Use of two drag coefficient concept for the investigation of flapping wings dynamics

Micro aerial vehicles design represents a challenge that lasted for years and the fact that they operate in a low Reynolds range, which makes the unsteady aerodynamic effect more influential, made the direct computational fluid dynamics simulation expensive in time and money, and an alternative method especially in the early phase of the design would be very beneficial and rentable. In this work the flight a flapping wings operated micro aerial vehicle was investigated by the simulation of the mechanical equations of motion in order to have an approximation of the true motion behavior and the flying condition of the vehicle, in the same time this approach present a model that can be electronically implemented to make the MAV auto-controlled by imposing some criteria. The equations were developed in spherical coordinates system, and simulated using the software Mathcad, and some of the constant related to the size of the vehicle are variated to match different range of existing flying animals from insects to birds, a concept of two different drag coefficient for the upstroke and down stroke was used successfully to model the flapping wing. And giving the fact that lots of parameter were simplified or neglected which lessen the accuracy, it gave good approximation, and the model can be used for auto-control by predefined flying path. Beside the main simulation work a small experimentation on a model wing covered in feather was conducted in a subsonic wind tunnel in order to present a practical alternative that economize energy by reducing the drag in upstroke, and it was found that the direction of the feather plays a significant role in the drag reduction and we concluded that the use of such materials can greatly improve the performances, and economize the energy used to operate such vehicles

Synthesis and Optimization of Wind Energy Conversion Devices

An approximate method for the analysis of interaction between wind flow and rigid flat blades is considered. The method allows synthesis and optimization of wind energy conversion systems without using space-time-programming procedures. By this method, the action of wind flow on the blade is subdivided on frontal pressure and vacuum (depression) on leeward side. The method was tested by computer simulation and experiments in wind tunnel. Examples of optimization tasks are solved in application to blades with simple shape. New wind energetic device with controlled orientation of flat blades to air flow is developed. Theoretical and experimental analysis of blade’s interaction with airflow is performed. Aerodynamic coefficients for blade’s drag and lifting forces are determined experimentally in wind tunnel. Optimization of system parameters is made. To increase the efficiency of energy transformation, it is proposed to change, by special law, the orientation of blade’s working surface relative to airflow during rotation of the rotor. It is shown that the optimal angular rotation frequency ratio between rotor and blade is equal to two. Serviceability and main advantages of the proposed method are confirmed by experiments with physical model of airflow device

CONVEYOR-TYPE SMALL HYDROPOWER PLANT FOR SHALLOW RIVER WATERS

This paper deals with the development of a small conveyor-type hydropower plant intended for operation in shallow river waters without construction of a dam. The proposed design offers a closed-shaped flattened conveyor equipped with flat-shaped blades. The conveyor is oriented perpendicular to the fluid flow. Several identical flat blades interacting with fluid flow are mounted on conveyor belt and move together with the belt in one straight line direction. Then after turning in the reversing mechanism, blades move in the opposite direction. The conveyor system has a built-in energy generator which drive shaft is connected with one of the reversing ends of the plant. Conveyor belt system dynamics analysis is performed on the base of equivalent model with one degree of freedom. The interaction of a moving conveyor flat blade in translation motion with fluid flow is studied by computer simulation with program Mathcad using a superposition principle. In accordance with this approach, a fast-chaotic motion of fluid particles (Brownian motion) is separated from the slow-directed flow motion, with the given average velocity. Optimization of system parameters (blade orientation angle to fluid flow, interaction constants of the braking generator) is performed, using a generated power as criterion. Simulation results confirm the serviceability and operational efficiency of the proposed hydropower plant in shallow river waters.

Methods and Devices for Wind Energy Conversion

The chapter deals with the analysis and optimization of the operational safety and efficiency of wind energy conversion equipment. The newly proposed method of wind energy conversion involves flat blades or space prisms that perform translation motion due to the interaction with air flow. Air flow interactions with 2D moving prisms (convex, concave) are studied by computer simulation. Optimization of prism shape is made using as criteria maximum of generating force and power. Theoretical results obtained are used in the designing of new devices for energy extraction from airflow. Models of wind energy conversion devices equipped with one vibrating blade are developed (quasi translatory blade’s motion model; model with vibrating blade equipped with crank mechanism). The operation of the system due to the action of air flow is simulated with computer programs. Possibilities to obtain energy with generators of different characteristics, using mechatronic control, have been studied. The effect of wind flow with a constant speed and also with a harmonic or polyharmonic component is considered. Partial parametric optimization of the electromechanical system has been performed. The serviceability and main advantages of the proposed methods and devices are confirmed by experiments with physical models in a wind tunnel

Vibration analysis of perforated plate in non-stationary motion

Fluid, non-stationary rigid body interaction is a commonly occurring phenomenon seen in many engineering practices. The article offers a new method using laws of classical mechanics for obtaining simplified analytical relations in analysis and optimisation tasks without using space time programming methods. In the proposed method the fluid space around the rigid body prisms is divided into two zones, pressure and suction (vacuum). The method is extensively discussed which is further extended for calculation of interaction forces and coefficients for non-stationary perforated plate with total area of perforations maintained at half the area of the complete flat plate. Experiments were performed for perforated plate in an Arm-field wind tunnel at constant speed of 10 m/s. The present work offers analysis and synthesis of specific engineering task of energy extraction from fluid in a unique way by making use of external fluid flow over a perforated plate. The fluid is assumed continuous and incompressible

Investigations of rotating blade for energy extraction from fluid flow

Device for energy extraction from fluid (air or water) is investigated. The device consists of a one central rotor with energy generator and several plane blades. All blades are connected to the central rotor with gear system which allows automatically change the orientation of their working surfaces to the direction of the incoming fluid flow. It is considered task that axis of the rotor and blades are perpendicular to fluid flow. System has one degree of freedom as rotation angle of central rotor. Theoretical analysis of the one blade interaction with the fluid flow is given. Calculation of system with one blade is done with MathCAD

ENGINEERING FOR RURAL DEVELOPMENT USING PENALTY FUNCTION METHOD FOR ANALYSIS OF DYNAMIC BEHAVIOUR OF VISCOELASTIC MATERIALS

Abstract. The present article investigates the application of the penalty function method in the analysis of behaviour of viscoelastic materials, particularly silicon rubbers, under dynamic loading. To perform the analysis, the mathematical model of the object was chosen, and the Matlab code for the mathematical model was developed. The dynamic force was applied to the given model. To find the most precise element describing the behaviour of elastic material from some set of available alternatives, the penalty method, which replaces a constrained optimization problem by a series of unconstrained problems, was used. Keywords: elastic materials, penalty function, dynamic load. Introduction Silicon rubbers are materials with highly non-linear behaviour patterns. The hypothesis states that the penalty function algorithm for solving non-linear problems with linear lower level problems could be especially useful in elastic material modelling. The dynamic load conditions analyzed in the given paper are the stress and strain, and it is assumed the silicon rubber material could be described as a viscoelastic material having the properties both of elasticity and viscosity. The mechanical model chosen to describe viscoelastic response under dynamic load is the three-element model (Standard Linear Solid). Because viscoelastic material modelling under dynamic load resulted into graphs with highly nonlinear behaviour, some chaotic behaviour analysis and error estimation were done. The objective of the paper was to define, whether using the penalty function could be sophisticated problem-solving algorithm for analysis of behaviour of viscoelastic materials under dynamic loading. Matlab program and additional Matlab-based modeling system were used to meet the objective