CFD Fuel Slosh Modeling of Fluid-Structure Interaction in Spacecraft Propellant Tanks with Diaphragms

Liquid sloshing within spacecraft propellant tanks causes rapid energy dissipation at resonant modes, which can result in attitude destabilization of the vehicle. Identifying resonant slosh modes currently requires experimental testing and mechanical pendulum analogs to characterize the slosh dynamics. Computational Fluid Dynamics (CFD) techniques have recently been validated as an effective tool for simulating fuel slosh within free-surface propellant tanks. Propellant tanks often incorporate an internal flexible diaphragm to separate ullage and propellant which increases modeling complexity. A coupled fluid-structure CFD model is required to capture the damping effects of a flexible diaphragm on the propellant. ANSYS multidisciplinary engineering software employs a coupled solver for analyzing two-way Fluid Structure Interaction (FSI) cases such as the diaphragm propellant tank system. Slosh models generated by ANSYS software are validated by experimental lateral slosh test results. Accurate data correlation would produce an innovative technique for modeling fuel slosh within diaphragm tanks and provide an accurate and efficient tool for identifying resonant modes and the slosh dynamic response

The Effectiveness of Augmented Reality as a Facilitator of Information Acquisition in Aviation Maintenance Applications

Until recently, in the field of Augmented Reality (AR) little research attention has been paid to the cognitive benefits of this emerging technology. AR, the synthesis of computer images and text in the real world, affords a supplement to normal information acquisition that has yet to be fully explored and exploited. AR achieves a more smooth and seamless interface by complementing human cognitive networks, and aiding information integration through multimodal sensory elaboration (visual, verbal, proprioceptive, and tactile memory) while the user is performing real world tasks. AR also incorporates visuo-spatial ability, which involves the representations of spatial information in memory. The use of this type of information is an extremely powerful form of elaboration. This study examined four learning paradigms: print (printed material) mode, observe (video tape) mode, interact (text annotations activated by mouse interaction) mode, and select (AR) mode. The results of the experiment indicated that the select (AR) mode resulted in better learning and recall when compared to the other three conventional learning modes

A STUDY OF HYDRODYNAMIC CHARACTERISTICS OF BOUNDARY LAYER WITH ALGAE ROUGHNESS

ABSTRACT Filamentous algae fouling such as Enteromorpha clathrata is a soft and hairy-like substance that can protrude even through a normal boundary layer. Typically, such fouling has been treated as traditional roughness functions to yield hydrodynamic characteristic

A Combined Approximation Based Matlab Code For Dynamic Re-Analysis Of Aerospace Structures

Achieving a high strength-to-weight ratio is one of the most important goals in the design of aerospace structures. Designers are continuously striving to find the optimum solutions that will make aerospace vehicles simultaneously strong and light. During the design process, the structure experiences several changes to reach this goal. Any change to the geometry and/or material property directly influences the global stiffness of the structure. Modification of the applied loading or stiffness impacts the solution of displacements. Each design change requires the implicit analysis equation to be resolved. In large scale models with thousands of degrees of freedom, the cost and time of repeated reanalysis, even for a small change, is significant. A combined approximation approach (CA) was previously developed to provide an efficient and accurate reanalysis of large structures, even with great changes in the design. High quality results have also been obtained through utilizing the CA method for dynamic reanalysis. This approach involves the combination of local and global approximation methods including series expansion, reduced basis vector, matrix factorization, and Gram-Schmidt orthonormalization. In this study, a combined approximation based MATLAB code for dynamic reanalysis has been developed. Changes in both baseline design properties and excitation frequency range have been introduced. The response of the modified system is calculated as a function of these changes, directly via inversion of the dynamic stiffness matrix and approximately via combined approximation method. A reanalysis example of a simplified aircraft wing spar model using this code is presented. Both methods are compared for solution accuracy. Copyright © 2010 by ASME

Augmented Reality as a Training Medium for Aviation/Aerospace Application

Augmented Reality (AR) has the potential to transform aviation/aerospace training by creating new mixed reality worlds that serve as a medium for gaining work related skills. --from the publicatio

Hybrid control system for spacecraft antenna boom

Sensitive equipment utilized in aerospace applications experience vibrations from mechanical and thermal disturbances. Without proper vibration suppression systems, the delicate equipment can be severely damaged. A comparison between passive, active and hybrid control of light weight boom structure for space vehicles is carried out. Numerical and experimental analyses using NASTRAN finite element software are performed. Different control methods are applied, and a PID controller is implemented in the experiment. The main target of this research is to study the dynamic response of sensitive and light spacecraft structure like a boom antenna. In this experiment, the source of vibration disturbance is the force applied to one end of the structure and the response signal is captured by an accelerometer sensor at the free end of the beam. Piezoelectric Translator (PTS30 nanopositioning stage) (which is a linear actuator suitable for static and dynamic applications) is used for the reducing the vibration characteristics and thus damping out the vibrations. The maximum displacement provided by this actuator is +/- 15 mm and they provide pushing or pulling force of up to 30 N. The linear speed range of the PTS30 is 0 to 500 micrometer per second. The input to the actuator is provided by the accelerometer sensor through a power amplifier which is connected through a computer. The measured acceleration is integrated to obtain the corresponding velocities. Effectiveness of the control system highly depends on the position of the actuators. The average energy level taken over a frequency bandwidth of 4 Hz to 8 Hz will be considered as a parameter to be minimized. This research focuses on the reduction of vibration behavior of satellite boom structures over a wide frequency bandwidth using hybrid vibration control system. Here we present the results of damping effectiveness for different excitation amplitudes. Copyright © 2010 by ASME