In the present study, a new experimental setup for the investigation of the aerodynamic in-teract... more In the present study, a new experimental setup for the investigation of the aerodynamic in-teraction between a helicopter and ground obstacles is presented and assessed. The motorised helicopter model, which includes the fuselage, can be positioned in different positions relative to a model building in order to replicate different configurations. Moreover the current setup can also be used in a wind tunnel in order to replicate interference effects in windy conditions. The use of a helicopter model with a six-component balance and a building model with several pressure taps allows a database to be compiled for the loads on the helicopter and obstacle. A physical interpretation of the flow phenomena can be obtained through analysis of the obstacle pressure measurements and particle image velocimetry surveys of relevant configurations.
The correct identification of the aerodynamic loads due to interaction between rotorcraft and obs... more The correct identification of the aerodynamic loads due to interaction between rotorcraft and obstacles requires to run computationally intensive numerical models characterized by a high level of uncertainty. Wind tunnel data can be used as a source of information to improve those models. The present paper investigates the aerodynamic interaction of a helicopter and ship airwake exploiting wind tunnel data. A series of wind tunnel experiment, using a scaled helicopter model and Simple Frigate Shape 1, has been performed to measure forces and moments acting on the rotor, while the helicopter is approaching the flight deck. In addition, the velocity components along the longitudinal symmetry plane of the rotor have been visualized using PIV technique. With the rotor positioned at the starting point of the landing trajectory, the load measurements are used to modify the distribution of the inflow over the rotor in multibody simulation environment, in order to generate same loads, inclu...
The present paper describes the experimental activity carried out to evaluate the effectiveness o... more The present paper describes the experimental activity carried out to evaluate the effectiveness of the CFD-based shape optimisation of several components of a common helicopter platform of the heavy-weight class. The considered geometry is basically the same of the model tested in the frame of the GOAHEAD project. The comprehensive wind tunnel campaign includes both the original helicopter configuration and the optimised version to assess the optimisation effectiveness by comparison. The optimised components included different hub-cap configurations, a set of fairings for the blade-stubs attachments and the sponsons. Moreover, the effects on drag reduction produced by an array of vortex generators positioned on the back-ramp were investigated. Different measurement techniques were employed as loads and moments measurements, steady and unsteady pressure surveys and stereo particle image velocimetry. The performed measurements confirm a overall drag reduction of about 6% at cruise att...
The paper presents the wind tunnel simulation of a helicopter model in shipboard operations. The ... more The paper presents the wind tunnel simulation of a helicopter model in shipboard operations. The test rig consists of a scaled helicopter model and a simplified ship model, based on the geometry of the Simple Frigate Shape 1. In the first phase of the experiment, pressure and Particle Image Velocimetry survey of the flow field on the flight deck were performed without the presence of the helicopter, to study the flow features on the ship deck, for several wind conditions obtained modifying the wind speed and direction. The influence of Atmospheric Boundary Layer was investigated as well. Then, the rotorcraft was positioned in a series of points representative of both a typical fore-aft landing trajectory toward the deck, and a vertical descent on the deck. Loads generated by the rotor were monitored by means of a six-axis load cell. Particle Image Velocimetry of the ship wake and of the helicopter inflow were carried out in order to have a better understanding of how the interacting...
Particle Image velocimetry surveys were carried out around the blade section at 65% radius of a f... more Particle Image velocimetry surveys were carried out around the blade section at 65% radius of a four-bladed articulated rotor model to evaluate the airloads coefficients from velocity data. The blade section aerodynamic loads were calculated using the control volume approach and compared with the results of the blade element momentum theory in hovering for validation. As the compressibility effects for the present test case are not negligible, the pressure on the contour of the control surface was computed from the measured local velocity using the isentropic relations. The vertical force coefficient calculated from PIV data shows a quite good agreement with blade element theory results. The experimental campaign included also surveys around the blade section equipped with passive Gurney flap with different height. Thus, the method to obtain the aerodynamic loads from PIV data was employed to evaluate the effect of the flap on the vertical aerodynamic force acting on the blade secti...
ABSTRACT The European tilt-rotor aircraft ”ERICA” presents innovative and interesting features th... more ABSTRACT The European tilt-rotor aircraft ”ERICA” presents innovative and interesting features that make this project quite unique in the field of tilt-rotor aircraft. The basic idea is to have an aircraft that can efficiently operate as an airplane, including horizontal take off and landing and quite high speed cruise, with the additional capability of vertical take off and landing. A wide wind tunnel test campaign on the tilt-rotor ERICA 1/8 scale model has been carried out in order to obtain a large database useful to define the final aerodynamic project of the aircraft. The tests were carried out at Politecnico di Milano large wind tunnel with a setup allowing for a full 360◦ side-sleep sweep and for an incidence sweep going from −30◦ to 30◦. A purposely built strut has been employed to extend the tests to high incidence attitudes, allowing for an incidence sweep going from 60◦ to 120◦ and a few tests to be carried out at −90◦. The tests produced a large amount of data on global and partial aerodynamic loads at many different configurations and attitudes.
Computational Fluid Dynamics was used to investigate the effects of perpendicular blade vortex in... more Computational Fluid Dynamics was used to investigate the effects of perpendicular blade vortex interactions on the aerodynamic performance of an oscillating airfoil. In particular, the test case studied was a stream-wise vortex impacting on the leading edge of a NACA 23012 airfoil oscillating in light dynamic stall regime, representing a typical condition of the retreating blade of a helicopter in forward flight. The results of time-accurate simulations were validated by comparison with particle image velocimctry survcys. Thc analysis of thc numerical results enabled to achieve a detailed insight about the overall effects on the interacting flow field and on aerodynamic loads acting on the oscillating airfoil due to the vortex interaction. Indeed, the comparison with the clean airfoil case shows a severe loss of performance produced by vortex interaction during downstroke motion of the airfoil, as the vortex impact triggers the local stall of the blade section.
This paper deals with the activities conducted in the GARTEUR Action Group HC/AG-24 to address no... more This paper deals with the activities conducted in the GARTEUR Action Group HC/AG-24 to address noise scattering of helicopter rotors in presence of the fuselage. The focus of the paper is on the design for a generic “tail rotor” noise source used in the fuselage scattering study. The main design criterion is that the generic rotor noise source should resemble the main characteristics of the tail rotor with clear harmonic components. A two bladed simplified tail rotor model is considered. The performance of the tail rotor model in terms of thrust and torque with respect to the advance ratio is calibrated in the POLIMI wind tunnel. Acoustic measurements of the tail rotor model were tested in the DLR Acoustic Wind tunnel Braunschweig AWB. The results of the rotor performance and the rotor acoustic characteristics are described. The spectral variations resulting from unsteadiness of the source are explored in both with and without wind. The noise characteristics such as the spectral con...
The present paper describes the experimental activity carried out at Politecnico di Milano large ... more The present paper describes the experimental activity carried out at Politecnico di Milano large wind tunnel in the frame of CleanSky programme to assess the effectiveness of the CFD-based air-intake duct shape optimisation of the European platform tiltrotor ERICA. The tests were carried out on a 1/2.5 scaled model including the nacelle, the external portion of the wing and two interchangeable internal ducts reproducing the baseline and optimised shape. In addition, the model presented the rotor hub equipped with rotating blade stubs. A comprehensive experimental campaign was carried out including model configurations reproducing different forward flight conditions of the aircraft. The assessment of the optimised shape performance was evaluated by comparison of directional probes measurements performed at the Aerodynamic Interface Plane (AIP). Moreover, pressure measurements were also carried out on the duct internal surface. The experimental results confirmed an improved performanc...
The present paper describes the experimental set up of the wind tunnel activity to assess the eff... more The present paper describes the experimental set up of the wind tunnel activity to assess the effectiveness of the CFD-based air-intake shape optimisation of the European platform tiltrotor (ERICA). The wind tunnel campaign is carried out in the framework of the CleanSky TETRA project. The wind tunnel model was appositely designed and manufactured including the nacelle, the external wing and two interchangeable internal ducts (original and optimized). The performance evaluation is then made by the comparison of the pressure losses over the duct and the flow behavior at the engine face for both original and optimized intake duct shapes. Moreover, the evaluation of the internal flow field is made by means of an endoscopic PIV measurements performed in critical regions.
The rotor-rotor aerodynamic interaction is one of the key phenomena that characterise the flow an... more The rotor-rotor aerodynamic interaction is one of the key phenomena that characterise the flow and the performance of most of the new urban air mobility vehicles (eVTOLs) developed in the recent years. The present article describes a numerical activity that aimed to the systematic study of the rotor-rotor aerodynamic interaction with application to the flight conditions typical of eVTOL aircraft. The activity considers the use of a novel mid-fidelity aerodynamic solver based on vortex particle method. In particular, numerical simulations were performed when considering two propellers both in side-by-side and tandem configuration with different separation distances. The results of numerical simulations showed a slight reduction of the propellers performance in side-by-side configuration, while a remarkable loss of thrust in the order of 40% and a reduction of about 20% of the propulsive efficiency were found in tandem configuration, particularly when the propeller disks are completel...
In the present study, a new experimental setup for the investigation of the aerodynamic in-teract... more In the present study, a new experimental setup for the investigation of the aerodynamic in-teraction between a helicopter and ground obstacles is presented and assessed. The motorised helicopter model, which includes the fuselage, can be positioned in different positions relative to a model building in order to replicate different configurations. Moreover the current setup can also be used in a wind tunnel in order to replicate interference effects in windy conditions. The use of a helicopter model with a six-component balance and a building model with several pressure taps allows a database to be compiled for the loads on the helicopter and obstacle. A physical interpretation of the flow phenomena can be obtained through analysis of the obstacle pressure measurements and particle image velocimetry surveys of relevant configurations.
The correct identification of the aerodynamic loads due to interaction between rotorcraft and obs... more The correct identification of the aerodynamic loads due to interaction between rotorcraft and obstacles requires to run computationally intensive numerical models characterized by a high level of uncertainty. Wind tunnel data can be used as a source of information to improve those models. The present paper investigates the aerodynamic interaction of a helicopter and ship airwake exploiting wind tunnel data. A series of wind tunnel experiment, using a scaled helicopter model and Simple Frigate Shape 1, has been performed to measure forces and moments acting on the rotor, while the helicopter is approaching the flight deck. In addition, the velocity components along the longitudinal symmetry plane of the rotor have been visualized using PIV technique. With the rotor positioned at the starting point of the landing trajectory, the load measurements are used to modify the distribution of the inflow over the rotor in multibody simulation environment, in order to generate same loads, inclu...
The present paper describes the experimental activity carried out to evaluate the effectiveness o... more The present paper describes the experimental activity carried out to evaluate the effectiveness of the CFD-based shape optimisation of several components of a common helicopter platform of the heavy-weight class. The considered geometry is basically the same of the model tested in the frame of the GOAHEAD project. The comprehensive wind tunnel campaign includes both the original helicopter configuration and the optimised version to assess the optimisation effectiveness by comparison. The optimised components included different hub-cap configurations, a set of fairings for the blade-stubs attachments and the sponsons. Moreover, the effects on drag reduction produced by an array of vortex generators positioned on the back-ramp were investigated. Different measurement techniques were employed as loads and moments measurements, steady and unsteady pressure surveys and stereo particle image velocimetry. The performed measurements confirm a overall drag reduction of about 6% at cruise att...
The paper presents the wind tunnel simulation of a helicopter model in shipboard operations. The ... more The paper presents the wind tunnel simulation of a helicopter model in shipboard operations. The test rig consists of a scaled helicopter model and a simplified ship model, based on the geometry of the Simple Frigate Shape 1. In the first phase of the experiment, pressure and Particle Image Velocimetry survey of the flow field on the flight deck were performed without the presence of the helicopter, to study the flow features on the ship deck, for several wind conditions obtained modifying the wind speed and direction. The influence of Atmospheric Boundary Layer was investigated as well. Then, the rotorcraft was positioned in a series of points representative of both a typical fore-aft landing trajectory toward the deck, and a vertical descent on the deck. Loads generated by the rotor were monitored by means of a six-axis load cell. Particle Image Velocimetry of the ship wake and of the helicopter inflow were carried out in order to have a better understanding of how the interacting...
Particle Image velocimetry surveys were carried out around the blade section at 65% radius of a f... more Particle Image velocimetry surveys were carried out around the blade section at 65% radius of a four-bladed articulated rotor model to evaluate the airloads coefficients from velocity data. The blade section aerodynamic loads were calculated using the control volume approach and compared with the results of the blade element momentum theory in hovering for validation. As the compressibility effects for the present test case are not negligible, the pressure on the contour of the control surface was computed from the measured local velocity using the isentropic relations. The vertical force coefficient calculated from PIV data shows a quite good agreement with blade element theory results. The experimental campaign included also surveys around the blade section equipped with passive Gurney flap with different height. Thus, the method to obtain the aerodynamic loads from PIV data was employed to evaluate the effect of the flap on the vertical aerodynamic force acting on the blade secti...
ABSTRACT The European tilt-rotor aircraft ”ERICA” presents innovative and interesting features th... more ABSTRACT The European tilt-rotor aircraft ”ERICA” presents innovative and interesting features that make this project quite unique in the field of tilt-rotor aircraft. The basic idea is to have an aircraft that can efficiently operate as an airplane, including horizontal take off and landing and quite high speed cruise, with the additional capability of vertical take off and landing. A wide wind tunnel test campaign on the tilt-rotor ERICA 1/8 scale model has been carried out in order to obtain a large database useful to define the final aerodynamic project of the aircraft. The tests were carried out at Politecnico di Milano large wind tunnel with a setup allowing for a full 360◦ side-sleep sweep and for an incidence sweep going from −30◦ to 30◦. A purposely built strut has been employed to extend the tests to high incidence attitudes, allowing for an incidence sweep going from 60◦ to 120◦ and a few tests to be carried out at −90◦. The tests produced a large amount of data on global and partial aerodynamic loads at many different configurations and attitudes.
Computational Fluid Dynamics was used to investigate the effects of perpendicular blade vortex in... more Computational Fluid Dynamics was used to investigate the effects of perpendicular blade vortex interactions on the aerodynamic performance of an oscillating airfoil. In particular, the test case studied was a stream-wise vortex impacting on the leading edge of a NACA 23012 airfoil oscillating in light dynamic stall regime, representing a typical condition of the retreating blade of a helicopter in forward flight. The results of time-accurate simulations were validated by comparison with particle image velocimctry survcys. Thc analysis of thc numerical results enabled to achieve a detailed insight about the overall effects on the interacting flow field and on aerodynamic loads acting on the oscillating airfoil due to the vortex interaction. Indeed, the comparison with the clean airfoil case shows a severe loss of performance produced by vortex interaction during downstroke motion of the airfoil, as the vortex impact triggers the local stall of the blade section.
This paper deals with the activities conducted in the GARTEUR Action Group HC/AG-24 to address no... more This paper deals with the activities conducted in the GARTEUR Action Group HC/AG-24 to address noise scattering of helicopter rotors in presence of the fuselage. The focus of the paper is on the design for a generic “tail rotor” noise source used in the fuselage scattering study. The main design criterion is that the generic rotor noise source should resemble the main characteristics of the tail rotor with clear harmonic components. A two bladed simplified tail rotor model is considered. The performance of the tail rotor model in terms of thrust and torque with respect to the advance ratio is calibrated in the POLIMI wind tunnel. Acoustic measurements of the tail rotor model were tested in the DLR Acoustic Wind tunnel Braunschweig AWB. The results of the rotor performance and the rotor acoustic characteristics are described. The spectral variations resulting from unsteadiness of the source are explored in both with and without wind. The noise characteristics such as the spectral con...
The present paper describes the experimental activity carried out at Politecnico di Milano large ... more The present paper describes the experimental activity carried out at Politecnico di Milano large wind tunnel in the frame of CleanSky programme to assess the effectiveness of the CFD-based air-intake duct shape optimisation of the European platform tiltrotor ERICA. The tests were carried out on a 1/2.5 scaled model including the nacelle, the external portion of the wing and two interchangeable internal ducts reproducing the baseline and optimised shape. In addition, the model presented the rotor hub equipped with rotating blade stubs. A comprehensive experimental campaign was carried out including model configurations reproducing different forward flight conditions of the aircraft. The assessment of the optimised shape performance was evaluated by comparison of directional probes measurements performed at the Aerodynamic Interface Plane (AIP). Moreover, pressure measurements were also carried out on the duct internal surface. The experimental results confirmed an improved performanc...
The present paper describes the experimental set up of the wind tunnel activity to assess the eff... more The present paper describes the experimental set up of the wind tunnel activity to assess the effectiveness of the CFD-based air-intake shape optimisation of the European platform tiltrotor (ERICA). The wind tunnel campaign is carried out in the framework of the CleanSky TETRA project. The wind tunnel model was appositely designed and manufactured including the nacelle, the external wing and two interchangeable internal ducts (original and optimized). The performance evaluation is then made by the comparison of the pressure losses over the duct and the flow behavior at the engine face for both original and optimized intake duct shapes. Moreover, the evaluation of the internal flow field is made by means of an endoscopic PIV measurements performed in critical regions.
The rotor-rotor aerodynamic interaction is one of the key phenomena that characterise the flow an... more The rotor-rotor aerodynamic interaction is one of the key phenomena that characterise the flow and the performance of most of the new urban air mobility vehicles (eVTOLs) developed in the recent years. The present article describes a numerical activity that aimed to the systematic study of the rotor-rotor aerodynamic interaction with application to the flight conditions typical of eVTOL aircraft. The activity considers the use of a novel mid-fidelity aerodynamic solver based on vortex particle method. In particular, numerical simulations were performed when considering two propellers both in side-by-side and tandem configuration with different separation distances. The results of numerical simulations showed a slight reduction of the propellers performance in side-by-side configuration, while a remarkable loss of thrust in the order of 40% and a reduction of about 20% of the propulsive efficiency were found in tandem configuration, particularly when the propeller disks are completel...
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