scholarly journals The performance of a flapping foil for a self-propelled fishlike body

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Damiano Paniccia ◽  
Luca Padovani ◽  
Giorgio Graziani ◽  
Renzo Piva
Keyword(s):  
Swimming Performance ◽  
Real Life ◽  
Minimum Cost ◽  
The Body ◽  
Cost Of Transport ◽  
Locomotion Speed ◽  
Optimal Efficiency ◽  
The One ◽  
The Cost ◽  
Flapping Foils

AbstractSeveral fish species propel by oscillating the tail, while the remaining part of the body essentially contributes to the overall drag. Since in this case thrust and drag are in a way separable, most attention was focused on the study of propulsive efficiency for flapping foils under a prescribed stream. We claim here that the swimming performance should be evaluated, as for undulating fish whose drag and thrust are severely entangled, by turning to self-propelled locomotion to find the proper speed and the cost of transport for a given fishlike body. As a major finding, the minimum value of this quantity corresponds to a locomotion speed in a range markedly different from the one associated with the optimal efficiency of the propulsor. A large value of the feathering parameter characterizes the minimum cost of transport while the optimal efficiency is related to a large effective angle of attack. We adopt here a simple two-dimensional model for both inviscid and viscous flows to proof the above statements in the case of self-propelled axial swimming. We believe that such an easy approach gives a way for a direct extension to fully free swimming and to real-life configurations.

scholarly journals The rising cost of warming waters: effects of temperature on the cost of swimming in fishes

2011 ◽  
Vol 8 (2) ◽  
pp. 266-269 ◽  
Author(s):  
Andrew M. Hein ◽  
Katrina J. Keirsted
Keyword(s):  
Water Temperature ◽  
Fish Species ◽  
Global Climate ◽  
Swimming Performance ◽  
Metabolic Cost ◽  
Quantitative Model ◽  
The Body ◽  
Energetic Cost ◽  
Cost Of Transport ◽  
The Cost

Understanding the effects of water temperature on the swimming performance of fishes is central in understanding how fish species will respond to global climate change. Metabolic cost of transport (COT)—a measure of the energy required to swim a given distance—is a key performance parameter linked to many aspects of fish life history. We develop a quantitative model to predict the effect of water temperature on COT. The model facilitates comparisons among species that differ in body size by incorporating the body mass-dependence of COT. Data from 22 fish species support the temperature and mass dependencies of COT predicted by our model, and demonstrate that modest differences in water temperature can result in substantial differences in the energetic cost of swimming.

The Metabolic Cost of Swimming in Ducks

1970 ◽  
Vol 53 (3) ◽  
pp. 763-777 ◽  
Author(s):  
HENRY D. PRANGE ◽  
KNUT SCHMIDT-NIELSEN
Keyword(s):  
Oxygen Consumption ◽  
Swimming Speed ◽  
Swimming Performance ◽  
Water Channel ◽  
Minimum Cost ◽  
Metabolic Cost ◽  
Power Input ◽  
Cost Of Transport ◽  
Overall Efficiency ◽  
The Cost

1. The metabolic cost of swimming was studied in mallard ducks (Anas platyrhynchos) which had been trained to swim steadily in a variable-speed water channel. 2. At speeds of from 0.35 to 0.50 m/sec the oxygen consumption remained relatively constant at approximately 2.2 times the resting level. At speeds of 0.55 m/sec and higher the oxygen consumption increased rapidly and reached 4.1 times resting at the maximum sustainable speed of 0.70 m/sec. 3. The maximum sustainable swimming speed of the ducks coincided with the limit predicted from hydrodynamic considerations of the water resistance of a displacement-hulled ship of the same hull length as a duck (0.33 m). 4. The cost of transport (metabolic rate/speed) reached a minimum of 5.77 kcal/kg km at a swimming speed of 0.50 m/sec. Ducks swimming freely on a pond were observed to swim at the speed calculated in experimental trials to give minimum cost of transport. 5. Drag measurements made with model ducks indicated a maximum overall efficiency (power output/power input) for the swimming ducks of about 5%. Ships typically have maximum efficiencies of 20-30%. Because of the difficulty in delimiting the cost of swimming activity alone from the other bodily functions of the duck, overall efficiency may present an incorrect description of the swimming performance of the duck relative to that of a ship. An hydrodynamic parameter such as speed/length ratio [speed/(hull length)½] whereby a duck excels conventional ships may present a more appropriate comparison.

Hydrodynamic drag in steller sea lions (Eumetopias jubatus)

2000 ◽  
Vol 203 (12) ◽  
pp. 1915-1923 ◽  
Author(s):  
L.L. Stelle ◽  
R.W. Blake ◽  
A.W. Trites
Keyword(s):  
Minimum Cost ◽  
The Body ◽  
Hydrodynamic Drag ◽  
Eumetopias Jubatus ◽  
Steller Sea Lions ◽  
California Sea Lions ◽  
Cost Of Transport ◽  
Sea Lions ◽  
Drag Forces ◽  
The Individual

Drag forces acting on Steller sea lions (Eumetopias jubatus) were investigated from ‘deceleration during glide’ measurements. A total of 66 glides from six juvenile sea lions yielded a mean drag coefficient (referenced to total wetted surface area) of 0.0056 at a mean Reynolds number of 5.5×10(6). The drag values indicate that the boundary layer is largely turbulent for Steller sea lions swimming at these Reynolds numbers, which are past the point of expected transition from laminar to turbulent flow. The position of maximum thickness (at 34 % of the body length measured from the tip of the nose) was more anterior than for a ‘laminar’ profile, supporting the idea that there is little laminar flow. The Steller sea lions in our study were characterized by a mean fineness ratio of 5.55. Their streamlined shape helps to delay flow separation, reducing total drag. In addition, turbulent boundary layers are more stable than laminar ones. Thus, separation should occur further back on the animal. Steller sea lions are the largest of the otariids and swam faster than the smaller California sea lions (Zalophus californianus). The mean glide velocity of the individual Steller sea lions ranged from 2.9 to 3.4 m s(−)(1) or 1.2-1.5 body lengths s(−)(1). These length-specific speeds are close to the optimum swim velocity of 1.4 body lengths s(−)(1) based on the minimum cost of transport for California sea lions.

scholarly journals Relations between morphology, buoyancy and energetics of requiem sharks

2016 ◽  
Vol 3 (10) ◽  
pp. 160406 ◽  
Author(s):  
Gil Iosilevskii ◽  
Yannis P. Papastamatiou
Keyword(s):  
Body Temperature ◽  
Negative Selection ◽  
Swimming Performance ◽  
Ontogenetic Changes ◽  
Cost Of Transport ◽  
Pectoral Fins ◽  
Confined Spaces ◽  
Reef Sharks ◽  
The Cost ◽  
Derivatives Of

Sharks have a distinctive shape that remained practically unchanged through hundreds of millions of years of evolution. Nonetheless, there are variations of this shape that vary between and within species. We attempt to explain these variations by examining the partial derivatives of the cost of transport of a generic shark with respect to buoyancy, span and chord of its pectoral fins, length, girth and body temperature. Our analysis predicts an intricate relation between these parameters, suggesting that ectothermic species residing in cooler temperatures must either have longer pectoral fins and/or be more buoyant in order to maintain swimming performance. It also suggests that, in general, the buoyancy must increase with size, and therefore, there must be ontogenetic changes within a species, with individuals getting more buoyant as they grow. Pelagic species seem to have near optimally sized fins (which minimize the cost of transport), but the majority of reef sharks could have reduced the cost of transport by increasing the size of their fins. The fact that they do not implies negative selection, probably owing to decreased manoeuvrability in confined spaces (e.g. foraging on a reef).

Solar Array and Battery Sizing for a Photovoltaic Building in Malaysia

2013 ◽  
Vol 64 (4) ◽  
Author(s):  
Hadi Nabipour Afrouzi ◽  
Saeed Vahabi Mashak ◽  
Zulkurnain Abdul-Malek ◽  
Kamyar Mehranzamir ◽  
Behnam Salimi
Keyword(s):  
Minimum Cost ◽  
Solar Irradiation ◽  
Solar Array ◽  
Pv System ◽  
Pv Array ◽  
Pv Module ◽  
Mathematical Equations ◽  
The One ◽  
The Right ◽  
The Cost

Renewable energy plays an important role in the national energy policy especially in reducing greenhouse gas emissions. For a photovoltaic (PV) system, one important consideration is the cost of the system. One needs to select the best PV array from a range of selection, that is, the one which is the most efficient and with a best price. This article illustrates a method to compute the size and cost of a required PV array, and then after to compute the required battery for the case of a photovoltaic building in Malaysia. The computation is simulated using Matlab integrated with suitable mathematical equations. The generated current and power of the PV array are calculated for daily solar irradiation in Malaysia. The computation enables the user to quickly compute the initial cost needed to be spent if a given PV system is to be installed. A typical building requiring 12 kWh daily energy with 6 kW peak demand load was shown to need at least 114 solar modules at a cost of about RM53k. It is noted that the main cost of the whole PV system is mainly contributed by the cost of the chosen PV array. Hence, the right choice of a PV module is vital in achieving the minimum cost.

scholarly journals A Framework for Modeling "Real-Life" Airline Networks

2009 ◽  
Vol 8 (3) ◽  
Author(s):  
Volodymyr Bilotkach
Keyword(s):  
Airline Industry ◽  
Real Life ◽  
Cost Savings ◽  
Hub And Spoke ◽  
Mixed Network ◽  
One Stop ◽  
Set Up ◽  
Point To Point ◽  
The One ◽  
The Cost

This paper develops a new model, which allows for the co-existence of hub-and-spoke and point-to-point networks in the airline industry. Passengers are segmented between the non-stop and one-stop services. In the baseline model, the monopoly airline’s ability to segment the market and effectively set up the mixed network depends on the cost savings due to the through-hub service relative to exogenous quality difference between the one-stop and non-stop flights. Socially inefficient entry with the new non-stop service where an incumbent is operating the hub-and-spoke network is possible.

scholarly journals Simulated hemiparesis increases optimal spatiotemporal gait asymmetry but not metabolic cost

2021 ◽  
Author(s):  
Russell T Johnson ◽  
Nicholas August Bianco ◽  
James Finley
Keyword(s):  
Gait Speed ◽  
Metabolic Cost ◽  
The Body ◽  
Musculoskeletal Modeling ◽  
Cost Of Transport ◽  
Gait Patterns ◽  
Post Stroke ◽  
The Cost ◽  
Future Work ◽  
Isometric Muscle

Several neuromuscular impairments, such as weakness (hemiparesis), occur after an individual has a stroke, and these impairments primarily affect one side of the body more than the other. Predictive musculoskeletal modeling presents an opportunity to investigate how a specific impairment affects gait performance post-stroke. Therefore, our aim was to use to predictive simulation to quantify the spatiotemporal asymmetries and changes to metabolic cost that emerge when muscle strength is unilaterally reduced. We also determined how forced spatiotemporal symmetry affects metabolic cost. We modified a 2-D musculoskeletal model by uniformly reducing the peak isometric muscle force in all muscles unilaterally. We then solved optimal control simulations of walking across a range of speeds by minimizing the sum of the cubed muscle excitations across all muscles. Lastly, we ran additional optimizations to test if reducing spatiotemporal asymmetry would result in an increase in metabolic cost. Our results showed that the magnitude and direction of effort-optimal spatiotemporal asymmetries depends on both the gait speed and level of weakness. Also, the optimal metabolic cost of transport was 1.25 m/s for the symmetrical and 20% weakness models but slower (1.00 m/s) for the 40% and 60% weakness models, suggesting that hemiparesis can account for a portion of the slower gait speed seen in people post-stroke. Adding spatiotemporal asymmetry to the cost function resulted in small increases (~4%) in metabolic cost. Overall, our results indicate that spatiotemporal asymmetry may be optimal for people post-stroke, who have asymmetrical neuromuscular impairments. Additionally, the effect of speed and level of weakness on spatiotemporal asymmetry may explain the well-known heterogenous distribution of spatiotemporal asymmetries observed in the clinic. Future work could extend our results by testing the effects of other impairments on optimal gait strategies, and therefore build a more comprehensive understanding of the gait patterns in people post-stroke.

A qualitative study of the optimal control model for an electric power generating system

2012 ◽  
Vol 23 (2) ◽  
pp. 65-72
Author(s):  
Yidiat O. Aderinto ◽  
Mathias O. Bamigbola
Keyword(s):  
Optimal Control ◽  
Electric Power ◽  
Real Life ◽  
Minimum Cost ◽  
Fuel Cost ◽  
Transmission Losses ◽  
Factors Affecting ◽  
Real Life Data ◽  
The Cost ◽  
Generating System

The economic independence of any nation depends largely on the supply of abundant and reliable electric power and the extension of electricity services to all towns and villages in the country. In this work, the mathematical study of an electric power generating system model was presented via optimal control theory, in an attempt to maximize the power generating output and minimize the cost of generation. The factors affecting power generation at minimum cost are operating efficiencies of generators, fuel cost and transmission losses, but the most efficient generator in the system may not guarantee minimum cost as it may be located in an area where fuel cost is high. We choose the generator capacity as our control ui(t), since we cannot neglect the operation limitation on the equipment because of its lifespan, the upper bound for ui(t) is choosing to be 1 to represent the total capability of the machine and 0 to be the lower bound. The model is analyzed, generation loss free equilibrium and stability is established, and finally applications using real life data is presented using one generator and three generator systems respectively.

scholarly journals Modelling the project transport support optimal option

2021 ◽  
Vol 1 (2(57)) ◽  
pp. 43-48
Author(s):  
Svitlana Rusanova ◽  
Varvara Piterska ◽  
Svitlana Onyshchenko
Keyword(s):  
Large Scale ◽  
Research Result ◽  
Optimization Criterion ◽  
Project Planning ◽  
Cost Of Transport ◽  
Logistics System ◽  
Complete Control ◽  
Transport Services ◽  
The One ◽  
The Cost

The object of research is the processes of planning transport provision of projects. The vast majority of projects involve the creation of tangible objects as a product. The implementation of such projects is associated with the use of various types of materials and equipment, which necessitates transport services for the functioning of the project logistics system. Vehicles with different characteristics can be used to solve the same transportation problems. Also, for large-scale infrastructure projects, rental of vehicles is often used for the duration of the project. This allows, on the one hand, to save on transportation costs, on the other hand, to gain complete control over the transportation processes in the project. As a research result, an optimization model has been developed for determining the option of transport support for the project. The variant of transport support of the project is understood as a set of combinations of types and types of vehicles, their characteristics and conditions of use in the project for the work of the project that provide for transport services. Acquisition, lease or transport services from the project suppliers are considered as conditions for the use of vehicles in the project. The optimization criterion is the cost of transport support, taking into account their possible increase, as well as the potential risks of losses associated with the failure to complete the work. Constraints take into account costs, time to receive a project product, and availability of transportation options. Experimental calculations, a fragment of which is presented in the research, demonstrated the efficiency of the developed model, its adequacy and reliability of the results obtained with its help. The area of practical use of the model is making decisions about transportation at the stage of project planning. The model allows for «what-if» experiments, which reflect various scenarios that are possible in the transportation of the project. And this, in turn, allows at the stage of project planning to assess the possible risks associated with transportation, and to establish their impact on the project as a whole.

scholarly journals Bioenergetic and kinematic consequences of limblessness in larval Diptera

1993 ◽  
Vol 179 (1) ◽  
pp. 245-259 ◽  
Author(s):  
D. Berrigan ◽  
J. R. Lighton
Keyword(s):  
Minimum Cost ◽  
Cost Of Transport ◽  
Terrestrial Locomotion ◽  
Contraction Frequency ◽  
Fly Larvae ◽  
The Cost ◽  
Peristaltic Contractions ◽  
The Relationship ◽  
Very High ◽  
Kinematic Properties

We report the cost of transport and kinematics of terrestrial locomotion by larval blowflies (Protophormia terraenovae, Diptera: Calliphoridae). We contrast inter- and intra-individual methods for estimating minimum cost of transport (MCOT) and the relationship between speed, contraction frequency and distance traveled per contraction. The minimum cost of transport calculated from intra-individual data is 2297 +/− 317 J kg-1 m-1 (S.E.M.) and the MCOT calculated from inter-individual comparisons is statistically indistinguishable at 1910 +/− 327 J kg-1 m-1. These values are almost ten times higher than the predicted value for a similar-sized limbed arthropod. Fly larvae travel by repeated peristaltic contractions and individual contractions cost about the same amount as individual strides in limbed insects. Both contraction frequency and distance traveled per contraction increase linearly with speed. Doubling the contraction frequency or the distance traveled per contraction approximately doubles speed. The cost of transport in fly larvae is among the highest recorded for terrestrial locomotion, confirming the suggestion that biomechanical and kinematic properties of limbless organisms with hydraulic skeletons lead to very high costs of transport.

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