Mechanics of ostraciiform propulsion

1981 ◽  
Vol 59 (6) ◽  
pp. 1067-1071 ◽  
Author(s):  
R. W. Blake
Keyword(s):  
Drag Coefficient ◽  
Drag Force ◽  
Thrust Force ◽  
The Body ◽  
Small Specimen ◽  
Caudal Fin ◽  
Drag Coefficients ◽  
Order Of Magnitude ◽  
Tail Beat

Two hydromechanical models are employed to analyse the motions of the caudal fin of a small specimen of Ostracion lentiginosum (Ostraciidae). Values of the drag coefficient of the body of the fish are inferred by equating the impulse of the thrust force produced over the tail beat cycle with the impulse of the drag force acting on the body over the same period of time. On average, the inferred values for the drag coefficient are within 15% of experimentally determined values. Drag coefficients for ostraciiform fish are an order of magnitude greater than those for streamlined fish. The hydromechanical efficiency of the caudal fin propeller of O. lentiginosum is calculated to be of the order of 0.5. This result is predicted by the hydromechanical theory.

scholarly journals Modelling of Drag Force Reduction for a Waterjet Propulsion System

2021 ◽  
Vol 58 (5) ◽  
pp. 3-14
Author(s):  
M. Cerpinska ◽  
M. Irbe ◽  
A. Pupurs ◽  
K. Burbeckis
Keyword(s):  
Drag Coefficient ◽  
Drag Force ◽  
Velocity Ratio ◽  
The Body ◽  
Inlet Velocity ◽  
Minimum Drag ◽  
Simulation Results ◽  
Force Reduction ◽  
Design Options ◽  
Coefficient Reduction

Abstract The paper provides simulation results for SUP (Stand Up Paddle) board appendage resistance. Additional propulsion is added to the SUP board. It is equipped with a waterjet. The waterjet is attached to the board rudder. This increases the drag coefficient for rudder five times. To reduce the drag variable, design options for the waterjet duct were proposed. The simulation tests were performed using SolidWorks Flow software using two types of simulations, namely, the pressure on the body and the flow around the body. The objective was to streamline the bluff duct of the waterjet and thus to create the appendage design with minimum drag force from fluid flow and possibly greater Inlet Velocity Ratio. Calculations showed that rounding-off the edges of waterjet duct resulted in 35 % of drag coefficient reduction, while further streamlining reduced it by additional 10 %.

scholarly journals Preliminary study of software tracker usage to analyze inhibitory style on free fall movie events

2018 ◽  
Vol 197 ◽  
pp. 02012
Author(s):  
Seni Susanti ◽  
Ea Cahya Septia Mahen ◽  
Ade Yeti Nuryantini
Keyword(s):  
Drag Coefficient ◽  
Drag Force ◽  
Free Fall ◽  
Force Analysis ◽  
Drag Coefficients ◽  
Drag Forces ◽  
Preliminary Study ◽  
Free Falling ◽  
Good Agreement

This paper presents drag force analysis of free falling object using software tracker. We use video cupclips that have been embedded in this software. The video featured cupcakes to which hung a number of different paper clips were dropped simultaneously. We track the trajectory of free falling cupclips using the software to get the information of position, speed, and acceleration of each cupcake against time. From the data we get the value of drag forces and drag coefficients for each time. The result shows that the drag force value increased to almost constant value, otherwise the drag coefficient is reduced to almost constant values well. According to the results, the analyzed data has good agreement with the theory. Thus, software tracker can be used as media to learn drag force easily and inexpensively.

scholarly journals ‘Steady’ Swimming Kinematics of Tiger Musky, an Esociform Accelerator, and Rainbow Trout, a Generalist Cruiser

1988 ◽  
Vol 138 (1) ◽  
pp. 51-69 ◽  
Author(s):  
PAUL W. WEBB
Keyword(s):  
Rainbow Trout ◽  
Lateral Displacement ◽  
Phase Relationship ◽  
Total Body Length ◽  
The Body ◽  
Salmo Gairdneri ◽  
Trailing Edge ◽  
Drag Coefficients ◽  
Total Body ◽  
Tail Beat

Locomotor kinematics of tiger musky (Esox sp.) and rainbow trout (Salmo gairdneri) were measured at ‘steady’ swimming speeds of up to 85 cm s−1. Tail beat frequencies of musky were approximately 2 Hz higher than those of trout at any swimming speed, but tail beat amplitudes were 0.04L (where L is total body length) smaller. The product of these two variables was similar for the two species at any speed. The length of the propulsive wave was independent of speed, and was 0.8L for musky, somewhat smaller than the value for trout, 0.9L. The depth of the caudal fin trailing edge of trout was greater than that of musky, but the greater depth of the posteriorly located median fins of musky also contributed to thrust production. The cosine of the angle of the trailing edge to its beat plane showed the same phase relationship with lateral displacement in both musky and trout. It increased with speed for both species, and values for musky were slightly smaller. Thrust power requirements of musky and trout were similar. Thrust (= drag) coefficients of musky were 1.55 times larger than those for trout: this is roughly as expected on the basis of the larger proportion of the total area of musky located caudally and the higher drag coefficients in this region of the body. Lateral recoil movements of musky were unexpectedly smaller than for trout and were associated with smaller energy wastage from undamped recoil movements. The large recoil expected for the body form of musky was damped to some extent by higher tail beat frequencies, although this entailed some loss in Froude efficiency. Otherwise, no hydrodynamic explanation for the small recoil movements of musky was apparent. It is suggested that the myotomal muscles could be involved in minimizing recoil. The esociform morphology incurs costs in steady swimming, in comparison with generalist cruises, because of reduced sprint speeds for fish of a given length or increased power requirements for fish of a given mass.

scholarly journals Influence of the Diffuser on the Drag Coefficient of a Solar Car

2020 ◽  
Vol 22 (2) ◽  
pp. 509-520
Author(s):  
Paula Mierzejewska ◽  
Artur Cieśliński ◽  
Daniel Jodko
Keyword(s):  
Drag Coefficient ◽  
Pressure Distribution ◽  
Drag Force ◽  
Lift Force ◽  
The Body ◽  
Cfd Simulations ◽  
Car Body ◽  
Ansys Cfx

AbstractThe purpose of the research was to design a solar vehicle for Bridgestone World Solar Challenge competition which takes place biannually in Australia. The article, however, presents the aerodynamic research on the car body, especially on the exit diffuser. Numerous CFD simulations of different diffuser shapes were performed in ANSYS CFX software. The paper presents the results of pressure distribution on the body and velocity contours. The drag force acting on the car body is dependent on the pressure distribution. The article includes comparison of corresponding drag coefficient values for different cases. Furthermore, the variation of the lift force depending on the shape of the bodywork was also taken into consideration. The research shows that slight differences in the construction of the exit diffuser correspond to noticeable changes in the drag coefficient values (0.138 minimum, 0.168 maximum) and significant changes in the lift force (minimum 71 N, maximum 160 N).

Gliding flight: drag and torque of a hawk and a falcon with straight and turned heads, and a lower value for the parasite drag coefficient

2000 ◽  
Vol 203 (24) ◽  
pp. 3733-3744 ◽  
Author(s):  
V.A. Tucker
Keyword(s):  
Wind Tunnel ◽  
Mathematical Models ◽  
Drag Coefficient ◽  
High Speed ◽  
Aerodynamic Drag ◽  
The Body ◽  
Head Turning ◽  
Drag Coefficients ◽  
Spiral Path ◽  
Gliding Flight

Raptors - falcons, hawks and eagles in this study - such as peregrine falcons (Falco peregrinus) that attack distant prey from high-speed dives face a paradox. Anatomical and behavioral measurements show that raptors of many species must turn their heads approximately 40 degrees to one side to see the prey straight ahead with maximum visual acuity, yet turning the head would presumably slow their diving speed by increasing aerodynamic drag. This paper investigates the aerodynamic drag part of this paradox by measuring the drag and torque on wingless model bodies of a peregrine falcon and a red-tailed hawk (Buteo jamaicensis) with straight and turned heads in a wind tunnel at a speed of 11.7 m s(−)(1). With a turned head, drag increased more than 50 %, and torque developed that tended to yaw the model towards the direction in which the head pointed. Mathematical models for the drag required to prevent yawing showed that the total drag could plausibly more than double with head-turning. Thus, the presumption about increased drag in the paradox is correct. The relationships between drag, head angle and torque developed here are prerequisites to the explanation of how a raptor could avoid the paradox by holding its head straight and flying along a spiral path that keeps its line of sight for maximum acuity pointed sideways at the prey. Although the spiral path to the prey is longer than the straight path, the raptor's higher speed can theoretically compensate for the difference in distances; and wild peregrines do indeed approach prey by flying along curved paths that resemble spirals. In addition to providing data that explain the paradox, this paper reports the lowest drag coefficients yet measured for raptor bodies (0.11 for the peregrine and 0.12 for the red-tailed hawk) when the body models with straight heads were set to pitch and yaw angles for minimum drag. These values are markedly lower than value of the parasite drag coefficient (C(D,par)) of 0.18 previously used for calculating the gliding performance of a peregrine. The accuracy with which drag coefficients measured on wingless bird bodies in a wind tunnel represent the C(D,par) of a living bird is unknown. Another method for determining C(D,par) selects values that improve the fit between speeds predicted by mathematical models and those observed in living birds. This method yields lower values for C(D,par) (0.05-0.07) than wind tunnel measurements, and the present study suggests a value of 0.1 for raptors as a compromise.

Numerical Evaluation of AASHTO Drag Force Coefficients of Water Flow Around Bridge Piers

2017 ◽  
Vol 139 (2) ◽  
Author(s):  
Amin Almasri ◽  
Shadi Moqbel
Keyword(s):  
Drag Coefficient ◽  
Drag Force ◽  
Bridge Piers ◽  
Design Codes ◽  
Force Coefficient ◽  
Drag Coefficients ◽  
Design Specifications ◽  
A Value ◽  
Similar Range ◽  
Aashto Lrfd

Drag force is usually exerted on bridge piers due to running river water. This force is calculated empirically based on drag coefficients stated in design codes and specifications. Different values of drag coefficients have been reported in literature. For example, AASHTO LRFD Bridge Design Specifications uses a drag coefficient of 1.4 and 0.7 for square-ended and semicircular-nosed pier, respectively, while Coastal Construction Manual (FEMA P-55) recommends a value of two and 1.2 for square and round piles, respectively. In addition, many researchers have obtained other different values of drag coefficient under similar conditions (i.e., similar range of Reynolds number) reaching to 2.6 for square object. The present study investigates the drag coefficient of flow around square, semicircular-nosed, and 90 deg wedged-nosed and circular piers numerically using finite element method. Results showed that AASHTO values for drag force coefficient varied between very conservative to be under-reckoning. The study recommends that AASHTO drag coefficient values should be revised for different circumstances and under more severe conditions.

scholarly journals Rancang Bangun Body Fibercarbon dan Simulasi Aerodinamis dengan Ansys untuk Mobil Hemat Energi Kategori Prototype

2021 ◽  
Vol 5 (2) ◽  
pp. 90
Author(s):  
Yusuf Eko Nurcahyo ◽  
Pongky Lobas Wahyudi
Keyword(s):  
Drag Coefficient ◽  
Drag Force ◽  
Lift Force ◽  
Lift Coefficient ◽  
Maximum Velocity ◽  
Simulation Software ◽  
The Body ◽  
Maximum Pressure ◽  
Body Type ◽  
Carbon Fiber Material

<p><em>Body is one of mandatory components for the main vehicle, which is a car because the face of the car is located on the body. Moreover, the car used for the body competition must not only be good visually but also have to look at its aerodynamics. In this study, discussing the aerodynamics of a prototype energy-efficient car body with carbon fiber material before it is produced and applied it must first be simulated aerodynamically on an aerodynamic simulation software. The vehicle to be simulated uses a 1:1 scale assuming the actual conditions. From the simulations carried out by the three body type models, the results are Model 1 with maximum Velocity of 64.0925 m/s and a maximum pressure of 1663.09 Pa and a Drag coefficient of: 309.85976, Lift coefficient of: 125.52961, Drag force of : 189.7891 N and Lift force of: 76.886889 N. Model 2 with a maximum Velocity of 58.14 m/s and a maximum pressure of 1350.55 Pa, Drag coefficient of : 399.09712, Lift coefficient of: 455.23564 , Drag force of : 244.44699N and Lift force of: 278.83183 N. Model 3 with a maximum Velocity of 59.8387 m/s and a maximum pressure of 1136.72 Pa, Drag coefficient of : 610,89875, Lift coefficient of: 764,99562, Drag force of: 374,17548 N and Lift force of: 468,55982 N. Based on results analysis using ansys software, Model 1 was chosen because it has the smallest Drag Coefficient, Lift Coefficient, Drag Force and Lift Force.</em></p>

scholarly journals Normal and Tangential Drag Forces of Nylon Nets, Clean and with Fouling, in Fish Farming. An Experimental Study

Water ◽  
2020 ◽  
Vol 12 (8) ◽  
pp. 2238
Author(s):  
Yarko Niño ◽  
Kevin Vidal ◽  
Aldo Tamburrino ◽  
Luis Zamorano ◽  
Juan Felipe Beltrán ◽  
...  
Keyword(s):  
Reynolds Number ◽  
Drag Coefficient ◽  
Drag Force ◽  
Fish Farming ◽  
Operating Conditions ◽  
Relevant Parameter ◽  
Sea Lion ◽  
Drag Coefficients ◽  
Average Value ◽  
Drag Forces

Experiments in a laboratory tank have provided measurements of the normal and tangential drag forces exerted on flat nets for different flow conditions. From those forces, normal and tangential drag coefficients of the nets have been obtained as functions of the Reynolds number and the solidity index. The experiments used two types of nets employed in the operation of a cultivation center: the fish net and the sea lion net, for the clean situation and for real operating conditions, with fouling adhered to the nets. Polyethylene ropes were used to characterize the presence of fouling in the nets. The experiments were carried out to determine equations for the normal and tangential drag coefficients. For the normal drag coefficient, the equations are linear with the Reynolds number, and the coefficients of the equations are linear with the solidity index. The equations are not so accurate for the tangential drag coefficient. The Reynolds number is not a relevant parameter for this coefficient and neither is the solidity index for the fish net, but the coefficient grows slightly with it for single and double sea lion nets with fouling. The literature review on the drag forces of nets reports that the tangential drag force is around 30% of the normal drag force. This value is approximately an average value of the ratio for the sea lion net and is higher for the clean fish net in this article.

On the origin of the drag force on dimpled spheres

2019 ◽  
Vol 879 ◽  
pp. 147-167 ◽  
Author(s):  
Nikolaos Beratlis ◽  
Elias Balaras ◽  
Kyle Squires
Keyword(s):  
Reynolds Number ◽  
Numerical Simulations ◽  
Drag Coefficient ◽  
Drag Force ◽  
Direct Numerical Simulations ◽  
Critical Regime ◽  
Drag Coefficients ◽  
Wall Flow ◽  
Smooth Sphere ◽  
Near Wall

It is well established that dimples accelerate the drag crisis on a sphere. The result of the early drag crisis is a reduction of the drag coefficient by more than a factor of two when compared to a smooth sphere at the same Reynolds number. However, when the drag coefficients for smooth and dimpled spheres in the post-critical regime are compared, the latter is higher by a factor of two to three. To understand the origin of this behaviour, we conducted direct numerical simulations of the flow around a dimpled sphere, which is similar to commercially available golf balls, in the post-critical regime. By comparing the results to those for a smooth sphere, it is found that dimples, although effective in accelerating the drag crisis, impose a local drag penalty, which contributes significantly to the overall drag force. This finding challenges the broadly accepted view that dimples only indirectly affect the drag force on a sphere by energizing the near-wall flow and delaying global separation.

ANALGESIC AND ANTI-INFLAMMATORY EFFECTS OF ACETYLSALICYLIC ACID: PHYSIOLOGICAL MECHANISMS

2020 ◽  
Vol 6(72) (1) ◽  
pp. 197-219
Author(s):  
I. V. Cheretaev ◽  
D. R. Khusainov ◽  
E. N. Chuyan ◽  
M. Yu. Ravaeva ◽  
A. N. Gusev ◽  
...  
Keyword(s):  
Acetylsalicylic Acid ◽  
Physiological Mechanism ◽  
The Body ◽  
Physiological Mechanisms ◽  
Scientific Publications ◽  
Thermal Pain ◽  
Order Of Magnitude ◽  
Anti Inflammatory ◽  
Number Of Publications ◽  
Electrical Stimuli

The purpose of the review is to summarize current literature data and the results of our own research on the analgesic and anti-inflammatory effects of acetylsalicylic acid, as well as the physiological mechanisms underlying them. This acid is the most studied reference representative of salicylates, which is convenient to consider the physiological effects characteristic in general for this group of chemical and medicinal products. Acetylsalicylic acid has analgesic properties against thermal pain and pain caused by electrical stimuli, as well as a pronounced anti-inflammatory effect. The realization of these properties depends on the peculiarities of aspirin metabolism in the body, ion and synaptic mechanisms for controlling the functional state of the cell, neurotransmitter systems of the сentral nervous system, and mechanisms of peripheral and сentral analgesia. Analgesic properties of acetylsalicylic acid founded not only in normal, but also in ultra-small doses. Various physical and especially chemical factors significantly change their effects. This increases the interest in studying the analgesic activity of salicylates and their physiological mechanisms, since such studies can serve as a basis for creating new non-steroidal anti-inflammatory drugs with low toxicity and high safety for patients, and improve the strategy of their practical use. Currently, the most detailed study of the physiological mechanism of analgesic and anti-inflammatory action of aspirin and its main metabolite – salicylic acid. However, it should be note that despite the abundance of existing data obtained in scientific studies of the effects of aspirin and its practical use, there are a number of unexplained aspects of the action of this drug, the mechanism of which has not yet been deciphered. The continuing interest in the effects and mechanisms of action of this drug and in connection with the expansion of its use evidenced by a consistently high number of scientific publications on aspirin in the most famous foreign and domestic publications. At the same time, the number of publications about aspirin is an order of magnitude higher than about any other drug known to humanity.

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