X-ray detector on 2U cubesat BeEagleSAT of QB50

BeEagleSAT is a 2 Unit cubesat to be launched within the EU FP7 project QB 50. It is been produced by Istanbul Technical University and Turkish Air Force Academy. Sabanci University will provide a CdZnTe based semiconductor X-ray detector and associated readout electronics. The detector will utilize cross strip geometry to test the detection system in space, but it will not carry a mask for imaging. The readout will be established by an application specific integrated circuit controlled by a microcontroller. The system will have its own battery and will be turned on intermittently due to power and telemetry constraints. It will characterize the hard X-ray background in 20-150 keV at low Earth orbit conditions as a function of altitude

Computational and asymptotic methods in aeroacoustics with applications

In this article the computational and asymptotic methods used in aeroacoustics are reviewed. In particular, two different aeroacoustic applications are demonstrated.In the first problem we investigate the first and second order asymptotic predictions of the thickness and loading noise of a subsonic B-bladed helicopter rotor in the far field and compare the SPL noise results with those of full numerical computations. The results of the second order asymptotic formula seem to be in better agreement with full numerical computations than the first order asymptotic formula. In the second problem, the effect of acoustic wave propagation in transonic nozzle flow is investigated by solving the unsteady quasi-one-dimensional transonic nozzle equations in conservative form using high order computational aeroacoustic schemes, where a novel non-reflecting boundary condition is implemented in addition to the standard non-reflecting boundary condition using characteristics. Excellent agreement with the exact solution is obtained in each case.Publisher's Versio

Numerical Simulation of incompressible laminar flow over three dimensional rectangular cavity

Bu çalışmada basit bir geometriye sahip olmasına rağmen oldukça karmaşık bir akım yapısı sergileyen ve gerek askeri gerekse de endüstriyel pekçok uygulamada sıkça karşılaşılan iki veya üç boyutlu kaviteler üzerindeki zamana bağlı, sıkıştırılamaz akış sayısal olarak incelenmiştir. Bu çalışmanın ana amacı, düşük Reynolds sayılarındaki kavite akışı hakkındaki bilgileri ilerletmek ve 3 boyutlu kavite akışı ile 2 boyutlu (2B) veya 3 boyutlu (3B) kavite üzerindeki akımın 3 boyutluluk etkilerini incelemektir. Sayısal çalışmada, Navier-Stokes denklemleri, zamana bağlı, 3B’lu, sıkıştırılamaz bir akış için Fluent ticari yazılımıyla sonlu hacimler yöntemi kullanılarak çözülmüştür ve türbülans modellemesi için de Large Eddy Simülasyonu (LES) yaklaşımı kullanılmıştır. Çalışmada uzunluğunun derinliğine oranı (L/h) 4 olan ve uzunluğunun genişliğine oranı (L/w) 0.8 olan dikdörtgensel bir kavite ele alınmıştır. Yaklaşmakta olan akımın tipi laminer olarak seçilmiştir. Kavite derinliği ve serbest akış hızına göre hesaplanan Reynolds sayısı 4000’dir. LES kullanılarak yapılan sayısal çalışmanın doğruluğu, 2 farklı Re sayısı için (4000 ve 13000) için Özsoy ve diğerleri (2005)’nin yapmış olduğu deneysel çalışma kullanılarak sağlanmıştır. Doğrulama yapıldıktan sonra 2B’lu bir kavite üzerindeki akımın 3B’lu yapısı ile, 3B’lu bir kavite üzerindeki akış yapısı sırasıyla incelenmiştir. Hem 2B’lu hem de 3B’lu kavite akışının içerdikleri akım ayrılması, kayma tabakası, vorteks üretimi, vorteks yayınma mekanizması ve vorteks-duvar etkileşimleri nedeniyle oldukça karmaşık bir yapıya sahip oldukları gözlemlenmiştir. 2B’lu ve 3B’lu çözümlerin kavite orta düzleminde yapılan karşılaştırmaları ortalama akış büyüklükleri cinsinden benzer sonuçlar verse de türbülanslı büyüklükler açısından farklılıklar içerdiği ve özellikle duvara yakın bölgelerde duvar etkisi nedeniyle oldukça farklı bir akış yapısı sergiledikleri gözlemlenmiştir. Anahtar Kelimeler: Kavite akışı, LES, Vorteks, Laminer akım.There are many engineering structures which require some form of cavities on their surfaces in order to perform the task they are designed for.  However, these cavities can also be a source of various problems if structures with cavities are subjected to flow conditions. It is well known that the flow over a cavity is a complex phenomenon due to there usually being strong pressure, velocity and sometimes density fluctuations. These in turn can lead to increased drag forces, excessive noise and vibrations problems in structures. It is therefore essential to understand the cavity-flow physics and to be able to model, analyze and predict the outcome of such flows with acceptable accuracy if the adverse effects are to be controlled and minimized. Although many studies have been conducted about the cavity flows most of them have mainly focused on supersonic and compressible flows because of their relevance to aeronautical applications. However, much less attention has been given to very low Mach number cavity flows that are encountered in various grounds, industrial and environmental applications so far. There have been some studies dealing with incompressible cavity flow, but these were mainly focused on flow inside or around two-dimensional cavities and there have been very few investigations on flow inside a three-dimensional cavity. Therefore, there is a real need for better understanding of the three-dimensional effects in cavity flows at very low Reynolds numbers. The main purpose of this work is to study the three-dimensional effects on the characteristics of the cavity flow at very low Mach numbers and to improve the understanding of this type of flow. Therefore this study presents a numerical study into the problem of incompressible laminar flow passing a two and three-dimensional rectangular cavity with a view to understanding the complex nature of the flow and the three-dimensional structure of the cavity. The study is based on the solution of the unsteady, three-dimensional, incompressible Navier-Stokes equations by using finite volume method and Large Eddy Simulation approach. A cavity with length to depth ratio of 4 under an incoming laminar boundary layer is investigated for Re is equal to 4000 (based on cavity depth and free stream velocity). To validate the used computational procedure and simulations, the study of Özsoy et al. (2005) on two dimensional cavities under laminar incoming flow with L/h ratio of 4 is used.  After this validation step, three-dimensional flow features of incompressible cavity flows with an incoming laminar boundary layer is investigated. The influence of the recirculating flow inside the cavity on the separated shear layer, the nature of the interactions between the large-scale eddies and the trailing edge corner and the dynamic behavior of the vortex structures occurring in a cavity are studied. The results obtained from computations show that the flow field inside the cavity has a three dimensional structure, even in two-dimensional cavity geometries including vortex shedding mechanism, stretching, wall vortex interaction like clipping or partially escape and so on. Time-averaged parameters in 3D analyses of 3D cavity reveal that the characteristics of the flow change significantly due to the side wall effects.  As expected the wall effects are stronger at locations closer to the wall.   Another important result from 3D analyses is that if the instantaneous flow field is considered, flow structures are quite different at different stations and highly time dependent. . When 3D flow characteristics are compared to those of 2D it is found that the mean flow features are almost the same for 3D and 2D only at the middle of the cavity. However, this is not the case when the results are compared outside this plane.  The 2D and 3D results are significantly different at planes away from the symmetry plane. Although the mean flow quantities are about the same for 2D and 3D in the middle plane, turbulence behavior is quite different. It is believed that the validated computational procedure presented in this study for the analyses of flow over cavities can be used to determine the forces acting to the structures due cavities and this information can also be used for design purposes.  Also, the validated computational procedure in this work can help future researchers to perform similar analyses for various kinds of cavities with high level of confidence and to optimize the geometry of the cavities for minimum drag, noise and vibration. Keywords: Cavity flow, vortex, LES, laminar flow.

Laboratory performance of x-ray detector on 2U cubesat beeaglesat

A CdZnTe based semiconductor X-ray detector (XRD) and its associated readout electronics has been developed by the Space Systems Design and Testing Laboratory of Istanbul Technical University and the High Energy Astrophysics Detector Laboratory of Sabanci University along with an SME partner. The XRD will be the secondary science mission on board BeEagleSat, which is developed as one of the double CubeSats for the QB50 project. QB50 is a European Framework 7 project carried out by a number of international organizations led by the von Karman Institute of Belgium. The heart of the XRD is a 2.5 mm thick, 15 mm x 15 mm CdZnTe crystal with orthogonal electrode strips on top and bottom for position resolution on the crystal. There are 3 sets of steering electrodes in between anodes. A commercial off the shelf (COTS) high voltage source provides necessary potential difference to transport electrons and holes towards electrodes. The signals from each strip are read by a COTS ASIC, RENA-3b, controlled my MSP 430. The XRD board (single ~10 cm x 10 cm board) also carries the necessary power regulators and 7 COTS batteries. In a previous paper presented at the IAC 2014, we discussed the main design of the XRD and provided results from some of the early vibration tests of the mechanical design. At the time, the CdZnTe crystal has not been attached, and the readout electronics and software were still in development phase. In this paper, we present the laboratory performance of the electronic readout system and discuss the current phase of the XRD development

Development and in orbit testing of an x ray detector within a 2U cubesat

A CdZnTe based semiconductor X-ray detector (XRD) and its associated readout electronics is developed by the Space Systems Design Laboratory of Istanbul Technical University and High Energy Astrophysics Detector Laboratory of Sabanci University along with an SME partner. The detector will utilize 30 orthogonal cross strip electrodes (and 3 steering electrodes in between anodes) whose geometry is optimized by an extensive set of simulations and energy resolution measurements. The signals will be read by RENA 3b ASIC controlled by MSP 430 microcontroller. The system will have its own battery and will be turned on intermittently due to power constraints. CdZnTe based X-ray detectors have been utilized in space, but they are either pixellated (NuStar), or they consist of many individual crystal pieces (BAT in Swift satellite). The aim of the XRD is to show that large volume crystals with orthogonal strips are viable alternatives, especially for small satellite systems with medium energy resolution requirement. XRD will also characterize the hard X-ray background in 20-200 keV at low Earth orbit conditions as a function of altitude. Due to power and telemetry constraints, the individual events will be corrected for hole trapping on-board, histogrammed, and only the X-ray spectra will be transmitted to the ground station along with a small set of raw data for diagnostic purposes. The XRD is planned to travel into space, as a secondary science mission, on board BeEaglesat which is a 2U CubeSat developed as one of the possible double (2U) CubeSats for the QB50 project. QB50 is a European Framework 7 (FP7) project carried out by a number of international organizations led by the von Karman Institute of Belgium. Its main scientific objective is to study in situ the temporal and spatial variations of a number of key constituents and parameters in the lower thermosphere with a network of about 50 double and triple CubeSats, separated by few hundred kilometers and carrying a determined set of sensors

Space technology capacity building in support of SDG 2030 through CubeSat SharjahSat-l

The SHARJAH-SAT-1 would be the first CubeSat mission to be developed by the Sharjah Academy for Astronomy, Space Sciences, and Technology (SAASST)students and researchers, with the aim of not only designing, fabricating, testing & launching the CubeSat itself, but also building the capacities and expertise for future SAASST CubeSat missions as well. For the project, SAASST is working in close collaboration with an experienced international partner, the Istanbul Technical University, Space Systems Design and Test Laboratory which has already developed and launched 5 CubeSats into low earth orbit. Overall, the project, puts the human capacity development in its center, in support of UN SDG 2030 for an equal world

X-ray detector XRD on BeEagleSat and the development of the improved x-ray detector iXRD

Many interesting astrophysical objects are intense X-ray emitters. Hard X-ray observatories in various sizes have been operating in space and providing exciting scientific results that we cannot obtain in our laboratories on Earth. Nanosatellites with CdZnTe hard X-ray detectors have been launched into orbit as well, and the future holds great promise with such small satellites contributing significantly to high energy astrophysics. One of those satellites is the BeEagleSat which carried the X-ray detector (XRD)to low Earth orbit. The XRD has a 15⨯15⨯3 mm 3 volume CdZnTe detector, a cross-strip electrode design, a RENA readout chip controlled by an MSP 430 microcontroller. Due to a communication problem with the receiver, no science data could have been downloaded from the XRD. Recently, an improved version of the XRD has been designed (called the iXRD)and currently it is in the production phase. The improvements compared to the XRD are the larger volume crystal with almost three times the collecting area, a collimator to limit the field of view for focused scientific return, and a motherboard-daughterboard design to reduce electronic noise

Unterwegs nach Troia. Reisende in der Troas von Ruy González de Clavijo bis Heinrich Schliemann

In der römischen Kaiserzeit hatte Troia-Ilion eine große Bedeutung für das iulisch-claudische Kaiserhaus, das sich von Aeneas und seinem Sohn Iulus ableitete.Nach Verschwinden des Ortes wurden die Namen Troia und Ilion in der Region nie vergessen. Gab es schon Identifizierungsvorschläge in der Kreuzfahrerzeit (Saewulf), so versuchten seit dem16. Jh. verstärkt europäische Reisende, Troia irgendwo zwischen Kyzikos im Norden und Adramyttion im Süden wiederzufinden. Aber erst mit Hilfe von Lechevaliers Karte vomJahre 1791 konzentrierte man die Suche auf die Skamander-Ebene. 1793 konnte der Hügel Hisarlık von Kauffer mit Troia identifiziert werden.During the Roman Empire, great importance was attached to Troia-Ilion because the Julio-Claudian Emperors traced their ancestry back to Aeneas and his son, Iulus. Even after the city was abandoned, the names Troia and Ilion were never forgotten in the region. First attempts to identify the place were made during the time of the crusaders (Saewulf). Beginning in the 16 th century, European travellers tried to rediscover Troia somewhere between Cyzicus in the North and Adramittium in the South. Only with the help of Lechevalier’s map of 1791 the search was narrowed to the plain of the Scamander. In 1793 Kauffer located Troia at the hill of Hisarlık

Troas Bölgesi'nde Göçler, Diller ve Kültürler

Because of its strategic location the Troad was from the Early Bronze Age to the Archaic Period confronted with the many differents immigrations. The transition to the Early Iron Age took place around 1130 BC. During this short transition period, former traditions were maintained while new elements emerged at the same time. Most scholars agreed that the settlement transformed into another local culture. However, this settlement was also brought to an end by destruction later on, the Early Iron Age, Troy VIIb2 and VIIb3 under influence of the Balkans lasted from 1150 BC to 950 BC. The archaeological evidence shows, that these two different cultures lived in peace on the Troad. During the Archaic period, the Greeks arrived in the region. According to Herodot and Strabon, the Greeks also had a process of acculturation with the local cultures