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The certification process of external loads designed for aircraft needs to satisfy various criteria where compatibility with existing systems is one of the essential requirements. Flight flutter testing is a critical part of a... more
The certification process of external loads designed for aircraft needs to satisfy various criteria where compatibility with existing systems is one of the essential requirements. Flight flutter testing is a critical part of a certification process that requires many preliminary studies. Computational flutter analysis must precede actual flutter test to determine an approximately safe flight envelope to ensure the safety of the personnel and aircraft. To be able to perform flutter analysis of an aircraft, an accurate structural model such as finite element (FE) model is required. An accurate FE model can be obtained from a coarse model using ground vibration test (GVT) which is also the primary test campaign for certification of a new external load, new aircraft design, or modification on existing aircraft. On the other hand, performing GVT for each configuration of an aircraft is both time consuming and costly. It would be more practical to determine the critical configurations for...
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Pressure fluctuations that cause acoustic radiation from vessel models with concentric and eccentric blunt stenoses are investigated. Large eddy simulations of non-pulsatile flow condition are performed using OpenFOAM. Calculated... more
Pressure fluctuations that cause acoustic radiation from vessel models with concentric and eccentric blunt stenoses are investigated. Large eddy simulations of non-pulsatile flow condition are performed using OpenFOAM. Calculated amplitude and spatial-spectral distribution of acoustic pressures at the post-stenotic region are compared with previous experimental and theoretical results. It is found that increasing the Reynolds number does not change the location of the maximum root mean square wall pressure, but causes a general increase in the spectrum level, although the change in the shape of the spectrum is not significant. On the contrary, compared to the concentric model at the same Reynolds number, eccentricity leads to an increase both at the distance of the location of the maximum root mean square wall pressure from the stenosis exit and the spectrum level. This effect becomes more distinct when radial eccentricity of the stenosis increases. Both the flow rate and the eccent...
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Modern fighter aircraft, together with their interceptor roles, are utilized as aerial bomb and long-/short-range missile carriers. Separation of those external stores from aircraft is still a challenge where the external store has to... more
Modern fighter aircraft, together with their interceptor roles, are utilized as aerial bomb and long-/short-range missile carriers. Separation of those external stores from aircraft is still a challenge where the external store has to clear the carrier aircraft following the ejection process. Aircraft and store aerodynamics coupled with their individual flight conditions may result in an unsafe ejection where the store may interfere with the carrier aircraft instead of a clear separation. Store ejection is the initial phase of the launching process, which dominates the separation of the store by generating the initial conditions. Any error introduced to the store separation analysis during this phase will propagate to the complete trajectory solution, which is used for determining whether the store separation is safe or not. The objective of this paper is to present a computational methodology that includes not only the store aerodynamics but also the interactions of the store with ...
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Research Interests: Finite Element, Vibration, Multidisciplinary, Elastic waves, Elasticity, and 15 moreFinite Element Analysis, Software, Humans, Computer Simulation, Viscosity, Mathematical Computing, Experimental Study, Numerical Integration, Finite element simulation, Medical Diagnosis, Cardiovascular system, Soft Tissue, Shear Waves, Surface Wave, and auscultation
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ABSTRACT In this paper, we study the kinematics of a legged robot with half-circular leg morphology. In particular, our focus is on the RHex hexapod platform. A new kinematic model for RHex is developed considering the leg shape and its... more
ABSTRACT In this paper, we study the kinematics of a legged robot with half-circular leg morphology. In particular, our focus is on the RHex hexapod platform. A new kinematic model for RHex is developed considering the leg shape and its consequences, which was over simplified in the previous models seen in literature. The formulation is an accurate kinematic representation of the robot in the sagittal plane that is based on a four-link mechanism analogy. When only pure rolling motion of the legs are considered, it is found that when front and rear pairs of legs are in contact with the ground, the robot becomes a one degree-of-freedom mechanism and position of the middle pair of legs are redundant. The problem is solved in two steps; the first one being the determination of the initial configuration of the leg angular positions which defines the initial value of the variable distance of the front and rear leg and ground contact points. After the initial configuration of the system is set, pitch angle of the robot body can be manipulated by controlling one of the leg angular positions and the results are presented on an example case; positioning a body fixed unactuated sensor by controlling robot body pitch angle through the actuation of one of the legs. The results are a good display of the multi-functional aspect of the legs in addition to their use for locomotion.
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Ultrasound (US) medical imaging technology is enhanced by integrating a simultaneous noninvasive audible frequency measurement of biological sounds that could be indicative of pathology. Measurement of naturally‐occurring biological... more
Ultrasound (US) medical imaging technology is enhanced by integrating a simultaneous noninvasive audible frequency measurement of biological sounds that could be indicative of pathology. Measurement of naturally‐occurring biological acoustic phenomena can augment conventional imaging technology by providing unique information about material structure and system function. Sonic phenomena of diagnostic value are associated with a wide range of biological functions, such as breath sounds, bowel sounds, and vascular ...
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Research Interests: Ultrasound, Finite Element, Multidisciplinary, Elastic waves, Elasticity, and 15 moreFinite Element Analysis, Software, Humans, Computer Simulation, Mathematical Computing, Experimental Study, Numerical Integration, Finite element simulation, Medical Diagnosis, Cardiovascular system, Blood Flow, Soft Tissue, Shear Waves, Surface Wave, and auscultation
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ABSTRACT Constricted flow in a thin cylindrical shell with an idealized blunt constriction is modeled using ADINA. Highly disturbed recirculation region is observed at the constriction exit where pressure fluctuations and consequential... more
ABSTRACT Constricted flow in a thin cylindrical shell with an idealized blunt constriction is modeled using ADINA. Highly disturbed recirculation region is observed at the constriction exit where pressure fluctuations and consequential vessel wall vibrations display broadband spectral content over a range of several hundred Hz. Maximum dynamic pressure and vibration amplitudes are observed around the reattachment point and they gradually decrease along downstream of flow. Results obtained by numerical simulations are compared with relevant studies in the literature and are in good agreement in terms of general spectral behavior. However, the amplitudes were significantly lower as compared to experimental results.