Aerodynamic Flutter and Flight Surface Actuation

2007 ◽  
Author(s):  
S. A. Gadsden ◽  
S. Habibi
Keyword(s):  
Bulk Modulus ◽  
Small Amplitude ◽  
Mechanical Load ◽  
Impedance Control ◽  
Hydraulic Oil ◽  
Effective Bulk Modulus ◽  
Two Parameters

This paper proposes a novel form of impedance control in order to reduce the effects of aerodynamic flutter on a flight surface actuator. The forces generated by small amplitude flutter were studied on an electrohydrostatic actuator (EHA). The effects of flutter were modeled and analyzed. Through analysis, it was found that in EHA systems, two parameters would impact the response of flutter: damping (B) of the mechanical load, and the effective bulk modulus of the hydraulic oil (βe). These can be actively controlled as proposed here in order to provide variable impedance. The results of changing these variables are discussed and presented here.

Modeling and Experimental Validation of the Effective Bulk Modulus of a Mixture of Hydraulic Oil and Air

2014 ◽  
Vol 136 (5) ◽  
Author(s):  
Hossein Gholizadeh ◽  
Doug Bitner ◽  
Richard Burton ◽  
Greg Schoenau
Keyword(s):  
Experimental Data ◽  
Bulk Modulus ◽  
Theoretical Models ◽  
Operating Conditions ◽  
Air Bubbles ◽  
Pressure Sensitivity ◽  
Hydraulic Oil ◽  
Effective Bulk Modulus ◽  
Experimental Apparatus ◽  
Major Factors

It is well known that the presence of entrained air bubbles in hydraulic oil can significantly reduce the effective bulk modulus of hydraulic oil. The effective bulk modulus of a mixture of oil and air as pressure changes is considerably different than when the oil and air are not mixed. Theoretical models have been proposed in the literature to simulate the pressure sensitivity of the effective bulk modulus of this mixture. However, limited amounts of experimental data are available to prove the validity of the models under various operating conditions. The major factors that affect pressure sensitivity of the effective bulk modulus of the mixture are the amount of air bubbles, their size and the distribution, and rate of compression of the mixture. An experimental apparatus was designed to investigate the effect of these variables on the effective bulk modulus of the mixture. The experimental results were compared with existing theoretical models, and it was found that the theoretical models only matched the experimental data under specific conditions. The purpose of this paper is to specify the conditions in which the current theoretical models can be used to represent the real behavior of the pressure sensitivity of the effective bulk modulus of the mixture. Additionally, a new theoretical model is proposed for situations where the current models fail to truly represent the experimental data.

Experimental Investigation on Effective Bulk Modulus and Effective Volume in an External Gear Pump

2016 ◽  
Author(s):  
Shuichi Nakagawa ◽  
Takayoshi Ichiyanagi ◽  
Takao Nishiumi
Keyword(s):  
Bulk Modulus ◽  
Gear Pump ◽  
Hydraulic Systems ◽  
Hydraulic Oil ◽  
Positive Displacement ◽  
Effective Bulk Modulus ◽  
Source Impedance ◽  
Displacement Pump ◽  
External Gear Pump ◽  
Pressure Ripples

Pressure ripples generated by a positive displacement pump in a hydraulic system can lead to severe noise and vibration problems. The source impedance of a positive displacement pump has a considerable impact on the generation of pressure ripples. It is, therefore, important to be able to predict the source impedance in order to design quiet hydraulic systems. The source impedance of a positive displacement pump depends, amongst other things, on bulk modulus and volume. However, it is known that the mathematical model that takes into account the bulk modulus of hydraulic oil and the volume of a discharge room in the pump results in an estimated value of the source impedance that is greater than the measured value. In this study, the factors which affect the source impedance of an external gear pump for an agricultural tractor have been investigated. In particular, the effect of the following factors has been investigated experimentally: the effective bulk modulus as determined by the components of the pump: leakage in the pump: the specific volume ratio of entrained air to hydraulic oil: and the volume of the tooth space of the pump. In addition, the effect of volumetric change of the discharge room by pumping action has been investigated using CFD with moving mesh technique.

Modelling and Experimental Validation of the Effective Bulk Modulus of a Mixture of Hydraulic Oil and Air

2013 ◽  
Author(s):  
Hossein Gholizadeh ◽  
Doug Bitner ◽  
Richard Burton ◽  
Greg Schoenau
Keyword(s):  
Experimental Data ◽  
Bulk Modulus ◽  
Theoretical Models ◽  
Operating Conditions ◽  
Air Bubbles ◽  
Pressure Sensitivity ◽  
Hydraulic Oil ◽  
Effective Bulk Modulus ◽  
Experimental Apparatus ◽  
Major Factors

It is well known that the presence of entrained air bubbles in hydraulic oil can significantly reduce the effective bulk modulus of hydraulic oil. The effective bulk modulus of a mixture of oil and air as pressure changes is considerably different than when the oil and air is not mixed. Theoretical models have been proposed in the literature to simulate the pressure sensitivity of the effective bulk modulus of this mixture. However, limited amounts of experimental data are available to prove the validity of the models under various operating conditions. The major factors that affect pressure sensitivity of the effective bulk modulus of the mixture are the amount of air bubbles, their size and the distribution and rate of compression of the mixture. An experimental apparatus was designed to investigate the effect of these variables on the effective bulk modulus of the mixture. The experimental results were compared with existing theoretical models and it was found that the theoretical models only matched the experimental data under specific conditions. The purpose of this paper is to specify the conditions in which the current theoretical models can be used to represent the real behavior of the pressure sensitivity of the effective bulk modulus of the mixture. Additionally, a new theoretical model is proposed for situations where the current models fail to truly represent the experimental data.

Measurement of Effective Bulk Modulus for Hydraulic Oil at Low Pressure

2012 ◽  
Vol 134 (2) ◽  
Author(s):  
Sunghun Kim ◽  
Hubertus Murrenhoff
Keyword(s):  
Bulk Modulus ◽  
Volume Change ◽  
Suction Side ◽  
Pressure Change ◽  
Low Pressure ◽  
Simulation Accuracy ◽  
Hydraulic Oil ◽  
Effective Bulk Modulus ◽  
Entrained Air ◽  
Low Pressures

Oil properties are very important input parameters for the simulation of hydraulic components. Precise values of effective bulk modulus at low pressures are especially required to improve the simulation accuracy of the pumps suction side or of cavitation in pumps or valves. So far, theoretical equations to compute the effective bulk modulus of hydraulic oil have not been experimentally verified, and only poor measured data are available to calculate the effective bulk modulus at low pressure. Therefore in this paper, the theoretical equation was verified for effective bulk moduli based on measurements of pressure change as a function of volume change at low pressures, varying temperature, entrained air content, and type of state change. Furthermore, the comparison of effective bulk moduli calculated with three different methods (mass-change, volume-change, and sound-speed method) shows that the effective bulk modulus can be calculated well from the measurement results of all three methods. The calculated effective bulk moduli values show little variation among the methods. Additionally, the release pressure of dissolved air in oil and the change of the polytropic gas constant depending on the speed of volume change rate were identified in this study.

Optimal Bounds on the Effective Bulk Modulus of Polycrystals

1989 ◽  
Vol 49 (3) ◽  
pp. 824-837 ◽  
Author(s):  
Marco Avellaneda ◽  
Graeme W. Milton
Keyword(s):  
Bulk Modulus ◽  
Effective Bulk Modulus ◽  
Optimal Bounds

Effect of the Interphase Zone on the Bulk Modulus of a Particulate Composite

1996 ◽  
Vol 63 (4) ◽  
pp. 855-861 ◽  
Author(s):  
M. P. Lutz ◽  
R. W. Zimmerman
Keyword(s):  
Exact Solution ◽  
Bulk Modulus ◽  
Spherical Inclusion ◽  
Particulate Composite ◽  
Constant Term ◽  
Stress Concentrations ◽  
Infinite Body ◽  
Effective Bulk Modulus ◽  
Random Dispersion ◽  
Frobenius Series

An exact solution is found for the problem of hydrostatic compression of an infinite body containing a spherical inclusion, with the elastic moduli varying with radius outside of the inclusion. This may represent an interphase zone in a composite, or the transition zone around an aggregate particle in concrete, for example. Both the shear and the bulk moduli are assumed to be equal to a constant term plus a power-law term that decays away from the inclusion. The method of Frobenius series is used to generate an exact solution for the displacements and stresses. The solution is then used to estimate the effective bulk modulus of a material containing a random dispersion of these inclusions. The results demonstrate the manner in which a localized interphase zone around an inclusion may markedly affect both the stress concentrations at the interface, and the overall bulk modulus of the material.

Poroelasticity of Fluid-Saturated Nanoporous Media

2009 ◽  
Vol 614 ◽  
pp. 35-40 ◽  
Author(s):  
Vincent Pensée ◽  
Qi Chang He ◽  
H. Le Quang
Keyword(s):  
Bulk Modulus ◽  
Size Effects ◽  
Solid Phase ◽  
Hollow Spheres ◽  
Pore Surface ◽  
Nanoporous Media ◽  
Surface Stresses ◽  
Effective Bulk Modulus ◽  
Nanometric Size

The purpose of this work is to extend the equations of linear poroelasticity to the case of materials with nanopores. We consider a model of microstructure which corresponds to an assemblage of hollow spheres saturated by a fluid. The solid phase is linearly elastic and isotropic; pores are assumed to be of nanometric size. To account for the pore surface stresses, the Young-Laplace model is used. The nanopore size effects on the effective bulk modulus, Biot’ modulus and coefficient are shown. When pores are sufficiently large, the classical relations of linear poroelasticity are retrieved.

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