RANS and DES Computations for a Wing with Ice Accretion

A computational investigation was performed to assess the effectiveness of Detached Eddy Simulation (DES) as a tool for predicting icing effects. The AVUS code, a public domain flow solver, was employed to compute solutions for an iced wing configuration using DES and steady Reynolds Averaged Navier-Stokes (RANS) equation methodologies. The wing section considered here was a business jet airfoil (GLC305) with a 22.5-minute glaze ice accretion (944-ice shape). The section was extruded to form a rectangular planform. The model was mounted between two walls so no tip effects were considered. The numerical results were validated by comparison with experimental data for the same configuration. The time-averaged DES computations showed some improvement in lift and drag results near stall when compared to steady RANS results. However, comparisons of the flow field details did not show the level of agreement suggested by the integrated quantities. More validation is needed to determine what role DES can play as part of an overall icing effects prediction strategy

PENGARUH LATIHAN PASSING BERPASANGAN TERHADAP KEMAMPUAN PASSING BAWAH SISWA SEKOLAH SEPAKBOLA KALASAN USIA 10-12 TAHUN

ABSTRAK Passing yang dilakukan siswa sekolah sepakbola Kalasan usia 10-12 tahun masih terlalu kencang dan kurang akurat, sehingga teman sulit untuk menerima bola. Penelitian ini bertujuan untuk mengetahui pengaruh latihan passing berpasangan terhadap kemampuan passing bawah siswa sekolah sepakbola Kalasan usia 10-12 tahun. Jenis penelitian adalah eksperimen dengan desain “The One Group Pretest Posttest Design”. Populasi penelitian adalah siswa SSB Kalasan Sleman, berusia 10-12 tahun yang berjumlah 27 orang. Instrumen yang digunakan adalah tes mengoperkan bola rendah dari Subagyo Irianto (1995: 9) dengan validitas sebesar 0,812 dan reliabilitas sebesar 0,856. Analisis data menggunakan uji t dengan taraf signifikansi 5%. Hasil penelitian menunjukkan bahwa ada pengaruh yang signifikan latihan passing berpasangan terhadap kemampuan passing bawah siswa sekolah sepakbola Kalasan usia 10-12 tahun, dengan nilai t hitung 6,574 > t 2,09, dan nilai signifikansi 0,000 < 0,05, dan kenaikan persentase sebesar 37,69%. tabe

Radiation induced degradation of elastomers.

An attempt has been made to evaluate the kinetics of the thermal and combined thermal/radiative degradation of a peroxide cured polydimethylsiloxane elastomer (PDMS), and a vinylidene fluoride-hexafluoropropylene elastomer (Viton E60-C),by chemical stress relaxation measurements. It was observed that the PDMS elastomer degraded thermally by hydrolytic scission of the main chain and chain reformation by condensation of the silanol chain end groups. However,predominant chain reformation was observed during thermal degradation studies and it was believed that this was a consequence of the reformation of chains cut during the test,and also the reformation of chains cut prior to the test in the post cure operation. These two components of the observed chain reformation response were subsequently rationalized by a model. Thermal degradation of the Viton E60-C elastomer appeared to take place by hydrolytic scission of the amine crosslinkages, and subsequent crosslink reformation by condensation,indicating that the material had not been subjected to a suitable post cure treatment in order to remove water generated by the vulcanization reaction. At temperatures above 200&deg;C predominant crosslinking was observed and this was attributed to the presence of a concurrent reaction which leads to the formation of ring structures. Thermal/radiative degradation studies indicated that temperature and radiation had a synergistic effect on the overall rate of induced chain scission in the PDMS elastomer but the mechanisms responsible for this phenomenon have yet to be established

Analisa Tegangan Pipa Bawah Laut pada Proses Instalasi Akibat Gerakan Lay Barge dengan Metode S-Lay

Respon struktur Lay Berge akibat eksitasi gelombang akan mempengaruhi tegangan pipa pada saat instalasi. Untuk mencegah terjadinya tegangan berlebih yang akan berakibat pada kegagalan, maka dibutuhkan tensioner sebagai pemberi tension terhadap pipa guna menjaga bentuk pipa (catenary shape). Pada penelitian ini. Akan dibahas mengenai gerakan Lay Barge apa yang paling berpengaruh terhadap tegangan pipa pada metode S-Lay. Penelitian ini menggunkan software Orcaflex yang berbasis analisa time domain untuk pemodelan dinamisnya Simulasi pada penelitian ini dilakukan selama 10 menit. Sturktur Lay Barge yang digunakan adalah CASTORO II milik Saipem, dengan material pipa grade X-65 berdiameter 26 inc~ konfigurasi mooring 30<J sebanyak 8 buah dan panjang stinger yang digunakan sepanjang 30 m dengan sudut datang 13,6°. Hasil penelitian ini didapatkan bahwa titik kritis terjadinya tegangan tebesar adalah 31.25 m dari ujung stem barge pada daerah overbend sebesar 136384 kN/m2 . Dan gerakan tunggal yang memiliki kontribusi terbesar terhadap tegangan pipa adalah gerakan pitch sebesar 98.56 %, dengan distribusi statistik lognormal untuk variasi tegangan.. ================================================================================================================================= The response of a Lay Barge structure induced by wave excitation will influence the stresses of pipe during the installation process. To prevent the over stress which is consequence to failure, therefore it needed a tensioner machine to give tension for maintaining a catenary shape. The aim of this research is to know the most influence of the motion on the Lay Barge which will produce the maximum bending stress on the pipe using the S-Lay method. This research performed by Orcaflex software based on time domain for the dynamic modelling. The simulation has been taken about 10 minutes. Lay Barge structure CASTORO II provided by Saipem, material grade X-65 and 26 inch OD for the pipe, mooring configuration at 30° for 8 lines and the length of stinger is about 30m with depature angel 13,6° has been used in this research. The result of this research are: the critical point is at 31.25 m from the end of stem barge at the overbend region with a value about 136384 kN/m2 • And the single motion which gives the significant contribution is pitch about 98.56 %~ with statistic distribution lognormal for its various stresses