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International Review of Aerospace Engineering - April 2010 - Papers

A DES Procedure Applied to the Flow over a NACA0012 Airfoil
Quick Access Recorder (QAR) Data Analysis Software for Studies of Windshear, Turbulence and Wake Vortex
The Wake Asymmetry of an Airfoil with a Gurney Flap and their Connection with the Observed Lift Increase
Extracting Essential Qualities of Magnetic Torquer Core Helping New Experimental Technique
Solid Rocket Grain Geometry Modifications for Axial Combustion Instability Symptom Suppression
Initial Thermal Study of the ITASAT Satellite in Transient Regime
Hypersonic Wind Tunnel Experiments on Icy Body and Their Potential Contribution to Astrobiology
Using USAF DATCOM to Predict Nonlinear Aerodynamics of Structurally Impaired Aircraft

International Review of Aerospace Engineering - Papers

A DES Procedure Applied to the Flow over a NACA0012 Airfoil
by Radoslav Bozinoski, Roger L. Davis

Vol. 3. n. 2, pp. 68-76

Abstract - This work describes a detached-eddy simulation (DES) for massively separated flow over a NACA 0012 airfoil at off design conditions. Simulations were performed using the MBFLO[1],[2] simulation procedure. The Navier-Stokes equations are solved using an explicit, multi-grid procedure for the steady-flow Reynolds-averaged (RANS) computations. A dual time-step procedure is used for unsteady Reynolds-averaged (URANS) or DES. A two-equation k-ω turbulence model is used for the entire turbulence field in the RANS and URANS simulations as well as in the near-wall regions of the DES. The DES results are obtained using the model presented by Bush and Mani[3] and are compared with the unsteady Reynolds-averaged Navier-Stokes solutions and experimental data for the NACA 0012 airfoil at an angle of attack of 60°. The results of the two- and three-dimensional computations are compared to each other as well as to experimental results. Differences between two- and three-dimensional computations are observed in terms of the coefficients of lift and drag as well as vorticity and entropy contours. The two-dimensional DES showed an improvement in lift and drag predictions when compared to two- and three-dimensional URANS, however, the three-dimensional DES lift and drag are closer to the experimental results in the literature as expected. A method accounting for the three-dimensional DES effects in two-dimensional DES is also explored.

Keywords: Detached-Eddy Simulation, Three-dimensional Effects, Stalled Flow.

Quick Access Recorder (QAR) Data Analysis Software for Studies of Windshear, Turbulence and Wake Vortex
by Henk Haverdings , P. W. Chan

Vol. 3. n. 2, pp. 77-88

Abstract - For analysis of low-level windshear, turbulence and wake vortex events at the Hong Kong International Airport (HKIA), besides pilot reports routinely received from Air Traffic Control, Quick Access Recorder (QAR) data are obtained from the local airlines by the Hong Kong Observatory (HKO). Instead of using directly the wind data recorded on the aircraft by the flight management system (FMS), there has been a collaborative study between HKO and the National Aerospace Laboratory (NLR) in The Netherlands to develop a QAR data analysis software to calculate the meteorological quantities. Such quantities include the three components of the wind, windshear hazard factor and turbulence intensity parameters, taking into account the aircraft’s aerodynamic factors (e.g. sideslip angle, angle-of-attack). This paper describes the main features of the calculation software, named WINDSTURB, and illustrates its application to windshear, turbulence and wake vortex studies through selected cases at HKIA.

Keywords: QAR Data, Windshear, F-Factor, Turbulence, Eddy Dissipation Rate.

The Wake Asymmetry of an Airfoil with a Gurney Flap and their Connection with the Observed Lift Increase
by U. Boldes, J. S. Delnero, J. Marañon Di Leo, J. Colman, M. E. Camocardi

Vol. 3. n. 2, pp. 89-95

Abstract - The present research analyzes the asymmetry in the rolling up shear layers downstream the blunt trailing edge of airfoils with Gurney flaps as a lift enhancing mechanism. Experimental investigations relating the asymmetry of the vortex flow in the near wake region, able to distort the flow increasing the downwash of an airfoil, have been performed. We examine the lift behaviour and near wake region characteristics of the low Reynolds number airfoil HQ17 without and with Gurney mini-flaps of different lengths. The flow immediately downstream the trailing edge down to 2 mini-flap lengths is explored in order to identify signs of asymmetry of the initial counter rotating vortex structures. Experimental evidence is presented showing that for typical lifting conditions the shear layer rollup process within the near wake is different for the upper and lower vortices: the shear layer separating from the pressure side of the airfoil begins its rollup immediately behind the trailing edge creating a stronger vortex while the shear layer from the suction side begins its rollup more downstream creating a weaker vortex. Aspects of a mechanism connecting the different evolution and pattern of these initial vortex structures with the lift increase due to these flaps are presented.

Keywords: Flow Control, Low Reynolds Aerodynamics, High Lift Device, Shear Layers.

Extracting Essential Qualities of Magnetic Torquer Core Helping New Experimental Technique
by Mohamad Fakhari Mehrjardi, Mehran Mirshams

Vol. 3. n. 2, pp. 96-101

Abstract - Magnetic torquers are used on most low-earth orbiting spacecraft as attitude control actuators. Their magnetic linear output range is very significant and core magnetic saturation. Linear relationship between input current and magnetic flux density is a necessary quality in order to provide a simple workable control algorithm for instances in which the direction of the net moment contribution of all torquers must be changed quickly. This paper has developed a different test system concept to determine the relative permeability of a soft magnetic core and removing its magnetic residual. The system consists of magnetic torquer, magnetometer and power source which use to depict the features of core. Test methodology, experimental setups, and test results are presented in detail. This test system can apply to determine the relative permeability of every magnetic core. Accordingly with this test system B-H curve and relative permeability of CK30 alloy is extracted. This study provides a creative experimental technique to found relative permeability of a soft magnetic core.

Keywords: Magnetic Torquer, Magnetometer, Magnetic Flux Density, B-H Curve.

Solid Rocket Grain Geometry Modifications for Axial Combustion Instability Symptom Suppression
by D. R. Greatrix, C. Baczynski

Vol. 3. n. 2, pp. 102-108

Abstract - In the present paper, the modification of the internal propellant grain geometry of a solid-propellant rocket motor as a means for suppressing axial combustion instability symptoms is examined. The effectiveness of left-to-right (upstream-to-downstream) expansions and contractions in the internal grain port as a suppression technique is assessed through the usage of a comprehensive internal ballistic simulation model. The effect of upstream-to-downstream port area ratio, area transition position along the grain, and the corresponding steepness of the area transition are included in this evaluation. Among the trends identified, the present study reveals that left-to-right contractions are more effective than expansions in reducing the limit axial pressure wave magnitude appearing in the motor chamber, and, the steeper the transition (expansion or contraction), the more effective it appears to be as a means of symptom suppression.

Keywords: Axial Combustion Instability, Solid Rocket Motor, Grain Geometry.

Initial Thermal Study of the ITASAT Satellite in Transient Regime
by D. F. Silva, E. C. Garcia

Vol. 3. n. 2, pp. 109-114

Abstract - This work presents the preliminary thermal behavior, in transient condition, of the ITASAT satellite (an experimental satellite developed by Technological Institute of Aeronautics - ITA). The flight critical cases and some parametric analysis were evaluated. ITASAT will be the first Brazilian duty satellite developed by universities and its main function will be data relay. This program is being directed by ITA with collaboration of others Brazilian universities. National Institute of Space Researches (INPE) supports technically and the Brazilian Space Agency (AEB) sponsors the program. The thermal analyzer SINDA/FLUINT has been used as computational platform. Parameters such as orbit type and attitude of the satellite influence directly the intensity of the external heat loads. Associating these loads with the equipment’s dissipation is possible to calculate the temperature distribution in the satellite. This study is part of the thermal control project that will guarantee that the high and low acceptable temperature limits for all equipment can be obtained. The presented results are physically coherent for Low Earth Orbit satellites.

Keywords: ITASAT, Heat Loads, Thermal Control, Satellite.

Hypersonic Wind Tunnel Experiments on Icy Body and Their Potential Contribution to Astrobiology
by Kojiro Suzuki, Osamu Imamura

Vol. 3. n. 2, pp. 115-124

Abstract - In this paper, we demonstrate that the hypersonic aerothermodynamics plays an important role in the field of “Astrobiology”. When an extraterrestrial object enters the early earth’s atmosphere, the ablation at the surface due to the aerodynamic heating causes various chemical reactions in the high temperature shock layer and the significant change in its shape and aerodynamic characteristics during the atmospheric flight. The viscous shock-layer analysis with the ablation injection shows that prebiotic molecules can be formed around an entry object made from ice in the early atmosphere composed of CO2 and N2. In the hypersonic wind tunnel experiments using a spherical icy model at Mach number 7, it is found that not only the recession in the stagnation region but also the growth of icy columns in the shoulder region occur on the surface. The maximum diameter of the body increases and the forebody shape becomes flat. Hence the drag force significantly increases in the hypersonic flow. The temporal variation of the drag force and the mass loss rate is quantitatively described in terms of the change in the volume. The effects of the freestream conditions and the properties of the icy body are experimentally investigated.

Keywords: Hypersonic Flow, Wind Tunnel, Ablation, Ice, Atmospheric Entry, Astrobiology.

Using USAF DATCOM to Predict Nonlinear Aerodynamics of Structurally Impaired Aircraft
by Bilal A. Siddiqui, Ayman H. Kassem, Ahmed Z. Al-Garni

Vol. 3. n. 2, pp. 125-133

Abstract - This paper presents an approach to predict the nonlinear aerodynamics of a structurally damaged aircraft model based on the engineering level aerodynamic prediction methods, DATCOM. Raw results from the code provide good correlation with wind tunnel data at very low angles of attack, but accuracy deteriorates rapidly as the angle of attack increases. A new methodology is then proposed which combines the experimental results of healthy aircraft with the predicted aerodynamics of the damaged cases, to yield better correlation between experimental and predicted aerodynamic coefficients for damaged aircraft. Three damage-configurations are studied at supersonic speeds. The methodology can be used to quickly generate aerodynamic model for damaged aircraft for simulation and reconfigurable control.

Keywords: Damage Aerodynamics, DATCOM, Aerodynamic Prediction.