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Drag is a force that opposes motion due to an object's shape, material, and speed. This project defined what drag force is, derived the governing equation for drag and listed some applications of drag forces. Derivation of the drag equation was achieved using the Buckingham π theorem, a dimensional analysis tool. Lastly, this project explored the p...
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Stick-slip vibration is an important issue which shall be considered in applications requiring high-precision motion. A straightforward example is presented for the understanding of this phenomena specially in complex systems. A three-degrees of freedom mass-damper-spring is considered. This system is excited by a friction force imposed from a movi...
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... In fluid dynamics, the drag force can be described using the drag equation. The equation is attributed to Lord Rayleigh [35]. We can express the drag force d is as follows: ...
In this paper, we describe a sheet-shaped throwable transforming robot. Sheet-type robots can change their shape to perform tasks according to the situation. Therefore, they are expected to be useful in places with many restrictions, such as disaster sites. However, most of them can only move slowly on the ground. Therefore, in order to actually deliver the robot to the disaster site, it must be carried manually. To solve this problem, we are developing a sheet-shaped robot that can be thrown from the sky. Previously developed prototypes could only move in the forward direction, and the transition from falling to walking was complicated and uncertain. In this paper, we report on a new prototype that improves on these shortcomings.
... The movement of ships or submarines in a fluid medium (such as water or seawater) is always accompanied by a resistive force known as hydrodynamic drag [1]. This force acts in the opposite direction of motion and depends on the geometry, speed, and materials of the watercraft or underwater-craft [1][2][3]. ...
... The movement of ships or submarines in a fluid medium (such as water or seawater) is always accompanied by a resistive force known as hydrodynamic drag [1]. This force acts in the opposite direction of motion and depends on the geometry, speed, and materials of the watercraft or underwater-craft [1][2][3]. In the realm of geometry, the resistive force is termed hydrodynamic form drag [1,2]. ...
... This force acts in the opposite direction of motion and depends on the geometry, speed, and materials of the watercraft or underwater-craft [1][2][3]. In the realm of geometry, the resistive force is termed hydrodynamic form drag [1,2]. This mechanical force emerges due to the interaction of the hull with the surrounding fluid, resulting in increased resistance, decreased velocity, and higher fuel consumption for the ship or submarine [4]. ...
In this research, surfaces inspired by shark skin were engineered for aluminum (Al) slabs to investigate the influences of riblets on the collapse dynamics of nanobubbles and the resultant erosion on the slab surfaces. These effects were probed through molecular dynamics simulations. Specifically, surfaces with flat profiles as well as those with small and high sawtooth-shaped nano riblets were modelled for analysis. Near the flat surface, due to the absence of riblets, the water nanohammer, with its semi-spherical shape containing water beads under approximately 30 GPa pressure and 5000 K temperature, impulse the Al slab, transferring both temperature and pressure, thereby inducing maximum erosion. Conversely, surfaces containing riblets separate some parts of water vortices, leading to a shorter collapse time of the nanobubble and the creation of a water nanohammer with a smaller volume compared to their values near a flat surface. Moreover, due to the initial impulse of the water nanohammer to the peak of the riblet, the nanohammer splits into two or three inclined shapes. Then, they diagonally impact the main part of the Al slab, resulting in erosion. The decentralization and diagonal impulse of the water nanohammer in the presence of riblets create a lower erosion volume and depth compared to these values on a flat surface. In summary, it can be inferred that riblets can serve as a passive control method for managing erosion, thereby increasing the lifetime of hulls for ships or submarines.
... The movement of ships or submarines in a fluid medium (such as water or seawater) is always accompanied by a resistive force known as hydrodynamic drag [1]. This force acts in the opposite direction of motion and depends on the geometry, speed, and materials of the watercraft or underwater-craft [1][2][3]. ...
... The movement of ships or submarines in a fluid medium (such as water or seawater) is always accompanied by a resistive force known as hydrodynamic drag [1]. This force acts in the opposite direction of motion and depends on the geometry, speed, and materials of the watercraft or underwater-craft [1][2][3]. In the realm of geometry, the resistive force is termed hydrodynamic form drag [1,2]. ...
... This force acts in the opposite direction of motion and depends on the geometry, speed, and materials of the watercraft or underwater-craft [1][2][3]. In the realm of geometry, the resistive force is termed hydrodynamic form drag [1,2]. This mechanical force emerges due to the interaction of the hull with the surrounding fluid, resulting in increased resistance, decreased velocity, and higher fuel consumption for the ship or submarine [4]. ...
... The movement of ships or submarines in a fluid medium (such as water or seawater) is always accompanied by a resistive force known as hydrodynamic drag [1]. This force acts in the opposite direction of motion and depends on the geometry, speed, and materials of the watercraft or underwater-craft [1][2][3]. ...
... The movement of ships or submarines in a fluid medium (such as water or seawater) is always accompanied by a resistive force known as hydrodynamic drag [1]. This force acts in the opposite direction of motion and depends on the geometry, speed, and materials of the watercraft or underwater-craft [1][2][3]. In the realm of geometry, the resistive force is termed hydrodynamic form drag [1,2]. ...
... This force acts in the opposite direction of motion and depends on the geometry, speed, and materials of the watercraft or underwater-craft [1][2][3]. In the realm of geometry, the resistive force is termed hydrodynamic form drag [1,2]. This mechanical force emerges due to the interaction of the hull with the surrounding fluid, resulting in increased resistance, decreased velocity, and higher fuel consumption for the ship or submarine [4]. ...
... The movement of ships or submarines in a fluid medium (such as water or seawater) is always accompanied by a resistive force known as hydrodynamic drag [1]. This force acts in the opposite direction of motion and depends on the geometry, speed, and materials of the watercraft or underwater-craft [1][2][3]. ...
... The movement of ships or submarines in a fluid medium (such as water or seawater) is always accompanied by a resistive force known as hydrodynamic drag [1]. This force acts in the opposite direction of motion and depends on the geometry, speed, and materials of the watercraft or underwater-craft [1][2][3]. In the realm of geometry, the resistive force is termed hydrodynamic form drag [1,2]. ...
... This force acts in the opposite direction of motion and depends on the geometry, speed, and materials of the watercraft or underwater-craft [1][2][3]. In the realm of geometry, the resistive force is termed hydrodynamic form drag [1,2]. This mechanical force emerges due to the interaction of the hull with the surrounding fluid, resulting in increased resistance, decreased velocity, and higher fuel consumption for the ship or submarine [4]. ...
... When the shell flow rate increases and the pressure extruding the core layer remains constant, the drag force experienced by the core-shell filament increases, which causes the filament to stretch, and the core diameter decreases as a result. The effect drag force has on the flow rate can be assessed by combining Eq. (3) [29] and Eq. (4) [30]: ...
Creating multi-layered channels for mimicking human blood vessels in thick tissues is the main challenge to overcome in organ biofabrication. Current three-dimensional (3D) printing strategies cannot effectively manufacture hollow channels with multiple layers. This study aims to propose a coaxial nozzle-assisted embedded 3D printing method in which core-shell filaments can be formed in a yield-stress matrix bath by extruding different ink materials through the corresponding channels. The materials selected for the core ink, shell ink, and matrix bath are Pluronic F127 (F127) and calcium chloride (CaCl2), sodium alginate (NaAlg), and poly(ethylene glycol) diacrylate (PEGDA) and nanoclay, respectively. After crosslinking the matrix bath and shell, the core layer made from the sacrificial ink (F127) is removed to generate a hollow channel. In this work, the effects of ink material properties and operating conditions on core-shell filament formation have been systematically studied. The rheological and mechanical properties of the yield-stress matrix bath have been characterized as well. A thick tissue-like structure with embedded single-layered, hollow channels has been successfully printed for demonstration. Since it is feasible to design coaxial nozzles with a core-shell-shell architecture, the proposed method is technically extendable to create double-layered channels within a cellular tissue construct, accurately mimicking human blood vascular networks in thick tissues.
... a final position eternally, crossing infinite points forever, as Zeno described [30]. Previous authors did not investigate the connection between Zeno's paradoxes and motions with viscous friction forces F = −bv , despite the fact that this type of force exists in every Newtonian fluid. ...
In this paper, we connected Zeno’s paradoxes and motions with the viscous friction force F=-bv. For the progressive version of the dichotomy paradox, if the body speed is constant, the sequences of positions and instants are infinite, but the series of distances and time variations converge to finite values. However, when the body moves with force F=-bv, the series of time variations becomes infinite. In this case, the body crosses infinite points, approximating to a final position forever, as the progressive version of the dichotomy paradox describes. The same procedures with constant speed and motion with force F=-bv result in different spatial sequences and the same series for the regressive version of the dichotomy paradox. Nonetheless, the regressive version of the dichotomy paradox does not describe a body that approximates a final position forever. Finally, for the Achilles paradox, we find the positional and temporal sequences of the man and the tortoise at constant speeds. Analogously to the progressive version of the dichotomy paradox, the positional and temporal sequences are infinite, but the spatial and temporal series converge to finite values. If Achilles and the tortoise are identical points that move with force F=-bv, and the turtle’s position in function of time presents a temporal advantage, the man and the animal will cross successive infinite places forever, and the quick hero will never overtake the slow reptile, as the paradox described. We conclude that the progressive version of the dichotomy and Achilles paradoxes can describe motions when the force is F=-bv.
... Drag is a force that opposes the direction of motion of an object, which is caused by the resistance of the object. Longitudinal Stability is the moment force of the aircraft during the pitching motion [4][5][6]. ...
LSU-05NG is a drone manufactured and developed by LAPAN. The horizontal tail of the aircraft is used to maintain longitudinal stability, however, there has been no study on a tail modification that could improve the performance. The study of tail modification will examine the impact of modifying the airfoil to NACA 2412 and NACA 63-215. The base model of LSU-05NG uses NACA 0012 as the airfoil profile which is used in the horizontal tail. The performance is measured from the value of the lift coefficient, drag coefficient, and longitudinal stability. The results are obtained using ANSYS CFX Software. Based on the study, the modification of the horizontal tail has no impact on the lift and drag coefficient, however, impacts greatly on the pitching coefficient which determines the longitudinal stability. The airfoil profile that produces the highest longitudinal stability is NACA 63-215, followed by NACA 2412, and the last is the basic model using NACA 0012
... As shown in Figure 1, this net force component along the flow of direction is called drag force [15]. It is defined as a force that opposes motion due to the shape, material, and speed of an object [12,16]. It is called aerodynamic drag force if the fluid is air and drag force has the greatest attention as compared to other forces due to its significant impact on fuel consumption [17][18][19][20][21]. [15] Previous findings have annotated that the shape of car model geometry is important and varieties of vehicle design have been applied in both experimental and numerical studies [1,4,12,[22][23][24]. ...
The aerodynamic characteristics of a vehicle play a vital role in steering stability, performance, comfort, and safety of a car. The fuel efficiency of a vehicle is determined by the performance of the internal combustion engine and the aerodynamic design of the body. One of the most important aspects of automobile design is aerodynamic styling. A vehicle with low drag resistance provides advantages in terms of cost and efficiency. This article will review design characteristics and implementation of various specific reference models on drag issues using Computational Fluid Dynamics (CFD) techniques. The benefits and limitations of these models are analysed, and the validity of results in developing guidelines to improve the performance and stability of cars are described. This review paper covers significant studies that utilise the CFD model and simulation on a simplified vehicle model using various turbulence models to generate drag coefficient. Characteristics and impacts of various vehicle design models with and without external factors such as side mirrors and door handles are also discussed. Results obtained from the research focuses on the physics flow structures such as static pressure contours, are presented for the three types of car model geometry. The simplified generic models are more efficient and advocated to apply compared to the specific model geometry based on the result acquired by the latest studies. Simplified generic models are preferred due to their cost-effectiveness, procurement of optimum time, and better simulation effects. Moreover, the study also demonstrates the importance of having a car with suitable turbulence models that are appropriate to be applied for simulations in terms of its applicability, time effectiveness, and cost.
... where F a is the air drag force, C f is the drag coefficient, ρ is the air density, S is the frontal area, and v r is the particle relative velocity [22]. ...
Printed circuit boards (PCBs) are made of several materials, including platinum, gold, silver, and rare earth elements, which are very valuable from a circular economy perspective. The PCB end of life management starts with the component removal, then the PCBs are shredded into small particles. Eventually, different separation methods are applied to the pulverized material to separate metals and non-metals. The corona electrostatic separation is one of the methods that can be used for this purpose since it is able to separate the conductive and non-conductive materials. However, the lack of knowledge to set the process parameters may affect the efficiency of the corona electrostatic separation process, ultimately resulting in the loss of valuable materials. The simulation of particle trajectory can be very helpful to identify the effective process parameters of the separation process. Thus, in this study, a simulation model to predict the particles trajectories in a belt type corona electrostatic separator is developed with the help of COMSOL Multiphysics and MATLAB software. The model simulates the particle behavior taking into account the electrostatic, gravitational, centrifugal, electric image, and air drag forces. Moreover, the predicted particles trajectories are used to analyze the effects of the roll electrode voltage, angular velocity of roll electrode, and size of the particles on the separation process.
