Aerodynamic Testing Research Articles

터보프롭 항공기용 흡입구 덕트 및 가변형 관성분리기 조립체 설계 및 시험

A turboprop aircraft for this study is required to operate at icing condition in order that it performs its given mission. So an air intake system of the turboprop aircraft should be designed and verified not only to provide the maximum possible total pressure at engine inlet at normal flight condition, but also to include an inertial separator which protects Foreign Object Debris (FOD) like ice or snow at icing condition from entering into the engine inlet screen which can cause or lead an catastrophic engine failure like engine flame-out or severe damage. So an air intake assembly incorporating a variable geometry inertial separator has been designed and then CFD/structural analysis for the assembly was performed to see its design results. Then 35% scaled model of the air intake assembly was manufactured and wind tunnel test was done. This paper describes the detailed design results for the aerodynamic design, analysis and wind tunnel testing during the development process of the air intake assembly.

FRAMEWORK OF WIND–VEHICLE–BRIDGE INTERACTION ANALYSIS AND ITS APPLICATIONS

Under strong winds, bridges may exhibit large dynamic responses. Wind may also endanger the safety of moving vehicles on the roadways as well as on bridges. For regular aerodynamic study of long-span bridges, traffic loads are not typically considered, assuming that bridges will be closed to traffic at high wind speeds. Therefore, bridges are usually tested in wind tunnels or analyzed numerically without considering moving vehicles on them. However, there are numerous possible scenarios under which vehicles may still be on the bridge when higher wind speeds occur. These scenarios include unexpected increase in hurricane forward speed or intensity, evacuation traffic gridlock, accidents/stalled vehicles or rainfall flooding blocking the road ahead, etc. Wind, together with vehicles, will also cause serviceability and bridge fatigue damage issues. The present study will present the framework of wind–vehicle–bridge interaction analysis and its applications, developed in the last decade by the authors' group, focused on the vehicle and bridge safety issues. It consists of the following five parts: (1) A three dimensional finite element analysis framework considering the interaction of wind, bridge and vehicles; (2) experimental facilities development and studies for both static and aerodynamic tests of bridge section models and vehicles; (3) Computation fluid dynamic (CFD) prediction of loading on vehicles; (4) performance evaluation of vehicle safety and bridge fatigue; and (5) bridge vibration mitigations. Case study will also be presented and future research needs are discussed.

Scaling of Lift Degradation Due to Antiicing Fluids

In recent years, North American civil airworthiness authorities have conducted research to develop the allowance times for aircraft operations in ice-pellet precipitation. These allowance times are critical to ensure the safety and efficient operation of commercial and cargo flights. Wind-tunnel testing with uncontaminated antiicing fluids and fluids contaminated with simulated ice pellets has been carried out to better understand the flowoff characteristics and resulting aerodynamic effects. The percent lift loss was determined at an 8 deg angle of attack and used as one of the evaluation criteria in determining the allowance times. This paper describes how the lift loss was related to the loss in the maximum lift of a Boeing 737-200ADV airplane through the aerodynamic acceptance test performed for fluids qualification. A loss in the maximum lift coefficient of 5.24% on the B737-200ADV airplane (which was adopted as the threshold in the aerodynamic acceptance test) corresponds to a lift loss of 7.3% on the test model at an 8 deg angle of attack. A statistical analysis was performed to account for data scatter in the correlation and indicated that the upper limit of lift loss on the test model was 9.2%. Therefore, for cases resulting in lift loss from 7.3 to 9.2%, extra scrutiny of the visual observations is required for evaluating fluid performance with contamination and establishing appropriate allowance times.

Design and calibration method for a novel six-component piezoelectric balance

Wind tunnel balance is one of the most important measurement equipments in aerodynamic testing. In this paper, a new six-component piezoelectric balance is developed to measure the dynamic impact loading force in the wind tunnel. The arrangement mode of the triaxial piezoelectric load cells is confirmed based on the theory analysis. Furthermore, the mathematical model is established according to the calibration experimental results. Support vector machine is proposed to develop the piezoelectric balance calibration. It is an effective method to predict the model using small samples and reduce the duration of the calibration. The results of prediction are compared to the conventional calibration and the dynamic step response. The linearity and repeatability of the balance are within 0.2% and 0.5%, respectively, and the interference error has been reduced using the support vector machine method. The experimental results have shown that the four supports arrangement mode can reduce the area of attack and enhance the measuring range of the balance. The dynamic characteristics of the piezoelectric balance performed by the step response test show that the designed balance is feasible to measure the dynamic impact airloads in a wind tunnel.

Nasalance Scores of Children With Repaired Cleft Palate Who Exhibit Normal Velopharyngeal Closure During Aerodynamic Testing

To determine if children with repaired cleft palate and normal velopharyngeal (VP) closure as determined by aerodynamic testing exhibit greater acoustic nasalance than control children without cleft palate. Pressure-flow procedures were used to identify 2 groups of children based on VP closure during the production of /p/ in the word hamper: (a) children with repaired cleft palate and normal VP closure ( n = 23) and (b) controls without cleft palate and with normal VP closure ( n = 16). Acoustic nasalance scores were obtained for all children during the production of syllables with high-pressure consonants and sentences with low-pressure consonants (i.e., low-pressure sentences). Nasalance scores were generally higher for children with repaired cleft palate and normal VP function as compared to controls; however, a significant difference occurred only for low-pressure sentences ( p = .005). Results partially support a pressure-sensitive theory of VP function in that some children with repaired cleft palate may achieve VP closure during the production of high-pressure consonants but fail to do so during the production of vowels and low-pressure consonants. Clinical implications are discussed.

AEROELASTIC MODEL TEST STUDY ON A BRIDGE PYLON CONSIDERING THE INTERFERENCE EFFECTS OF SURROUNDING STRUCTURES

The interference effect between buildings has been a popular issue in structural wind engineering for a long time. Most researches about this issue have been focused mainly on high-rise buildings. For long-span bridges, the interference effects between structures are rarely discussed. In this paper, an aerodynamic elastic model test of a free-standing bridge pylon located adjacent to two large-scale cooling towers is presented. Through the mode analysis, the structure mode shapes are obtained. Then by the simulation of the two cooling towers in the boundary layer during the aeroelastic model test, the vibration responses of the bridge pylon in smooth and turbulence flows are obtained respectively. The study shows that the interference effect of the two huge-volume cooling towers on the wind induced vibration responses of the bridge pylon should not be neglected. In smooth flow, due to the regular shedding vortex from the upwind cooling towers, the interference effect is evident in that strong resonant responses are induced on the lower-order modes of the downwind bridge pylon. However, in turbulence flow, this kind of interference effect is greatly reduced. Moreover, more attention should be paid to the case when the cooling towers are located at the perfectly right upwind direction of the bridge pylon. Their interference effect will certainly cause great resonant vibrations in the longitudinal direction, which cannot be ignored for granted. Furthermore, the turbulence flow at the bridge pylon considering the interference effect is measured through a 1:500 flow experiment to discover the interference effect of the cooling towers. In the end, a dynamic magnification factor is proposed to take the interference effect into consideration, with a value of 2.25 suggested for the design of pylons.

Aerodynamic shape optimization using the adjoint Euler equations

PurposeAn aerodynamic shape optimization algorithm is presented, which includes all aspects of the design process: parameterization, flow computation and optimization. The purpose of this paper is to show that the Class‐Shape‐Refinement‐Transformation method in combination with an Euler/adjoint solver provides an efficient and intuitive way of optimizing aircraft shapes.Design/methodology/approachThe Class‐Shape‐Transformation method was used to parameterize the aircraft shape and the flow was computed using an in‐house Euler code. An adjoint solver implemented into the Euler code was used to compute the required gradients and a trust‐region reflective algorithm was employed to perform the actual optimization.FindingsThe results of two aerodynamic shape optimization test cases are presented. Both cases used a blended‐wing‐body reference geometry as their initial input. It was shown that using a two‐step approach, a considerable improvement of the lift‐to‐drag ratio in the order of 20‐30 per cent could be achieved. The work presented in this paper proves that the CSRT method is a very intuitive and effective way of parameterizating aircraft shapes. It was also shown that using an adjoint algorithm provides the computational efficiency necessary to perform true three‐dimensional shape optimization.Originality/valueThe novelty of the algorithm lies in the use of the Class‐Shape‐Refinement‐Transformation method for parameterization and its coupling to the Euler and adjoint codes.

Experimental Investigation of Propeller Propulsion Model for a Small UAV Using Wind Tunnel

Propulsion system modeling including propeller performance characteristics has a very important effect in the design and performance prediction of propeller-driven Unmanned Aerial Vehicles (UAVs). Motivated by modeling and simulation of small propeller-driven UAVs, the present paper focuses on the investigation of an accurate propeller-propulsion model used in these UAVs. First, propeller performance characteristics are measured in wind tunnel. Then, the engine model is identified based on experimental measurements of the engine input and output signals. The complete propeller-propulsion model, combining propeller and engine models, is then developed. Aerodynamic tests are performed at a low speed subsonic wind tunnel to measure both propeller static and dynamic characteristics. A special test rig is designed and manufactured in which the engine, propeller and all sensors are mounted. The propeller dynamic test is conducted by changing the advance ratio. This can be done by changing either throttle position or wind tunnel airspeed while keeping the other one constant. Both ways are used to collect dynamic performance data which allow covering the whole range of advance ratios until reaching the braking and windmill modes. For each advance ratio, thrust, torque and power coefficients and hence the efficiency are obtained. For the propeller static test, thrust and torque are measured in stationary air over a range of propeller rotational speeds (RPM). The relation between the coefficient of thrust, torque, power and the static efficiency were obtained at a large range of RPM. The results show good agreement with published data. Engine and its servo motor is identified using experimental data as either first or second order transfer function model. The complete propeller-propulsion model is developed, validated with a very good agreement between simulation and experimental data.

Dereverberation of a closed test section of a wind tunnel with a mult imicrophones cesptral method

Today, the manufacturers of aircraft want to perform at the same time aeroacoustic and classical aerodynamic tests in the wind tunnels with closed test sections in order to reduce test duration and costs involved in new aircraft developments. However, this kind of wind tunnels is not optimal for acoustics testing because the measurements are often masked by background noise (i.e., noise generated by the wind tunnel flow mechanism) and reverberations on the walls without acoustic liner within the test section. This is a serious problem because these unwanted phenomena limit the accuracy of identification, and quantification of acoustic sources. The reduction of background noise can be obtained with subspace techniques or noise subtraction based on a noise reference measurement. Concerning the reduction of the contamination of the echos, it can be achieved with an inverse filtering technique or with a single microphone cepstral method. A new approach is proposed in this study to remove the spurious effects of the echos. It is based on multi microphones cesptral technique. This new technique has been successfully applied on numerical simulations, and experimental data. The theoretical developments of this method and the obtained results will be presented in the full paper.

An algorithm for parameter estimation of twin-rotor multi-input multi-output system using trust region optimization methods

The twin-rotor, multi-input, multi-output system is a typical lab-scale helicopter system, since it resembles behavior of helicopter systems. This experimental complex aerodynamic test rig needs precise modeling to assure satisfactory control performance. Therefore, this article is intended to provide a gray-box approach for the modeling of the twin-rotor, multi-input, multi-output system. An algorithm is proposed by dividing the system into independent subsystems that can be estimated for an excitation input or a characteristic response. The proposed algorithm uses trust region optimization methods for successive estimations. The iterative optimization methods of Levenberg–Marquardt, gradient descent active set, and interior point are compared with respect to trust region methods. The model is validated with various sets of scenarios: different inputs, different types of motion, and different operating points. Effect of operating point selection on the parameter estimation process is investigated. Time domain response comparison of the single-degree-of-freedom vertical, single-degree-of-freedom horizontal, and two-degrees-of-freedom models are acceptable.

Wind-induced response and loads for the Confederation Bridge -Part II: derivation of wind loads

This paper uses ten years of on-site monitoring data for the Confederation Bridge to derive wind loads and investigate whether the bridge has experienced its design wind force effects since its completion in 1997. The load effects derived using loads from the on-site monitoring data are compared to the load effects derived using loads from the 1994 and 2009 wind tunnel aerodynamic model tests. The research shows, for the first time, that the aerodynamic model-based methodology originally developed in 1994 is a very accurate method for deriving wind loads for structural design. The research also confirms that the bridge has not experienced its specified (i.e., unfactored) wind force effects since it was opened to traffic in 1997, even during the most severe event that has occurred during this period.

Manufacturing of flexible micro hot-film probes for aeronautical purposes

In this work we present the design, fabrication and characterization of flexible AeroMEMS hot-film probes. The hot-films are fabricated on polyimide foil (PI). The foil is bonded onto a glass or silicon substrate in order to get a rigid structure for using standard silicon bulk-micromachining processes. After micro fabrication is finished the PI foil can be easily removed from the substrate. The foil itself is flexible enough to be placed on complex curved contours typically used in aerodynamic tests. This study discusses the failures introduced by geometry effects which occur due to isotropic wet etching of the metal layers. After these investigations, one hot-film design was chosen to create a sensor array for special measurements of wall shear stress in fluid mechanics. The array consists of 32 hot-film sensors custom made for an aerodynamic test. The properties of the sensing elements are optimized for the measurement set-up, providing a simple implementation. The sensing elements were finally made of Nickel, while the wiring was electroplated with 2μm of Copper. Using the advantages of both materials is unique. It is assumed that due to the extremely flat design, the sensor including its Cu wiring has no influence on the flow. The foil, including the thin wiring is bendable enough to lead the contacts into the wing, making the electrical connection very convenient.

Comparison of Voice Quality after Laser Cordectomy with That after Radiotherapy or Chemoradiotherapy for Early Glottic Carcinoma

Purpose of the Study: The present study aimed to compare the voice quality after each type of cordectomy with that after radiotherapy (RT) or chemoradiotherapy (CRT) for early glottic carcinoma. Procedures: The GRBAS perceptive scale [consisting of 5 domains: grade (G), roughness (R), breathiness (B), asthenia (A), and strain (S)], aerodynamic tests and acoustic analyses, and the Voice Handicap Index questionnaire were evaluated for 58 laser cordectomy cases and 40 RT or CRT cases. Multiple comparison tests were conducted between each type of cordectomy and RT or CRT. Results: No statistical difference was found between type I/II cordectomy and RT for T1 glottic carcinoma (T1RT), whereas T1RT showed a significantly better outcome than type III cordectomy (G score: p = 0.016, maximum phonation time: p < 0.01, mean flow rate: p < 0.01). Type IV cordectomy was equivalent to RT or CRT for T2 glottic carcinoma (T2RT/CRT), while types V and VI showed a worse voice quality than T2RT/CRT (G score: p = 0.038 to type VI, B score: p = 0.025 to type V and p = 0.032 to type VI, A score: p = 0.017 to type VI). Conclusions: Voice quality after laser cordectomy differs according to the type of cordectomy. Surgeons should inform patients about the expected voice quality after each treatment modality.

Turbulent friction drag reduction using electroactive polymer and electromagnetically driven surfaces

This work reports aerodynamic testing of two spanwise-oscillating surfaces fabricated out of electroactive polymers (EAPs) in the dielectric form of actuation, and of an electromagnetic-driven linear motor. Hot-wire and PIV measurements of velocity and direct measurement of friction drag using a drag balance are presented. A maximum of 16 % surface friction reduction, as calculated by the diminution of the wall-normal streamwise velocity gradient, was obtained. Among other quantities, the spatial dependence of the drag reduction was investigated. When this spatial transient and portions which are static are accounted for, the direct drag measurements complement the hot-wire data. PIV measurements, where the laser beam was parallel to the oscillating surface at y + ≈ 15, support the hot-wire data. The two actuators are original in design, and significant contributions have been made to the development of EAPs. This experiment is the first to aerodynamically test EAP actuators at such a large scale and at a relatively moderate Re.

APU용 구심터빈의 공력리그시험

175.74mm . 터빈 입구에서의 상세 유동이 측정되었다 노즐의 허브면에서 측정한 압력과 노즐의 쉬라우드 면과 터 . 빈 휠 케이싱에서 측정한 압력 분포를 볼 때 터빈 내부에서의 팽창과정이 적절함을 확인할 수 있었다. Abstract: An aerodynamic rig test of a radial turbine for an auxiliary power unit (APU) was performed at a high-temperature turbine test facility at the Korea Aerospace Research Institute. The pressure ratio, Mach number, and flow coefficient in the rig test are the same as those under normal engine operation conditions. The design pressure ratio is 3.096, design test speed is 34909 rpm, and turbine inlet temperature is 160°C. The turbine has airfoil-type nozzles, and the diameter of the turbine wheel is 175.74 mm. The turbine map is experimentally measured, and the detailed flow at the turbine inlet is measured. The pressure distribution in the nozzle at both the hub and the shroud sides and the pressure distribution along the shroud casing of the turbine wheel were measured, and this confirmed that the expansion process in the turbine wheel is acceptable.

Fatigue Failure of a Distortion Screen during Testing

Abstract A distress was observed in a distortion screen during testing. This screen is positioned in front of an aero engine during testing to check the engine performance with a distorted air intake. To ensure a distorted air intake, the screen contains dense meshes in some areas whereas in other areas they are less dense. Non-uniformity in the mesh density results in distorted air flow into the engine thereby facilitating evaluation of the engine performance with disturbed aerodynamic inlet. The component, i.e. the distortion screen was under development and was subjected to aerodynamic tests on the test bench. It was found to have fractured from a rib connecting two meshes. Loose end of the mesh had detached and resulted in permanent deformation of the adjoining ribs and meshes. The fractured surface exhibited glossy crystalline appearance. Scanning electron microscope revealed striations at higher magnifications (>500X) as was observed in the case of fatigue failure. Two crack fronts were adjacent and near to one corner of the rib, and the third crack front had originated from the other corner placed diagonally opposite to the other two crack fronts. This observation indicated failure of the screen under reverse bending fatigue condition. Design and material condition were reviewed. After modification it was found that the newly modified distortion screen did not show any sign of deformation after testing.

Efficient Response Surface Methods Based on Generic Surrogate Models

Surrogate models are used for global approximation of responses generated by expensive computer experiments like CFD applications. In this paper, we make use of structural similarities which are shared by a class of related problems. We identify these structures by applying statistical shape models. They are used to build a generic surrogate model approximation to sample data of a new problem of the same class. In a variable-fidelity framework the generic surrogate model is combined with the sample data to generate an efficient and globally accurate interpolation model, which requires less costly sample evaluations than ordinary response surface methods. We demonstrate our method with an aerodynamic test case and show that it significantly improves the approximation quality.

Ares I Aerodynamic Testing at the Boeing Polysonic Wind Tunnel

Throughoutthreefulldesignanalysiscycles, theAres Iproject withintheConstellationprogram has consistently relied on the Boeing Polysonic Wind Tunnel (PSWT) for aerodynamic testing of the subsonic, transonic and supersonic portions of the atmospheric flight envelope (Mach=0.5 to 4.5). Each design cycle required the development of aerodynamic databases for the 6 degree-of-freedom (DOF) forces and moments, as well as distributed line-loads databases covering the full range of Mach number, total angle-of-attack, and aerodynamic roll angle. The high fidelity data collected in this facility has been consistent with the data collected in NASA Langley’s Unitary Plan WindTunnel (UPWT)at the overlapping conditionof Mach=1.6. Muchinsight into the aerodynamic behavior of the launch vehicle during all phases of flight was gained through wind tunnel testing. Important knowledge pertaining to slender launch vehicle aerodynamics in particular was accumulated. In conducting these wind tunnel tests and developing experimental aerodynamic databases, some challenges were encountered and are reported as lessons learned in this paper for the benefit of future crew launch vehicle aerodynamic developments.

Ares I Aerodynamic Testing at the Boeing Polysonic Wind Tunnel

Covers advancements in spacecraft and tactical and strategic missile systems, including subsystem design and application, mission design and analysis, materials and structures, developments in space sciences, space processing and manufacturing, space operations, and applications of space technologies to other fields.

Ares I and Ares I-X Stage Separation Aerodynamic Testing

Covers advancements in spacecraft and tactical and strategic missile systems, including subsystem design and application, mission design and analysis, materials and structures, developments in space sciences, space processing and manufacturing, space operations, and applications of space technologies to other fields.