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Aerodynamics and Fluid Mechanics Commons™

Open Access. Powered by Scholars. Published by Universities.®

2004

Articles 1 - 7 of 7

Full-Text Articles in Aerodynamics and Fluid Mechanics

Quantifying Initial Condition And Parametric Uncertainties In A Nonlinear Aeroelastic System With An Efficient Stochastic Algorithm, Daniel R. Millman Sep 2004

Quantifying Initial Condition And Parametric Uncertainties In A Nonlinear Aeroelastic System With An Efficient Stochastic Algorithm, Daniel R. Millman

Theses and Dissertations

There is a growing interest in understanding how uncertainties in flight conditions and structural parameters affect the character of a limit cycle oscillation (LCO) response, leading to failure of an aeroelastic system. Uncertainty quantification of a stochastic system (parametric uncertainty) with stochastic inputs (initial condition uncertainty) has traditionally been analyzed with Monte Carlo simulations (MCS). Probability density functions (PDF) of the LCO response are obtained from the MCS to estimate the probability of failure. A candidate approach to efficiently estimate the PDF of an LCO response is the stochastic projection method. The objective of this research is to extend the …

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Aerodynamic Analysis Of Lattice Grid Fins In Transonic Flow, Karl S. Orthner Jun 2004

Aerodynamic Analysis Of Lattice Grid Fins In Transonic Flow, Karl S. Orthner

Theses and Dissertations

Lattice grid fins have been studied for missile tail control for several years. A lattice grid fin can be described as an unconventional missile control surface comprised of an outer frame supported by an inner lattice grid of lifting surfaces. This unconventional fin design offers favorable lift characteristics at high angle of attack as well as almost zero hinge moments allowing the use of small and light actuators. In addition, they promise good storability for potential tube-launched and internal carriage dispenser-launched applications. The drawback for the lattice grid fins is the high drag and potentially poor radar cross section performance …

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Magnetogasdynamic Flow Acceleration In A Scramjet Nozzle, Brian H. Harrington Jun 2004

Magnetogasdynamic Flow Acceleration In A Scramjet Nozzle, Brian H. Harrington

Theses and Dissertations

The effect of magnetogasdynamic (MGD) interactions on flow acceleration and thrust in a scramjet accelerator/nozzle are examined numerically at a free-stream flight condition of Mach 8. The parameters of conductivity pattern and load factor are varied in both inviscid and viscous flow regimes with the intent of increasing axial force exerted on the flow through a scramjet accelerator. The numerical code solves the Navier-Stokes equations with additional source terms for the MGD forces and energy interactions. An accelerating Lorentz force is applied to the flow resulting from a constant magnetic field and an electric field produced by two continuous side …

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Cold Flow Testing Of A Modified Subscale Model Exhaust System For A Space Based Laser, David B. Jarrett Jun 2004

Cold Flow Testing Of A Modified Subscale Model Exhaust System For A Space Based Laser, David B. Jarrett

Theses and Dissertations

The aim of this research was a continued study of gas-dynamic phenomena that occurred in a set of stacked nozzles as reported by Captains Ian Bautista in 2003 and Scott Bergren in 2002. The arrangement of the stacked nozzles was a modified version of a 1/5th scale-model of one quadrant of the conceptual Space Based Laser Integrated Flight Experiment (SBL IFX) gas dynamic laser. Rather than cylindrical rings of nozzles, the stacked nozzles were flat and able to be rotated about a vector normal to the nozzle exits. This set of stacked flat nozzles was installed on a blow-down/vacuum wind …

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Experimental Investigation Into The Aerodynamic Performance Of Both Rigid And Flexible Wing Structured Micro-Air-Vehicles, Anthony M. Deluca Mar 2004

Experimental Investigation Into The Aerodynamic Performance Of Both Rigid And Flexible Wing Structured Micro-Air-Vehicles, Anthony M. Deluca

Theses and Dissertations

The Air Force Research Lab, Munitions Directorate, Eglin Air Force Base, Florida has designed a man-portable carbon-fiber Micro-Air-Vehicle (MA V) used for on-the-spot surveillance by Special Operations Forces (SOF) for enemy reconnaissance as well as post-strike Battle Damage Assessment (BDA).The main goals of this experiment are: 1) characterize the flow quality of the new AFIT 3' x 3' wind tunnel and 2) determine the aerodynamic performance characteristics of the 24" span, 6" chord flexible and rigid wing MA V s. The turbulent intensity of the wind tunnel was approximately 2%. Both MA Vs had an average lift slope within 3.5% …

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Flow Around An Object Projected From A Cavity Into A Supersonic Freestream, Scott T. Bjorge Mar 2004

Flow Around An Object Projected From A Cavity Into A Supersonic Freestream, Scott T. Bjorge

Theses and Dissertations

The pressure and flow field of a supersonic flow over a cavity, with and without a store, was the focus of this experiment. One cavity geometry (length to depth ratio 3.6) was studied; the freestream Mach number and the placement of the store relative to the cavity floor were varied. The pressure spectra on the cavity floor were markedly different between Mach numbers of 1.8 and 2.9. The Mach 1.8 case exhibited clear spectral peaks consistent with predictions by Rossiter, whereas the Mach 2.9 flow did not. With the store placed within the free shear layer, the pressure fluctuations on …

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Magnetogasdynamic Flow Control Of A Mach Reflection, Brian E. Earp Mar 2004

Magnetogasdynamic Flow Control Of A Mach Reflection, Brian E. Earp

Theses and Dissertations

Two-dimensional regular and Mach reflections have been studied in the Mach 4.96 dual-solution domain for a 25° and 26° double-fin inlet. The steady-state computational Mach and regular reflections were subjected to magnetogasdynamic forces to determine whether these forces could be used as a possible flow control mechanism. The numerical code employed for this research solved the inviscid Euler equations with added source terms for the ponderomotive force and accompanying energy interactions. The 25° regular reflection was determined to be extremely sensitive to a decelerating Lorentz force. Transient application of the force led to the transition of the regular reflection to …

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