We have studied the drag force acting on an object moving with low velocity through a granular medium. Although the drag force is a dynamic quantity, its behavior in this regime is dominated by the inhomogeneous distribution of stress in static granular media. We find experimentally that the drag force on a vertical cylinder is linearly dependent on the cylinder diameter, quadratically dependen...

It is said that a forkball has a large drag force among various pitched balls in baseball games. To investigate this reason, the authors solve flows around a rotating baseball thrown in several conditions and visualized them. We found that the wake of the forkball is strongly influenced by the seam position and changes its direction like a knuckle ball because its spin is slow. The strong drag ...

1. The tail thrust of bluefish Pomatomus saltatrix was measured using a body accelerometer at different water speeds, buoyancies, and angles of water flow to determine the contribution of tail thrust in overcoming parasitic drag, induced drag, and weight directed along the track. The lengths and weights of the fish averaged 0.52 m and 1.50 kg respectively. 2. The tail thrust overcoming parasiti...

Computing the forces acting from a surrounding air phase onto a particle-based fluid or rigid object is challenging. Simulating the air phase and modeling the interactions using a multiphase approach is computationally expensive. Furthermore, stability issues may arise in such multiphase simulations. In contrast, the effects from the air can be approximated efficiently by employing a drag equat...

We investigate theoretically the onset of capillary-gravity waves created by a small object moving at the water-air interface. It is well established that, for straight uniform motion, no steady waves appear at velocities below the minimum phase velocity c(min)=23 cm/s. At higher velocities, the emission of capillary-gravity waves creates an additional drag force. The behavior of this force nea...

This study proposes a way to reduce energy losses in the form of rolling resistance friction during manual wheelchair propulsion by increasing the size of the front caster wheels and adjusting the weight distribution. Drag tests were conducted using a treadmill and a force transducer. Three different casters diameter (4 in., 5 in., and 6 in.) and six different mass distribution combinations (ba...

The measurement of drag while swimming (i.e. active drag) is a controversial issue. Therefore, in a group of six elite swimmers two active drag measurement methods were compared to assess whether both measure the same retarding force during swimming. In method 1 push-off forces are measured directly using the system to measure active drag (MAD-system). In method 2 (the velocity perturbation met...

We compute the force on a small neutral polarizable object moving at velocity ~v relative to a photon gas equilibrated at a temperature T We find a drag force linear in ~v. Its physical basis is identical to that in recent formulations of the dissipative component of the Casimir force. We estimate the strength of this universal Casimir drag force for different dielectric response functions and ...

A small flying machine based upon a new mechanism was realized. The flying machine driven by magnetic torque had hard magnetic rims as wings and a soft magnetic wire as a body, respectively. The wing has two hinges, which create different drag during up and down strokes, and produced lifting force. Shape magnetic anisotropy of the body stabilized the attitude, The flying machine flew without po...

To coordinate the robot manipulator along the desired trajectory, the exact model of the dynamics is required. The added mass and added moment of inertia, buoyancy, drag force, and friction mainly affect the dynamics of the undersea robot manipulator, and they are quite complex and unknown. In this reason, the exact model of the undersea robot manipulator is difficult to obtain. In this paper, ...