Effect of Rear Wing on Time-Averaged Ground Vehicle Wake With Variable Slant Angle

The slant angle plays a crucial role in the flow property of hatchback ground vehicles. An optimum slant angle is obligatory for better handling the ground vehicles when fitted with a rear wing. In this regard, the variation of time-averaged flow properties around a wing-attached hatchback ground vehicle (Ahmed body) due to a variable slant angle is accessed by this paper. The design includes a scaled Ahmed body as a reference ground vehicle and a rear wing with NACA 0018 profile. The computational studies are executed with Reynolds-averaged Navier–Stokes based k-epsilon turbulence model with nonequilibrium wall function. The vehicle's model is scaled to 75% of the actual model, and analyses are conducted with Reynolds number 2.7 × 106. After the study, it is observed that a 15 deg slant angle is the critical angle for the wing attached state in which the drag coefficient is maximum. After this angle, a sudden reduction of coefficients is observed, where 25 deg is critical for without wing condition. Besides this, the two counter-rotating horseshoe vortices in the separation bubble and side edge c-pillar vortices also behave differently due to the wing's presence. The turbulent kinetic energy variation and the variation in coefficients of surface pressure are also affected by the rear wing attachment. This paper will assist in finding the optimum slant angle for hatchback ground vehicles in the presence of a rear wing. Thus the study will help in increasing stability and control for hatchback ground vehicles.

Combination of experiments and CFD analysis for in-flight wings deflections estimation

Purpose This study aims to develop a new correlation method for prediction of in-flight wings deflections by integration of the experimental ground tests with computational fluid dynamics (CFD) analysis. Design/methodology/approach The ground test results are implemented in the curve fitting process to determine deflections at 66 specific points (SPs) on the front and rear wing torque box. By using the obtained deflections and the corresponding applied loads, an experimental deflection equation (EDE) for each point is established through the Castigliano’s theorem. The CFD aerodynamic loads of typical aircraft, which have been obtained earlier by the authors, are once again used in the current research. The total applied loads to each part are achieved via summation of inertia and aerodynamic loads. The obtained loads are transformed to the equivalent concentrated loads at the SPs. By substituting the concentrated load values in the EDEs, the SPs deflections are achieved for mentioned flight conditions. The resulted deflections and the corresponding input flight parameters, i.e. M and α, are incorporated into a linear regression method for development of the appropriate in-flight deflection equations (IFDEs). The validity of IFDEs is approved by comparing IFDEs’ deflections with the corresponding ones calculated through EDEs for different flight conditions. Findings As an alternative approach to the fairly expensive flight tests, the IFDEs can be used to predict the in-flight wing deflections with comparable degree of accuracy. Originality/value Prediction of actual wing deflections distributions without flight tests execution at any given flight condition.

Inventarisasi serangga dan tingkat kerusakan yang ditimbulkan pada tegakan jati (Tectona grandis LINN. F) di areal hutan tanaman rakyat (HTR) negeri Hila Kabupaten Maluku Tengah

The study aims to determine the types of insects that attack teak plants, diagnose the symptoms of attack and estimate the magnitude and intensity of attacks caused by teak pest attacks. The results found two types of pests that attack teak stands namely Woodhoppers (Valanga nigricornis) and Caterpillars (Hyblaea puera) with moderate damage intensity. Wooden Grasshopper (Valanga nigricornis) measuring 45 - 55 mm (male) and 1575 mm (female), has a head, chest, thorax and abdomen, yellowish brown with a dark blue hue on the wings. The rear wing is visible when flying and is red. Teak caterpillars (Hyblaea puera) are found to be brown with a pair of small yellow stripes on each side, and between two lines are dark brown with a length of 3.5 cm, while the cocoon is dark brownish black, with an average length of 1.4-1, 9 cm, and an average weight of 0.7-1.3 mg. Valanga nigricornis attack area of 29.58% belong to the category of moderate attack and Hyblaea puera of 23.41% belonging to the category of mild attack

Optimization of fastener pattern in airframe assembly

Purpose The authors consider the problem of optimizing temporary fastener patterns in aircraft assembly. Minimizing the number of fasteners while maintaining final product quality is one of the key enablers for intensifying production in the aerospace industry. The purpose of this study is to formulate the fastener pattern optimization problem and compare different solving approaches on both test benchmarks and rear wing-to-fuselage assembly of an Airbus A350-900. Design/methodology/approach The first considered algorithm is based on a local exhaustive search. It is proved to be efficient and reliable but requires much computational effort. Secondly, the Mesh Adaptive Direct Search (MADS) implemented in NOMAD software (Nonlinear Optimization by Mesh Adaptive Direct Search) is used to apply the powerful mathematical machinery of surrogate modeling and associated optimization strategy. In addition, another popular optimization algorithm called simulated annealing (SA) was implemented. Since a single fastener pattern must be used for the entire aircraft series, cross-validation of obtained results was applied. The available measured initial gaps from 340 different aircraft of the A350-900 series were used. Findings The results indicated that SA cannot be applicable as its random character does not provide repeatable results and requires tens of runs for any optimization analysis. Both local variations (LV) method and MADS have proved to be appropriate as they improved the existing fastener pattern for all available gaps. The modification of the MADS' search step was performed to exploit all the information the authors have about the problem. Originality/value The paper presents deterministic and probabilistic optimization problem formulations and considers three different approaches for their solution. The existing fastener pattern was improved.

Pengaruh Penambahan Gurney Flap pada Airfoil Jenis Mshd pada Mobil Fastback dengan Variasi Ketinggian Gurney Flap dan Kemiringan Sudut Airfoil Dengan Metode Permodelan CFD

<div class="WordSection1"><p>Faktor aerodinamika merupakan faktor penting dalam mendesain suatu kendaraan. Faktor aerodinamika menjadi penting karna sangat berpengaruh pada performa kendaraan dan faktor keselamatan dari kendaraan itu sendiri. Salah satu cara untuk meningkatkan faktor aerodinamika pada kendaraan darat (<em>ground vehicle</em>) adalah dengan menambahkan rear wing dengan <em>Gurney Flap</em>. Penggunaan rear wing dengan <em>Gurney Flap</em> ini dapat meningkatkan nilai koefisien <em>lift</em> negatif dari suatu kendaraan, sehingga meningkatkan performa mobil pada saat kecepatan tinggi dan pada saat berbelok ataupun mengerem. Penelitian ini akan membahas tentang karakteristik aerodinamik dari salah satu jenis high <em>lift</em> airfoil yaitu airfoil MSHD dengan penambahan <em>Gurney Flap</em> dengan variasi kemiringan sudut serang dari airfoil, dan ketinggian dari <em>Gurney Flap</em>. Penelitian ini dilakukan dengan mensimulasikan variasi airfoil yang diberikan yang dipasang pada ahmed body dengan kemiringan sudut rear slant 15⁰ atau menyerupai mobil tipe sedan (<em>fastback</em>). Simulasi digunakan dengan computational fluid dynamic (CFD) dengan variasi 3 kemiringan sudut airfoil yaitu 0⁰, 7,5⁰, dan 15⁰ dan 5 ketinggian <em>Gurney Flap</em> sebesar 0%, 0,5%, 1%, 1,5% dan 2% dari panjang chord line untuk setiap kemiringan sudut airfoil. Hasil dari penelitian ini, didapat nilai koefisien <em>lift</em>/<em>drag</em> terendah pada variasi kemiringan sudut airfoil 15⁰ dengan ketinggian <em>Gurney Flap</em> 2%c dengan nilai -1,465 yang terdapat peningkatan nilai sebesar 17,77% dibandingkan dengan tanpa <em>Gurney Flap</em>.<em></em></p></div><em><br clear="all" /></em><div class="WordSection1"><p>Faktor aerodinamika merupakan faktor penting dalam mendesain suatu kendaraan. Faktor aerodinamika menjadi penting karna sangat berpengaruh pada performa kendaraan dan faktor keselamatan dari kendaraan itu sendiri. Salah satu cara untuk meningkatkan faktor aerodinamika pada kendaraan darat (<em>ground vehicle</em>) adalah dengan menambahkan rear wing dengan <em>Gurney Flap</em>. Penggunaan rear wing dengan <em>Gurney Flap</em> ini dapat meningkatkan nilai koefisien <em>lift</em> negatif dari suatu kendaraan, sehingga meningkatkan performa mobil pada saat kecepatan tinggi dan pada saat berbelok ataupun mengerem. Penelitian ini akan membahas tentang karakteristik aerodinamik dari salah satu jenis high <em>lift</em> airfoil yaitu airfoil MSHD dengan penambahan <em>Gurney Flap</em> dengan variasi kemiringan sudut serang dari airfoil, dan ketinggian dari <em>Gurney Flap</em>. Penelitian ini dilakukan dengan mensimulasikan variasi airfoil yang diberikan yang dipasang pada ahmed body dengan kemiringan sudut rear slant 15⁰ atau menyerupai mobil tipe sedan (<em>fastback</em>). Simulasi digunakan dengan computational fluid dynamic (CFD) dengan variasi 3 kemiringan sudut airfoil yaitu 0⁰, 7,5⁰, dan 15⁰ dan 5 ketinggian <em>Gurney Flap</em> sebesar 0%, 0,5%, 1%, 1,5% dan 2% dari panjang chord line untuk setiap kemiringan sudut airfoil. Hasil dari penelitian ini, didapat nilai koefisien <em>lift</em>/<em>drag</em> terendah pada variasi kemiringan sudut airfoil 15⁰ dengan ketinggian <em>Gurney Flap</em> 2%c dengan nilai -1,465 yang terdapat peningkatan nilai sebesar 17,77% dibandingkan dengan tanpa <em>Gurney Flap</em>.<em></em></p></div><em><br clear="all" /></em>