Techno Press
Tp_Editing System.E (TES.E)
Login Search


You have a Free online access.
aas
 
CONTENTS
Volume 2, Number 2, April 2015
 

Abstract
This paper deals with the aerodynamic and aerothermodynamic trade-off analysis of a hypersonic flying test bed. Such vehicle will have to be launched with an expendable launcher and shall reenter the Earth atmosphere allowing to perform several experiments on critical re-entry phenomena. The demonstrator under study is a re-entry space glider characterized by a relatively simple vehicle architecture able to validate hypersonic aerothermodynamic design database and passenger experiments, including thermal shield and hot structures. A summary review of the aerodynamic characteristics of two flying test bed concepts, compliant with a phase-A design level, has been provided hereinafter. Several design results, based both on engineering approach and computational fluid dynamics, are reported and discussed in the paper.

Key Words
hypersonic flow; re-entry vehicles; aerodynamics; aerothermodynamics; computational fluid dynamics

Address
Giuseppe Pezzella: Fluid Dynamics Laboratory, Aerothermodynamics Section, Italian Aerospace Research Centre, via Maiorise I-81043 Capua, Italy

Abstract
Dynamic aeroelastic behavior of structurally nonlinear Joined Wings is presented. Three configurations, two characterized by a different location of the joint and one presenting a direct connection between the two wings (SensorCraft-like layout) are investigated. The snap-divergence is studied from a dynamic perspective in order to assess the real response of the configuration. The investigations also focus on the flutter occurrence (critical state) and postcritical phenomena. Limit Cycle Oscillations (LCOs) are observed, possibly followed by a loss of periodicity of the solution as speed is further increased. In some cases, it is also possible to ascertain the presence of period doubling (flip-) bifurcations. Differences between flutter (Hopf

Key Words
joined wings; limit cycle oscillations; aeroelasticity; flutter; bifurcations

Address
Rauno Cavallaro: Department of Aerospace Engineering, San Diego State University, 5500 Campanile Dr., San Diego, CA, USA; Department of Structural Engineering, University of California San Diego, 9500 Gilman Dr., La Jolla, CA, USA
Andrea Iannelli: Department of Aerospace Engineering, University of Pisa, via G.Caruso 8, Pisa, Italy
Luciano Demasi and Alan M. Razon: Department of Aerospace Engineering, San Diego State University, 5500 Campanile Dr., San Diego, CA, USA

Abstract
Aeronautics engine cooling is one of the biggest problems that engineers have tried to solve since the beginning of human flight. Systems like radiators should solve this purpose and they have been studied extensively and various solutions have been found to aid the heat dissipation in the engine zone. Special interest has been given to air coolers in order to guide the air flow on engine and lower the high temperatures achieved by the engine in flow conditions. The aircraft companies need faster and faster tools to design their solutions so the development of tools that allow to quickly assess the effectiveness of an cooling system is appreciated. This paper tries to develop a methodology capable of providing such support to companies by means of some application examples. In this work the development of a new methodology for the analysis and the design of oil cooling systems for aerospace applications is presented. The aim is to speed up the simulation of the oil cooling devices in different operative conditions in order to establish the effectiveness and the critical aspects of these devices. Steady turbulent flow simulations are carried out considering the air as ideal-gas with a constant-averaged specific heat. The heat exchanger is simulated using porous media models. The numerical model is first tested on Piaggio P180 considering the pressure losses and temperature increases within the heat exchanger in the several operative data available for this device. In particular, thermal power transferred to cooling air is assumed equal to that nominal of real heat exchanger and the pressure losses are reproduced setting the viscous and internal resistance coefficients of the porous media numerical model. To account for turbulence, the k-

Key Words
CFD simulation; aerodynamics; oil cooling; flow field; numerical simulation; porous media

Address
A. Carozza: Fluid Dynamics Department, CIRA, ITALIAN AEROSPACE RESEARCH CENTRE, Capua, 81043, Italy

Abstract
Scramjets are a class of hypersonic airbreathing engine that are associated with realizing the technology required for economical, reliable access-to-space and high-speed atmospheric transport. Afterburning augments the thrust produced by the scramjet nozzle and creates a more robust nozzle design. This paper presents a numerical study of three parameters and the effect that they have on thrust augmentation. These parameters include the injection pressure, injection angle and streamwise injection position. It is shown that significant levels of thrust augmentation are produced based upon contributions from increased pressure, mass flow and energy in the nozzle. Further understanding of the phenomenon by which thrust augmentation is being produced is provided in the form of a force contribution breakdown, analysis of the nozzle flowfields and finally the analysis of the surface pressure and shear stress distributions acting upon the nozzle wall.

Key Words
after-burning; combustion; CFD; hypersonic flow; nozzle; scramjet

Address
Michael J. Candon, Hideaki Ogawa and Graham E. Dorrington: School of Aerospace, Mechanical and Manufacturing Engineering, RMIT University, GPO Box 2476, Melbourne, VIC 3001, Australia

Abstract
This study focuses on the limit cycle oscillations (LCOs) of cantilever swept-back wings containing a cubic nonlinearity in an incompressible flow. The governing aeroelastic equations of two degrees-of-freedom swept wings are derived through applying the strip theory and unsteady aerodynamics. In order to apply strip theory, mode shapes of the cantilever beam are used. The harmonic balance method is used to calculate the frequencies of LCOs. Linear flutter analysis is conducted for several values of sweep angles to obtain the flutter boundaries.

Key Words
limit cycle oscillations; sweep angle; harmonic balance method

Address
Seher Eken and Metin Orhan Kaya: Faculty of Aeronautics and Astronautics, Istanbul Technical University, Maslak Campus, 34469, Istanbul, Turkey

Abstract
To prevent over-testing of the test-item during random vibration testing Scharton proposed and discussed the force limited random vibration testing (FLVT) in a number of publications. Besides the random vibration specification, the total mass and the turn-over frequency of the load (test item), C2 is a very important parameter for FLVT. A number of computational methods to estimate C2 are described in the literature, i.e., the simple and the complex two degrees of freedom system, STDFS and CTDFS, respectively. The motivation of this work is to evaluate the method for the computation of a realistic value of C2 to perform a representative random vibration test based on force limitation, when the adjacent structure (source) description is more or less unknown. Marchand discussed the formal description of getting C2, using the maximum PSD of the acceleration and maximum PSD of the force, both at the interface between load and source. Stevens presented the coupled systems modal approach (CSMA), where simplified asparagus patch models (parallel-oscillator representation) of load and source are connected, consisting of modal effective masses and the spring stiffness

Key Words
force limited vibration testing

Address
J.J. Wijker and A. de Boer: Faculty Engineering Technology, Department Applied Mechanics, University Twente, Drienerlolaan 5, 7522 NB Enschede, The Netherlands
M.H.M. Ellenbroek: Faculty Engineering Technology, Department Applied Mechanics, University Twente, Drienerlolaan 5, 7522 NB Enschede, The Netherlands; Dutch Space BV, Mendelweg 30, 2333 CS Leiden, The Netherlands


Techno-Press: Publishers of international journals and conference proceedings.       Copyright © 2017 Techno-Press
P.O. Box 33, Yuseong, Daejeon 34186 Korea, Tel: +82-42-828-7996, Fax : +82-42-828-7997, Email: info@techno-press.com