Daniel Micallef | University of Malta (original) (raw)

Papers by Daniel Micallef

Numerical investigation of the wake interaction between two model wind turbines with span-wise of... more Numerical investigation of the wake interaction between two model wind turbines with span-wise offset Sasan Sarmast, Hamid Sarlak Chivaee, Stefan Ivanell et al. Numerical analysis of the tip and root vortex position in the wake of a wind turbine S Ivanell, J N Sørensen, R Mikkelsen et al. Reduced order model of the inherent turbulence of wind turbine wakes inside an infinitely long row of turbines S J Andersen, J N Sørensen and R Mikkelsen The relationship between loads and power of a rotor and an actuator disc Gijs A M van Kuik Flow performance of highly loaded axial fan with bowed rotor blades L Chen, X J Liu, A L Yang et al.

The performance of a wind turbine located above a cubic building is not well understood. This iss... more The performance of a wind turbine located above a cubic building is not well understood. This issue is of fundamental importance for the design of small scale wind turbines. One variable which is of particular importance in this respect is the turbine height above roof level. In this work, the power performance of a small wind turbine is assessed as a function of the height above the roof of a generic cubic building. A 3D Computational Fluid Dynamics model of a 10m x 10m x 10m building is used with the turbine modelled as an actuator disc. Results have shown an improvement in the average power coefficient even in cases where the rotor is partially located within the roof separation zone. This goes against current notions of small wind turbine power production. This study can be of particular importance to guide the turbine installation height on building roof tops.

The blade of a scaled down Horizontal Axis Wind Turbine working in Yawed Flow conditions has been... more The blade of a scaled down Horizontal Axis Wind Turbine working in Yawed Flow conditions has been investigated by means of Stereoscopic Particle Image Velocimetry. The goal was to obtain, simultaneously, the 3D velocity field surrounding the blade, the pressure distribution around it and the aerodynamic loads being exerted on the blade, responsible for thrust and torque.

The velocity elds of the dierent cross sectional planes of a horizontal axis wind turbine working... more The velocity elds of the dierent cross sectional planes of a horizontal axis wind turbine working in axial ow condition have been inspected by means of the stereoscopic PIV technique. These 3D velocity measurements bring a better understanding of the ow phenomena in each of the elements of the rotating blade and represent a way of reconstruction of the pressure eld around the airfoils without the need of pressure tabs and their inherent set up complexity. Furthermore, they provide the means for calculating the aerodynamic forces impinged on each section of the wind turbine. Data analyzed herein were acquired at the Open Jet Facility at TU Delft from a two bladed upwind rotor, 2 m in diameter, operating at Ω = 400 rpm and tip speed ratio λ = 7. Phase locked 3D PIV velocity measurements were obtained at cross sectional positions of the blade, spaced 10mm to 30mm spanwise between each other, from the tip to the root. The pressure eld was obtained by solving the Poisson equation in all ...

Lifting line vortex approaches have been widely used to predict rotor flow fields. Nonetheless, t... more Lifting line vortex approaches have been widely used to predict rotor flow fields. Nonetheless, there could be some deficiencies in the flow field close to the blade due to the assumption that blade vorticity is concentrated on a line. The present study thoroughly assessed the errors arising from this approximation by prescribing the bound circulation as a boundary condition on the flow, using an inverse lifting-line free-wake vortex approach. The prescribed bound circulation was calculated front two independent sources using (1) experimental results from PIV and (2) data generated from a 3D panel free-wake vortex approach, where the blade geometry is fully modelled. The flow field around the blades from the inverse lifting line vortex model was then compared with those directly produced by SPIV and the 3D panel model.

Fig 1: Flow streamlines and velocity magnitude contours over a flat roof having three rows of pho... more Fig 1: Flow streamlines and velocity magnitude contours over a flat roof having three rows of photovoltaic panels. Wind speed at inlet and at the building height is 6m/s. Research summary In a Mediterranean climate, given the absence of snow, flat roofs are typical of both vernacular and modern architecture. Thermal mass, cross ventilation and night time cooling are standard passive design aids that inhibit indoor temperature build-up on hot summer days. Such flat roofs provide a golden opportunity for free-orientation of PV (photovoltaic) panels, unlike pitched roofs. There is established scientific evidence that their presence on flat roofs also helps curtail surface temperatures of the heavy mass structure, by means of (i) solar shading and (ii) convective cooling at given angles. Both factors in turn lower the convective heat transfer coefficient (CHTC) of the roof structure, thus inhibiting early seasonal temperature build-up. This contributes to lower cooling loads, thus reducing both the carbon footprint of the building as well as lowering energy costs for the owners. Such a holistic contribution is deemed to uphold the social, environmental and economic challenges of today. This study purports to do just that. Through CFD (computational fluid dynamics) this study investigates the effect of flow fields over a typical flat roof building mass in a free field for a range of wind velocities. Results indicate that for a higher wind speed, the convective cooling is more significant than at lower wind speeds. This will in turn influence the elemental U-value of the roof structure, thus reducing cooling loads indoors.

The effect of roof mounted photovoltaics on the heat transfer performance of roofs has primarily ... more The effect of roof mounted photovoltaics on the heat transfer performance of roofs has primarily been investigated in the context of the resulting shading effect. The convective heat transfer coefficient will change as a result of the blockage caused by the photovoltaic panels. In this work, a quantification is given of the differences between heat transfer coefficients on a bare roof and a roof with photovoltaic panels having a specified configuration. A computational fluid dynamics approach is used. The study is only preliminary and hence a standard k-e turbulence model is used. The presence of photovoltaics is found to increase the convective heat transfer coefficients by around 26% for a north wind. The influence on the U-Value depends on the type of roof construction but for summer conditions an increase in U-value is observed which has positive cooling effects.

Friction stir welding (FSW) of steel is an advanced joining process which is expected to deliver ... more Friction stir welding (FSW) of steel is an advanced joining process which is expected to deliver considerable technical and commercial benefits to the European waterborne manufacturing sector. A microstructure and property evaluation of friction stir welded DH36 6mm plate has been undertaken. The study examined a wide range of process parameters and, from this, a process parameter envelope has been developed and an initial process parameter set established that gives good welding properties. Thermo-mechanical deformation studies were developed to generate flow stress regimes over a range of stain rates and temperatures and these data will support the on-going local numerical modelling development. A preliminary thermo-fluid model has been developed to predict temperature and material flow during the FSW of steel grade DH36. In parallel, a global numerical model is being developed to predict the inherent residual stresses and distortion of FSW butt welded assemblies often in excess of 6m long plate.

The main motivation behind this work is to create a purely analytical engineering model for wind ... more The main motivation behind this work is to create a purely analytical engineering model for wind turbine wake upward deflection due to shear flow, by developing a closed form solution of the velocity field due to an oblique vortex ring. The effectiveness of the model is evaluated by comparing the results with those of a free-wake model. The solution of

Absorption refrigeration systems are an alternative to vapour compression systems by being therma... more Absorption refrigeration systems are an alternative to vapour compression systems by being thermally activated. Such heat energy may come from the sun or even from hot exhaust gases from a particular engineering process. Vapour absorption systems utilize four major heat exchangers: an evaporator, condenser, absorber and generator. The operating temperatures of these units affect dramatically the performance of the system.

Wind turbine structures and components suffer excessive loads and premature failures when key aer... more Wind turbine structures and components suffer excessive loads and premature failures when key aerodynamic phenomena are not well characterized, fail to be understood, or are inaccurately predicted. Turbine blade rotational augmentation remains incompletely characterized and understood, thus limiting robust prediction for design. Pertinent rotational augmentation research including experimental, theoretical, and computational work has been pursued for some time, but large scale wind tunnel testing is a relatively recent development for investigating wind turbine blade aerodynamics. Because of their large scale and complementary nature, the MEXICO and UAE Phase VI wind tunnel experiments offer unprecedented synergies to better characterize and understand rotational augmentation of blade aerodynamics.

Laboratory measurements of the motion and rotor performance of a model floating wind turbine were... more Laboratory measurements of the motion and rotor performance of a model floating wind turbine were undertaken under simple wind and wave conditions. The model consisted of a 40cm diameter rotor mounted on a fully submerged cylinder supported vertically by four arms to form a tension leg floater. The laboratory facility involved a low-wind speed straight-through wind tunnel assembled on the water wave generator. The turbine was connected to a DC generator and an electrical variable-resistance load to vary the rotor speed. Tests were undertaken for one fixed wind speed, varying the rotor tip speed ratio and wave conditions. Four different one-dimensional wave conditions were considered, each with a different wavelength and frequency. Sensors were installed to measure the unsteady wave height and surge of the turbine platform. Other sensors were installed to measure the rotor speed and the generator output power.

The primary objective of the MEXICO (Model Experiments in Controlled Conditions) project was to g... more The primary objective of the MEXICO (Model Experiments in Controlled Conditions) project was to generate experimental data from which the uncertainties of the computational tools employed to predict wind turbine performance and loads. Pressure sensors were used for pressure measurements while PIV was used with the major aim of tracking the tip vortex trajectory. The aerodynamic forces on the blades were derived found from the pressure measurements and were used in an inverse free wake lifting line model to compute the positions of the tip vortices. From these the wake skew angle was derived. A relationship between the skew angle and the thrust coefficient was thus drawn.

48th AIAA Aerospace Sciences Meeting Including the New Horizons Forum and Aerospace Exposition, 2010

The primary objective of the MEXICO (Model Experiments in Controlled Conditions) project was to g... more The primary objective of the MEXICO (Model Experiments in Controlled Conditions) project was to generate experimental data for validation of models for wind turbines. Kulite c pressure sensors were used for pressure measurements while Particle Image Velocimetry was used with the aim of tracking the tip vortex trajectory. The pressure measurements were carried out for both axial and yawed flow conditions with yaw angles of 15 o , 30 o and 45 o . For the Particle Image Velocimetry measurements data was gathered for axial flow and for the ±30 o yaw cases at a single tip speed ratio.

By means of carefully devised assumptions, a simple linear model is presented for an absorption r... more By means of carefully devised assumptions, a simple linear model is presented for an absorption refrigeration unit employing either water-lithium bromide or ammonia-water refrigerant-absorbent pairs. Absorption systems are an alternative to vapour compression systems by being thermally activated. Such heat energy may come from the sun or even from hot exhaust gases from a particular engineering process. A thorough investigation of the optimal operating temperatures is necessary to ensure effective operation of the system. By means of this simulation, the system response to varying absorber, generator and condenser temperatures was analyzed.

Understanding the impact of wave induced effects on the aerodynamic performance of Floating Offsh... more Understanding the impact of wave induced effects on the aerodynamic performance of Floating Offshore Wind Turbines (FOWTs) is crucial towards developing floating wind turbines cost-effectively to harness wind energy in deep water sites. The complexity of the wake of an FOWT has not yet been fully understood and both experimental together with numerical techniques are essential in this regard. An open source free-wake vortex code was used to determine whether experimentally-observed effects of the wave motions on floating rotor aerodynamics could be reproduced numerically by the lifting line method. From free-wake simulations on a large scale FOWT, complex wake phenomena were observed under the impact of extreme wave conditions. It was found that the difference between the mean power coefficient under platform surge conditions and the steady power coefficient depends on platform surge frequency, surge amplitude and the rotor operating conditions. Using the results from the free-wake vortex simulations, an analysis of a number of wind turbine wake characteristics under floating conditions was carried out in order to identify possible reasons behind the increase in the aerodynamic torque and thrust variations with tip speed ratio.

The velocity elds of the dierent cross sectional planes of a horizontal axis wind turbine working... more The velocity elds of the dierent cross sectional planes of a horizontal axis wind turbine working in axial ow condition have been inspected by means of the stereoscopic PIV technique. These 3D velocity measurements bring a better understanding of the ow phenomena in each of the elements of the rotating blade and represent a way of reconstruction of the pressure eld around the airfoils without the need of pressure tabs and their inherent set up complexity. Furthermore, they provide the means for calculating the aerodynamic forces impinged on each section of the wind turbine. Data analyzed herein were acquired at the Open Jet Facility at TU Delft from a two bladed upwind rotor, 2 m in diameter, operating at Ω = 400 rpm and tip speed ratio λ = 7. Phase locked 3D PIV velocity measurements were obtained at cross sectional positions of the blade, spaced 10mm to 30mm spanwise between each other, from the tip to the root. The pressure eld was obtained by solving the Poisson equation in all ...

The effect of roof mounted photovoltaics on the heat transfer performance of roofs has primarily ... more The effect of roof mounted photovoltaics on the heat transfer performance of roofs has primarily been investigated in the context of the resulting shading effect. The convective heat transfer coefficient will change as a result of the blockage caused by the photovoltaic panels. In this work, a quantification is given of the differences between heat transfer coefficients on a bare roof and a roof with photovoltaic panels having a specified configuration. A computational fluid dynamics approach is used. The study is only preliminary and hence a standard k-e turbulence model is used. The presence of photovoltaics is found to increase the convective heat transfer coefficients by around 26% for a north wind. The influence on the U-Value depends on the type of roof construction but for summer conditions an increase in U-value is observed which has positive cooling effects.

Numerical investigation of the wake interaction between two model wind turbines with span-wise of... more Numerical investigation of the wake interaction between two model wind turbines with span-wise offset Sasan Sarmast, Hamid Sarlak Chivaee, Stefan Ivanell et al. Numerical analysis of the tip and root vortex position in the wake of a wind turbine S Ivanell, J N Sørensen, R Mikkelsen et al. Reduced order model of the inherent turbulence of wind turbine wakes inside an infinitely long row of turbines S J Andersen, J N Sørensen and R Mikkelsen The relationship between loads and power of a rotor and an actuator disc Gijs A M van Kuik Flow performance of highly loaded axial fan with bowed rotor blades L Chen, X J Liu, A L Yang et al.

The performance of a wind turbine located above a cubic building is not well understood. This iss... more The performance of a wind turbine located above a cubic building is not well understood. This issue is of fundamental importance for the design of small scale wind turbines. One variable which is of particular importance in this respect is the turbine height above roof level. In this work, the power performance of a small wind turbine is assessed as a function of the height above the roof of a generic cubic building. A 3D Computational Fluid Dynamics model of a 10m x 10m x 10m building is used with the turbine modelled as an actuator disc. Results have shown an improvement in the average power coefficient even in cases where the rotor is partially located within the roof separation zone. This goes against current notions of small wind turbine power production. This study can be of particular importance to guide the turbine installation height on building roof tops.

The blade of a scaled down Horizontal Axis Wind Turbine working in Yawed Flow conditions has been... more The blade of a scaled down Horizontal Axis Wind Turbine working in Yawed Flow conditions has been investigated by means of Stereoscopic Particle Image Velocimetry. The goal was to obtain, simultaneously, the 3D velocity field surrounding the blade, the pressure distribution around it and the aerodynamic loads being exerted on the blade, responsible for thrust and torque.

The velocity elds of the dierent cross sectional planes of a horizontal axis wind turbine working... more The velocity elds of the dierent cross sectional planes of a horizontal axis wind turbine working in axial ow condition have been inspected by means of the stereoscopic PIV technique. These 3D velocity measurements bring a better understanding of the ow phenomena in each of the elements of the rotating blade and represent a way of reconstruction of the pressure eld around the airfoils without the need of pressure tabs and their inherent set up complexity. Furthermore, they provide the means for calculating the aerodynamic forces impinged on each section of the wind turbine. Data analyzed herein were acquired at the Open Jet Facility at TU Delft from a two bladed upwind rotor, 2 m in diameter, operating at Ω = 400 rpm and tip speed ratio λ = 7. Phase locked 3D PIV velocity measurements were obtained at cross sectional positions of the blade, spaced 10mm to 30mm spanwise between each other, from the tip to the root. The pressure eld was obtained by solving the Poisson equation in all ...

Lifting line vortex approaches have been widely used to predict rotor flow fields. Nonetheless, t... more Lifting line vortex approaches have been widely used to predict rotor flow fields. Nonetheless, there could be some deficiencies in the flow field close to the blade due to the assumption that blade vorticity is concentrated on a line. The present study thoroughly assessed the errors arising from this approximation by prescribing the bound circulation as a boundary condition on the flow, using an inverse lifting-line free-wake vortex approach. The prescribed bound circulation was calculated front two independent sources using (1) experimental results from PIV and (2) data generated from a 3D panel free-wake vortex approach, where the blade geometry is fully modelled. The flow field around the blades from the inverse lifting line vortex model was then compared with those directly produced by SPIV and the 3D panel model.

Fig 1: Flow streamlines and velocity magnitude contours over a flat roof having three rows of pho... more Fig 1: Flow streamlines and velocity magnitude contours over a flat roof having three rows of photovoltaic panels. Wind speed at inlet and at the building height is 6m/s. Research summary In a Mediterranean climate, given the absence of snow, flat roofs are typical of both vernacular and modern architecture. Thermal mass, cross ventilation and night time cooling are standard passive design aids that inhibit indoor temperature build-up on hot summer days. Such flat roofs provide a golden opportunity for free-orientation of PV (photovoltaic) panels, unlike pitched roofs. There is established scientific evidence that their presence on flat roofs also helps curtail surface temperatures of the heavy mass structure, by means of (i) solar shading and (ii) convective cooling at given angles. Both factors in turn lower the convective heat transfer coefficient (CHTC) of the roof structure, thus inhibiting early seasonal temperature build-up. This contributes to lower cooling loads, thus reducing both the carbon footprint of the building as well as lowering energy costs for the owners. Such a holistic contribution is deemed to uphold the social, environmental and economic challenges of today. This study purports to do just that. Through CFD (computational fluid dynamics) this study investigates the effect of flow fields over a typical flat roof building mass in a free field for a range of wind velocities. Results indicate that for a higher wind speed, the convective cooling is more significant than at lower wind speeds. This will in turn influence the elemental U-value of the roof structure, thus reducing cooling loads indoors.

The effect of roof mounted photovoltaics on the heat transfer performance of roofs has primarily ... more The effect of roof mounted photovoltaics on the heat transfer performance of roofs has primarily been investigated in the context of the resulting shading effect. The convective heat transfer coefficient will change as a result of the blockage caused by the photovoltaic panels. In this work, a quantification is given of the differences between heat transfer coefficients on a bare roof and a roof with photovoltaic panels having a specified configuration. A computational fluid dynamics approach is used. The study is only preliminary and hence a standard k-e turbulence model is used. The presence of photovoltaics is found to increase the convective heat transfer coefficients by around 26% for a north wind. The influence on the U-Value depends on the type of roof construction but for summer conditions an increase in U-value is observed which has positive cooling effects.

Friction stir welding (FSW) of steel is an advanced joining process which is expected to deliver ... more Friction stir welding (FSW) of steel is an advanced joining process which is expected to deliver considerable technical and commercial benefits to the European waterborne manufacturing sector. A microstructure and property evaluation of friction stir welded DH36 6mm plate has been undertaken. The study examined a wide range of process parameters and, from this, a process parameter envelope has been developed and an initial process parameter set established that gives good welding properties. Thermo-mechanical deformation studies were developed to generate flow stress regimes over a range of stain rates and temperatures and these data will support the on-going local numerical modelling development. A preliminary thermo-fluid model has been developed to predict temperature and material flow during the FSW of steel grade DH36. In parallel, a global numerical model is being developed to predict the inherent residual stresses and distortion of FSW butt welded assemblies often in excess of 6m long plate.

The main motivation behind this work is to create a purely analytical engineering model for wind ... more The main motivation behind this work is to create a purely analytical engineering model for wind turbine wake upward deflection due to shear flow, by developing a closed form solution of the velocity field due to an oblique vortex ring. The effectiveness of the model is evaluated by comparing the results with those of a free-wake model. The solution of

Absorption refrigeration systems are an alternative to vapour compression systems by being therma... more Absorption refrigeration systems are an alternative to vapour compression systems by being thermally activated. Such heat energy may come from the sun or even from hot exhaust gases from a particular engineering process. Vapour absorption systems utilize four major heat exchangers: an evaporator, condenser, absorber and generator. The operating temperatures of these units affect dramatically the performance of the system.

Wind turbine structures and components suffer excessive loads and premature failures when key aer... more Wind turbine structures and components suffer excessive loads and premature failures when key aerodynamic phenomena are not well characterized, fail to be understood, or are inaccurately predicted. Turbine blade rotational augmentation remains incompletely characterized and understood, thus limiting robust prediction for design. Pertinent rotational augmentation research including experimental, theoretical, and computational work has been pursued for some time, but large scale wind tunnel testing is a relatively recent development for investigating wind turbine blade aerodynamics. Because of their large scale and complementary nature, the MEXICO and UAE Phase VI wind tunnel experiments offer unprecedented synergies to better characterize and understand rotational augmentation of blade aerodynamics.

Laboratory measurements of the motion and rotor performance of a model floating wind turbine were... more Laboratory measurements of the motion and rotor performance of a model floating wind turbine were undertaken under simple wind and wave conditions. The model consisted of a 40cm diameter rotor mounted on a fully submerged cylinder supported vertically by four arms to form a tension leg floater. The laboratory facility involved a low-wind speed straight-through wind tunnel assembled on the water wave generator. The turbine was connected to a DC generator and an electrical variable-resistance load to vary the rotor speed. Tests were undertaken for one fixed wind speed, varying the rotor tip speed ratio and wave conditions. Four different one-dimensional wave conditions were considered, each with a different wavelength and frequency. Sensors were installed to measure the unsteady wave height and surge of the turbine platform. Other sensors were installed to measure the rotor speed and the generator output power.

The primary objective of the MEXICO (Model Experiments in Controlled Conditions) project was to g... more The primary objective of the MEXICO (Model Experiments in Controlled Conditions) project was to generate experimental data from which the uncertainties of the computational tools employed to predict wind turbine performance and loads. Pressure sensors were used for pressure measurements while PIV was used with the major aim of tracking the tip vortex trajectory. The aerodynamic forces on the blades were derived found from the pressure measurements and were used in an inverse free wake lifting line model to compute the positions of the tip vortices. From these the wake skew angle was derived. A relationship between the skew angle and the thrust coefficient was thus drawn.

48th AIAA Aerospace Sciences Meeting Including the New Horizons Forum and Aerospace Exposition, 2010

The primary objective of the MEXICO (Model Experiments in Controlled Conditions) project was to g... more The primary objective of the MEXICO (Model Experiments in Controlled Conditions) project was to generate experimental data for validation of models for wind turbines. Kulite c pressure sensors were used for pressure measurements while Particle Image Velocimetry was used with the aim of tracking the tip vortex trajectory. The pressure measurements were carried out for both axial and yawed flow conditions with yaw angles of 15 o , 30 o and 45 o . For the Particle Image Velocimetry measurements data was gathered for axial flow and for the ±30 o yaw cases at a single tip speed ratio.

By means of carefully devised assumptions, a simple linear model is presented for an absorption r... more By means of carefully devised assumptions, a simple linear model is presented for an absorption refrigeration unit employing either water-lithium bromide or ammonia-water refrigerant-absorbent pairs. Absorption systems are an alternative to vapour compression systems by being thermally activated. Such heat energy may come from the sun or even from hot exhaust gases from a particular engineering process. A thorough investigation of the optimal operating temperatures is necessary to ensure effective operation of the system. By means of this simulation, the system response to varying absorber, generator and condenser temperatures was analyzed.

Understanding the impact of wave induced effects on the aerodynamic performance of Floating Offsh... more Understanding the impact of wave induced effects on the aerodynamic performance of Floating Offshore Wind Turbines (FOWTs) is crucial towards developing floating wind turbines cost-effectively to harness wind energy in deep water sites. The complexity of the wake of an FOWT has not yet been fully understood and both experimental together with numerical techniques are essential in this regard. An open source free-wake vortex code was used to determine whether experimentally-observed effects of the wave motions on floating rotor aerodynamics could be reproduced numerically by the lifting line method. From free-wake simulations on a large scale FOWT, complex wake phenomena were observed under the impact of extreme wave conditions. It was found that the difference between the mean power coefficient under platform surge conditions and the steady power coefficient depends on platform surge frequency, surge amplitude and the rotor operating conditions. Using the results from the free-wake vortex simulations, an analysis of a number of wind turbine wake characteristics under floating conditions was carried out in order to identify possible reasons behind the increase in the aerodynamic torque and thrust variations with tip speed ratio.

The velocity elds of the dierent cross sectional planes of a horizontal axis wind turbine working... more The velocity elds of the dierent cross sectional planes of a horizontal axis wind turbine working in axial ow condition have been inspected by means of the stereoscopic PIV technique. These 3D velocity measurements bring a better understanding of the ow phenomena in each of the elements of the rotating blade and represent a way of reconstruction of the pressure eld around the airfoils without the need of pressure tabs and their inherent set up complexity. Furthermore, they provide the means for calculating the aerodynamic forces impinged on each section of the wind turbine. Data analyzed herein were acquired at the Open Jet Facility at TU Delft from a two bladed upwind rotor, 2 m in diameter, operating at Ω = 400 rpm and tip speed ratio λ = 7. Phase locked 3D PIV velocity measurements were obtained at cross sectional positions of the blade, spaced 10mm to 30mm spanwise between each other, from the tip to the root. The pressure eld was obtained by solving the Poisson equation in all ...

The effect of roof mounted photovoltaics on the heat transfer performance of roofs has primarily ... more The effect of roof mounted photovoltaics on the heat transfer performance of roofs has primarily been investigated in the context of the resulting shading effect. The convective heat transfer coefficient will change as a result of the blockage caused by the photovoltaic panels. In this work, a quantification is given of the differences between heat transfer coefficients on a bare roof and a roof with photovoltaic panels having a specified configuration. A computational fluid dynamics approach is used. The study is only preliminary and hence a standard k-e turbulence model is used. The presence of photovoltaics is found to increase the convective heat transfer coefficients by around 26% for a north wind. The influence on the U-Value depends on the type of roof construction but for summer conditions an increase in U-value is observed which has positive cooling effects.

The fundamental physics of HAWT aerodynamics in yaw is reviewed with reference to some of the lat... more The fundamental physics of HAWT aerodynamics in yaw is reviewed with reference to some of the latest scientific research covering both measurements and numerical modelling. The purpose of this chapter is to enable a concise overview of this important subject in rotor aerodynamics. This will provide the student, researcher or industry professional a quick reference. Detailed references are included for those who need to delve deeper into the subject. The chapter is also restricted to the aerodynamics of single rotors and their wake characteristics. Far wake and wind turbine to turbine effects experienced in wind farms are excluded from this review. Finally, a future outlook is provided in order to inspire further research in yawed aerodynamics.