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Target Tracking by MSRSs. Principles of Interstation Plot and Track Correlation
Published in Victor S. Chernyak, Fundamentals of Multisite Radar Systems, 2018
In certain cases, however, the estimates z^k,j in (15.29) coming from different stations may really be considered as being statistically mutually independent. Such a situation takes place when a target moves along a deterministic (e.g., ballistic) trajectory so that the process noise μk in the target motion model (15.1) or (15.6) is absent. The condition of mutually independent estimates z^k,j for different j may be approximately satisfied when μk ≠ 0 if a target moves along a straight-line portion of its path with a constant speed so that μk is a stationary random process of small intensity in comparison with mutually independent measurement errors [Qk « Bξt, see (15.2) and (15.10a)].
Dynamics and Control of a 10-Thruster Flight Vehicle
Published in Nandan K. Sinha, N. Ananthkrishnan, Advanced Flight Dynamics with Elements of Flight Control, 2017
Nandan K. Sinha, N. Ananthkrishnan
In this section, we shall apply the guidance and control law derived above to simulate the closed-loop dynamics of an example DACS vehicle. Sample data for a DACS vehicle and the engagement geometry assumed for the simulation is as listed in Table 8.1. The target is assumed to be flying a ballistic trajectory with the only acceleration being that due to gravity. With the target velocity being fixed at 3 km/s, the relative velocity between the target and DACS is very close to 5 km/s at the closing stages. The initial separation between the target and DACS is taken to be nearly 50 km. Thus, the DACS flight time is approximately 10 s. The controller and guidance law gains are taken as specified in Table 8.1. Additionally, a limit on the DACS acceleration permissible is set as 5g along each axis.
Particle Characterization and Dynamics
Published in Wen-Ching Yang, Handbook of Fluidization and Fluid-Particle Systems, 2003
The larger particles were thrown high in the splash zone, higher than predicted by a ballistic trajectory using the bubble rise velocity as the initial velocity and neglecting any air drag. Later observations of this model showed that when bubbles erupt at the surface, the accompanying gas flow has a velocity much higher than the bubble rise velocity; see Glicksman and Piper (1987). This sets up a substantial gas bypass from the distributor to the surface of a relatively shallow bed. The observations from the model led to a mechanistic model for gas throughflow aided by the low resistance of the bubble cavity; see Yule and Glicksman (1988), and an accurate prediction of bubble volume flow rate and bed expansion; see Glicksman and Yule (1991).
Recent developments on the water entry impact of wedges and projectiles
Published in Ships and Offshore Structures, 2022
Ahmad Zamir Chaudhry, Yao Shi, Guang Pan
Wei et al. (2012) investigated the water entry of Disk-ogive head torpedo by dividing its trajectory into two parts, the initial water entry impact stage and the stage after the tail fully submerging. The wind tunnel test was conducted to investigate the ballistic trajectory of projectile during water entry process and the coefficient of drag of the projectile was calculated. From this study, it was found that when the torpedo enters water in a high speed, the vertical and bend torque caused by fluid impact will alter angular velocity around the horizontal axis and the low pressure phenomenon appearing on the wetting surface would be aggravated. When this phenomenon become serious, whip and ricochet behaviour will happen. In the same year, Gu et al. (2012) explored the cavity dynamics and underwater trajectories of hemispherical and general pistol bullets by a high-resolution cameras and it was concluded that the stability of the trajectory was significantly influenced by the head shape of the projectile. Shepard et al. (2014) considered the influence of density of the impacting sphere on the coefficient of drag for the same time phase used by May and Woodhull (1948).
Transmission of COVID-19 virus by cough-induced particles in an airliner cabin section
Published in Engineering Applications of Computational Fluid Mechanics, 2021
Yihuan Yan, Xueren Li, Xiang Fang, Ping Yan, Jiyuan Tu
A qualitative analysis was then conducted to illustrate the time-dependent trajectories of the particles released by passenger B with various size classifications (i.e. 0–10 µm, 10–50 µm, 50–100 µm, and >100 µm), respectively, as shown in Figure 7. It was noticed that the respiratory-induced particles were highly controlled by the cough jet in the first time interval (0–1.5 s), the particles traveled further horizontally and reached the seat in front. Larger particles, on the other hand, tended to settle rapidly in the first 1.5 s owing to gravity, particularly for particle sizes over 100 µm. During the period from 1.5 to 5 s, the effect of the cough flow was significantly reduced, the ventilated flow and passengers’ thermal plumes began to escalate their impact on the dispersion of the released particles. These factors appeared to delay the settling of larger particles (50–100, over 100 µm), while smaller size particles (0–10 and 10–50 µm) were relatively more buoyant, and thus remained suspended in the air. In the third time interval, owing to the limited seating arrangement, cough particles ejected by passenger B were more likely to bounce back from the seat in front and return to the passenger’s breathing zone after 5 s. From 5 to 10 s, particles were highly dominated by local airflow and passengers’ thermal plumes, and the cough-jet effect on particles was almost fully lost. It can be observed that, in this particular situation, large particles settled much more quickly than small particles. This is mainly because, for large particles, a higher Stokes number can lead to less effect of viscous dissipation forces. In addition, as particle size increases, the inertia terms of the particle become more dominant from the governing equation, resulting in a moe ballistic trajectory for the larger particles. The smaller particles, on the other hand, can be carried more easily by the drag force caused by the ventilated flow, losing their initial momentum and being rapidly affected by the viscous dissipation effect. Thus, the ventilation will keep the small particles suspended in this local region. These effects are weakened with larger self-weight particles. Particles of size group 50–100 µm are approximately the largest size group that can be carried by local flow after 5 s. Beyond this size group, it is reasoned that particles are more dominated by their initial momenta.