SIMULATION AND THEORETICAL STUDY OF SWIMMING AND RESISTIVE FORCES WITHIN GRANULAR MEDIA
- Project Research
- 1-5 Chapters
- Abstract : Available
- Table of Content: Available
- Reference Style: APA
- Recommended for : Student Researchers
- NGN 3000
ABSTRACT.
One way to investigate the physics of a medium is to study the forces on intruders moving through the media. A special case of intruders moving in media is the locomotion of organisms. Locomotion within fluids (flying in air and swimming in water) has been extensively studied and the complexity of interaction between intruders and fluids is well recognized. Locomotion within yielding substrates like sand, soil and debris that display both solid and fluid-like behavior has been less studied and is therefore less understood than to locomotion within fluids or on solid ground. In such materials, validated theories for describing the flow and resistive forces on intruders have not reached the levels of those for fluids. As a representative case of subsurface locomotion in granular media, we study on the undulatory sand-swimming of the sandfish lizard (Scincus scincus), a small (∼10 cm) desertdwelling lizard. We use numerical simulations and theoretical models of the interactions between granular media and simple objects, biological and robotic systems to reveal principles of undulatory locomotion in granular media. We also use the models to investigate the resistive forces on intruders with different orientations and shapes, which is essential for the understanding of locomotion ability and performance of locomotors. Previous experimental work using high speed x-ray imaging showed that the sandfish lizard swims within dry granular media without limb use by propagating a single period traveling sinusoidal wave along its body. The wave efficiency η, the ratio of the forward speed to the traveling wave speed, was approximately 0.5, independent of the packing state of the media (close and loose). To explain these results, we develop a resistive force model with empirical force laws to explain the swimming speed observed in the animal experiment. We show that the higher wave efficiency reached by the sandfish compared to the low Re swimmers (∼ 0.2) was because of the different functional form of the resistive forces on a rod dragged in granular media. We vary the ratio of undulation amplitude (A) to wavelength (λ) and demonstrate that an xii optimal waveform A/λ ≈ 0.2 for sand-swimming exists, which results from the competition between η and λ. To test assumptions in RFT and to study more detailed mechanics of sand-swimming, we developed a numerical model of the sandfish coupled to a discrete element method simulation of the granular medium. The numerical model confirmed that inertial forces are negligible and that the forces on the animal can be approximated by the forces on rods dragged at constant speed in granular media. The wave efficiency predicted by simulation qualitatively matched both the RFT model and the prediction of the optimal A/λ; However, the simulation revealed that the RFT over predicted the swimming speed because the reduction in magnitude of the resistive forces during velocity reversal was not considered. The RFT model and simulation helped the development of a sand-swimming robot, and the robot verified predictions from the RFT model and the simulation, such as the value of the wave efficiency, the actuator torque, and the effect of varying kinematic parameters including A/λ and number of periods. Inspired by the shovel-shaped head of the sandfish lizard, we studied the drag induced lift in granular media. We found that when a submerged intruder moves at a constant speed within a granular medium it experiences a lift force whose sign and magnitude depend on the intruder shape. We demonstrated that the lift forces and hence vertical position of the sand-swimming robot as it moves forward within granular media can be controlled by varying its head shape. The models together with robots explained biological observations of the kinematics of the animal and provide a hypothesis for the morphological adaptation (head shape) of the animal as well as guidance for building biophysically inspired robot that could explore challenging environments. The principles learned about the resistive forces can also help the design of the other machines that interact with granular media. My studies have given new insights into localized intrusion of simple and complex/composite shapes in granular media.
Related Project Materials
THE ROLE OF SOCIAL NETWORKING SITES ON POLITICAL CAMPAIGNS IN NIGERIA
ABSTRACT
The study looks at the role of social networking sites in political campaigns in Nigeria. It focuses on how politicians uses soc...
THE ECONOMIC IMPORTANCE OF BACTERIA IN THE ENVIRONMENT
Background of the Study
Environment is a comprehensive term, which comprises of all the factors which m...
THE ROLE OF VOCATIONAL EDUCATION IN SUPPORTING SUSTAINABLE AQUACULTURE PRACTICES
ABSTRACT: The role of vocational education in supporting sustainable aquaculture practices is critical for promoting environmentally friendly...
DETERMINATION OF OPTIMUM PACKAGING AND STORAGE PROPERTIES OF PACKAGED GARRI
ABSTRACT
This study was on the determination of optimum packaging and storage properties of packaged ga...
THE ROLE OF FORENSIC ACCOUNTANTS IN ASSET TRACING
Abstract: THE ROLE OF FORENSIC ACCOUNTANTS IN ASSET TRACING
This research explores the role of forensic accountants in asset tracing, foc...
FRAUD IN FINANCIAL INSTITUTION AND THE AUDITORS LIABILITY
BACKGROUND OF THE STUDY
The problem of fraud in financial institution in Nigeria has remained one of th...
TRADITIONAL MEDIA OF COMMUNICATION AS TOOLS FOR EFFECTIVE RURAL DEVELOPMENT
ABSTRACT
The study is a critical examination of the role of mass media in Traditional media of communication as tools fo...
STRUCTURAL DETAILING OF A REINFORCED CONCRETE STRUCTURE - DUPLEX,
INTRODUCTION
The work in the construction industry involves the client, the Architect, the Engineer, the quantity surve...
AN EXPLORATION OF INDUSTRY DEMAND FOR SPECIALIZED VOCATIONAL SKILLS
ABSTRACT: Addressing Industry Demand for Specialized Vocational Skills is critical for aligning vocational education with labor market needs....
INVESTIGATION OF THE HOUSING CONDITION AND SOCIO ECONOMIC LIFESTYLES OF SLUM DWELLERS IN AKURE NIGERIA
BACKGROUND TO THE STUDY
The poorest urban populations in Africa live in slums. Slum dwellers' homes are typically di...
