Effect of Twin Vertical Stabilizers on Lateral Directional Static Stability of an Aircraft – A Computational Study

The advantages of twin vertical Stabilizers over a single vertical Stabilizer of an aero plane are the rationale for this study. For conventional aero planes, the use of double vertical Stabilizers is being considered. The contribution to lateral stability has been examined for this application. XFLR5 software was used to conduct the overall analysis. The analysis was conducted for a single vertical Stabilizer as well as twin vertical Stabilizers, and the findings were compiled and correlated. It is critical to be able to fully explain and evaluate the stability and control parameters. It is crucial to understand the relationship between the aerodynamics of the airframe and its stability characteristics in order to increase flight endurance and deployment effectiveness. The stability analysis based on the dynamic model of the twin boom vertical Stabilizer is presented in this paper. The lateral-directional stability of an aero plane with a single vertical tail is determined to be 20% more efficient than that with twin boom vertical Stabilizers. The trim condition is moderately satisfied by an aircraft with twin vertical Stabilizers.

Numerical and Experimental Analysis of Portable Underwater Robots with a Movable Float Device

This report describes a numerical and experimental study of a posture control device based on a movable float for portable underwater robots. We numerically analyzed the static stability using a stability curve and allowable spatial range of a center-of-gravity shift caused by a payload shift or manipulator configuration. Further, we proposed a feedback controller based on direct pitch and roll signals to change and maintain robot posture. We tested the feedback control using a numerical simulator and conducted experiments in a water tank using two portable underwater robots to demonstrate the effectiveness of the movable float device and proposed controller. The results of the field experiments showed that the device and proposed controller can be employed for effective underwater operations of portable underwater robots.

STATIC STABILITY OF AERODYNAMICALLY SUPPORTED PLATFORMS MOVING ABOVE WATER

The motion stability is the most important problem of high-speed marine vehicles that utilize aerodynamic support. A simplified analysis and calculations of longitudinal static stability of several basic platforms moving above water are carried out in this study. The analysis is based on the extreme ground effect theory and the assumption of hydrostatic deformations of the water surface. Effects of the underlying surface type, Froude number, and several geometrical parameters on main aerodynamic characteristics, including the static stability margin, are presented. If the underlying surface is water instead of a rigid plane, the static stability worsens for platforms with flat or S-shaped lower surfaces, but it slightly improves for a horizontal platform with a flap. The static stability margin remains positive for S-shaped profiles at sufficiently low Froude numbers, while it is negative for other configurations.

Simulation and Analysis of Grid Formation Method for UAV Clusters Based on the 3 × 3 Magic Square and the Chain Rules of Visual Reference

Large-scale unmanned aerial vehicle (UAV) formations are vulnerable to disintegration under electromagnetic interference and fire attacks. To address this issue, this work proposed a distributed formation method of UAVs based on the 3 × 3 magic square and the chain rules of visual reference. Enlightened by the biomimetic idea of the plane formation of starling flocks, this method adopts the technical means of airborne vision and a cooperative target. The topological structure of the formation’s visual reference network showed high static stability under the measurement of the network connectivity index. In addition, the dynamic self-healing ability of this network was analyzed. Finally, a simulation of a battlefield using matlab showed that, when the loss of UAVs reaches 85% for formations with different scales, the UAVs breaking formation account for 5.1–6% of the total in the corresponding scale, and those keeping formation account for 54.4–65.7% of the total undestroyed fleets. The formation method designed in this paper can maintain the maximum number of UAVs in formation on the battlefield.

A Comparison of Initial Developments Between Explosive and Ordinary Mid-latitude Cyclones Off the East Asian Coast in Winter

Explosive cyclones (ECs) off the East Asian coast post challenges in forecasting and significant threats to human life and property. In searching for the key features that distinguish explosive cyclones (ECs) from ordinary extratropical cyclones (OCs), this study presents detailed comparison of winter ECs versus OCs in the perspective of potential vorticity (PV) using 10 years of reanalysis data with high temporal and spatial resolutions. ECs feature greater low-level baroclinity and stronger PV than OCs. The decomposition of local PV tendency shows the important contribution of cold advection (with correlation coefficient of 0.8) in the initial development of ECs. A stronger cold advection for ECs increases upstream static stability, leading to intrusion of higher PV along the steeper isentropic surfaces. The importance of cold advection is further proved by numerical experiments with the Weather Research and Forecast (WRF) model on a typical winter EC. The weakening of cold advection within low-troposphere in sensitivity experiment can significantly decrease PV and stop the cyclone from explosive deepening. In addition to the consensus that diabatic processes play important roles in the intensification of explosive cyclogenesis, this study emphasizes the importance of horizontal cold advection (which is also associated with baroclinic instability) in the preconditioning PV for explosive cyclogenesis.

Model and algorithms for a decision support system on the application of rescue intends in case of a beyond design-basis rapid accident of a river passenger vessel

The problem of determination of threshold values of changes in stability characteristics of a river displacement ship is studied. A model and a data preparation scheme are being developed for the algorithmic implementation of the construction of curves of threshold values of lateral stability characteristics until the moment corresponding to the command given by the ship’s captain to bring life-saving appliances to a state of readiness or to use them. For the case of flooding of two adjacent hull compartments of a three-deck river passenger motor ship under the action of an external static inclining moment, illustrating data of calculations of hydrostatic characteristics and ship trim are presented, and an ensemble of diagrams of its static stability with threshold values is built. The results of the studies performed are intended for the software and hardware implementation of a digital system for active monitoring of the ship’s hull condition, predicting the development of a dangerous situation, supporting decision-making by the captain of a river vessel on the use of standard rescue equipment in the event of the threat of the ship being flooded and overturned.

Estimation of the stability of a fishing vessel during purse seining

One of the reasons for the emergency of a fishing vessel, as well as for the failure of fishing equipment, is the sudden tension of the purse rope, which occurs when the fishing equipment is pulled. As a result of the loss of stability the vessel may enter the encircled seine area and even capsize. There are a number of measures to improve stability during the operation of the vessel. However, when designing fishing equipment, it is necessary to know forces acting on the vessel from the seine side. The article presents a method for assessing the static stability of a vessel with a static application of the tension force of the purse rope. As a result of the study, an expression for determining the static heel angle using a three-dimensional representation of the vessel is given. During simulation the geometrical parameters of the purse rope in the process of purse seine were taken into account. The tension force of the purse rope is also presented as a variable.

Indicators of the critical state of the ship’s stability

According to the main criterion, the vessel stability according to the main criterion is standardized by the Rules of the Russian Register by the assumption that the units of the stability margin are practically equal, which is the ratio of listing and restoring moments characterizing the equality of their work. That is, the current domestic and international standards allow the achievement of a shipborne borderline hazardous state, after which it will either capsize, or an uncontrolled inflow of water into the hull and emergency flooding will begin. The characteristics of the vessel that affect stability during its assessment, both at the design stages and during operation, are determined with some error. It is caused by the assumptions of the Rules to the displacement value determination and the coordinates of the gravity center, incomplete compliance with the predicted cruise conditions, due to the ship falling into possible more severe conditions, the construction of a static stability diagram, which is the dependence of the reduced restoring moment on the inclination angle, with a flat waterline, while it is three-dimensional, and other factors related to the vessel’s type and purpose, which are not taken into account when calculating stability. In this paper, we consider a group of such factors, in relation to ships of inland and mixed (river-sea) navigation, the features and reasons for their occurrence, taking into account in verification calculations. A mathematical stability safety factor form, reflecting the expected increments of permissible values, which will improve the safety of the ship, is proposed.