Aerospace Engineering Copyright (c) 2013 California Polytechnic State University All rights reserved. http://digitalcommons.calpoly.edu/aero_fac Recent documents in Aerospace Engineering en-us Fri, 25 Jan 2013 15:47:43 PST 3600 Location effects of passive damping material in cross-ply laminates on natural frequency and mode shape http://digitalcommons.calpoly.edu/aero_fac/92 http://digitalcommons.calpoly.edu/aero_fac/92 Tue, 06 Mar 2012 13:22:17 PST This study presents an experimental investigation of the free vibration of cantilevered composite laminated plates with embedded passive damping material at different stages. A total of five composite laminated plates are considered. The lay-up sequences for the five composite laminated plates with and without two embedded layers of passive damping material are [90°/0°/90°/0°]s, [90°/0°/90°/0°/d]s, [90°/0°/90°/d/0°]s, [90°/0°/d/90°/0°]s, and [90°/d/0°/90°/0°]s. The passive damping material employed is a 3M material, SJ-2015 ISD 112, with peak damping properties in the ambient temperature range of 32°F to 140°F. The composite material used is a carbon fiber (977-2)/epoxy resin (IM7). The effect of the passive damping system employed in this study for the composite plates are discussed. Modal testing is performed on these plates to determine resonant frequencies, amplitude and mode shape information. The study included white noise and sinusoidal dynamic testing techniques, a PC computer based data acquisition system, and a virtual instrument dynamic analysis. The different locations of the passive damping material in the cross-ply laminated plates resulted in degradation effects on the natural frequency, damping and mode of shape.

]]> E. I. Elghandour et al. Bodner-Partom Viscoplastic Constitutive Model and the Non Linear Finite Element Analysis of a Stress Concentration at High Temperature http://digitalcommons.calpoly.edu/aero_fac/91 http://digitalcommons.calpoly.edu/aero_fac/91 Tue, 06 Mar 2012 13:22:11 PST The design and analysis of structural components to operate at elevated temperature and severe stress levels, such as a low-cycle fatigue-limited jet engine disk, require an accurate prediction of the nonlinear stress-strain . response encountered during the cyclic loading conditions. Nonlinear analysis of such components is normally carried out by a finite element code making use of constitutive theories in which the material response is separated into the two important groups of phenomena known as rate dependent "creep" and rate independent "plasticity." A number of viscoplastic. constitutive theories in which "creep" and ''plasticity" effects are combined _into a unified plastic strain model have recently been proposed and are still undergoing active development. In this paper, an elastic-plastic finite element model incorporating the Bodner-Partom model of nonlinear time dependent material behavior is presented. The parameters in the constitutive model are numerically extracted by a least-square fit to experimental data obtained from unaxial stress-strain and creep tests at 65ifC. The finite element model of a double notched specimen is employe_d to determine the elastic-plastic strain and comparison is , made to experimental data. e The constitutive model parameters evaluated in this paper are found to be in good agreement with those obtained 'by other investigators. However, this numerical technique tends to give better agreement with the respo11Se curves than does the graphical methods used by the other investigators. The model calculated ef4$1jc-plastic strain agreed well with the experimental.

]]> Faysal A. Kolkailah et al. Mixed Mode Stable Crack Extensions Through Stiffened Specimens http://digitalcommons.calpoly.edu/aero_fac/90 http://digitalcommons.calpoly.edu/aero_fac/90 Thu, 23 Feb 2012 15:10:56 PST This study presents an experimental investigation of fracture mechanics for isotropic material, aluminum alloy D16AT. The problem of stable crack growth (SCG) has been addressed in this paper. Experimental results are presented for symmetrically stiffened and unstiffened three point bend specimens subjected to different modes, mode I and mixed mode. The stiffeners are doubly bonded to the fatigue pre-cracked specimens parallel to the length at a certain distance behind the crack tip using an adhesive Redux 410 NA. Results concerning load displacement variation, growth of plastic zones, instantaneous crack edge profiles, and tunneling are presented. There is evidence that the whole stable growth can be characterized by the crack opening angle criterion. The stiffening helps to increase both initiation and maximum fracture loads substantially.

]]> Abdel-Hamid I. Mourad et al. Sensors Location Effect on the Dynamic Behaviour of the Composite Structure with Flaw Detection http://digitalcommons.calpoly.edu/aero_fac/89 http://digitalcommons.calpoly.edu/aero_fac/89 Thu, 23 Feb 2012 15:10:52 PST In this paper presents an experimental and numerical investigation ofthe natural frequency of composite material cantilever plates. The stacking sequence of tbe composite plate is Quasi-isotropic laminated plate is [2(0j/±45°/2(90°)]" The plate was subjected to incremental cuts and tests to determine changes in new modal properties. The study included white noise and sinusoidal dynamic testing techniques and a virtual instrument dynamic analyzer. In this study also, determining the resonant frequencies of the undamaged and damaged plate, and evaluating the capabilities of piezoelectric ceramics (PZT's) for fault detection based on their sensitivity and accuracy changes in modal parameters. Numerical results are obtained using finite element software for the composite materials plates. The experimental and numerical results are very good agreement for the composite material cantilever plates with and without damage.

]]> Eltahry Elghandour et al. The Study of Empirical Methodology To Observe Damping Characteristics of Various Laminate Composite Plates http://digitalcommons.calpoly.edu/aero_fac/88 http://digitalcommons.calpoly.edu/aero_fac/88 Thu, 23 Feb 2012 15:10:48 PST Modifying the stiffness of the structure is usually not a feasible solution to enhancing damping, since changing the stiffiless effects the natural frequency changing and eventually the condition of resonance will be reached. Therefore, one of the recommendatory ways to reduce the response on structural elements is to improve damping characteristics. The objectives of this study are to present empirical methodology to detect damping characteristics of structural elements, and determine the optimal location of sensor to detect structural failure by analyzed data from both experimental and numerical analysis. Using orthotropic composite plates comprised of 977-2 Carbon fiber/IM7 epoxy, the natural frequencies ofstructural bending modes and damping ratio of the composite plates were experimented by free vibration test, and then comparison was made between the experimental results and the numerical analysis done by finite element method. The effectiveness of crack on a structure in damped free vibration was confirmed by the analysis using edge-notched composite plate. The results represented the natural frequency of a composjte plate was consistent with changing sensor location, and showed good agreement for both experimental and numerical analysis.

]]> Faysal A. Kolkailah et al. Effects of Filament Reinforced Plexiglass Pressure Vessel on Failure Analysis http://digitalcommons.calpoly.edu/aero_fac/87 http://digitalcommons.calpoly.edu/aero_fac/87 Thu, 23 Feb 2012 15:10:44 PST This paper presents an investigation into the effect of reinforcing a Plexiglas tube with fiberglass/epoxy threads wound at different angles. This paper shows an experimental analysis approach to find the ultimate failure pressure of these vessels. The properties of the Plexiglas, fiberglass, orientation (wind) angle and the matrix were taken into account to determine their effects on the ultimate failure pressure of the vessels. Mandrels were wound at +/- 75, +/- 65, and +/- 55 deg, and specimen were cut out from each to 19.05 cm long, 7.62 cm inner diameter and outer diameters dependent of the wind angle. The composite material used is an E-type Fiberglass and Epoxy Laminating Systems EZ-10 epoxy with EZ-83 hardener. The Dura-Wound Inc. Cobra Filament Winding Machine was used to wind the specimens. The specimens were tested with a hydrostatic test-rig to analyze the ultimate failure pressure and failure modes. An INSTRON machine was used to test the specimens under compression to determine the Young's modulus and Poisson's ratio. The experimental results indicate that the wind angle affects the mechanical properties and has strong effects on the failure modes of the reinforced vessels. The failure mode however does not differ by varying the wind angle.

]]> Faysal A. Kolkailah et al. Numerical Representation of Bodner Viscoplastic Constitutive Model http://digitalcommons.calpoly.edu/aero_fac/86 http://digitalcommons.calpoly.edu/aero_fac/86 Thu, 23 Feb 2012 15:10:39 PST Nonlinear analyses of structural components are normally carried out by finite element codes making Use of constitutive theories in which the material response is separated into the two important groups of phenomena known as rate‐dependent “creep” and rate‐independent “plasticity.” A number of viscoplastic constitutive theories in which creep and plasticity effects are combined into a unified plastic strain model have recently been proposed and are still undergoing active development. In this paper, the constitutive equations of the Bodner‐Partom model are used to present the time dependent, inelastic properties of Inconel 718 at 650 °C. This representation covers a wide range of loading conditions. The developed numerical technique to establish the Bodner parameters is based on simulation with fourth‐order Runge‐Kutta integration coupled to a least square measure for good curve fitting to a series of tests. To determine the eight Bodner parameters, an error function consisting of the square of the difference between experimental and model strains was minimized in the time domain by a direct search method. The specific material parameters for the Bodner model were determined to best fit sets of tensile and creep data. The parameters so obtained are in good agreement with those obtained by other investigators. The present parameters generate better response curves than those from graphical methods used in earlier investigations.

]]> Faysal A. Kolkailah et al. An Embedded Boundary Cartesian Grid Scheme for Viscous Flows using a New Viscous Wall Boundary Condition Treatment http://digitalcommons.calpoly.edu/aero_fac/85 http://digitalcommons.calpoly.edu/aero_fac/85 Mon, 25 Jul 2011 15:39:12 PDT This work presents a new viscous wall boundary condition technique for embedded Cartesian grid schemes in order to model laminar viscous flows. The development of viscous effects modeling using pure Cartesian grids with cut cells at the surface has been hampered by the widely varying control volume sizes associated with the mesh refinement and the cut cells associated with the solid surface. This scheme removes the cells adjacent to the surface from the control volume formulation. These cells are instead solved via an interpolation technique which utilizes the wall boundary conditions to build the interpolating functions. Two different interpolation techniques are presented, one without considering wall curvature and one considering wall curvature. Results are compared to subsonic and supersonic two-dimensional airfoil cases.

]]> David D. Marshall et al. A New Inviscid Wall Boundary Condition Treatment for Embedded Boundary Cartesian Grid Schemes http://digitalcommons.calpoly.edu/aero_fac/84 http://digitalcommons.calpoly.edu/aero_fac/84 Mon, 25 Jul 2011 15:39:10 PDT This work presents a new inviscid wall boundary condition technique for embedded Cartesian grid schemes. This scheme eliminates the time step restrictions associated with the arbitrarily small control volumes that can result when the surface cuts the Cartesian control volumes. The cells adjacent to the surface are removed from the control volume formulation and are instead solved via an interpolation technique which utilizes the wall boundary conditions to build the interpolating functions. Two different interpolation techniques are presented, one without considering wall curvature and one considering wall curvature. Results are compared to a two-dimensional airfoil case and a three-dimensional wing case.

]]> David D. Marshall et al. An Evaluation of Proposed Formula 1 Aerodynamic Regulations Changes Using Computational Fluid Dynamics http://digitalcommons.calpoly.edu/aero_fac/83 http://digitalcommons.calpoly.edu/aero_fac/83 Tue, 19 Jul 2011 08:39:07 PDT This report evaluates the proposed FIA Formula 1 World Championship aerodynamics rules changes intended to increase on track passing for the 2009 season. Two full Formula 1 cars were modeled under close drafting conditions, both under the current regulations and the proposed 2009 regulations to determine whether or not the FIA's goals of reducing down force by 50% and improving sensitivity to leading car wakes would be met. Under the current regulations, a car following another at 2.4 car lengths loses approximately 17% of it down force compared to isolation. The new regulations were counter productive and ineffective, failing both to reduce down force by 50% and lower that 17% performance detriment. Instead the cars became more sensitive - losing 26% of their down force in 2009 compared to 17% under current conditions. Though the new cars create an overall cleaner wake, the wake's effects are now concentrated near parts of the car which were previously insensitive.

]]> Robert L. Perry et al. Towards Efficient Viscous Modeling Based on Cartesian Methods for Automated Flow Simulation http://digitalcommons.calpoly.edu/aero_fac/82 http://digitalcommons.calpoly.edu/aero_fac/82 Tue, 19 Jul 2011 08:39:04 PDT The advanced Computational Fluid Dynamics (CFD) techniques that address the current limitations of Cartesian-based Navier-Stokes CFD schemes are explored in current investigation. Three promising methods of implementing improved wall boundary conditions are applied: (1) the enhanced diamond path stencil approach, (2) the reformulated extended extrapolation boundary condition, and (3) the ghost cell method. Several initial testing cases have been conducted with all these three boundary conditions, including the flow past a circular cylinder, flow past a flat plate at different inclined angles and flow past an AGARD RAE2822 airfoil. All the results show the effectiveness of these boundary conditions in resolving both laminar and turbulent boundary layer. Among all these methods, the extended extrapolation boundary condition attains the better results than the other two methods.

]]> Patrick Hu et al. Supersonic Channel Airfoils for Reduced Drag http://digitalcommons.calpoly.edu/aero_fac/81 http://digitalcommons.calpoly.edu/aero_fac/81 Tue, 19 Jul 2011 08:39:00 PDT A proof-of-concept study is performed for a supersonic channel-airfoil concept,which can be applied to the leading edges of wings, tails, fins, struts, and other appendages of aircraft, atmospheric entry vehicles, and missiles in supersonic flight. It is designed to be beneficial at conditions in which the leading edge is significantly blunted and the Mach number normal to the leading edge is supersonic.The supersonic channel-airfoil concept is found to result in significantly reduced wave drag and total drag (including skin-friction drag) and significantly increased lift/drag although maximum heat-transfer rate was increased for the geometries tested.

]]> Stephen M. Ruffin et al. Part 2: Preparation for Wind Tunnel Model Testing and Verification of Cal Poly’s AMELIA 10 Foot Span Hybrid Wing-Body Low Noise CESTOL Aircraft http://digitalcommons.calpoly.edu/aero_fac/80 http://digitalcommons.calpoly.edu/aero_fac/80 Thu, 14 Jul 2011 13:47:48 PDT A collaboration between California Polytechnic Corporation with Georgia Tech Research Institute (GTRI) and DHC Engineering worked on a NASA NRA to develop predictive capabilities for the design and performance of Cruise Efficient, Short Take-Off and Landing (CESTOL) subsonic aircraft. The focus of this work presented in this paper gives details of a large scale wind tunnel effort to validate predictive capabilities for this NRA for aerodynamic and acoustic performance during takeoff and landing. The model, Advanced Model for Extreme Lift and Improved Aeroacoustics (AMELIA), was designed as a 100 passenger, N+2 generation, regional, cruise efficient short takeoff and land (CESTOL) airliner with hybrid blended wing-body with circulation control. AMELIA is a 1/11 scale with a corresponding 10 ft wing span. The National Full-Scale Aerodynamic Complex (NFAC) 40 ft by 80 ft wind tunnel was chosen to perform the large-scale wind tunnel test in the scheduled to start summer of 2011. The NFAC was chosen because both aerodynamic and acoustic measurements will be obtained simultaneously, the tunnel is large enough that the downwash created by the powered lift will not impinge on the tunnel walls, and the schedule and cost fit into Cal Poly’s time frame and budget. Several experimental measurement techniques will be used to obtain the necessary data to validate predictive codes being developed as apart of this effort: stationary microphones will be used to obtain far-field acoustic measurements including a 48 element phased array, the Fringe-Image Skin Friction (FISF) technique will be used to measure the global skin friction on the wing, and the a micro flow measurement device will measure the velocity profiles in the in the boundary and shear layers is still in development and presented in this paper. 1

]]> Kristina Jameson et al. Part 1: The Wind Tunnel Model Design and Fabrication of Cal Poly's AMELIA 10 Foot Span Hybrid Wing-Body Low Noise CESTOL Aircraft http://digitalcommons.calpoly.edu/aero_fac/79 http://digitalcommons.calpoly.edu/aero_fac/79 Thu, 14 Jul 2011 13:47:43 PDT A collaboration between California Polytechnic Corporation with Georgia Tech Research Institute (GTRI) and DHC Engineering worked on a NASA NRA to develop predictive capabilities for the design and performance of Cruise Efficient, Short Take-Off and Landing (CESTOL) subsonic aircraft. In addition, a large scale wind tunnel effort to validate these predictive capabilities for this NRA for aerodynamic and acoustic performance during takeoff and landing has been undertaken. The model, Advanced Model for Extreme Lift and Improved Aeroacoustics (AMELIA), was designed as a 100 passenger, N+2 generation, regional, cruise efficient short takeoff and land (CESTOL) airliner with hybrid blended wing-body with circulation control and upper surface blowing. The model design was focused on fuel-savings and noise goals set out by the NASA N+2 definition. The AMELIA has a 10 ft wing span. PatersonLabs was chosen to build AMELIA. The National Full-Scale Aerodynamic Complex (NFAC) 40 ft by 80 ft wind tunnel was chosen to perform the large-scale wind tunnel test in the summer of 2011.

]]> Kristina K. Jameson et al. Improved Meshing Technique for the Engine Exhaust of an Over-the-Wing Engine and Circulation Control Wing Configuration http://digitalcommons.calpoly.edu/aero_fac/78 http://digitalcommons.calpoly.edu/aero_fac/78 Thu, 14 Jul 2011 13:47:39 PDT This paper details the results of ongoing efforts to improve upon the meshing techniques required to produce accurate RANS CFD solutions for attached and separated flows for a Circulation Control aircraft. Work, thus far, under the current NASA Research Announcement (NRA) project has revolved around an unstructured near-body volume mesh due to its robustness for complicated geometries. However, it has been found that this technique does a poor job capturing detailed flow features such as the boundary layer, shear layer, and wake of large velocity-gradient regions. Its hindrance is primarily due to the limitations of current computational resources, thus new techniques are investigated to improve the quallty of CFD solutions while not impeding on resources. High quality hybrid near-body volume meshes that combine structured and unstructured meshing have been utilized to meet the goals of the project. The area around the engine and circulation control slots serves as the basis for improved meshing techniques. So far, a hybrid mesh has been successfully generated around the engine and the results of the CFD solutions have improved immensely.

The focus of this paper is to show a comparison of the quality of the CFD solution of old and new meshing techniques. In addition, preilminary results of a hybrid mesh around the circulation control slots are discussed and will be the focus of future work. It has been determined that the primary meshing software used, ICEM CFD does not allow enough user control to adequately refine particular regions in the flow field, thus, alternative meshing software will have to be explored. Current computing resources limit the total size of the mesh to about 35 million. However, given this constraint, the results clearly show that the hybrid mesh attains more refined and stable CFD solutions.

]]> John Pham et al. Investigation of the Unsteady Behavior of a Circulation Control Wing Using Computational Fluid Dynamics http://digitalcommons.calpoly.edu/aero_fac/77 http://digitalcommons.calpoly.edu/aero_fac/77 Thu, 14 Jul 2011 13:47:34 PDT This paper details the results of an investigation into the unsteady behavior of a circulation control wing using computational fluid dynamics. Oscillations in the lift coefficient of up to 10% are observed for steady state simulations. An investigation into the source of the unsteadiness is underway, and the results to date are presented. It is shown that the periodic oscillations are independent of the above the wing mounted engine effects on the cruise efficient short take-off and landing aircraft. The oscillations are also a viscous phenomenon that does not dampen as the solution marches through steady state. It is proposed that the cause of the oscillations is due to high streamline curvature at the trailing edge inboard wing section, due to flow turning caused by the slot flow normal condition at the circulation control slots. This paper presents the results into the origin of this unsteadiness.

]]> Jonathon A. Lichtwardt et al. A Scientific Software Verification Library Based on the Method of Manufactured Solutions http://digitalcommons.calpoly.edu/aero_fac/76 http://digitalcommons.calpoly.edu/aero_fac/76 Thu, 14 Jul 2011 13:47:29 PDT A software library, avali, is being developed in the C++ programming language that applies the Method of Manufactured Solutions (MMS) to a variety of partial differential equation (PDE) problems. This library will allow researchers to utilize MMS as a software verification process without developing significant amounts of testing code. The library is split into 3 components: solution classes which can be used as manufactured solutions to PDE problems; PDE problem classes which represent specific types of PDEs to be solved (such as linear convection-diffusion equation or Poisson's equation); and post-processing classes that collect the convergence information and can perform various analysis techniques to the convergence data. In use, any solution class can be used with any PDE problem class and vice versa. This creates a significant amount of flexibility in this architecture and allows the end users to customize their MMS testing process. In addition, end users are able to develop their own solution classes in one of three ways: inheriting from the solution base class and implementing their own class; providing the functions (as source code to be compiled or as a software library with exported functions) required to evaluate the solution and its derivatives; or providing the solution equation as a string to be parsed by the library into a function. This paper will demonstrate a number of features of this library, as well as demonstrate its application in a typical use case.

]]> David D. Marshall A Surface Parameterization Method for Airfoil Optimization and High Lift 2D Geometries Utilizing the CST Methodology http://digitalcommons.calpoly.edu/aero_fac/75 http://digitalcommons.calpoly.edu/aero_fac/75 Thu, 30 Jun 2011 10:17:57 PDT For aerodynamic modeling and optimization, it is desirable to limit the number of design variables to reduce model complexity and the requirements of the applied optimization scheme. The Class/Shape Transformation (CST) surface parameterization method presented by Kulfan has proven to be particularly useful for this while maintaining a wide range of applications. These include everything from smooth airfoils to 3D axi-symmetric bodies and wings. However, the CST method is confined to smooth geometries. This limits the CST method in applications incorporating discontinuous surfaces such as high lift aerodynamics with circulation control (CC) slots and flaps. The trailing edge slot on a circulation control wing (CCW) airfoil is not well modeled by the CST method. A parameterization of a CCW airfoil will result in the trailing edge slot being smoothed over. Therefore, a modified CST method must be utilized. For the case of parameterizing a known CCW airfoil, this is accomplished by detecting drastic changes in curvature and beginning a new parameterization in a "multi-surface parameterization" method. For creating a new CCW airfoil, this is achieved by modifying the 2D CST equations to incorporate a slot thickness term that also includes the horizontal location. These two methods can then be extended into 3D to model a circulation control wing (CCW) or even a blended wing body (BWB) aircraft incorporating CCW. The multi-surface parameterization modification can also be used to model other complex geometries to further enhance the robust nature of the CST method, thus creating a valuable design tool.

]]> Kevin A. Lane et al. Inverse Airfoil Design Utilizing CST Parameterization http://digitalcommons.calpoly.edu/aero_fac/74 http://digitalcommons.calpoly.edu/aero_fac/74 Fri, 24 Jun 2011 14:48:02 PDT An inverse airfoil design process is presented that makes use of the CST parameterization method. The CST method is very powerful in that it can easily represent any airfoil shape within the entire design space of smooth airfoils. This makes it an ideal modeling technique for an inverse design process because accurate airfoil geometry treatment is required. The downfall of some inverse design processes is that they do not accurately handle the leading edge region due to large flow gradients and high curvature distributions. One way to account for this is by representing airfoils with smooth analytic functions, such as the CST method. The inverse airfoil design process presented is based on the relation between pressure residuals and the required airfoil shape change. The pressure residuals give the sign of the normal vector with which to modify the airfoil shape. The CST method is then used as the smoothing algorithm. The inverse design method is simple, accurate, and efficient. It is shown to accurately determine the airfoil geometry in both subsonic and transonic flows. Since this method simply examines pressure distributions to modify the airfoil shape, the flow solver can be kept separate from the inverse design process, allowing any delity flow solver to be used.

]]> Kevin A. Lane et al. Lift Superposition and Aerodynamic Twist Optimization for Achieving Desired Lift Distributions http://digitalcommons.calpoly.edu/aero_fac/73 http://digitalcommons.calpoly.edu/aero_fac/73 Fri, 24 Jun 2011 14:47:59 PDT A method for achieving an arbitrary lift distribution with an arbitrary planform is presented. This is accomplished through optimizing aerodynamic twist for a given number of either known airfoils or airfoils to be designed. The spanwise locations of these airfoils are optimized to get as close to the desired lift distribution as possible. Airfoils are linearly interpolated between these points. After aerodynamic twist, the planform is twisted geometrically using radial basis functions to model the twist distribution. The aerodynamic influence of each twist distribution is determined and all are superimposed to determine the function weights of each twist function, yielding the optimal twist to match the given lift. This method has been shown to match both an elliptical and a triangular lift distribution for an arbitrary planform. This method can also be used with any delity model, creating a powerful design tool.

]]> Kevin A. Lane et al.