Direct numerical simulations of transition in a compressor cascade: The influence of free-stream turbulence

Copyright © Cambridge University Press 2010.The flow through a compressor passage without and with incoming free-stream grid turbulence is simulated. At moderate Reynolds number, laminar-to-turbulence transition can take place on both sides of the aerofoil, but proceeds in distinctly different manners. The direct numerical simulations (DNS) of this flow reveal the mechanics of breakdown to turbulence on both surfaces of the blade. The pressure surface boundary layer undergoes laminar separation in the absence of free-stream disturbances. When exposed to free-stream forcing, the boundary layer remains attached due to transition to turbulence upstream of the laminar separation point. Three types of breakdowns are observed; they combine characteristics of natural and bypass transition. In particular, instability waves, which trace back to discrete modes of the base flow, can be observed, but their development is not independent of the Klebanoff distortions that are caused by free-stream turbulent forcing. At a higher turbulence intensity, the transition mechanism shifts to a purely bypass scenario. Unlike the pressure side, the suction surface boundary layer separates independent of the free-stream condition, be it laminar or a moderate free-stream turbulence of intensity Tu ~ 3%. Upstream of the separation, the amplification of the Klebanoff distortions is suppressed in the favourable pressure gradient (FPG) region. This suppression is in agreement with simulations of constant pressure gradient boundary layers. FPG is normally stabilizing with respect to bypass transition to turbulence, but is, thereby, unfavourable with respect to separation. Downstream of the FPG section, a strong adverse pressure gradient (APG) on the suction surface of the blade causes the laminar boundary layer to separate. The separation surface is modulated in the instantaneous fields of the Klebanoff distortion inside the shear layer, which consists of forward and backward jet-like perturbations. Separation is followed by breakdown to turbulence and reattachment. As the free-stream turbulence intensity is increased, Tu ~ 6.5%, transitional turbulent patches are initiated, and interact with the downstream separated flow, causing local attachment. The calming effect, or delayed re-establishment of the boundary layer separation, is observed in the wake of the turbulent events.Air Force Office of Scientific Researc

Analisis Pengaruh Citra Merek Dan Kualitas Layanan Terhadap Minat Beli Konsumen Produk Kartu Prabayar Simpati Di Kota Palembang

This study aims to analyze the influence of brand image and service quality of the prepaid card products sympathies of the people buying interest in the city of Palembang. Population used is the consumer prepaid cards of simpati in the city of Palembang. In this study, researchers spread as many as 100 sheets of questionnaires to the users of prepaid card products Simpati brand in the city of Palembang. Deployment of 100 questionnaires was done as a precaution, so that the data in this study is sufficient to serve as the study sample. Deployment of 100 pieces of questionnaire will be carried out evenly across the city of Palembang, namely 50 questionnaires at the Ulu Palembang and 50 questionnaires in the city of Palembang Ilir. The technique in the determination of the sample was purposive sampling with the specified criteria for the study was duration of use of prepaid cards Simpati at least 1 year and at least 17 years old and over, and reside in the region of Palembang. The reason for the use of such methods because researchers want to get the right information in a practical way. These results indicate that the brand image of a prepaid card Simpati no significant effect on the buying interest because it has a significance value greater than 0.05. While the quality of service significantly influence the buying public interest because it has a significance value less than 0.05. Adjusted R Square value generated in this study is equal to 0.026. This indicates that the variable of brand image and service quality has a percentage of 2.6% effect on consumer buying interest on the prepaid card products Simpati. While the remaining 97.4% influenced by other factors beyond the quality of service and brand image such as product prices, quality products and the other is not examined

Direct numerical simulation of heat transfer from the stagnation region of a heated cylinder affected by an impinging wake

Copyright © 2011 Cambridge University Press.The effect of an incoming wake on the flow around and heat transfer from the stagnation region of a circular cylinder was studied using direct numerical simulations (DNSs). Four simulations were carried out at a Reynolds number (based on free-stream velocity and cylinder diameter D) of Re = 13200: one two-dimensional (baseline) simulation and three three-dimensional simulations. The three-dimensional simulations comprised a baseline simulation with a uniform incoming velocity field, a simulation in which realistic wake data - generated in a separate precursor DNS - were introduced at the inflow plane and, finally, a simulation in which the turbulent fluctuations were removed from the incoming wake in order to study the effect of the mean velocity deficit on the heat transfer in the stagnation region. In the simulation with realistic wake data, the incoming wake still exhibited the characteristic meandering behaviour of a near-wake. When approaching the regions immediately above and below the stagnation line of the cylinder, the vortical structures from the wake were found to be significantly stretched by the strongly accelerating wall-parallel (circumferential) flow into elongated vortex tubes that became increasingly aligned with the direction of flow. As the elongated streamwise vortical structures impinge on the stagnation region, on one side they transport cool fluid towards the heated cylinder, while on the other side hot fluid is transported away from the cylinder towards the free stream, thereby increasing the heat transfer. The DNS results are compared with various semi-empirical correlations for predicting the augmentation of heat transfer due to free-stream turbulence.German Research Foundatio

IEC Fusor Mobile Shielding Unit

The VCU Inertial Electrostatic Confinement (IEC) Fusor Senior Design Project provides Virginia Commonwealth University (VCU) with a mobile fusor complete with the necessary shielding to protect operators as well as the general public from potentially hazardous radiation. The VCU IEC fusor is a Farnsworth-Hirsch type reactor, and consists of five basic components; a high voltage power supply, vacuum system, gas regulation system, primary reactor vessel assembly, and radiation shielding. These components were serviced and reassembled on a customized mobile cart. In addition to these components, a specimen holder and viewing monitor were added to the design. The specimen holder provides a practical method for neutron activation experiments, while the viewing monitor allows for safer visualization and operation of the fusor. An engineered cart provides the operator easy transportation of the shielding, fusor, and necessary components. The shielding consists of layers of High Density Polyethylene (HDPE), Borated Polyethylene (BPE), and lead to minimize radiation dose exposure to limits acceptable by the Nuclear Regulatory Commission (NRC). A camera inside the shielding is connected to a display monitor in order to provide a visual depiction of the deuterium ionization and fusion process. This allows operators and audiences to view the internal workings of the fusor from a safe distance. Lastly, an operator’s manual has been drafted to assist future operators with running the fusor. With these additions to the existing design, the fusor assembly serves as a vital asset for researchers, as well as an educational tool for students and teachers.https://scholarscompass.vcu.edu/capstone/1199/thumbnail.jp

Biofiltration Kinetics of Tofu Industry Wastewater Using of Zeolite Medium

This researchwas aimed to investigate reactionkinetic of tofu industrywastewater using zeolitemedium. A staticfilter reactor using zeolitemediumwas constructed to carry out this research. Tofuwastewaterwas resirculatedthrough themedium with various hydraulic retention times (HRT): 0, 3, 6, 12, 24, 36, and 48 hours. First orderreactionwas then applied on this kinetics. The results showed that pHincreased from4.1 to 8.02. Total P in thewastewater decreased from12,1mg/L to 6,91mg/L (42%reduction),while in themedia totalP increased from3,04 mg/L to 5,97 mg/L within 48 hours of filtration. N-NH4+ decreased from 64.184 mg/L to 12.85 mg/L(79.9%reduction). Total Solids decreased from 10.404mg/L to 4003m(61.5%reduction)

Kelalaian Birokrasi dan Ketidakadilan Pelayanan Publik di Kantor Dinas Kependudukan dan Pencatatan Sipil Kota Pekanbaru

Orang sering kecewa karena janji penyelesaian urusan mereka tidak dijaga. Pelayanan juga dipengaruhi oleh status sosial, semakin tinggi status sosial layanan semakin cepat. Penelitian ini bertujuan untuk menguji apakah masih ada birokrasi dan ketidakadilan dalam pelayanan publik? Jika masih membuktikan apa penyebabnya dan USAha apa yang bisa dilakukan untuk mengurangi perilaku buruk tersebut. Penelitian ini menggabungkan pendekatan kuantitatif dan kualitatif. Variabel Birokrasi Kelalaian terdiri dari 4 item dan variabel Ketidakadilan Birokrasi juga terdiri dari 4 item. Data diolah dengan menggunakan SPSS versi 20. Data dianalisis dengan menggunakan frekuensi dan uji deskriptif. Hasil analisis data kuantitatif diperdalam dengan data wawancara mendalam kepada informan kunci. Kuesioner penelitian telah diisi oleh 65 pegawai yang bekerja di Dinas Kependudukan dan Catatan Sipil Kota Pekanbaru. Hasil penelitian menunjukkan bahwa variabel kelalaian birokrasi tertinggi tidak dapat memberikan kepastian kapan waktu penyelesaian dokumenkarena setiap perserikatan berhubungan dengan sub-bagian lainnya. Sedangkan variabel ketidakadilan birokrasi yang paling banyak adalah ketika pejabat keluarga / VIP datang untuk berhadapan, maka diberikan pelayanan khusus kepada mereka. Sifat alami juga akan menjadi bentuk jika tidak ada diskriminasi dalam pelayanan. Karyawan harus mengubah pola pikir bahwa melayani masyarakat juga merupakan sholeh amal sebagai badan amal keagamaan lainnya