Submarine Maneuvering Simulations of ONR Body 1

2007 ◽  
Author(s):  
Ganesh Venkatesan ◽  
William Clark
Keyword(s):  
Degrees Of Freedom ◽  
Stokes Equations ◽  
Equations Of Motion ◽  
Solution Procedure ◽  
Control Surface ◽  
Computational Domain ◽  
Instantaneous Position ◽  
Sliding Interfaces ◽  
And Control ◽  
Maneuvering Simulations

The application of computational fluid dynamics method to the submarine maneuvering simulations of ONR Body 1 is presented. ONR Body 1 is an unclassified submarine radio controlled model with propeller and control surfaces. Unsteady Reynolds-averaged Naviers-Stokes equations of fluid flow is coupled to the six degrees-of-freedom equations of motion of a rigid body via user coding to predict the instantaneous position and body orientation. Propeller and control surface motions are accounted for by using the moving mesh feature integrated into the solution procedure which allows sliding interfaces between different mesh blocks of the computational domain (for propeller rotation), as well as mesh distortion (for control surface deflection). This offers the flexibility of using a single computational grid for the entire simulation period. The maneuvers simulated include a constant depth and heading run as well as a horizontal overshoot maneuver using conditions consistent with the experiment. Predicted results show favorable agreement with experimental measurements.

Finite Element Simulation of a Gust Response of an Ultralight 2-DOF Airfoil

2014 ◽  
Author(s):  
Jaromír Horáček ◽  
Petr Sváček
Keyword(s):  
Finite Element ◽  
Differential Equations ◽  
Ordinary Differential Equations ◽  
Degrees Of Freedom ◽  
Stokes Equations ◽  
Turbulent Viscosity ◽  
Equations Of Motion ◽  
Sudden Change ◽  
Computational Domain ◽  
Arbitrary Lagrangian Eulerian

Flexibly supported two-degrees of freedom (2-DOF) airfoil in two-dimensional (2D) incompressible viscous turbulent flow subjected to a gust (sudden change of flow conditions) is considered. The structure vibration is described by two nonlinear ordinary differential equations of motion for large vibration amplitudes. The flow is modeled by Reynolds averaged Navier-Stokes equations (RANS) and by k–ω turbulence model. The numerical simulation consists of the finite element (FE) solution of the RANS equations and the equations for the turbulent viscosity. This is coupled with the equations of motion for the airfoil by a strong coupling procedure. The time dependent computational domain and a moving grid are taken into account with the aid of the arbitrary Lagrangian-Eulerian formulation. In order to avoid spurious numerical oscillations, the SUPG and div-div stabilizations are applied. The solution of the ordinary differential equations is carried out by the Runge-Kutta method. The resulting nonlinear discrete algebraic systems are solved by the Oseen iterative process. The aeroelastic response to a sudden gust is numerically analyzed with the aid of the developed FE code. The gust responses exhibit similar oscillations as those found in literature.

The Integrated Mission Simulator

SIMULATION ◽  
1964 ◽  
Vol 2 (2) ◽  
pp. R-9-R-23
Author(s):  
Edward E. Markson ◽  
John L. Stricker
Keyword(s):  
Degrees Of Freedom ◽  
Equations Of Motion ◽  
Landing Site ◽  
Euler Angle ◽  
Space Mission ◽  
Six Degrees Of Freedom ◽  
Guidance And Control ◽  
Manned Space ◽  
And Control ◽  
Guidance Technique

Space mission simulator programs may be divided into two broad categories: (1) training tools (quali tative devices often simulating a continuous mission), and (2) laboratory tools (quantitative devices treating the mission in phases, each phase being programmed separately to obtain optimum scaling). This paper describes the development of an analog program capable of continuously simulating an entire lunar mission in six degrees of freedom with high resolu tion throughout. The reported work logically traces the program development through the equations of motion, the guidance and control equations, and the analog mechanization. The translation equations are de veloped using a modified form of Encke's method; two reference origins are utilized at the two points of primary interest—the landing site and the target vehicle—such that the displacements are approach ing a minimum in the regions where the highest reso lution is required. The variables are rescaled as this region is approached to obtain maximum accuracy. Relays, stepping switches and diode gates are used for rescaling and to re-reference origins. A particular Euler angle sequence is selected based on matrix validity criteria applied to the mission. A previously reported guidance technique is shown to be appli cable to all phases of the mission. It is concluded that the method demonstrated in this paper leads to minimum computer loading for simulating a manned space mission without program discontinuities. Supporting data include an analog- computed trajectory representative of a long-dura tion mission, which is compared in detail with a digital solution.

Effects of Hull and Control Surface Roughness on Ship Maneuvering

2020 ◽  
pp. 1-10
Author(s):  
John C. Daidola
Keyword(s):  
Surface Roughness ◽  
Equations Of Motion ◽  
Control Surface ◽  
Ship Maneuvering ◽  
Single Screw ◽  
Operation And Maintenance ◽  
Hydrodynamic Derivatives ◽  
Turning Maneuver ◽  
And Control ◽  
Surface Vessel

The effects of hull roughness on ship maneuvering characteristics are investigated. The hydrodynamic derivatives in the equations of motion for surface vessel maneuvering are modified to incorporate roughness of the hull and rudder. Vessel lifetime roughness profiles are postulated based on construction, coatings, operation, and maintenance for a vessel life of 25 years. These are then applied to the turning maneuver for single screw cargo ships with block coefficients from .60 to .80. The implications for naval missions are discussed.

Numerical Simulation of Glottal Flow in Interaction with Self Oscillating Vocal Folds: Comparison of Finite Element Approximation with a Simplified Model

2012 ◽  
Vol 12 (3) ◽  
pp. 789-806 ◽  
Author(s):  
P. Sváček ◽  
J. Horáček
Keyword(s):  
Finite Element ◽  
Degrees Of Freedom ◽  
Stokes Equations ◽  
Finite Element Approximation ◽  
Vocal Folds ◽  
Multistep Method ◽  
Element Approximation ◽  
Computational Domain ◽  
Arbitrary Lagrangian Eulerian ◽  
Stabilized Finite Element Method

AbstractIn this paper the numerical method for solution of an aeroelastic model describing the interactions of air flow with vocal folds is described. The flow is modelled by the incompressible Navier-Stokes equations spatially discretized with the aid of the stabilized finite element method. The motion of the computational domain is treated with the aid of the Arbitrary Lagrangian Eulerian method. The structure dynamics is replaced by a mechanically equivalent system with the two degrees of freedom governed by a system of ordinary differential equations and discretized in time with the aid of an implicit multistep method and strongly coupled with the flow model. The influence of inlet/outlet boundary conditions is studied and the numerical analysis is performed and compared to the related results from literature.

Numerical Simulations of Nonlinear Post-Critical Vibrations of an Airfoil After Flutter Instability

2011 ◽  
Author(s):  
Jaromi´r Hora´cˇek ◽  
Miloslav Feistauer ◽  
Petr Sva´cˇek
Keyword(s):  
Numerical Simulations ◽  
Degrees Of Freedom ◽  
Stokes Equations ◽  
Mass Matrix ◽  
Vertical Direction ◽  
Navier Stokes ◽  
Computational Domain ◽  
Arbitrary Lagrangian Eulerian ◽  
Navier Stokes Equations ◽  
Classical Flutter

The contribution deals with the numerical simulation of the flutter of an airfoil with three degrees of freedom (3-DOF) for rotation around an elastic axis, oscillation in the vertical direction and rotation of a flap. The finite element (FE) solution of two-dimensional (2-D) incompressible Navier-Stokes equations is coupled with a system of nonlinear ordinary differential equations describing the airfoil vibrations with large amplitudes taking into account the nonlinear mass matrix. The time-dependent computational domain and a moving grid are treated by the Arbitrary Lagrangian-Eulerian (ALE) method and a suitable stabilization of the FE discretization is applied. The developed method was successfully tested by the classical flutter computation of the critical flutter velocity using NASTRAN program considering the linear model of vibrations and the double-lattice aerodynamic theory. The method was applied to the numerical simulations of the post flutter regime in time domain showing Limit Cycle Oscillations (LCO) due to nonlinearities of the flow model and vibrations with large amplitudes. Numerical experiments were performed for the airfoil NACA 0012 respecting the effect of the air space between the flap and the main airfoil.

A Unified Framework for Dynamics and Lyapunov Stability of Holonomically Constrained Rigid Bodies

2005 ◽  
Vol 9 (4) ◽  
pp. 387-394 ◽  
Author(s):  
Khoder Melhem ◽  
◽  
Zhaoheng Liu ◽  
Antonio Loría ◽  
◽  
...  
Keyword(s):  
System Dynamics ◽  
Lyapunov Stability ◽  
Degrees Of Freedom ◽  
Equations Of Motion ◽  
Rigid Bodies ◽  
Minimal Realization ◽  
State Variables ◽  
Unified Framework ◽  
Constrained System ◽  
And Control

A new dynamic model for interconnected rigid bodies is proposed here. The model formulation makes it possible to treat any physical system with finite number of degrees of freedom in a unified framework. This new model is a nonminimal realization of the system dynamics since it contains more state variables than is needed. A useful discussion shows how the dimension of the state of this model can be reduced by eliminating the redundancy in the equations of motion, thus obtaining the minimal realization of the system dynamics. With this formulation, we can for the first time explicitly determine the equations of the constraints between the elements of the mechanical system corresponding to the interconnected rigid bodies in question. One of the advantages coming with this model is that we can use it to demonstrate that Lyapunov stability and control structure for the constrained system can be deducted by projection in the submanifold of movement from appropriate Lyapunov stability and stabilizing control of the corresponding unconstrained system. This procedure is tested by some simulations using the model of two-link planar robot.

scholarly journals Diagonally dominant backstepping autopilot for aircraft with unknown actuator failures and severe winds

2014 ◽  
Vol 118 (1207) ◽  
pp. 1009-1038 ◽  
Author(s):  
S. Ismail ◽  
A. A. Pashilkar ◽  
R. Ayyagari ◽  
N. Sundararajan
Keyword(s):  
Dynamic Models ◽  
Controller Design ◽  
Design Method ◽  
Equations Of Motion ◽  
Control Surface ◽  
Actuator Failures ◽  
Time Scale Separation ◽  
Diagonally Dominant ◽  
Trajectory Following ◽  
And Control

Abstract A novel formulation of the flight dynamic equations is presented that permits a rapid solution for the design of trajectory following autopilots for nonlinear aircraft dynamic models. A robust autopilot control structure is developed based on the combination of the good features of the nonlinear dynamic inversion (NDI) method, integrator backstepping method, time scale separation and control allocation methods. The aircraft equations of motion are formulated in suitable variables so that the matrices involved in the block backstepping control design method are diagonally dominant. This allows us to use a linear controller structure for a trajectory following autopilot for the nonlinear aircraft model using the well known loop by loop controller design approach. The resulting autopilot for the fixed-wing rigid-body aircraft with a cascaded structure is referred to as the diagonally dominant backstepping (DDBS) controller. The method is illustrated here for an aircraft auto-landing problem under unknown actuator failures and severe winds. The requirement of state and control surface limiting is also addressed in the context of the design of the DDBS controller.

Out-of-Plane Solutions and Bifurcations of Submersibles in Free Positive Buoyancy Ascent

1994 ◽  
Vol 38 (04) ◽  
pp. 259-271
Author(s):  
Fotis A. Papoulias ◽  
Ibrahim Aydin
Keyword(s):  
Degrees Of Freedom ◽  
Pitchfork Bifurcation ◽  
Control Surface ◽  
Geometric Properties ◽  
Six Degrees Of Freedom ◽  
Out Of Plane ◽  
Bifurcation Solution ◽  
Extreme Sensitivity ◽  
And Control ◽  
Surface Deflections

The problem of motion stability of submersible vehicles in free positive buoyancy ascent is analyzed. Motion is allowed to occur in combined vertical and horizontal planes. Continuation and catastrophe theory techniques are employed to trace all possible steady-state solutions in six degrees of freedom, while local linearization reveals their stability properties. Vehicle geometric properties and control surface deflections are used as the primary bifurcation parameters. It is shown that multiple solutions may exist in the form of pitchfork bifurcation, solution separation, hysteresis, and teardrop branches. Regions in parameter spaces are identified where extreme sensitivity of solutions to geometric properties and hydrodynamic modeling is present.

Limit Cycle Stability Reversal via Singular Perturbation and Wing-Flap Flutter

2002 ◽  
Author(s):  
Daniele Dessi ◽  
Franco Mastroddi
Keyword(s):  
Singular Perturbation ◽  
Limit Cycles ◽  
Degrees Of Freedom ◽  
Perturbation Technique ◽  
Equations Of Motion ◽  
Control Surface ◽  
System Response ◽  
Singular Perturbation Technique ◽  
Nonlinear Springs ◽  
Time Marching

A three degrees of freedom aeroelastic typical section with control surface is theoretically modeled including nonlinear springs and augmented states for linear unsteady aerodynamic description. The system response is determined by time marching of the governing equations by using a standard Runge-Kutta algorithm in conjunction with a ‘shooting method’ to find out stable and unstable limit cycles along with stability reversal in the neighborhood of the Hopf bifurcation. Furthermore, the equations of motion are analyzed by a singular perturbation technique, specifically, by using a normal form method. Approximate analytical expressions for amplitudes and frequencies of limit cycles are obtained and the terms which are responsible of the nonlinear system behavior are identified.

Aerodynamic and flight dynamic interaction in spin

2019 ◽  
Vol 91 (3) ◽  
pp. 437-447
Author(s):  
Ewa Marcinkiewicz ◽  
Zdobyslaw Jan Goraj ◽  
Marcin Figat
Keyword(s):  
Degrees Of Freedom ◽  
Equations Of Motion ◽  
Integrated Approach ◽  
Dynamic Interaction ◽  
Euler Method ◽  
Computational Method ◽  
Control Surface ◽  
Sideslip Angle ◽  
Flight Tests ◽  
Content Type

PurposeThe purpose of this paper is to describe an integrated approach to spin analysis based on 6-DOF (degrees of freedom) fully nonlinear equations of motion and a three-dimensional multigrid Euler method used to specify a flow model. Another purpose of this study is to investigate military trainer performance during a developed phase of a deliberately executed spin, and to predict an aircraft tendency while entering a spin and its response to control surface deflections needed for recovery.Design/methodology/approachTo assess spin properties, the calculations of aerodynamic characteristics were performed through an angle-of-attack range of −30 degrees to +50 degrees and a sideslip-angle range of −30 degrees to +30 degrees. Then, dynamic equations of motion of a rigid aircraft together with aerodynamic loads being premised on stability derivatives concept were numerically integrated. Finally, the examination of light turboprop dynamic behaviour in post-stalling conditions was carried out.FindingsThe computational method used to evaluate spin was positively verified by comparing it with the experimental outcome. Moreover, the Euler code-based approach to lay down aerodynamics could be considered as reliable to provide high angles-of-attack characteristics. Conclusions incorporate the results of a comparative analysis focusing especially on comprehensive assessment of output data quality in relation to flight tests.Originality/valueThe conducted calculations take into account aerodynamic and flight dynamic interaction of an aerobatic-category turboprop in spin conditions. A number of manoeuvres considering different aircraft configurations were simulated. The computational outcomes were subsequently compared to the results of in-flight tests and the collected data were thoroughly analysed to draw final conclusions.

Sign in / Sign up

Export Citation Format

Share Document