Three-Dimensional Simulation of a Complete Vertical Axis Wind Turbine Using Overlapping Grids

Three-dimensional simulations of the aerodynamic field around a three-blade straight-axis Vertical Axis Wind Turbine (VAWT) are presented for two values of the Tip Speed Ratio λ (TSR), namely λ=1.52 and λ=2.5. Numerical simulations were carried out using the over-set grid solver ROSITA (ROtorcraft Software ITAly). The Reynolds-Averaged Navier-Stokes equations are completed by the Spalart-Allmaras turbulence model. A strong interaction between the blade and the blade wakes is evidenced. Dynamic stall is observed in the case λ=2.5. The computed flow-field presents diverse three-dimensional effects, including the interaction between the blades and the tip vortices and the aerodynamic disturbances from the turbine shaft and the support arms. Three-dimensional effects are more relevant for λ=2.5. The comparison to experimental data confirms the general features of the flow

Preliminary Sizing of the Wing-Box Structure by Multi-Level Approach

The paper describes a procedure, dedicated to the preliminary sizing of an aircraft wing-box, based on a two level decomposition and on two independent optimizations. An engineering approach is followed and the most suitable model is exploited at each level in order to generate information about the wing-box structure without the need of a previous knowledge, a very important feature in the case of unconventional structures. The first level uses a commercial structural multidisciplinary optimization code and a stick model of the wing primary structure to minimize the structural mass under global design constraints; a set of physical design variables are used referring to a schematic representation of the cross-section in terms of equivalent axial thickness supporting pure axial stress and the thickness of a box resisting to both axial and shear stresses. The second level, based on a genetic optimization, provides the minimum mass optimal design of the wing cross sections, in terms of local design variables, which safely support the internal loads supplied by the first level, under local constraints, e.g. panel buckling and stiffeners crippling, providing also a cross section stiffness in compliance with the first level. The reported example, concerning the B747-100 wing structure, shows the capability of the approach to predict the structural weight of the wing box, an information to be used mainly in an early stage of the aircraft design, and to suggest a set of cross sections design solutions all in compliance with both global and local requirements

PyPAD: a Multidisciplinary Framework for Preliminary Airframe Design

The preliminary design of an aircraft is a complex task involving a lot of different disciplines and it is becoming more challenging in the future due to the reduced budget and compressed time. At the same time new projects present new technical challenges due to the request for highly demanding performances, in order to reduce the fuel consumption (cost and environment impact) and to increase the payload. The preliminary design problem involves different disciplines, like: Aerodynamics, Controls, Regulations, Performances, Systems Definition, Design, Loads & Aeroelasticity, Structural Sizing, etc.. The present work focuses on the development of an integrated framework suitable for preliminary airframe design, called PyPAD (Python module for Preliminary Aircraft Design). The modules developed until now allow for the definition of multi fidelity aero-structural models starting from a CPACS input file and to compute static loads (trim) and flutter margin with the minimum effort by the user. Moreover PyPAD is able to compute the dynamic response under all the different load conditions, including discrete and continuous gust, nodal forces, command inputs. The tool is also able to export the state-space aeroelastic models tacking advantage of the modern state space model realization. In this way all the loads prescribed by the regulations can be computed in a fully automatic approach. A complete test case, starting from the CPACS input and ending with the definition of structural, aerodynamic and aeroelastic models and with the computation of different design loads is reported

PyPAD: a Multidisciplinary Framework for Preliminary Airframe Design

Purpose: The purpose of this paper is to describe the development of an integrated framework suitable for preliminary airframe design, called PyPAD (Python module for Preliminary Aircraft Design), providing the capability to define models to compute loads and to perform the structural sizing. Design/methodology/approach: The modules developed until now allow for the definition of multi-fidelity aero-structural models starting from a Common Parametric Aircraft Configuration Schema (CPACS) input file and to compute static loads (trim) and flutter margin with minimum user effort. PyPAD take advantages of Abaqus-CAE, and the main functions are developed in Python, to take advantages of the simplicity in terms of software development and maintenance, but the core routines are developed in Fortran, taking advantages of parallel programming to get the best performances. Findings: A complete test case, starting from the CPACS input and ending with the definition of structural, aerodynamic and aero-elastic models, with the computation of different design loads, is reported. An example will show that the framework developed is able to handle different problematics of the preliminary projects using quite complex global models. Practical implications: All the tools developed in the framework, and the ones currently under development, could be a valid help during the preliminary design of a new aircraft, speeding up the iterative process and improving the design solution. Originality/value: PyPAD is the first framework developed around Abaqus-CAE for the preliminary aircraft design and is one of the few tools looking at the different problematics involved in a preliminary airframe design: design, loads and aero-elasticity, sizing and multi-disciplinary optimization

A Parametric Pilot/Control Device Model for Rotorcraft Biodynamic Feedthrough Analysis

This work presents a numerical model of the pilot/control device subsystem. The model is related to the left arm of a helicopter pilot holding a conventional collective control inceptor. A detailed biomechanical model of the pilot is developed within a general purpose multibody dynamics formulation. Linearized models about reference conditions are computed from the general analysis, for specific reference positions of the control inceptor and settings of the neuro-musculo-skeletal system that characterize specific flight conditions and tasks. The linearized models of the biodynamic feedthrough are used to produce coupled pilot/control device subsystem models that are parametrized with respect to the pilot biodynamic feedthrough characteristics and the mechanical properties of the control inceptor

Multilevel Structural Optimization for Preliminary Wing-Box Weight Estimation

This paper deals with the weight estimation of the wing box of a commercial aircraft by means of a procedure suitable for very large liners and/or unconventional configurations for which statistical data and empirical formulas may not be sufficiently reliable. Attention is focused on the need to account for aeroelastic interaction from a very preliminary stage of the design cycle. The procedure exploits the first of three levels of a multilevel structural optimization system conceived for the preliminary design of the wing primary structure and a simplified evaluation of the cross-sectional properties. The comparison between weight estimates obtained with the present procedure and predictions supplied by available literature shows a satisfactory agreement