A Reduced-Order Model for an Oscillating Hydrofoil Near the Free Surface

2015 ◽  
Author(s):  
Rory C. Kennedy ◽  
Dillon Helfers ◽  
Yin Lu Young
Keyword(s):  
Free Surface ◽  
High Speed ◽  
Equations Of Motion ◽  
Operating Conditions ◽  
Reduced Order Model ◽  
Order Model ◽  
Disturbing Force ◽  
Reduced Order ◽  
Resonance Frequencies ◽  
Force Components

The first objective of this work is to numerically investigate how the proximity to the free surface influences the hydrodynamic response and susceptibility to cavitation of a hydrofoil undergoing controlled pitching oscillations, for high-speed full-scale operating conditions. A second objective is to develop a time-domain Reduced Order Model (ROM) to predict the unsteady hydrodynamic loads (for rapid exploration of the design space and for real-time active/passive actuation/control). The ROM delineates the fluid-structure interaction (FSI) forces into fluid inertial, damping, and disturbing force components, and only predicts the primary oscillation frequency. In addition to predicting the unsteady loads, when coupled with the solid equations of motion, the ROM can also be used to calculate the natural resonance frequencies and damping characteristics with consideration for viscous and free surface effects. This will allow designers to better predict and control the dynamic response of lifting surfaces operating near the free surface.

New Swash Plate Damping Model for Hydraulic Axial-Piston Pump

1999 ◽  
Vol 123 (3) ◽  
pp. 463-470 ◽  
Author(s):  
X. Zhang ◽  
J. Cho ◽  
S. S. Nair ◽  
N. D. Manring
Keyword(s):  
Open Loop ◽  
Operating Conditions ◽  
Reduced Order Model ◽  
Piston Pump ◽  
Axial Piston Pump ◽  
Order Model ◽  
Nonlinear Simulation ◽  
Reduced Order ◽  
Swash Plate ◽  
Axial Piston

A new, open-loop, reduced order model is proposed for the swash plate dynamics of an axial piston pump. The difference from previous reduced order models is the modeling of a damping mechanism not reported previously in the literature. An analytical expression for the damping mechanism is derived. The proposed reduced order model is validated by comparing with a complete nonlinear simulation of the pump dynamics over the entire range of operating conditions.

Reduced Order Model of Two Coupled MEMS Parallel Cantilever Resonators Under DC and AC Voltage Near Natural Frequency

2012 ◽  
Author(s):  
Dumitru I. Caruntu ◽  
Kyle N. Taylor
Keyword(s):  
Frequency Response ◽  
Natural Frequency ◽  
Multiple Scales ◽  
Equations Of Motion ◽  
Reduced Order Model ◽  
Lagrange Equations ◽  
Order Model ◽  
Reduced Order ◽  
Dc Voltage ◽  
Ground Plate

This paper deals with a system of two coupled parallel identical MEMS cantilever resonators and a ground plate. Alternating Current (AC) and Direct Current (DC) voltages are applied between the first resonator and ground plate, and a DC voltage applied between the resonators. The AC voltage frequency is near natural frequency of the resonators. The electrostatic forces produced by voltages are nonlinear. System equations of motion are obtained using Lagrange equations, then nondimensionalized. The Method of Multiple Scales (MMS) is used to find the steady state frequency response. The Reduced Order Model (ROM) is used to validate MMS results. Matlab is used to find cantilever frequency response of the resonator tip. The DC voltage between resonators is showed to significantly influence the response of the first resonator.

Dynamics of a waveboard simplified

2020 ◽  
Vol 476 (2244) ◽  
pp. 20200486
Author(s):  
Anirvan DasGupta
Keyword(s):  
Kinetic Energy ◽  
Equations Of Motion ◽  
Translational Motion ◽  
Rolling Resistance ◽  
Reduced Order Model ◽  
Dynamic Parameters ◽  
Order Model ◽  
Reduced Order ◽  
Propulsion Mechanism ◽  
Subsequent Conversion

A study of dynamics of a waveboard is presented. The equations of motion are derived and analysed to understand the intriguing propulsion mechanism. A reduced order model is obtained, and the contributions of different terms are clearly brought out. The geometry of the castor wheels is found to play a key role in the conversion of the twisting oscillatory motion of the rider to the forward translational motion. The process of periodic gain in potential energy and its subsequent conversion to kinetic energy aids the propulsion. Interestingly, the dynamic analysis reveals that the efficacy of this propulsion mechanism tapers off as the speed increases. Rolling resistance in the wheels ultimately limits the speed of the device. The effect of various geometric and dynamic parameters on the motion and forces are studied, and optimality of design is indicated.

Solenoid Damping of the Pilot Poppet in a Forced-Feedback Metering Poppet Valve

2007 ◽  
Author(s):  
C. Harvey O. Cline ◽  
Roger Fales
Keyword(s):  
Dynamic Response ◽  
Operating Conditions ◽  
Reduced Order Model ◽  
The Self ◽  
Hydraulic Fluid ◽  
Order Model ◽  
Reduced Order ◽  
Poppet Valve ◽  
Spool Valves ◽  
Poppet Valves

Forced-feedback metering poppet valves offer several advantages over spool valves as metering elements in hydraulic circuits. Despite these advantages, dynamic instabilities in their performance could limit their acceptance in this role. The pilot poppet damping is a source of uncertainty in dynamic response at certain operating conditions. Presently, in the forced-feedback metering poppet valve, the pilot poppet is damped by the flow of hydraulic fluid through a channel or orifice running through the poppet. Here, it is proposed that the solenoid be used to provide damping to the pilot poppet. The damping input to the solenoid is determined using the pilot poppet velocity. In practice, this is a readily unavailable variable and is estimated according to the self-sensing actuator concept. The proposed damping method is developed and analyzed in simulations. Simulations development and analysis occurred via a simplified, reduced order model of the pilot poppet stage.

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