Thrust Force Generated by Heaving Motion of a Plate: The Role of Vortex-Induced Force

To understand the force acting on birds, insects, and fish, we take heaving motion as a simple example. This motion might deviate from the real one. However, since the mechanism of force generation is the vortex shedding due to the motion of an object, the heaving motion is important for understanding the force generated by unsteady motion. The vortices released from the object are closely related to the motion characteristics. To understand the force acting on an object, information about momentum change is necessary. However, in vortex systems, it is impossible to estimate the usual momentum. Instead of the momentum, the “virtual momentum,” or the impulse, is needed to generate the force. For calculating the virtual momentum, we traced all vortices over a whole period, which was carried out by using the vortex-element method. The force was then calculated based on the information on the vortices. We derived the thrust coefficient as a function of the ratio of the heaving to travelling velocity.

LNG Loading Lines High Surge Analysis

Proper design of LNG loading lines and verification of emergency shutdown (ESD) interlock systems are critical in ensuring overall safety of the LNG facility. During an emergency, ESD interlock is activated with ESD valves closure initiated simultaneously with all loading pumps trip and the kickback valves open. During the ESD valves closure, the pipeline can be exposed to a risk of high surge pressures exerted onto the wall. A pressure surge or liquid hammering phenomenon in piping systems can be caused by a fluid in motion forced to stop or change direction suddenly (rapid momentum change) and also due to cavitation effect. Cavitation is caused by the formation and instantaneous collapse of vapour bubbles. The collapsing bubbles exert severe localized impact forces that can result in pressure surges. This paper discusses the methodology used to evaluate any potential occurrence of surge and the peak pressure associated with it, using several case studies for analysis. This paper also shares best practice identified from the study to facilitate with safe operations at an LNG loading facility.

Edge Effect on Numerical Calculation of Nonlinear Radiation Forces for a Submerged Body

To investigate the edge effect on numerical calculation of nonlinear forces for a moving body in the time domain, a large body motion model with linear free surface condition is developed with higher-order boundary element method. Five numerical formulations are used to compute the nonlinear radiation forces on submerged surging bodies with sharp edge and a small chamfer radius at the edge. It is found that for those bodies with smooth surface, the nonlinear radiation forces obtained by all of the numerical formulations are close to each other, but large disperses exist for the body with sharp edge. Examination on the vertical nonlinear radiation forces shows that the method on momentum change rate is insensitive to the small edge radius even the chamfer radius is zero, but the other formulations diverse when the edge radius approaches zero. It is suggested that for a body with sharp edge, the method on momentum change rate should be used, or to replace the body surface by the body with a small radius at its sharp edge.

Observing momentum disturbance in double-slit “which-way” measurements

Making a “which-way” measurement (WWM) to identify which slit a particle goes through in a double-slit apparatus will reduce the visibility of interference fringes. There has been a long-standing controversy over whether this can be attributed to an uncontrollable momentum transfer. Here, by reconstructing the Bohmian trajectories of single photons, we experimentally obtain the distribution of momentum change. For our WWM, the change we see is not a momentum kick that occurs at the point of the WWM, but rather one that nonclassically accumulates during the propagation of the photons. We further confirm a quantitative relation between the loss of visibility consequent on a WWM and the total (late-time) momentum disturbance. Our results emphasize the role of the Bohmian momentum in giving an intuitive picture of wave-particle duality and complementarity.

Search for η-mesic 3He in non-mesonic final state

The experiment on searching for η-mesic 3He nucleus was performed in May 2014 at COSY accelerator in Juelich by WASA-at-COSY Collaboration. The measurements were carried out using ramped beam technique which allows for the slow and continuous beam momentum change near the threshold of η meson creation. The luminosity was obtained based on pd → 3Heη reaction and quasielastic proton-proton scattering. The bound state of η-meson and 3He nucleus is searched for in pd → 3He2γ and pd → 3He6γ channels. The analysis is still in progress and the estimated upper limit value is on the level of few nanobarns.

The Critical Velocity With Minimum Momentum Change in Pushing a Droplet Through a Constriction Channel

Models of squeezing a droplet through a constrictions have wide applications in nature and engineering. In the present research, we found the minimum impulse required (momentum change) to squeeze a droplet through at different velocities. Our theoretical work result in an analytical expression of the critical velocity with minimum impulse. At this expression, we found a force balance between the average surface tension and the dynamic pressure loss at the channel inlet and outlet. Finally, we also compared the analytical results with numerical simulations. These results are important to understand some biological process and design of microscale filters.

Massive Particle Reflection from Moving Mirrors

We investigate the reflection of massive particles from moving mirrors. The adoption of the formalism based on the energy-momentum allowed us to derive the most general set of formulas, valid for massive and, in the limit, also for massless particles. We show that the momentum change of the reflecting particle always lies along the normal to the mirror, independent of the mirror speed. The subject is interesting not only to physicists designing concentrators for fascicles of massive particles and electron microscopes but also to computer scientists working in raytracing operating in the photon sector. The paper, far from being only theoretical, has profound and novel practical applications in both domains of engineering design and computer science.