Latest issue

International Review of Aerospace Engineering - August 2010 - Papers

Mixing Characteristics of a Supersonic Jet in the Presence of Two Neighboring Jets
Titanium Foil Repair: an Accelerated Field Repair Method for Composite Aerospace Vehicles
Structural Optimization of a Primary Flight Control Assembly
Experimental Analysis of a Turbulent Boundary Layer Encountering a 2D Embedded Cavity Surface
Visualization of Unsteady Electrical Discharges in High-Speed Flow
CFD Flowfield Analysis on the Atmospheric Flight of the Subsonic Robotic Hellenic UAV Pegasus II
A Dynamic Method of Air Traffic Flow Management

International Review of Aerospace Engineering - Papers

Mixing Characteristics of a Supersonic Jet in the Presence of Two Neighboring Jets
by Mrinal Kaushik, E. Rathakrishnan

Vol. 3. n. 4, pp. 180-185

Abstract - The mixing characteristics of a Mach 1.6 axisymmetric jet in the presence of two Mach 2.5 axisymmetric jets canted away from the center jet axis has been investigated experimentally. It is found that, in the presence of surrounding jets the central (core) jet decays faster and there is a large expanse of subsonic portion downstream of the first shock cross-over point. The reason for this is found to be shielding to the mixing caused by the surrounding jets. The canted surrounding jets when operated alone possess stronger shock cells compared to the core alone or in the presence of core. This is because of the higher Mach number of the surrounding jets compared to the core jet. Also, the decay of the surrounding jets, operated alone or in the presence of core jet is faster than the core jet decay. In the presence of adverse, zero and favorable pressure gradients, the decay of the center jet in the presence of surrounding jets is higher than the decay of the center jet alone. The waves in the core jet field become weaker in presence of surrounding jets.

Keywords: Supersonic Jet, Mach number, axisymmetric jet.

Titanium Foil Repair: an Accelerated Field Repair Method for Composite Aerospace Vehicles
by Ruan E. Trouw, Peng H. Wang, Ronald Sterkenburg, Sergey Dubikovsky

Vol. 3. n. 4, pp. 186-191

Abstract - Research for carbon fiber has been of high demand ever since the aerospace industry took an interest in composite materials. One of the biggest problems with carbon fiber is the methods for repair. Current methods for repair without an oven or autoclave include wet lay-ups, and repair techniques using prepreg materials and curing equipment such as heat bonders and heat lamps. All of the above mentioned repair techniques require time to allow for resin curing. The purpose for the following research is to develop a new repair method that will restore the full functional ability of an aerospace vehicle with a shorter repair time. The United States Marine Corps specified that the repair will need to be performed in combat situations by personnel with minimum training. The new method described in this paper utilizes Titanium foil and an acrylic-epoxy adhesive. Titanium is used for the research due to its high tensile strength and the absence of corrosion when mated with carbon fiber. The results prove that the method will be a suitable repair technique for repairing composite aircraft structures.

Keywords: Carbon Repair, Titanium Foil, Adhesion, Interdisciplinary.

Structural Optimization of a Primary Flight Control Assembly
by A. Moosavian, S. M. Hashemi, F. Xi

Vol. 3. n. 4, pp. 192-207

Abstract - A primary flight control assembly of an in-production business jet aircraft was analyzed to obtain the structural responses. A series of investigations were performed to develop the proper parameters required to execute the optimization runs. Two distinct optimization problems were defined and solved. The first problem consisted of minimizing the compliance of the structure w. r. t. a volume fraction constraint, whereas the second one consisted of minimizing the volume of the structure w. r. t. a series of displacement constraints. Two sets of configurations were examined. The first set, referred to as the global set, included the optimization of all the components, whereas the second one, referred to as the local set, included the optimization of a portion of the flight control assembly. A new design was proposed and validated via Finite Element Analysis (FEA). OptiStruct^® and RADIOSS^TM were utilized as the optimization engine and the FE solver, respectively.

Keywords: Finite Element Method (FEM), Optimality Criteria, Solid Isotropic Material with Penalization (SIMP), Structural Optimization, Topology Optimization, Volume Fraction.

Experimental Analysis of a Turbulent Boundary Layer Encountering a 2D Embedded Cavity Surface
by Jonathon A. Smith, Amy W. Lang, Pablo Hidalgo, J. Nicole Wheelus, Leah Mendelson

Vol. 3. n. 4, pp. 208-213

Abstract - The characteristics of a turbulent boundary layer, initially formed over a flat plate, upon encountering a patterned surface consisting of two-dimensional embedded transverse cavities was experimentally studied using Digital Particle Image Velocimetry (DPIV). Results showed that the boundary layer initially responded to the grooved surface by forming an on-average accelerated region of fluid adjacent to the boundary. It is hypothesized that this is a result of the newly imposed partial slip condition produced on the outer boundary layer flow due to the embedded cavity vortices forming within the surface geometry, and under turbulent boundary layer conditions these embedded vortices are additionally energized by the injection of high-momentum fluid into the cavities by the fluctuating flow field. This higher momentum fluid closer to the surface can result in a flow separation control mechanism, which could be applied for various applications.

Keywords: turbulent boundary layer, partial-slip, separation control, cavity flow.

Visualization of Unsteady Electrical Discharges in High-Speed Flow
by Sergey B. Leonov

Vol. 3. n. 4, pp. 214-222

Abstract - Specific experimental technique, applied in Plasma-Assisted Aerodynamics, is considered in the paper. The results of several experiments are presented to demonstrate abilities of non-standard methods of visualization to make evident the gasdynamic effects appeared due to the plasma-flow interaction. These phenomena are mostly hidden for unaided eye. The examples shown include the unsteady near-surface discharge in supersonic flow; the DBD over a contoured airfoil; the high-power pulse discharge instability; and some others for the demonstration in appropriate presentation.

Keywords: Electrical discharge, High-speed airflow, Measurements and visualization.

CFD Flowfield Analysis on the Atmospheric Flight of the Subsonic Robotic Hellenic UAV Pegasus II
by Elias E. Panagiotopoulos, Spyridon D. Kyparissis, Dionissios P. Margaris

Vol. 3. n. 4, pp. 223-231

Abstract - Developed countries have made significant efforts to integrate Unmanned Aerial Vehicle (UAV) operations in controlled aerial space due to a rising interest of using UAVs for civilian as well as military purposes. Αpart from the obvious advantage of not placing human life at risk, the lack of a human pilot enables significant weight savings and lower costs. To realize these advantages, UAVs must have a high level of autonomy and preferably work cooperatively in groups. Exchanging information within these groups can greatly improve their capability. In the present work the low-speed flowfield for a subsonic small robotic Hellenic UAV Pegasus II is investigated numerically depending on the development of computational fluid dynamics techniques. The three dimensional steady state flow is modeled by the incompressible Navier-Stokes equations combined with inviscid, laminar and the Spalart-Allmaras turbulence models which are solved with the aid of a commercial CFD finite-volume code. Details about the fuselage and main wing – tail pressure flowfield distributions along selected span-wise positions at zero angle of attack are shown and discussed.

Keywords: CFD Flowfield Simulation, Unmanned Aerial Vehicle, Hellenic Pegasus II, Atmospheric Flight Motion.

A Dynamic Method of Air Traffic Flow Management
by Jacek Skorupski

Vol. 3. n. 4, pp. 232-237

Abstract - Air traffic management is a complex hierarchical system. Hierarchy levels can be defined according to decision making time horizon or to analysis area volume. For medium time horizon and wide analysis area, the air traffic flow management (ATFM) services were established. Their main task is to properly co-ordinate air traffic in airspace, so as to minimize delays arising in congested sectors. Those services have to assure high safety level in the same time. Thus it is very complex task, with many goals, many decision variables and many constraints.
In the paper a short review of selected methods developed for aiding air traffic flow management services is presented. More detailed description of a original dynamic method is given. This method is based on stochastic capacity and scenario analysis. The discrete multi-criterion programming problem was formulated on the assumption that expected values of airport capacity in discrete future moments in time are known. It leads to determination of the proper moment of passing the information of airport capacity change to ATFM services. Some problems in utilization of presented methods are also pointed out, so are the next research possibilities.

Keywords: air traffic management, air traffic safety, air traffic flow optimization.