Conservation-Theory-Based Analysis Method About Effect of External Wind Disturbance on Small Civilian UAV

2020 ◽  
Vol 19 (04) ◽  
pp. 2050037
Author(s):  
Wang Bohang ◽  
Wang Daobo
Keyword(s):  
Wind Field ◽  
Flight Simulation ◽  
Wind Disturbance ◽  
Model Reference ◽  
Conservation Of Energy ◽  
Momentum Theory ◽  
Small Uav ◽  
Disturbance Model ◽  
Triangle Theory ◽  
Energy And Momentum

In the future civilian UAV market, low-altitude low-speed small UAV will obtain a dominant position. In order to achieve small UAV accurate navigation, researchers have devoted lots of efforts on disturbance-model-reference controllers to reject the external wind disturbance. As we all know, accurate modeling helps the efficiency of controller’s parameters. However, almost all the design processes of disturbance-model-reference controllers are based on speed triangle theory which fails to adequately explain the effect of external wind field disturbances on UAV. First, conservation of energy and momentum theory is used to prove that the traditional speed triangle theory is unreasonable to analyze the influence of external wind field on UAV. Then, a more accurate method based on the conservation of energy and momentum theory is proposed to correctly illustrate the effect of wind disturbance on UAV. Finally, two external wind disturbance UAV flight simulation platforms based on speed triangle theory and conservation of energy and momentum theory are implemented separately, showing the big difference between these two types of methods about presenting effect of external wind field on UAV.

scholarly journals Engineering Comprehensive Model of Complex Wind Fields for Flight Simulation

Aerospace ◽  
2021 ◽  
Vol 8 (6) ◽  
pp. 145
Author(s):  
Jianwei Chen ◽  
Liangming Wang ◽  
Jian Fu ◽  
Zhiwei Yang
Keyword(s):  
Wind Field ◽  
Three Dimensional ◽  
Great Influence ◽  
Spatial Location ◽  
Flight Simulation ◽  
Comprehensive Model ◽  
Flight Trajectory ◽  
Wind Fields ◽  
Wind Field Simulation ◽  
Low Level Jet

A complex wind field refers to the typical atmospheric disturbance phenomena existing in nature that have a great influence on the flight of aircrafts. Aimed at the issues involving large volume of data, complex computations and a single model in the current wind field simulation approaches for flight environments, based on the essential principles of fluid mechanics, in this paper, wind field models for two kinds of wind shear such as micro-downburst and low-level jet plus three-dimensional atmospheric turbulence are established. The validity of the models is verified by comparing the simulation results from existing wind field models and the measured data. Based on the principle of vector superposition, three wind field models are combined in the ground coordinate system, and a comprehensive model of complex wind fields is established with spatial location as the input and wind velocity as the output. The model is applied to the simulated flight of a rocket projectile, and the change in the rocket projectile’s flight attitude and flight trajectory under different wind fields is analyzed. The results indicate that the comprehensive model established herein can reasonably and efficiently reflect the influence of various complex wind field environments on the flight process of aircrafts, and that the model is simple, extensible, and convenient to use.

Using three elementary particles to construct the physical world

2021 ◽  
Vol 34 (2) ◽  
pp. 236-247
Author(s):  
Huawang Li
Keyword(s):  
Electromagnetic Waves ◽  
Physical World ◽  
Elementary Particles ◽  
Average Kinetic Energy ◽  
Particle Collisions ◽  
Conservation Of Energy ◽  
Fundamental Particles ◽  
Energy And Momentum ◽  
Physical Phenomena ◽  
The Universe

In this paper, we conjecture that gravitation, electromagnetism, and strong nuclear interactions are all produced by particle collisions by determining the essential concept of force in physics (that is, the magnitude of change in momentum per unit time for a group of particles traveling in one direction), and further speculate the existence of a new particle, Yizi. The average kinetic energy of Yizi is considered to be equal to Planck’s constant, so the mass of Yizi is calculated to be <mml:math display="inline"> <mml:mrow> <mml:mn>7.37</mml:mn> <mml:mo>×</mml:mo> <mml:msup> <mml:mrow> <mml:mn>10</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>51</mml:mn> </mml:mrow> </mml:msup> </mml:mrow> </mml:math> kg and the average velocity of Yizi is <mml:math display="inline"> <mml:mrow> <mml:mn>4.24</mml:mn> <mml:mo>×</mml:mo> <mml:msup> <mml:mrow> <mml:mn>10</mml:mn> </mml:mrow> <mml:mn>8</mml:mn> </mml:msup> </mml:mrow> </mml:math> m/s. The universe is filled with Yizi gas, the number density of Yizi can reach <mml:math display="inline"> <mml:mrow> <mml:mn>1.61</mml:mn> <mml:mo>×</mml:mo> <mml:msup> <mml:mrow> <mml:mn>10</mml:mn> </mml:mrow> <mml:mrow> <mml:mn>64</mml:mn> </mml:mrow> </mml:msup> </mml:mrow> </mml:math> /m3, and Yizi has no charge. After abandoning the idealism of physics, I try to construct a physical framework from three elementary particles: Protons, electrons, and Yizis. (The elementary particles mentioned here generally refer to the indivisible particles that constitute objects.) The effects of Yizi on the conversion of light, electricity, magnetism, mass, and energy as well as the strong nuclear and electromagnetic forces are emphasized. The gravitation of electromagnetic waves is measured using a Cavendish torsion balance. It is shown experimentally that electromagnetic waves not only produce pressure (repulsion) but also gravitational forces upon objects. The universe is a combination of three fundamental particles. Motion is eternal and follows the laws of conservation of energy and momentum. There is only one force: The magnitude of change in momentum per unit time for a group of particles traveling in one direction. Furthermore, this corresponds to the magnitude of the force that the group of particles exerts in that direction. From this perspective, all physical phenomena are relatively easy to explain.

scholarly journals The motional effects of the maxwell æther-stress

1909 ◽  
Vol 83 (560) ◽  
pp. 109-119
Keyword(s):  
Continuous Medium ◽  
Poynting Vector ◽  
Present Condition ◽  
Conservation Of Energy ◽  
State Of Stress ◽  
Rate Of Increase ◽  
Electromagnetic Momentum ◽  
Energy And Momentum ◽  
Similar Element ◽  
Maxwell Stresses

There is an outstanding gap in electromagnetic theory in respect to the attempt to reconcile the analysis of æthereal stress on the lines initiated by Maxwell with Newton’s third law and the law of the conservation of energy. In the present condition of theory there is assigned to the æther a certain distribution of electromagnetic energy and momentum. The hypothetical distribution of energy is necessarily associated with the Poynting vector which measures its rate of transference. The distribution of momentum is so defined that the rate of increase of the total amount, within any given volume supposed at rest in the æther, is equivalent to the resultant of the Maxwell stresses on the bounding surface. There is, however, no connection established between the transference of energy across an area and the stress across that area. Such a connection would require that it should be possible to assign to the medium in which stress and energy reside a state of motion whereby the stresses might do the necessary amount of work, and this again would require the revision of the specification of stress, inasmuch as the ordinary expressions are computed for an element of surface which is at rest. Numerous other questions arise as soon as such a process is attempted, but the present paper seeks only to analyse what types of motion must be looked for, and to specify the field of stress upon the elements of area moving with the velocities obtained. Strictly, it is incorrect to speak of the stresses on elements of area in the æther at the same point having different velocities. The true stress in a continuous medium can only be estimated on an area moving with the medium. All that can be done in the absence of a knowledge of the velocity of the medium is to analyse the transference of momentum across an element of area having a specified velocity. Only when this velocity is that of the medium is it legitimate to interpret this transference as due to a state of stress in the medium. Thus, unless the æther is supposed at rest, the Maxwell expressions have no significance, except as giving the rate at which momentum is crossing an element of area at rest. If, however, the æther is assumed at rest, then no state of stress can give rise to any transfer of energy. 1. The flux of momentum across an element of area moving with velocity v differs from that across a similar element at rest by the vector v v g per unit area, g being the intensity of the electromagnetic momentum (=[EH]/4 πc ) and v v being the component of v normal to the area.

Stimulated Raman scattering from a fully focused relativistic electron beam in a waveguide

1986 ◽  
Vol 36 (1) ◽  
pp. 37-62
Author(s):  
Robert A. Schill ◽  
S. R. Seshadri
Keyword(s):  
Raman Scattering ◽  
Stimulated Raman Scattering ◽  
Signal Wave ◽  
Plasma Stream ◽  
Wave Interactions ◽  
Conservation Of Energy ◽  
Unbounded Medium ◽  
Parallel Plate Waveguide ◽  
Energy And Momentum ◽  
Stimulated Raman

Stimulated Raman scattering from a fully focused relativistically drifting electron plasma in a parallel-plate waveguide is studied. A set of internally consistent transport relations governing the three-wave interactions is developed. These transport relations lead to the proper conservation of energy and momentum. Including small wall and bulk plasma losses, parametric and nonlinear characteristics are investigated theoretically and numerically. It is found that in an unbounded medium the saturation period of the signal wave is considerably smaller than in a bounded medium. The signal energy comes from the plasma stream through the idler wave with small depletion of the pump wave amplitude.

scholarly journals A Framework for Parameterizing Eddy Potential Vorticity Fluxes

2012 ◽  
Vol 42 (4) ◽  
pp. 539-557 ◽  
Author(s):  
David P. Marshall ◽  
James R. Maddison ◽  
Pavel S. Berloff
Keyword(s):  
Stress Tensor ◽  
Potential Vorticity ◽  
Large Scale ◽  
Eddy Diffusivity ◽  
Linear Instability ◽  
Reynolds Stresses ◽  
Mean Flow ◽  
Conservation Of Energy ◽  
The Mean ◽  
Energy And Momentum

Abstract A framework for parameterizing eddy potential vorticity fluxes is developed that is consistent with conservation of energy and momentum while retaining the symmetries of the original eddy flux. The framework involves rewriting the residual-mean eddy force, or equivalently the eddy potential vorticity flux, as the divergence of an eddy stress tensor. A norm of this tensor is bounded by the eddy energy, allowing the components of the stress tensor to be rewritten in terms of the eddy energy and nondimensional parameters describing the mean shape and orientation of the eddies. If a prognostic equation is solved for the eddy energy, the remaining unknowns are nondimensional and bounded in magnitude by unity. Moreover, these nondimensional geometric parameters have strong connections with classical stability theory. When applied to the Eady problem, it is shown that the new framework preserves the functional form of the Eady growth rate for linear instability. Moreover, in the limit in which Reynolds stresses are neglected, the framework reduces to a Gent and McWilliams type of eddy closure where the eddy diffusivity can be interpreted as the form proposed by Visbeck et al. Simulations of three-layer wind-driven gyres are used to diagnose the eddy shape and orientations in fully developed geostrophic turbulence. These fields are found to have large-scale structure that appears related to the structure of the mean flow. The eddy energy sets the magnitude of the eddy stress tensor and hence the eddy potential vorticity fluxes. Possible extensions of the framework to ensure potential vorticity is mixed on average are discussed.

A Theoretical Framework for Energy and Momentum Consistency in Subgrid-Scale Parameterization for Climate Models

2009 ◽  
Vol 66 (10) ◽  
pp. 3095-3114 ◽  
Author(s):  
Tiffany A. Shaw ◽  
Theodore G. Shepherd
Keyword(s):  
Conservation Laws ◽  
Climate Models ◽  
Multiple Scale ◽  
Theoretical Framework ◽  
Momentum Conservation ◽  
Wave Activity ◽  
Subgrid Scale ◽  
Conservation Of Energy ◽  
Planetary Scale ◽  
Energy And Momentum

Abstract A theoretical framework for the joint conservation of energy and momentum in the parameterization of subgrid-scale processes in climate models is presented. The framework couples a hydrostatic resolved (planetary scale) flow to a nonhydrostatic subgrid-scale (mesoscale) flow. The temporal and horizontal spatial scale separation between the planetary scale and mesoscale is imposed using multiple-scale asymptotics. Energy and momentum are exchanged through subgrid-scale flux convergences of heat, pressure, and momentum. The generation and dissipation of subgrid-scale energy and momentum is understood using wave-activity conservation laws that are derived by exploiting the (mesoscale) temporal and horizontal spatial homogeneities in the planetary-scale flow. The relations between these conservation laws and the planetary-scale dynamics represent generalized nonacceleration theorems. A derived relationship between the wave-activity fluxes—which represents a generalization of the second Eliassen–Palm theorem—is key to ensuring consistency between energy and momentum conservation. The framework includes a consistent formulation of heating and entropy production due to kinetic energy dissipation.

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