Uncertainty-based design optimization of NLF airfoil for high altitude long endurance unmanned air vehicles

PurposeThe high probability of the occurrence of separation bubbles or shocks and early transition to turbulence on surfaces of airfoil makes it very difficult to design high-lift and high-speed Natural-Laminar-Flow (NLF) airfoil for high-altitude long-endurance unmanned air vehicles. To resolve this issue, a framework of uncertainty-based design optimization (UBDO) is developed based on an adjusted polynomial chaos expansion (PCE) method.Design/methodology/approachThe γ ̄Re-θt transition model combined with the shear stress transportk-ω turbulence model is used to predict the laminar-turbulent transition. The particle swarm optimization algorithm and PCE are integrated to search for the optimal NLF airfoil. Using proposed UBDO framework, the aforementioned problem has been regularized to achieve the optimal airfoil with a tradeoff of aerodynamic performances under fully turbulent and free transition conditions. The tradeoff is to make sure its good performance when early transition to turbulence on surfaces of NLF airfoil happens.FindingsThe results indicate that UBDO of NLF airfoil considering Mach number and lift coefficient uncertainty under free transition condition shows a significant deterioration when complicated flight conditions lead to early transition to turbulence. Meanwhile, UBDO of NLF airfoil with a tradeoff of performances under both fully turbulent and free transition conditions holds robust and reliable aerodynamic performance under complicated flight conditions.Originality/valueIn this work, the authors build an effective uncertainty-based design framework based on an adjusted PCE method and apply the framework to design two high-performance NLF airfoils. One of the two NLF airfoils considers Mach number and lift coefficient uncertainty under free transition condition, and the other considers uncertainties both under fully turbulent and free transition conditions. The results show that robust design of NLF airfoil should simultaneously consider Mach number, lift coefficient (angle of attack) and transition location uncertainty.

Acoustic Diagnostics Applications in the Study of the Oscillation Combustion in Lean Premixed Pre-Evaporation Combustor

The paper presents an experimental investigation of the thermoacoustic oscillations detection in a lean premixed pre-evaporation (LPP) combustor using acoustic signals. The LPP model combustion chamber oscillation combustion test platform was designed and built; the thermal parameters signal, the acoustic signal, and the dynamic pressure signal were collected under the steady condition and the transition condition, and been analyzed comparatively. The experimental result shows that, at the same inlet air speed, the dominant frequency of the combustion chamber is proportional to the thermal load, while at the same fuel flow, the main frequency of the combustion chamber does not change with the changing of air speed. In addition, the doubling frequency of the acoustic signal is more obvious than the pressure signals, which show that the interference of the acoustic signal is less. In the transition condition, the pulse energy of the acoustic signal is obviously increased after ignition. The dominant frequency energy increases when the working condition begins to change in the stable to oscillation combustion condition. The dominant frequency energy decreases when the working condition begins to change in the oscillation to stable combustion condition. During the flameout condition, the oscillating energy begins to decay from the high frequency region. For the acoustic signal is less disturbed than the pressure signal and it can obtain the same result with the pressure signal in the oscillation condition and the transition condition, acoustic diagnostic is an auxiliary method for combustion oscillation in LPP combustor.

SASTRA BANJAR KALIMANTAN SELATAN PASCA KEMERDEKAAN

Abstrak: Sastra Banjar Kalimantan Selatan pascakemerdekaan menggambarkan tentang peristiwa yang melatarbelakangi kehidupan penulis dan masyarakatnya. Peristiwa-peristiwa itu terjadi dalam kehidupan yang memiliki latar belakang berbeda dengan daerah lain. Sastra Banjar dan penulisnya memiliki kekhasan masing-masing dari waktu ke waktu. Perkembangan sastra pascakemerdekaan tahun 1950—1959 memiliki ciri yang khas, meskipun karya sastra yang berkembang memiliki kategori yang sama, yakni puisi, prosa, dan drama. Ciri-ciri yang khas itu, dapat dikatakan karena beberapa faktor, antara lain karena bangsa ini kondisi transisi pascakemerdekaan. Berdasarkan uraian itu, masalah dalam penelitian ini akan membahas tentang perkembangan sastra pascakemerdekaan tahun 1950—1959 dengan latar belakang kehidupan masyarakatnya sebagai pemilik sastra daerah Banjar di Kalimantan Selatan. Penelitian ini menggunakan metode deskriptif-kualitatif. Metode ini digunakan untuk memperoleh informasi tentang perkembangan sastra daerah di Kalimantan Selatan dan kemudian menjadi bahan analisis. Penelitian ini akan memberikan gambaran tentang kondisi kesusastraan di Kaliantan Selatan pasckemerdekaan.Kata kunci: Sastra Banjar, pascakemerdekaan. Abstract: Banjar literature of South Kalimantan post independence describes obaut event that becames the backgraound of the writei’s life and its society. Each events has different backgraound with other region. Banjar literature and the writer have special characteristic from time to time. The development of literature post independence age in 1950—1959 has special characteristic, even thougt the literature has the same catagoris, they are poem, prose, and drama. That special characteristic can be because of reveral factors, for example when this nation is in transition condition post independence. Base on the explanation, the problem in this study will discuss abaut the development of literature post independence in 1950—1959 whith the background of its social life as the owner of Banjar local literature in South Kalimantan. This study is used descriptive qualitative method. This method is uses to get information abaut the development of local literature in South Kalimantan and it becomes the data. This study will give description abaut the condition of literature is South Kalimantan post independence.Key words: Banjar literature, post independence.