scholarly journals Modelling of Helicopter Main Rotor Aerodynamic Loads in Manoeuvres

2019 ◽  
Vol 26 (4) ◽  
pp. 273-284
Author(s):  
Grzegorz Kowaleczko ◽  
Andrzej Leśniczak
Keyword(s):  
Mathematical Model ◽  
Aerodynamic Characteristics ◽  
Complex Model ◽  
Rotor Blades ◽  
Main Rotor ◽  
Aerodynamic Forces ◽  
Aerodynamic Loads ◽  
Helicopter Flight ◽  
Helicopter Main Rotor ◽  
The Mathematical Model

AbstractThe article discusses the method of modelling of the helicopter main rotor aerodynamic loads during steady state flight and manoeuvres. The ability to determine these loads was created by taking into account the motion of each blade relative to the hinges and was a result of the applied method of aerodynamic loads calculating. The first part of the work discusses the basic relationships that were used to build the mathematical model of helicopter flight. The focus was also on the method of calculating of the aerodynamic forces generated by the rotor blades. The results of simulations dedicated to the “jump to hover” manoeuvre were discussed, showing the possibilities of analysing aerodynamic loads occurring in unsteady flights. The main rotor is considered separately in an “autonomous” way and treated as a source of averaged forces and moments transferred to the hub. The motion of individual blades is neglected, and their aerodynamic characteristics are radically simplified. The motion of individual blades is neglected, and their aerodynamic characteristics are radically simplified. This can lead to significant errors when attempting to model dynamic helicopter manoeuvres. The more complex model of helicopter dynamics is discussed.

scholarly journals CALCULATED RESEARCH OF INFLUENCE OF HELICOPTER MAIN ROTORS GEOMETRY ON THE EFFICIENCY IN HOVER MODE BASED ON THE NONLINEAR VORTEX MODEL

2018 ◽  
Vol 21 (6) ◽  
pp. 43-53
Author(s):  
Yurii M. Ignatkin ◽  
Pavel V. Makeev ◽  
Alexander I. Shomov
Keyword(s):  
Aerodynamic Characteristics ◽  
Operating Conditions ◽  
Rotor Blades ◽  
Main Rotor ◽  
Rotor Aerodynamics ◽  
Vortex Model ◽  
Coaxial Rotor ◽  
Efficiency Increase ◽  
Helicopter Main Rotor ◽  
Geometric Layout

The efficiency of the helicopter main rotor in the hover mode is very important, because this mode essentially determines the performance characteristics of the helicopter. A feature of the helicopter rotor aerodynamics is a significant inductive blade influence that highly defines its aerodynamic characteristics. The problem of the influence of the blade twist and spatial geometric layout of the main rotor on its aerodynamic characteristics in the hover mode for a fixed value of the rotor solidity has been considered in this article. As a criterion of efficiency of the rotor in the hover mode relative efficiency (FoM – Figure of Merit) is used. The results are obtained by numerical simulation based on the nonlinear vortex blade model of the rotor, developed at the Helicopter Design Chair of the MAI. The model allows taking into account a complicated spatial shape of the free vortex path of the rotor blades that determines their inductive interaction. As the example of a four-blade main rotor with rectangular blades in plan, the influence of the value of the blades twist on the efficiency in the hover mode is studied. For different values of the rotor thrust, the values and ranges of the blade twist angles are determined, providing the maximum positive effect of the efficiency increase in hovering. For a fixed value of the blade twist, the rotor solidity, and the same operating conditions, the effect of various schemes and configurations of rotor on its efficiency in hover mode is studied. A single rotor with a different number of blades (from 2 to 6), an X-shaped rotor, coaxial rotor and rotor with crossed blades type "synchropter" are considered. The values of the efficiency increase in hovering depending on the rotor layout in comparison with the two-blade rotor are obtained. The comparative analysis of inductive velocities and streamlines for the "synchropter" rotor scheme, coaxial rotor scheme and its equivalent single rotor scheme is presented. The obtained results can be useful at the stage of preliminary design of vertically taking-off aircraft when selecting the parameters of their main rotor system.

scholarly journals Investigations of the vortex ring state on a helicopter main rotor based on computational methodology using URANS solver

2019 ◽  
Vol 304 ◽  
pp. 02011
Author(s):  
Wienczyslaw Stalewski ◽  
Katarzyna Surmacz
Keyword(s):  
Vortex Ring ◽  
Equations Of Motion ◽  
Rotor Blades ◽  
Main Rotor ◽  
Simplified Approach ◽  
Helicopter Flight ◽  
Computational Methodology ◽  
Helicopter Main Rotor ◽  
Sudden Decrease ◽  
Vortex Ring State

Computational investigations of the Vortex Ring State (VRS) on a helicopter main rotor have been conducted. The VRS phenomenon is a condition of powered flight that occurs most frequently during the vertical or nearly vertical descent of a rotorcraft. The characteristic feature of the VRS is a torus-shaped vortex around a rotor. The occurrence of this extensive vortex structure is a dangerous phenomenon that usually causes sudden decrease of main-rotor thrust, finally leading to an increase of the rate of descent and vibration level, disturbances of a helicopter balance, deterioration of manoeuvrability and deficit of power. The investigations presented in the paper, have been conducted based on computational methodology developed and implemented by the Authors. The methodology is based on a coupling of several methods of Computational Fluid Dynamics and Flight Dynamic. The approach consists of calculation of unsteady aerodynamic forces acting on the flying rotorcraft by simultaneous solution of the URANS equations, the equations of motion of the helicopter as well as the equations describing fluid-structure-interaction phenomena. Flow effects caused by rotating rotor blades, are modelled using a simplified approach based on the Virtual Blade Model. Using the described methodology, a series of helicopter flight simulations, in a vicinity of the VRS boundaries, have been conducted. Selected results of these simulations have been discussed in the paper.

scholarly journals MATHEMATICAL MODELS OF THE RADAR SIGNAL REFLECTED FROM A HELICOPTER MAIN ROTOR IN APPLICATION TO INVERSE SYNTHESIS OF ANTENNA APERTURE

2019 ◽  
Vol 22 (3) ◽  
pp. 74-87 ◽  
Author(s):  
Sergey R. Heister ◽  
Thai T. Nguyn
Keyword(s):  
Mathematical Models ◽  
Vertical Plane ◽  
Rotor Blades ◽  
Radar Signal ◽  
Main Rotor ◽  
Antenna Aperture ◽  
Radar Images ◽  
Aerial Vehicles ◽  
Propeller Blades ◽  
Helicopter Main Rotor

Introduction. The basis for solving the problem of aircraft recognition is the formation of radar portraits, reflecting the constructive features of aerial vehicles. Portraits, which are radar images of the propellers of aerial vehicles, have high informativeness. These images allow us to distinguish the number and relative position of the propeller blades, as well as the direction of its rotation. The basis for obtaining such images are mathematical models of reflected signals. Objective. The aim of this paper is to develop mathematical models of the radar signal reflected from the helicopter main rotor applied to inverse synthetic aperture radar (ISAR). Methods and materials. ISAR processing is used to produce a radar image of a propeller in a radar with a monochromatic probing signal. The propeller blades in the models are approximated by different geometric shapes. The models used to describe the reflection from the propellers of helicopters and fixed-wing aircraft have significant differences. In the process of moving each blade of the helicopter main rotor makes characteristic movements (flapping, dragging, feathering), as well as bends in a vertical plane. Such movements and bendings of the blades are influence the phase of the signal reflected from the main rotor. It is necessary to take the phase change of the reflected signal into account as accurately as possible when developing an ISAR algorithm for imaging the main rotor. Results. We found that in the centimeter wavelength range the mathematical model of the signal reflected from the helicopter main rotor as a system of blades is most accurately described by representing each blade with a set of isotropic reflectors located on the main rotor’s blade leading and trailing edges. Taking into account the flapping movements and curved shapes of the blades in the model allows you to get as close as possible to the features of the real signal. Conclusion. The developed model which takes into account the flapping movements and bends of the helicopter main rotor blades can be used to improve the ISAR algorithms providing the radar imaging of aerial vehicles.

Correlation of predicted and free-flight responses near departure conditions of a high incidence research model

1987 ◽  
Vol 91 (909) ◽  
pp. 397-405 ◽  
Author(s):  
A. Jean Ross ◽  
Geraldine F. Edwards
Keyword(s):  
Mathematical Model ◽  
Research Model ◽  
Free Flight ◽  
Wind Tunnel Experiments ◽  
Aerodynamic Forces ◽  
Lateral Control ◽  
Flight Behaviour ◽  
High Incidence ◽  
The Mathematical Model ◽  
High Angles Of Attack

Summary The mathematical model of aerodynamic forces and moments is described, based on results from various wind-tunnel experiments with the RAE High Incidence Research Model (HIRM). Simulations of the responses due to longitudinal and lateral control inputs at high angles of attack are compared with the responses measured on free-flight models of the configuration. It is shown that the main features of the flight behaviour are reproduced, in particular such phenomena as roll-off, wing rock and nose slice.

scholarly journals Physical modeling of a skip pneumatic winder

2021 ◽  
pp. 64-73
Author(s):  
Aleksandr Leontiev ◽  
Keyword(s):  
Mathematical Model ◽  
Physical Modeling ◽  
Aerodynamic Characteristics ◽  
Volumetric Efficiency ◽  
Similarity Criteria ◽  
Experimental Sample ◽  
Point Analysis ◽  
Analytical Phase ◽  
The Mathematical Model ◽  
Parameters Calculation

Introduction. The analytical phase of research on mine skip pneumatic winders has been passed, so the theoretical provisions have to be tested by the methods of physical modeling which is aimed at confirming the mathematical model adequacy and assessing the effectiveness of different types of sealing devices. Research methods. Physical modeling phases have been formulated, including modeling by geometric and aerodynamic similarity criteria, constructing aerodynamic characteristics of the installation, carrying out experiments with non-contacting and combined seals, and calculating the values of the installation volumetric efficiency based on the experimental data obtained. Research results. The lifting time of the skip model with different masses of material and seal types has been determined. The installation working points in the “flow rate–pressure” coordinate system have been identified, and the values of the volumetric efficiency have been calculated for each working point. Analysis of the results. A satisfactory convergence of calculated and experimental parameters of the physical model has been established. The model's volumetric efficiency has reached a technically acceptable level. The expected value of the experimental model’s volumetric efficiency has been calculated according to the similarity constants. Conclusions. The model's study revealed the convergence of the experimentally obtained volumetric efficiency of the model with its calculated values and proved the applicability of the mathematical model to experimental sample parameters calculation. The volumetric efficiency of the installation with both non-contacting and combined seals is quite high allowing to recommend the studied sealing devices for mine pneumatic winders.

scholarly journals АНАЛІЗ КОНСТРУКТИВНО-ТЕХНОЛОГІЧНИХ ОСОБЛИВОСТЕЙ ЛОПАТЕЙ НЕСУЧИХ ГВИНТІВ ВАЖКИХ ТРАНСПОРТНИХ ВЕРТОЛЬОТІВ

2021 ◽  
pp. 59-103
Author(s):  
А. Г. Гребеников ◽  
Ю. В. Дьяченко ◽  
В. В. Коллеров ◽  
В. Ю. Коцюба ◽  
И. В. Малков ◽  
...  
Keyword(s):  
Service Life ◽  
Rotor Blade ◽  
Parametric Modeling ◽  
Rotor Blades ◽  
Parametric Models ◽  
Space Distribution ◽  
Main Rotor ◽  
Mixed Design ◽  
Helicopter Main Rotor ◽  
Main Rotor Blade

The analysis of the design and technological features of the rotor blades of heavy transport helicopters is carried out. The main performance characteristics of heavy helicopters are presented. General requirements to helicopter main rotor blades design and specifications for their production are formulated. The design and force diagram of heavy helicopter main rotor blades is considered. The features of structural materials for the main rotor blades of heavy transport helicopters are marked. The main rotor blades differ in their design due to different approaches to materials, manufacturing and layout of blade elements. The main rotor blades of an all-metal design, for design and technological reasons, are divided into two groups: a frame structure with a tubular steel spar and an aluminum extruded spar. As a result of a number of design and technological measures the service life of the main rotor blade of helicopter Mi-6 was brought from 50 hours to 1500 hours. The principal peculiarity of the steel tubular spar of the main rotor blade of the Mi-26 helicopter is the absence of the shaft lug. The features of mixed design main rotor blades are presented. The method of parametric modeling of helicopter main rotor blades is presented. The application of the three-dimensional parametric models of structural elements in practice of designing and construction enables to perform numerical calculations of aerodynamic and strength characteristics both of separate aggregates, units and details and of the helicopter as a whole by means of the finite element method. The method of parametric modeling of the main rotor blade of the transport helicopter with the computer system CATIA V5 is a modification of the method of integrated designing of the elements of aviation constructions. Parametric master geometry of the main rotor blade is a linear surface, created by basic profiles of the blade. On the basis of parametric master geometry a space distribution model is created that determines the position of axial planes of the power set of the blade for further creation of the blade detail models. Technological flowchart of main rotor blade manufacturing is presented, manufacturing and surface hardening technology of steel tubular spar is considered. The technology of manufacturing and molding the nose part of the blade of the main rotor mixed design. The technological features of slipway assembly-gluing of the main rotor blade are considered, the content of off-slipway work is given.These materials can be useful in theoretical and experimental studies to extend the service life of the rotor blades of Mi-26 helicopters, which are currently in operation in Ukraine.

Performance of Quiet Helicopter

2020 ◽  
Vol 2020 (1) ◽  
pp. 1-17
Author(s):  
Jarosław Stanisławski
Keyword(s):  
Equations Of Motion ◽  
Rotor Blades ◽  
Main Rotor ◽  
Rotor Speed ◽  
Flexible Rotor ◽  
Slowing Down ◽  
Helicopter Flight ◽  
Operational Envelope ◽  
The Galerkin Method ◽  
Lower Limits

AbstractNoise generated by helicopters is one of the main problems associated with the operation of rotorcrafts. Requirements for reduction of helicopter noise were reflected in the regulations introducing lower limits of acceptable rotorcraft noise. A significant source of noise generated by helicopters are the main rotor and tail rotor blades. Radical noise reduction can be obtained by slowing down the blade tips speed of main and tail rotors. Reducing the rotational speed of the blades may decrease rotor thrust and diminish helicopter performance. The problem can be solved by attaching more blades to main rotor. The paper presents results of calculation regarding improvement of the helicopter performance which can be achieved for reduced rotor speed but with increased number of rotor blades. The calculations were performed for data of hypothetical light helicopter. Results of simulation include rotor loads and blade deformations in chosen flight conditions. Equations of motion of flexible rotor blades were solved using the Galerkin method which takes into account selected eigen modes of the blades. The simulation analyzes can help to determine the performance and loads of a quiet helicopter with reduced rotor speed within the operational envelope of helicopter flight states.

scholarly journals A study of a quasilinear model of the particles of a suspension that are aggregated and settled in an inhomogeneous field

2020 ◽  
Keyword(s):  
Mathematical Model ◽  
Initial Conditions ◽  
Lower Boundary ◽  
Complex Model ◽  
Discontinuity Surface ◽  
Inhomogeneous Field ◽  
Compact Zone ◽  
Quasilinear Systems ◽  
Cartesian Coordinate ◽  
The Mathematical Model

The mathematical model of the sedimentation process of suspension particles is usually a quasilinear hyperbolic system of partial differential equations, supplemented by initial and boundary conditions. In this work, we study a complex model that takes into account the aggregation of particles and the inhomogeneity of the field of external mass forces. The case of homogeneous initial conditions is considered, when all the parameters of the arising motion depend on only one spatial Cartesian coordinate x and on time t. In contrast to the known formulations for quasilinear systems of equations (for example, as in gas dynamics), the solutions of which contain discontinuities, in the studied formulation the basic system of equations occurs only on one side of the discontinuity line in the plane of variables (t; x). On the opposite side of the discontinuity surface, the equations have a different form in general. We will restrict ourselves to considering the case when there is no motion in a compact zone occupied by settled particles, i.e. all velocities are equal to zero and the volumetric contents of all phases do not change over time. The problem of erythrocyte sedimentation in the field of centrifugal forces in a centrifuge, with its uniform rotation with angular velocity ω = const is considered. We have studied the conditions for the existence of various types of solutions. One of the main problems is the evolution (stability) problem of the emerging discontinuities. The solution of this problem is related to the analysis of the relationships for the characteristic velocities and the velocity of the discontinuity surface. The answer depends on the number of characteristics that come to the jump, and the number of additional conditions set on the interface. The discontinuity at the lower boundary of the area occupied by pure plasma is always stable. But for the surface separating the zones of settled and of moving particles, the condition of evolution may be violated. In this case, it is necessary to adjust the original mathematical model.

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