlab Deep Learning Toolbox. The NARX structure has its core in the neural networks’ architecture. Data is collected from the TRMS testbed which is used to train the network. ANN as a Hybrid intelligent control strategy of ANN in combination with Pattern Search and Genetic Algorithm, is then utilized to optimize the parameters of the neural networks. At the end it was validated, tested and the optimized system run in simulation and compared with other intelligent and conventional controllers, with the proposed controller outperforming them, giving a very fast tracking control, stable and optimal performance that satisfactorily met all our design requirements.

Design and analysis of a bionic‐inspired single‐rotor MAV with a foldable wing

AbstractMicroaerial vehicles (MAVs) have achieved rapid advancement and vast applications. Energy efficiency and friction loss are common problems of MAVs, and exploring novel structural design and enhancing flight performance are critical research directions. Here, a bionic‐inspired single‐rotor MAV with a foldable wing is fabricated by imitating winged achene in nature. The structural design of the wing based on origami principle, overall aerodynamic modeling analysis, kinematic analysis, and control system design is carried out. The prototype weighs 75 g and equipped with only one motor, achieved the desired flight attitude of vertical takeoff and landing, hovering and horizontal flight, and so forth. During nonflight, the wings fold down can reduce 70% storage area for easier transportation. The vehicle combines high flight efficiency with compactness, superior stability, simple structure, economical manufacturing cost, low flight noise, and spin deceleration safety protection, which has good potential for application in the aerial vehicle fields.

Scaling the Momentum Coefficient for Active Flow Control at Various Operating Conditions

The momentum coefficient is one of the most commonly used parameters to quantify the aerodynamic performance and system output of active flow control (AFC). Estimating the momentum coefficient accurately through experiments is challenging. Several approaches exist to estimate the momentum coefficient in laboratory conditions. However, the question arises as to whether these models hold as ambient and supply conditions change during operation in flight. Therefore, computational fluidic dynamic (CFD) simulations were carried out on two exemplary AFC actuators (i.e., a fluidic oscillator and a steady jet nozzle) in a quiescent environment with supply pressure ratios ranging from 1.5 to 4; supply temperatures at 293, 550, and 800 K; and ambient altitude conditions at sea level and 10 km. When scaled with Tsup/P∞, the mass flow for different conditions collapses as a function of the pressure ratio. Furthermore, the momentum coefficient collapses when scaled with 1/P∞. The existing models to calculate the momentum coefficient hold for changing ambient and supply conditions. Therefore, these models, in conjunction with scaling parameters, can be employed during the operation of an AFC system in flight with changing conditions in order to provide the desired momentum output. The paper discusses the details of the CFD results and the derivation of the scaling parameters.

Experiments on Tuned UHBR Open-Test-Case Fan ECL5/CATANA: Performance and Aerodynamics

Abstract With the advancement of modern fan architectures, the lack of experimental benchmarks for the research community became apparent in the recent years. Enormous effort in the method development could not be validated on representative geometries and motivated the development of the open-test-case ECL5/CATANA. A carbon fiber fan stage has been designed by Ecole Centrale de Lyon and shared with the community in 2021. The fan is representative of a modern ultra high bypass ratio (UHBR) architecture with sonic design speed. The reference configuration has been investigated experimentally on a novel test facility with multiphysical instrumentation. In this publication, the results of the first experimental campaign are presented with a detailed analysis of the aerodynamic performance and system symmetry. The presented results comprise full stage mappings across the whole operating range for three main speedlines (55%, 80%, and 100%) using performance rakes, unsteady wall pressure arrays, tip clearance, and stagger angle measurements. Radial profiles of intake boundary layer and rotor exit conditions at selected conditions complete the full validation dataset for steady and unsteady aerodynamic simulations. Results are discussed in comparison to blind-test Reynolds-averaged Navier–Stokes (RANS) simulations of different international institutes. Significant prediction inaccuracies of the tip flow and corner separations of the stator are observed and reveal the requirement of real blade geometry measurements at running conditions. This article is accompanied by a publication with a focus on aeroelastic instabilities observed near the stability limit. The results represent a comprehensive dimensional benchmark dataset and allow method validation on multiple levels of fidelity for the aerodynamic and aeroelastic research community.

Unsteady aerodynamic characteristics of a morphing tail configuration

Morphing aircraft is an important trend in the future development of next-generation aircraft. This paper focuses on aircraft with a small aspect ratio flying wing configuration that includes morphing tails. The unsteady aerodynamic characteristics of the morphing tail configuration are numerically simulated using the unstructured overset grid technique and the dual-time method, focusing on the effects of the tail deflection angle over time, Mach number, and side slip angle on the unsteady aerodynamic characteristics of the entire aircraft and tails. The second derivative of the tail deflection angle with time should be continuous, and the maximum angular velocity and maximum angular acceleration should be minimized. The hysteresis loop area is closely related to the Mach number. The sideslip angle aggravates the nonlinearity of the unsteady aerodynamic characteristics of the entire aircraft. The unsteady aerodynamic characteristics during tail morphing are affected by static (wing downwash effect and projected area effect) and dynamic (flow field hysteresis effect, additional motion effect, and wall implication effect) characteristics. The enclosed research provides a reference for the aerodynamic and control system designs of morphing tail configurations.

Experimental Investigation of Low Reynolds Number Flow Around a Serrated NACA 0015 Airfoil

The study of low Reynolds number flows has triggered the interest of many researchers. This concern is attributed to the presence of various vortex structures that significantly affect aerodynamic performance. The study of such phenomena offers an opportunity to better understand and predict the behavior of fluid flows in three dimensions, leading to improved design strategies for aerodynamic systems. This study intends to examine the performance of different NACA 0015 airfoil configurations namely, baseline, serration, comb, comb-serration and poro-serrated, emphasizing on their influence on aerodynamic characteristics and flow structure. Experimental work is performed to provide valuable insights into the behavior of the flow field and the underlying physical phenomena. The current study has shown that the mean streamwise velocity of the serrated, combed, and comb-serrated configurations exhibit more stable flow patterns compared to the baseline airfoil. These patterns suggest a promising approach for delaying flow separation. In contrast, the poro-serrated model exhibited a more disordered flow pattern. Remarkably, when subjected to a 10-degree angle of attack, all the modified trailing-edge designs showcased minimal separation zones compared to the baseline configuration. At the same angle, the baseline's shear layer disintegrates, while the poro-serrated model displays increasing disturbance and separation. Conversely, the comb-serrated and serration models exhibit a smaller increase in unsteadiness. Furthermore, the study indicated that Musou black paint exhibits a higher rate of light absorption compared to flat black paint, but it demonstrates higher reflection levels on a poro-serrated surface. Collectively, the outcomes of this investigation hold significant implications for enhancing aerodynamic system designs.

The hybrid model test of floating offshore wind turbine based on an aerodynamic actuation system

The hybrid model test of floating offshore wind turbine based on an aerodynamic actuation system

Transonic Aerodynamic–Structural Coupling Characteristics Predicted by Nonlinear Data-Driven Modeling Approach

Accurate prediction of nonlinear aerodynamics is essential for the transonic aeroelastic analysis of flight vehicles. Though reduced-order aerodynamic models are cheap and reasonable tools, it is still a tough problem to accurately evaluate the unsteady pressure distributions on the surface of an elastic structure. This paper presents a nonlinear data-driven modeling approach based on the high-fidelity simulations in the following three steps. The first step is to compute the dominant modes of unsteady pressure distributions through the proper orthogonal decomposition. The pressure snapshots used for the feature extraction are sampled under a multilevel sine-sweep excitation. The second step is to obtain the low-dimensional temporal dynamics of the coefficients of these modes via polynomial nonlinear state-space identification. The linear estimation implemented by employing the dynamic mode decomposition with control algorithm serves as the initialization of the nonlinear optimization. The third step is to reconstruct the unsteady pressure distributions under arbitrary structural excitation from the temporal coefficients. The paper validates the approach via two numerical examples of the transonic aerodynamic–structural coupling problem. One is an NACA0012 airfoil, and the other is an AGARD 445.6 wing. The examples show that the proposed approach exhibits both accurate and robust performance in the prediction of unsteady pressure distributions, aerodynamic forces, and aeroelastic responses. In particular, the approach well predicts the physical features at the fluid–structure coupling interface, previously neglected in the system identification of aerodynamic systems. Therefore, the approach serves as a promising tool for data-driven aeroelastic analysis.