Physically Based Animation of sea Anemones in Real-Time

This paper presents a technique for modeling and animating fiberlike objects such as sea anemones tentacles in real-time. Each fiber is described by a generalized cylinder defined around an articulated skeleton. The dynamics of each individual fiber is controlled by a physically based simulation that updates the position of the skeleton’s frames over time. We take into account the forces generated by the surrounding fluid as well as a stiffness function describing the bending behavior of the fiber. High level control of the animation is achieved through the use of four types of singularities to describe the three-dimensional continuous velocity field representing the fluid. We thus animate hundreds of fibers by key-framing only a small number of singularities. We apply this algorithm on a seascape composed of many sea anemones. We also show that our algorithm is more general and can be applied to other types of objects composed of fibers such as seagrasse

Mechanics of a Plant in Fluid Flow

Plants live in constantly moving fluid, whether air or water. In response to the loads associated with fluid motion, plants bend and twist, often with great amplitude. These large deformations are not found in traditional engineering application and thus necessitate new specialised scientific developments. Studying Fluid-Structure Interactions (FSI) in botany, forestry and agricultural science is crucial to the optimisation of biomass production for food, energy, and construction materials. FSI are also central in the study of the ecological adaptation of plants to their environment. This review paper surveys the mechanics of FSI on individual plants. We present a short refresher on fluids mechanics then dive in the statics and dynamics of plant-fluid interactions. For every phenomenon considered, we present the appropriate dimensionless numbers to characterise the problem, discuss the implications of these phenomena on biological processes, and propose future research avenues. We cover the concept of reconfiguration while considering poroelasticity, torsion, chirality, buoyancy, and skin friction. We also cover the dynamical phenomena of wave action, flutter, and vortex-induced vibrations.Comment: 26 pages, 8 figure

CREATING DYNAMIC GRASS FOR \u3ci\u3eTARTAN TROUBLES\u3c/i\u3e

In computer animated movies, the setting and its environmental elements aid in storytelling. In Tartan Troubles, dynamic grass was created as a part of the highlands of Scotland set. This thesis discusses the importance of environmental elements in animation as well as the terminology, procedures, and techniques used to produce dynamic grass as seen in the animated short, Tartan Troubles. The scalability, control, and flexibility of the dynamic grass pipeline make this effect applicable for various solutions in computer animation

Tropical biogeomorphic seagrass landscapes for coastal protection:Persistence and wave attenuation during major storms events

The intensity of major storm events generated within the Atlantic Basin is projected to rise with the warming of the oceans, which is likely to exacerbate coastal erosion. Nature-based flood defence has been proposed as a sustainable and effective solution to protect coastlines. However, the ability of natural ecosystems to withstand major storms like tropical hurricanes has yet to be thoroughly tested. Seagrass meadows both stabilise sediment and attenuate waves, providing effective coastal protection services for sandy beaches. To examine the tolerance of Caribbean seagrass meadows to extreme storm events, and to investigate the extent of protection they deliver to beaches, we employed a combination of field surveys, biomechanical measurements and wave modelling simulations. Field surveys of sea- grass meadows before and after a direct hit by the category 5 Hurricane Irma documented that estab- lished seagrass meadows of Thalassia testudinum re- mained unaltered after the extreme storm event. The flexible leaves and thalli of seagrass and calci- fying macroalgae inhabiting the meadows were shown to sustain the wave forces that they are likely to experience during hurricanes. In addition, the seagrass canopy and the complex biogeomorphic landscape built by the seagrass meadows combine to significantly dissipate extreme wave forces, ensuring that erosion is minimised within sandy beach fore- shores. The persistence of the Caribbean seagrass meadows and their coastal protection services dur- ing extreme storm events ensures that a stable coastal ecosystem and beach foreshore is maintained in tropical regions

Mean Flow and Turbulence in a Laboratory Channel with Simulated Vegatation (HES 51)

U.S. Army Corps of Engineers, Waterways Experiment Station (Contract DACW39-94-K-0010)unpublishednot peer reviewe

Simulation levels of detail for plant motion

In this paper we describe a method for simulating motion of realistically complex plants interactively. We use a precomputation stage to generate the plant structure, along with a set of simulation levels of detail. The levels of detail are made by continuously grouping branches starting from the tips of the branches and working toward the trunk. Grouped branches are simulated as single branches that have similar simulation characteristics to the original branches. During run-time, we traverse the plant and determine the allowable error in the simulation of branch motion. This allows us to choose the appropriate simulation level of detail and we provide smooth transitions from level to level. Our level of detail approach affects only the simulation parameters, allowing geometry to be handled independently. Using this method we can significantly improve simulation times for complex trees

Foundation Effects of Trees Under Wind Loads

Winching tests were conducted on a mature 24-year-old Norway spruce tree. The tree was instrumented with strain gauges along the root structure and tilt sensors along the tree stem and was winched to failure. Tracked tree-root system response to failure load and the material properties of the tree-root-soil system were used to examine the applicability of simple engineering principles to tree stability analysis. Tree stability was studied using the principles of Winkler foundation model for the first time. In order to study the very complex windthrow phenomenon, a novel experimental technique was used. Tree saplings with complete structural root systems were placed in a custom built planter box fitted into wind tunnel floor and were tested to failure in the wind tunnel with clay or sand as soil media. Tree stem and roots were instrumented with strain gauges, accelerometers and high efficiency sensors. Tests were conducted with change in tree root architecture, soil and increase in wind loads. Rigorous analysis of the wind tunnel tests data gave a better understanding on dynamics of tree root soil interaction and soil root anchorage mechanics. Tree sway, damping, natural frequency and admittance estimates of tree-root system with increase in wind loading were made for the first time in this thesis. Geometric, elastic and stress similitude and dimensionless scaling parameters between the mature tree and saplings were examined. Dynamic loading and the resulting tree sapling response were analyzed in detail through rainflow technique. Static and dynamic load response was compared in detail through secant modulus of elasticity and dynamic load factor. The trenching effect on tree stability was also studied using wind tunnel testing. This study also supports the current trenching guidelines with the support of vigorous tree sapling response analysis in different soil media with increase in trenching volumes and wind load. Very different yet similar tree response was observed with change in soil media, downplaying the effect of soil strength on tree stability in windthrow researc

Visual anemometry: physics-informed inference of wind for renewable energy, urban sustainability, and environmental science

Accurate measurements of atmospheric flows at meter-scale resolution are essential for a broad range of sustainability applications, including optimal design of wind and solar farms, safe and efficient urban air mobility, monitoring of environmental phenomena such as wildfires and air pollution dispersal, and data assimilation into weather and climate models. Measurement of the relevant microscale wind flows is inherently challenged by the optical transparency of the wind. This review explores new ways in which physics can be leveraged to "see" environmental flows non-intrusively, that is, without the need to place measurement instruments directly in the flows of interest. Specifically, while the wind itself is transparent, its effect can be visually observed in the motion of objects embedded in the environment and subjected to wind -- swaying trees and flapping flags are commonly encountered examples. We describe emerging efforts to accomplish visual anemometry, the task of quantitatively inferring local wind conditions based on the physics of observed flow-structure interactions. Approaches based on first-principles physics as well as data-driven, machine learning methods will be described, and remaining obstacles to fully generalizable visual anemometry will be discussed.Comment: In revie

Computational Modelling of the Coastal Protection Function of Salt Marshes with Flexible Vegetation Cover

Salt marshes are intertidal coastal wetlands that are typically found in sheltered locations such as estuaries. They exhibit a diverse vegetation cover with flexible grasses and rigid shrubs. This vegetation provides coastal protection by attenuat-ing currents and waves. Unlike traditional hard defences, they offer co-benefits by stabilising shorelines and enhancing natural habitats. However, it has remained unclear how salt marshes with a flexible vegetation cover contribute to coastal protection under storms with surge and wave components.In this thesis, I have developed a new coupled current-wave-vegetation model which includes the effect of vegetation flexibility on wave attenuation. The wave-vegetation model builds on novel laboratory experiments using artificial vegeta-tion in the Swansea University Wave Flume, where wave damping, water velocity fields, and plant motion were measured simultaneously for the first time. A new work factor is introduced to explicitly account for vegetation flexibility in compu-tational models. Furthermore, a momentum sink term parameterisation is found to best resemble current-vegetation interactions. The advanced coupled model is successfully applied to simulate flood risk in the Taf Estuary under six contrast-ing vegetation scenarios.My results highlight how the vegetation cover affects the coastal protection pro-vided by salt marshes. All modelled vegetation species constrain flood currents to the main estuary channel and damp incoming waves. Although flexible grasses are 50% less effective in wave damping than rigid shrubs in the Taf Estuary. The wave conditions, wind conditions and local topography further affect the protec-tion provided. Additionally, rigid species can amplify orbital velocities above the canopy by inducing wave-averaged currents, but flexible species do not.It is recommended that the biomechanical properties of vegetation, including the flexibility, are included when modelling the coastal protection by salt marshes. My new computational modelling framework provides evidence to support the continuing uptake of salt marshes as sustainable coastal defences