Numerical solutions of the linearized Euler equations for unsteady vortical flows around lifting airfoils

A linearized unsteady aerodynamic analysis is presented for unsteady, subsonic vortical flows around lifting airfoils. The analysis fully accounts for the distortion effects of the nonuniform mean flow on the imposed vortical disturbances. A frequency domain numerical scheme which implements this linearized approach is described, and numerical results are presented for a large variety of flow configurations. The results demonstrate the effects of airfoil thickness, angle of attack, camber, and Mach number on the unsteady lift and moment of airfoils subjected to periodic vortical gusts. The results show that mean flow distortion can have a very strong effect on the airfoil unsteady response, and that the effect depends strongly upon the reduced frequency, Mach number, and gust wave numbers

Numerical solution of periodic vortical flows about a thin airfoil

A numerical method is developed for computing periodic, three-dimensional, vortical flows around isolated airfoils. The unsteady velocity is split into a vortical component which is a known function of the upstream flow conditions and the Lagrangian coordinates of the mean flow, and an irrotational field whose potential satisfies a nonconstant-coefficient, inhomogeneous, convective wave equation. Solutions for thin airfoils at zero degrees incidence to the mean flow are presented in this paper. Using an elliptic coordinate transformation, the computational domain is transformed into a rectangle. The Sommerfeld radiation condition is applied to the unsteady pressure on the grid line corresponding to the far field boundary. The results are compared with a Possio solver, and it is shown that for maximum accuracy the grid should depend on both the Mach number and reduced frequency. Finally, in order to assess the range of validity of the classical thin airfoil approximation, results for airfoils with zero thickness are compared with results for airfoils with small thickness

A finite-difference, frequency-domain numerical scheme for the solution of the linearized unsteady Euler equations

A numerical method is developed for solving periodic, three-dimensional, vortical flows around lifting airfoils in subsonic flow. The first-order method, that is presented, fully accounts for the distortion effects of the nonuniform mean flow on the convected upstream vortical disturbances. The unsteady velocity is split into a vortical component which is a known function of the upstream flow conditions and the Lagrangian coordinates of the mean flow, and an irrotational field whose potential satisfies a nonconstant-coefficient, inhomogeneous, convective wave equation. Using an elliptic coordinate transformation, the unsteady boundary value problem is solved in the frequency domain on grids which are determined as a function of the Mach number and reduced frequency. Extensive comparisons are made with known solutions to unsteady vortical flow problems, and it is seen that the agreement is generally very good for reduced frequencies ranging from 0 up to 4

Acoustic radiation from lifting airfoils in compressible subsonic flow

The far field acoustic radiation from a lifting airfoil in a three-dimensional gust is studied. The acoustic pressure is calculated using the Kirchhoff method, instead of using the classical acoustic analogy approach due to Lighthill. The pressure on the Kirchhoff surface is calculated using an existing numerical solution of the unsteady flow field. The far field acoustic pressure is calculated in terms of these values using Kirchhoff's formula. The method is validated against existing semi-analytical results for a flat plate. The method is then used to study the problem of an airfoil in a harmonic three-dimensional gust, for a wide range of Mach numbers. The effect of variation of the airfoil thickness and angle of attack on the acoustic far field is studied. The changes in the mechanism of sound generation and propagation due to the presence of steady loading and nonuniform mean flow are also studied

Penerapan Algoritma Stemming Nazief & Adriani Dan Similarity Pada Penerimaan Judul Thesis

Search information in the form of a document or a text known as Information Retrieval (IR) is a separation process documents that are relevant from a set of documents available. The increasing number of thesis documents are available allowing the similarity theme or topic of discussion was appointed as the thesis title. Stemming is a process that converts all the words in a text document into "rootword" or principal said. Rootwords are stored as an index. Each index which stored to be used as a comparison to the new document. By using the concept of Similarity, the index comparisons of old documents with new index documents can be obtained degree of similarity to certify the appropriateness of the thesis title

Towards automated support for extraction of reusable components

A cost effective introduction of software reuse techniques requires the reuse of existing software developed in many cases without aiming at reusability. This paper discusses the problems related to the analysis and reengineering of existing software in order to reuse it. We introduce a process model for component extraction and focus on the problem of analyzing and qualifying software components which are candidates for reuse. A prototype tool for supporting the extraction of reusable components is presented. One of the components of this tool aids in understanding programs and is based on the functional model of correctness. It can assist software engineers in the process of finding correct formal specifications for programs. A detailed description of this component and an example to demonstrate a possible operational scenario are given

Image reconstruction using iterative transpose algorithm for optical tomography

This paper describes a transpose algorithm for use with an optical tomography system. The measurement system consisted of two orthogonal arrays, each having ten parallel views, resulting in a total of twenty sensors. The measurement section is divided into hundred equi-sized pixels. The forward problem is modelled by allocating an optical attenuation coefficient to each pixel. The attenuation of incident collimated light beams is then modelled using the Lambert-Beer law. The inverse problem is defined and the transpose of the sensitivity matrix is used to obtain an estimate of the attenuation coefficients in each pixel. The iterative method is investigated as a means of improving reconstructed image qualit

TRANSFORMASI NILAI PANCASILA MELALUI ORGANISASI MAHASISWA GUNA MENINGKATKAN KESADARAN BERBANGSA DAN BERNEGARA (Studi Deskriptif HIMA PKnH FKIP Universitas Pasundan Bandung)

Penelitian ini bertujuan untuk mengetahui sejauhmana penerapan Nilai-Nilai Pancasila Melalui Organisasi Mahasiswa Guna Meningkatkan Kesadaran Berbangsa Dan Bernegara. Penelitian ini dilatarbelakangi oleh era baru fajar reformasi saat ini, dimana Pancasila kini seolah tidak pantas lagi dipakai dalam dialektik era reformasi, Pancasila sudah jarang dikutip, Pancasila sudah jarang dipakai dalam segala aspek ketatanegaraan, melupakan Pancasila sebagai dasar kehidupan dalam berbangsa dan bernegara. Penelitian ini mendeskripsikan beberapa rumusan masalah yaitu Sejauhmana Penerapan, Program apa saja yang dilakukan, Pendekatan, dan metode, Hambatan serta Upaya apakah yang dilakukan untuk menghadapi tantangan yang muncul dari penerapan nilai Pancasila guna meningkatkan kesadaran berbangsa dan bernegara dalam lingkungan Mahasiswa dalam proses transformasi nilai-nilai Pancasila di HIMA PKnH. Penelitian ini menggunakan metode Deskriptif dengan Pendekatan Kualitatif, Subjek dan Objek dalam Penelitian ini adalah Organisasi Mahasiswa HIMA PKnH FKIP UNPAS. Pengumpulan data dan Instrumen penelitian yang digunakan dalam Penelitian ini dengan melakukan wawancara, observasi serta media angket yang dijadikan sebagai data konkret. Hasil penelitian menunjukkan bahwa adanya hubungan antara nilai didalam Pancasila dengan program kerja yang diselenggarakan oleh HIMA PKnH FKIP UNPAS. Metode, pendekatan yang dilakukan oleh HIMA PKnH adalah pendekatan kekeluargaan, demokratis. Hambatan yang dihadapi oleh HIMA PKnH dalam melaksanakan setiap program kerjanya Upaya yang dilakukan untuk mengatasi hambatan tersebut adalah dengan melakukan pendekatan kembali serta melakukan pelatihan yang dilakukan sesuai dengan kebutuhan dalam menangani setiap hambatan yang dihadapi. Kata Kunci : Transformasi, Nilai Pancasila, Organisasi Mahasiswa, kesadaran berbangsa dan bernegar