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 %.

Aerodynamics of Cyclist Posture, Bicycle and Helmet Characteristics in Time Trial Stage

2012 ◽  
Vol 28 (3) ◽  
pp. 317-323 ◽  
Author(s):  
Vincent Chabroux ◽  
Caroline Barelle ◽  
Daniel Favier
Keyword(s):  
Statistical Analysis ◽  
Wind Tunnel ◽  
Drag Coefficient ◽  
Drag Force ◽  
Time Trial ◽  
Frontal Area ◽  
Significant Gain ◽  
Upper Limbs ◽  
Force Coefficient ◽  
Coefficient Reduction

The present work is focused on the aerodynamic study of different parameters, including both the posture of a cyclist’s upper limbs and the saddle position, in time trial (TT) stages. The aerodynamic influence of a TT helmet large visor is also quantified as a function of the helmet inclination. Experiments conducted in a wind tunnel on nine professional cyclists provided drag force and frontal area measurements to determine the drag force coefficient. Data statistical analysis clearly shows that the hands positioning on shifters and the elbows joined together are significantly reducing the cyclist drag force. Concerning the saddle position, the drag force is shown to be significantly increased (about 3%) when the saddle is raised. The usual helmet inclination appears to be the inclination value minimizing the drag force. Moreover, the addition of a large visor on the helmet is shown to provide a drag coefficient reduction as a function of the helmet inclination. Present results indicate that variations in the TT cyclist posture, the saddle position and the helmet visor can produce a significant gain in time (up to 2.2%) during stages.

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 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).

Minimizing Drag Coefficients Using Bezier Technique

1992 ◽  
Author(s):  
Reda Bata ◽  
Sunil Katragadda ◽  
Randolph Churchill ◽  
Wenguang Wang
Keyword(s):  
Drag Coefficient ◽  
The Body ◽  
Vehicle Body ◽  
Exhaust Gas ◽  
Control Points ◽  
Vehicle Performance ◽  
Minimum Drag ◽  
Beneficial Impact ◽  
Profile Design ◽  
Exhaust Gas Emissions

Abstract Optimizing the profile design of a vehicle body for minimum drag coefficient can have a beneficial impact upon the vehicle performance, energy conservation, and exhaust gas emissions. An interactive technique based on the fundamental concepts of Bezier equations was utilized to develop the body profile and its corresponding drag coefficient. The technique described could be used by automobiles, submarines, and aircraft designers. Since the technique is interactive, the profile can be changed and tested again, allowing flexibility to produce the desired shape for the designer. The cubic four point Bezier curve utilizes four control points of which the two end points are fixed to the curve and the other two are used to interpolate the smooth profile. The governing principles of aerodynamics are used to develop the algorithm for the optimization process. A feature of this algorithm is that it accounts for the turbulence of the wind at its interface with the structure.

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 Interactions between Two Deformable Droplets in Tandem Fixed in a Gas Flow Field of a Gas Well

2021 ◽  
Vol 11 (23) ◽  
pp. 11220
Author(s):  
Zhibin Wang ◽  
Tianli Sun ◽  
Zhongwei Yang ◽  
Guo Zhu ◽  
Hongyan Shi
Keyword(s):  
Reynolds Number ◽  
Flow Field ◽  
Drag Coefficient ◽  
Drag Force ◽  
High Reynolds Number ◽  
Droplet Breakup ◽  
Gas Well ◽  
Body Forces ◽  
Simulation Results ◽  
High Reynolds

Knowing the droplet-deformation conditions, the droplet-breakup conditions, and the drag force in the interaction between two droplets with a high Reynolds number is of importance for tracking droplet movement in the annular flow field of a gas well. The interactions between two droplets with a high Reynolds number in a tandem arrangement fixed in flowing gas was investigated. The volume of fluid (VOF) method was used to model the droplets’ surface structure. Two different body forces were exerted on both droplets to hold them suspended at a fixed location, which eliminated the effect of droplet acceleration or deceleration on the drag and decreased the amount of computation required. The exerted body forces were calculated using the Newton iteration procedure. The interactions between the two droplets were analyzed by comparison with the simulation results of a single isolated droplet. The effect of the separation distance on the drag force was investigated by changing the separation spacing. The simulation results showed that for droplets with a small separating space between them, the dynamics of the downstream droplet were influenced significantly by the upstream droplet. The drag coefficient of the downstream droplet decreased considerably to a small, even negative, value, especially for droplets with higher Weber numbers and smaller initial separating spaces between them, while the drag force of the upstream droplet was influenced only slightly. In addition, a formula for predicting the final drag coefficient of the downstream droplet was devised.

Tail shapes lead to different propulsive mechanisms in the body/caudal fin undulation of fish

2020 ◽  
pp. 095440622096768
Author(s):  
Jialei Song ◽  
Yong Zhong ◽  
Ruxu Du ◽  
Ling Yin ◽  
Yang Ding
Keyword(s):  
Numerical Simulation ◽  
Aspect Ratio ◽  
High Efficiency ◽  
The Body ◽  
Caudal Fin ◽  
Fish Model ◽  
Swimming Efficiency ◽  
Simulation Results ◽  
Propulsive Mechanism ◽  
High Depth

In this paper, we investigate the hydrodynamics of swimmers with three caudal fins: a round one corresponding to snakehead fish ( Channidae), an indented one corresponding to saithe ( Pollachius virens), and a lunate one corresponding to tuna ( Thunnus thynnus). A direct numerical simulation (DNS) approach with a self-propelled fish model was adopted. The simulation results show that the caudal fin transitions from a pushing/suction combined propulsive mechanism to a suction-dominated propulsive mechanism with increasing aspect ratio ( AR). Interestingly, different from a previous finding that suction-based propulsion leads to high efficiency in animal swimming, this study shows that the utilization of suction-based propulsion by a high- AR caudal fin reduces swimming efficiency. Therefore, the suction-based propulsive mechanism does not necessarily lead to high efficiency, while other factors might play a role. Further analysis shows that the large lateral momentum transferred to the flow due to the high depth of the high- AR caudal fin leads to the lowest efficiency despite the most significant suction.

scholarly journals Effect of Cutting Ratio and Catch on Drag Characteristics and Fluttering Motions of Midwater Trawl Codend

2021 ◽  
Vol 9 (3) ◽  
pp. 256
Author(s):  
Wei Liu ◽  
Hao Tang ◽  
Xinxing You ◽  
Shuchuang Dong ◽  
Liuxiong Xu ◽  
...  
Keyword(s):  
Drag Force ◽  
Mesh Size ◽  
Current Speed ◽  
Midwater Trawl ◽  
Minimum Drag ◽  
Fish Catch ◽  
Spatial Geometry ◽  
By Catch ◽  
Trawl Fisheries ◽  
Crucial Part

The codend of a trawl net is the rearmost and crucial part of the net for selective fish catch and juvenile escape. To ensure efficient and sustainable midwater trawl fisheries, it is essential to better understand the drag characteristics and fluttering motions of a midwater trawl codend. These are generally affected by catch, cutting ratio, mesh size, and twine diameter. In this study, six nylon codend models with different cutting ratios (no cutting, 6:1, 5:1, 4:1, 7:2, and 3:1) were designed and tested in a professional flume tank under two conditions (empty codends and codends with catch) and five current speeds to obtain the drag force, spatial geometry, and movement trend. As the cutting ratio of empty codends decreased, the drag force decreased, and the drag coefficient increased. The unfolding degree of codend netting and the height of empty codends were found to be directly proportional to the current speed and inversely proportional to the cutting ratio. The positional amplitude of codend with cutting ratio 4:1 was the smallest for catch. The drag force of codends with catch increased as the current speed increased, and first decreased and then increased as the cutting ratio decreased. To ensure the best stability and minimum drag force of the codend, it is recommended to use the 4:1 cutting ratio codend.

Survey on the Indirect Methods of Potential Flow Used for the Optimization of Airships Profile

2014 ◽  
Vol 554 ◽  
pp. 717-723
Author(s):  
Reza Abbasabadi Hassanzadeh ◽  
Shahab Shariatmadari ◽  
Ali Chegeni ◽  
Seyed Alireza Ghazanfari ◽  
Mahdi Nakisa
Keyword(s):  
Boundary Layer ◽  
Turbulent Boundary Layer ◽  
Flow Field ◽  
Drag Coefficient ◽  
Body Surface ◽  
Potential Flow ◽  
The Body ◽  
Indirect Methods ◽  
Singularity Method ◽  
Singularity Distribution

The present study aims to investigate the optimized profile of the body through minimizing the Drag coefficient in certain Reynolds regime. For this purpose, effective aerodynamic computations are required to find the Drag coefficient. Then, the computations should be coupled thorough an optimization process to obtain the optimized profile. The aerodynamic computations include calculating the surrounding potential flow field of an object, calculating the laminar and turbulent boundary layer close to the object, and calculating the Drag coefficient of the object’s body surface. To optimize the profile, indirect methods are used to calculate the potential flow since the object profile is initially amorphous. In addition to the indirect methods, the present study has also used axial singularity method which is more precise and efficient compared to other methods. In this method, the body profile is not optimized directly. Instead, a sink-and-source singularity distribution is used on the axis to model the body profile and calculate the relevant viscose flow field.

Simulation of Sphere’s Motion Induced by Shock Waves

2012 ◽  
Vol 134 (10) ◽  
Author(s):  
Dan Igra ◽  
Ozer Igra ◽  
Lazhar Houas ◽  
Georges Jourdan
Keyword(s):  
Shock Waves ◽  
Drag Coefficient ◽  
Drag Force ◽  
Stationary Flow ◽  
Experimental Results ◽  
Experimental Findings ◽  
Sphere Drag ◽  
Simulation Scheme ◽  
Good Agreement

Simulations of experimental results appearing in Jourdan et al. (2007, “Drag Coefficient of a Sphere in a Non-Stationary Flow: New Results,”Proc. R. Soc. London, Ser. A, 463, pp. 3323–3345) regarding acceleration of a sphere by the postshock flow were conducted in order to find the contribution of the various parameters affecting the sphere drag force. Based on the good agreement found between present simulations and experimental findings, it is concluded that the proposed simulation scheme could safely be used for evaluating the sphere’s motion in the postshock flow.

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