Hydrodynamic behaviors of self-propelled sperms in confined spaces

Animal flight represents a great challenge and model for biomimetic design efforts. Powered flight at low speeds requires not only appropriate lifting surfaces (wings) and actuator (engine), but also an advanced sensory control system to allow maneuvering in confined spaces, and take-off and landing. Millions of years of evolutionary tinkering has resulted in modern birds and bats, which are achieve controlled maneuvering flight as well as hovering and cruising flight with trans-continental non-stop migratory flights enduring several days in some bird species. Unsteady aerodynamic mechanisms allows for hovering and slow flight in insects, birds and bats, such as for example the delayed stall with a leading edge vortex used to enhance lift at slows speeds. By studying animal flight with the aim of mimicking key adaptations allowing flight as found in animals, engineers will be able to design micro air vehicles of similar capacities.

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Coupled Thermal Radiation and Mixed Convection Step Flow of Nongray Gas

Journal of Heat Transfer ◽

10.1115/1.4033095 ◽

2016 ◽

Vol 138 (7) ◽

Cited By ~ 8

Author(s):

M. Atashafrooz ◽

S. A. Gandjalikhan Nassab ◽

K. Lari

Keyword(s):

Mixed Convection ◽

Radiative Transfer Equation ◽

Convection Flow ◽

Mixed Convection Flow ◽

Discrete Ordinate ◽

Full Spectrum ◽

Step Flow ◽

Laminar Mixed Convection ◽

Gray Medium ◽

Hydrodynamic Behaviors

The main goal of this paper is to analyze the thermal and hydrodynamic behaviors of laminar mixed convection flow of a nongray radiating gas over an inclined step in an inclined duct. The fluid is considered an air mixture with 10% CO2 and 20% H2O mole fractions, which is treated as homogeneous, absorbing, emitting, and nonscattering medium. The full-spectrum k-distribution (FSK) method is used to handle the nongray part of the problem, while the radiative transfer equation (RTE) is solved using the discrete ordinate method (DOM). In addition, the results are obtained for different medium assumptions such as pure mixed convection and gray medium to compare with the nongray calculations as a real case. The results show that in many cases, neglecting the radiation part in computations and also use of gray simulations are not acceptable and lead to considerable errors, especially at high values of the Grashof number in mixed convection flow.

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Intelligent Exploration and Autonomous Navigation in Confined Spaces

2020 IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS) ◽

10.1109/iros45743.2020.9341525 ◽

2020 ◽

Author(s):

Aliakbar Akbari ◽

Puneet S Chhabra ◽

Ujjar Bhandari ◽

Sara Bernardini

Keyword(s):

Autonomous Navigation ◽

Confined Spaces

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A Magneto-Active Elastomer Crawler with Peristaltic and Caterpillar Locomotion Patterns

Actuators ◽

10.3390/act10040074 ◽

2021 ◽

Vol 10 (4) ◽

pp. 74

Author(s):

Tsam Lung You ◽

Hemma Philamore ◽

Fumitoshi Matsuno

Keyword(s):

Magnetic Field ◽

Experimental Data ◽

External Magnetic Field ◽

Mathematical Models ◽

Confined Spaces ◽

Low Mass ◽

Structural Simplicity

In this work we present a soft crawler fabricated using a magneto-active elastomer. The crawler is controlled by an external magnetic field to produce two locomotion patterns: peristaltic and caterpillar crawling. Due to its structural simplicity, low mass, wirelessly controlled actuation and compliant body the design of this crawler has the potential to address the key challenges faced by existing crawling robots. Experimental data were gathered to evaluate the performance of the crawler locomotion in a pipe. The results validated the mathematical models proposed to estimate the distance traveled by the crawler. The crawler shows potential for use in exploration of confined spaces.

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