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Dive into the research topics where Tiger L. Jeans is active.

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Featured researches published by Tiger L. Jeans.


Journal of Aircraft | 2009

Aerodynamic Analysis of a Generic Fighter Using Delayed Detached-Eddy Simulation

Tiger L. Jeans; David R. McDaniel; Russell M. Cummings; William H. Mason

The modular transonic vortex interaction configuration was developed at the NASA Langley Research Center to investigate the aerodynamic characteristics of a generic fighter incorporating a chined fuselage and delta wing. Previous experiments showed that the fuselage and leading-edge vortex interactions are detrimental to the vehicles aerodynamic characteristics for angles of attack greater than 23 deg at low angles of sideslip. This is largely due to abrupt asymmetric vortex breakdown, which leads to pronounced pitch-up and significant nonlinearities in lateral stability that could result in roll departure. An improved understanding of the exact origins of this nonlinear behavior would improve future fighter design, and predictive capabilities of such nonlinearities could drastically reduce the cost associated with flight testing new or modified aircraft. The nonlinearities experienced by the modular transonic vortex interaction configuration at a 30 deg angle of attack, Reynolds number of 2.68 x 10 6 , and Mach number of 0.4 are computed using delayed detached-eddy simulation. Computational predictions of rolling moment compare very well with previous wind-tunnel experiments at the same conditions, including the abrupt nonlinear increase in rolling moment as a function of sideslip angle at small sideslip angles. A detailed investigation of the computational fluid dynamic data confirms that this nonlinearity is due to a rapid change in the flowfield structures from symmetric to asymmetric vortex breakdown.


48th AIAA Aerospace Sciences Meeting Including the New Horizons Forum and Aerospace Exposition | 2010

Improved Methodologies for Maneuver Design of Aircraft Stability and Control Simulations

Adam Jirasek; Tiger L. Jeans; Matthew Martenson; Russell M. Cummings; Keith Bergeron

With many modern fighter aircraft experiencing unpredicted flight dynamics during flight tests, recent research has focused on developing methodologies for incorporating computational fluid dynamics into the aircraft development process. The goal of this approach is to identify configurations susceptible to stability and control issues early in the design process. Previous research has primarily focused on full aircraft configurations, however, to increase the rate of development the current study focused on a two-dimensional NACA0012 airfoil. The two-dimensional NACA0012 airfoil has the advantage of reducing the computational cost by orders of magnitude compared to full scale aircraft simulations, while still providing complicated aerodynamics at high angles of attack. Computationally predicted lift coefficients from a number of newly developed training maneuvers were used to generate reduced order aerodynamic loads models. For evaluation, these models were compared to generated static and dynamic validation data. Methods of improving both the computational training maneuver and the reduced order modeling approach are suggested.


ASME 2005 Fluids Engineering Division Summer Meeting | 2005

A Critical Review of Classical Force Estimation Methods for Streamlined Underwater Vehicles Using Experimental and CFD Data

Tiger L. Jeans; C. R. Baker; A. G. L. Holloway; Andrew G. Gerber; George D. Watt

Classical hydrodynamic force estimation methods are widely used by industrial designers of underwater vehicles for whom captive model experiments and CFD based simulations are uneconomical. They are also used in the preliminary design of submarines and when real time submarine simulations are required. These methods poorly estimate the contribution of the hull to the forces, especially at moderate to high incidence angles. This paper critically reviews the classical hull force estimation methods developed by Munk, Allen, Perkins and Jorgensen, and Sarpkaya. It compares the methods with experimentally validated CFD predictions of a streamlined body at incidence angles up to 30 degrees and for Reynolds numbers from 2.3 to 230 million. The comparison shows that inadequately modeled flow separation and leeside body vortices explain the poor force and moment predictions. This is partly due, at least, to the lack of a streamlined tail on the truncated missile shapes for which the estimation methods were developed.Copyright


47th AIAA Aerospace Sciences Meeting Including The New Horizons Forum and Aerospace Exposition | 2009

Lower-Order Aerodynamic Loads Modeling of a Maneuvering Generic Fighter Using DDES Simulations

Tiger L. Jeans; David R. McDaniel; Russell M. Cummings; Keith Bergeron

Unforeseen nonlinear aerodynamic behavior and/or fluid-structure interactions have affected the development of nearly every major fighter program since 1960. The development cost of each of these aircraft could have been drastically reduced if these aerodynamic issues had been identified earlier in the design process. Therefore, a highfidelity computational tool capable of reliably predicting or identifying configurations susceptible to handling quality instabilities prior to flight test would be of great interest to the stability and control community. The United States Air Force Academy Modeling and Simulation Research Center and the United States Air Force Seek Eagle Office have initiated a joint effort to develop nonlinear lower-order aerodynamic loads models from unsteady CFD solutions. A key step in the process is to perform “training maneuvers,” which are dynamic CFD simulations designed to excite the relevant nonlinear flow physics. A reduced-order model is then built using SIDPAC, a regression based modeling technique designed specifically for aircraft system identification. The approach is validated for an aircraft configuration with a known aerodynamic instability that occurs well within the flight envelope. The dynamic CFD simulations can reliably predict this instability for frequencies ranging from 1.43 to 17.1 Hertz. In addition, an aerodynamic model trained using a varying frequency chirp maneuver was then used to predict constant frequency aerodynamic loads at conditions where strongly nonlinear aerodynamic behavior occurred.


26th AIAA Applied Aerodynamics Conference | 2008

Aerodynamic Analysis of a Generic Fighter with a Chine Fuselage/Delta Wing Configuration Using Delayed Detached-Eddy Simulation

Tiger L. Jeans; David R. McDaniel; Russell M. Cummings; William H. Mason

The Modular Transonic Vortex Investigation (MTVI) program at NASA Langley Research Center investigated the transonic characteristics of generic fighter configurations with chined fuselages and delta wings. Previous experiments show that the fuselage and leading edge vortex interactions are detrimental to the vehicle’s aerodynamic characteristics for angles of attack greater than 23o at low angles of sideslip. This is largely due to abrupt asymmetric vortex breakdown, which leads to pronounced pitch-up and significant nonlinearities in lateral stability that could result in roll departure. An improved understanding of the exact origins of this nonlinear behavior would improve future fighter design, and predictive capabilities of such nonlinearities could drastically reduce the cost associated with flight testing new or modified aircraft. The nonlinearities experienced by the MTVI configuration at 30 degrees angle of attack, Reynolds number of 2.68x10 6 , and Mach number of 0.4 are computed using Delayed Detached-Eddy Simulation. Computational predictions of rolling moment compare very well with previous wind tunnel experiments at the same conditions, including the abrupt, nonlinear increase in rolling moment as a function of sideslip angle at small sideslip angles. A detailed investigation of the CFD data confirms that this nonlinearity is due to a rapid change in the flow field structures from symmetric to asymmetric vortex breakdown.


ASME 2005 Fluids Engineering Division Summer Meeting | 2005

Examination of the Flow Separation Characteristics Around a Streamlined Axisymmetric Shape

C. R. Baker; Tiger L. Jeans; Andrew G. Gerber; A. G. L. Holloway; George D. Watt

Using computational fluid dynamics (CFD), a study was conducted to predict the hydrodynamic forces and moments on an axisymmetric body over a range of yaw angles and Reynolds numbers. Computational results for hydrodynamic forces and moments show good agreement with experimental data, being within the experimental uncertainty range at most yaw angles. Deviations outside of the uncertainty range occurred for the lateral (Y) force values at yaw angles greater than 15 degrees. The development of the after-body vortex shows good agreement with experimental observation. Primary and secondary separation points and shear stress streamline behaviour are also compared with experiment data at a yaw angle of 24 degrees. Results are discussed with a view to identifying flow features critical to the development of new force estimation methods. The after-body vortex, at increasing yaw angles, influences the overall force and moment predictions through a complex interaction between the transport of after-body vorticity and the detachment/reattachment locations of the boundary layer. Adequate modeling of this after-body region is increasingly important at high yaw angles. One of the most important features that influences the overall forces and moments is the circumferential position of shear layer detachment and reattachment, which have a direct impact on the pressure distribution along the body.Copyright


46th AIAA Aerospace Sciences Meeting and Exhibit | 2008

Analysis of an Axisymmetric Bluff Body Wake using Fourier Transform and POD

Jurgen Seidel; Stefan Siegel; Tiger L. Jeans; Selin Aradag; Kelly Cohen; Thomas McLaughlin

The data from u nforced and open loop forced simulations of the wake behind an axisymmetric bluff body at Re D=1,500 is analyzed to explore the effect of forcing. In the unforced wake, because of the axial symmetry of the body , structures do no t maintain a constant azimuthal phase over time , which leads to inaccurate predictions of the flow field when applying POD . Forcing inside the “lock -in” region in amplitude -frequency space with a fixed azimuthal phase is therefore introduced to study the w ake in detail. The resulting flow field is analyzed using three methods , namely an azimuthal Fourier transform, a moment of inertia calculation, and a velocity vector histogram, to determine the a zimuthal phase of the wake structures . The overall goal is t o minimize the necessary data volume to analyze the flow for eventual implementation in real time feedback flow control experiments. It is shown that the methods used to determine the azimuthal phase all yield a measure of the phase angle of the symmetry p lane in the wake .


IEEE Journal of Oceanic Engineering | 2016

A Concept for Docking a UUV With a Slowly Moving Submarine Under Waves

George D. Watt; André R. Roy; Jason Currie; Colin B. Gillis; Jared Giesbrecht; Garry J. Heard; Marius Birsan; Mae L. Seto; Juan A. Carretero; Rickey Dubay; Tiger L. Jeans

Docking an unmanned underwater vehicle (UUV) with a submerged submarine in littoral waters in high sea states requires more dexterity than either the submarine or streamlined UUV possess. The proposed solution uses an automated active dock to correct for transverse relative motion between the vehicles. Acoustic, electromagnetic, and optical sensors provide position sensing redundancy in unpredictable conditions. The concept is being evaluated by building and testing individual components to characterize their performance, errors, and limitations, and then simulating the system to establish its viability at low cost.


ASME 2010 29th International Conference on Ocean, Offshore and Arctic Engineering | 2010

Intermediate Ocean Wave Termination Using a Cycloidal Wave Energy Converter

Stefan Siegel; Tiger L. Jeans; Thomas McLaughlin

We investigate a lift based wave energy converter (WEC), namely, a cycloidal turbine, as a wave termination device. A cycloidal turbine employs the same geometry as the well established Cycloidal or Voith-Schneider Propeller. The interaction of intermediate water waves with the Cycloidal WEC is presented in this paper. The cycloidal WEC consists of a shaft and one or more hydrofoils that are attached eccentrically to the main shaft and can be adjusted in pitch angle as the Cycloidal WEC rotates. The main shaft is aligned parallel to the wave crests and fully submerged at a fixed depth. We show that the geometry of the Cycloidal WEC is suitable for wave termination of straight crested waves. Two-dimensional potential flow simulations are presented where the hydrofoils are modeled as point vortices. The operation of the Cycloidal WEC both as a wave generator as well as a wave energy converter interacting with a linear Airy wave is demonstrated. The influence that the design parameters radius and submergence depth on the performance of the WEC have is shown. For optimal parameter choices, we demonstrate inviscid energy conversion efficiencies of up to 95% of the incoming wave energy to shaft energy. This is achieved by using feedback control to synchronize the rotational rate and phase of the Cycloidal WEC to the incoming wave. While we show complete termination of the incoming wave, the remainder of the energy is lost to harmonic waves travelling in the upwave and downwave direction.Copyright


ASME 2015 34th International Conference on Ocean, Offshore and Arctic Engineering | 2015

Experimental Investigation of Fish Farm Hydrodynamic Wake Properties on 1:15 Scale Model Circular Aquaculture Cages

Adam A. Turner; Tiger L. Jeans; Gregor Reid

Hydrodynamic experiments on 1:15 scale model arrays of circular fish cages, typically used in eastern Canada, have been completed in the recirculating flume tank located at the Fisheries and Marine Institute of Memorial University in St. Johns, Newfoundland. Scale model cages were designed with a high amount of detail from 100 m circumference cages used in industry. Two different cage spacings were tested, representing spacing of cages typically found at cage sites. A global force ratio scaling technique was developed and applied to the experiment to ensure geometric similarity between cages of model scale and full scale. Planes of 64 (8×8) wake velocity measurements at both cage spacings were taken behind individual cages within the array and at distances in the wake of the entire array, to observe velocity deficits, wake topology, wake recovery and unsteadiness in the flow field. Results show high velocity deficits behind the cages, causing accelerations in the flow underneath and around the sides of the cages. High amounts of unsteadiness is found to be generated at the bottom of the cages due to the presence of a shear layer in the wake of the cages. Dye release was also used to observe many features of the flow field at one time, and to verify results obtained from wake velocity measurements.Copyright

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George D. Watt

Defence Research and Development Canada

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Russell M. Cummings

United States Air Force Academy

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Andrew G. Gerber

University of New Brunswick

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David R. McDaniel

United States Air Force Academy

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Keith Bergeron

United States Air Force Academy

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Thomas McLaughlin

United States Air Force Academy

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A. Dagan

University of New Brunswick

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Adam Jirasek

United States Air Force Academy

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A. G. L. Holloway

University of New Brunswick

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