The effects of an airfoil at different angles of attack and a circular cylindrical rod within the edge of the boundary layer flow at the leading edge of a cavity as a device for controlling the large pressure fluctuations (resonance tones) in the cavity were investigated. The airfoil results were compared with the rod in crossflow method positioned at the same leading edge location. The cavity used for testing corresponded to a length to depth ratio, L/D of 11.0/2.25 with a length to width ratio, L/W of 11.0/3.00 at a freestream Mach 1.84 flow. The study included measurements of dynamic pressure transducer output at 40 kHz and Frequency Spectra calculations, using Schlieren techniques for shock wave structures with velocity and vorticity fields obtained from PIV measurements. All airfoil configurations experienced flow separation to varying degrees. The negative 10 degree angle of attack configuration experienced the greatest amount of flow separation. All airfoil configurations provided varying degrees of cavity (resonant) tone suppression. Of the airfoil configurations, the negative 10 degree airfoil provided the best noise suppression with a 5 dB SPL reduction in broadband noise and a 9 dB reduction in peak amplitude for the 3rd resonant mode. Although all the airfoil configurations provided various levels of noise suppression, none of the configurations performed to the level of the rod in crossflow technique which provided an 8 dB SPL reduction in broadband noise and a 22 dB reduction in peak amplitude for the 2nd resonant mode. Indications of shear flow lofting effects could not be studied within any of the configurations tested. Lofting effect testing would have required flow field visualization of the cavity trailing edge region. Dynamic pressure measurements at a location near the cavity trailing edge did not detect the rod vortex shedding frequency, clearly. Because PIV results showed strong indication of vortex shedding, the lack of vortex shedding frequency data was attributed to the dynamic pressure transducer being located a far distance of 44 rod diameters downstream of the rod location. All airfoil test configurations showed evidence of deflections to the cavity leading edge oblique shock wave. The mechanisms of the deflection were the airfoil trailing edge shocks interacting with the cavity leading edge shock.

The total worldwide base of installed wind energy peak capacity reached 94 GW by the end of 2007, including 1846 MW in Canada. Wind turbine systems are being installed throughout Canada and often in mountains and cold weather regions, due to their high wind energy potential. Harsh cold weather climates, involving turbulence, gusts, icing and lightning strikes in these regions, affect wind turbine performance. Ice accretion and irregular shedding during turbine operation lead to load imbalances, often causing the turbine to shut off. They create excessive turbine vibration and may change the natural frequency of blades as well as promote higher fatigue loads and increase the bending moment of blades. Icing also affects the tower structure by increasing stresses, due to increased loads from ice accretion. This can lead to structural failures, especially when coupled to strong wind loads. Icing also affects the reliability of anemometers, thereby leading to inaccurate wind speed measurements and resulting in resource estimation errors. Icing issues can directly impact personnel safety, due to falling and projected ice. It is therefore important to expand research on wind turbines operating in cold climate areas. This study presents an experimental investigation including three important fundamental aspects: 1) heat transfer characteristics of the airfoil with and without liquid water content (LWC) at varying angles of attack; 2) energy losses of wind energy while a wind turbine is operating under icing conditions; and 3) aerodynamic characteristics of an airfoil during a simulated icing event. A turbine scale model with curved 3-D blades and a DC generator is tested in a large refrigerated wind tunnel, where ice formation is simulated by spraying water droplets. A NACA 63421 airfoil is used to study the characteristics of aerodynamics and convective heat transfer. The current, voltage, rotation of the DC generator and temperature distribution along the airfoil, which are used to calculate heat transfer coefficients, are measured using a Data Acquisition (DAQ) system and recorded with LabVIEW software. The drag, lift and moment of the airfoil are measured by a force balance system to obtain the aerodynamics of an iced airfoil. This research also quantifies the power loss under various icing conditions. The data obtained can be used to valid numerical data method to predict heat transfer characteristics while wind turbine blades worked in cold climate regions. / October 2008

This thesis studies to simulate the axial flow fans by using the CFD software. Designing two geometries types of axial flow fans which had different twist angles and the same contour¡]70¡Ñ70¡Ñ15 mm¡^with the Joukowski airfoil; then, defining the boundaries shapes identical with the experimental instrument. In the part of numerical calculation, varying the rotation speed ¡]rpm¡^,volume flow rate¡]CFM¡^and seven types of turbulence models to simulate the flow fields and evaluate the axial flow fans performance curves. Utilizing the comparison of the experimental and simulate results to provide the appropriate turbulent models to periodic the performance curve precisely.

An experimental investigation was undertaken to test the effectiveness of a novel design for controlling the aerodynamics of an airfoil. A synthetic jet actuator (SJA) was placed inside a NACA 0015 airfoil with its jet at 12.5% of the chord length, hereby referred to as the leading edge actuator. Four centrifugal fans across the span were mounted at 70% of the chord and the jet formed by them was located at 99% of the chord, hereby referred to as the trailing edge actuator. The effects of these actuators on the aerodynamic properties were studied, separately and then in conjunction, with varying angles of attack. The leading edge actuator delays the onset of stall up to 24 degrees, the maximum angle of attack that could be attained. The control of the aerodynamics was achieved by controlling the amount of separated region. There was no effect of the actuation at lower angles of attack. The trailing edge actuator provides aerodynamic control at both low and high angles of attack. The study investigated the effect of jet momentum coefficient on the aerodynamic properties for various angles of attack. The data obtained shows that lift control (in both positive and negative direction) was achieved even at low angles. The actuator enhances the aerodynamic properties by changing the pressure distribution as well as by delaying flow separation. Study of the combined actuation shows that the synthetic jet actuator was very effective in delaying stall when the trailing edge jet was ejected from the upper surface. For the case when the jet is ejected from the lower surface, there is less control. This can be accounted for by the difference in aerodynamic loading for both cases.

The total worldwide base of installed wind energy peak capacity reached 94 GW by the end of 2007, including 1846 MW in Canada. Wind turbine systems are being installed throughout Canada and often in mountains and cold weather regions, due to their high wind energy potential. Harsh cold weather climates, involving turbulence, gusts, icing and lightning strikes in these regions, affect wind turbine performance. Ice accretion and irregular shedding during turbine operation lead to load imbalances, often causing the turbine to shut off. They create excessive turbine vibration and may change the natural frequency of blades as well as promote higher fatigue loads and increase the bending moment of blades. Icing also affects the tower structure by increasing stresses, due to increased loads from ice accretion. This can lead to structural failures, especially when coupled to strong wind loads. Icing also affects the reliability of anemometers, thereby leading to inaccurate wind speed measurements and resulting in resource estimation errors. Icing issues can directly impact personnel safety, due to falling and projected ice. It is therefore important to expand research on wind turbines operating in cold climate areas. This study presents an experimental investigation including three important fundamental aspects: 1) heat transfer characteristics of the airfoil with and without liquid water content (LWC) at varying angles of attack; 2) energy losses of wind energy while a wind turbine is operating under icing conditions; and 3) aerodynamic characteristics of an airfoil during a simulated icing event. A turbine scale model with curved 3-D blades and a DC generator is tested in a large refrigerated wind tunnel, where ice formation is simulated by spraying water droplets. A NACA 63421 airfoil is used to study the characteristics of aerodynamics and convective heat transfer. The current, voltage, rotation of the DC generator and temperature distribution along the airfoil, which are used to calculate heat transfer coefficients, are measured using a Data Acquisition (DAQ) system and recorded with LabVIEW software. The drag, lift and moment of the airfoil are measured by a force balance system to obtain the aerodynamics of an iced airfoil. This research also quantifies the power loss under various icing conditions. The data obtained can be used to valid numerical data method to predict heat transfer characteristics while wind turbine blades worked in cold climate regions.

A Horizontal Axis Wind Turbine (HAWT) experiences imbalanced loads when it operates under yaw loads. For each blade element of the aerodynamically imbalanced rotor, not only is the angle of attack unsteady, but also the corresponding incident velocity, a fact usually unfairly ignored. For the unsteady angle of attack, a pitch oscillating airfoil has been studied experimentally and numerically when 3.5×10⁴<Re<10⁵. For small wind tunnel airfoils, Particle Image Velocimetry (PIV) was utilized to determine the aerodynamic loads and the pressure field where other measurement techniques are either intrusive or very challenging. For dynamic airfoils in highly separated flow fields, i.e., deep dynamic stall phenomena, loads were calculated successfully based on the control-volume approach by exploring ways to reduce the level of uncertainties in particular for drag estimation. Consecutive high resolution PIV velocity fields revealed that increasing the reduced frequency was followed by an enriched vortex growth time and phase delay as well as a reduced number of vortices during upstroke motion. Moreover, the locations of the vortices after separation were influenced by each other. Laminar separation bubble height also showed a reducing trend as the reduced frequency increased. The nature of the vortex sheet vortices before stall were explored in two Reynolds numbers, with and without laminar separation bubbles, at low angles of attack. For all cases, a vortex sheet was the result of random vortex sheding while a longer vortex sheet was more favorable for lift augmentation. A wake study and averaged drag calculation at low angles of attack were also performed with Laser Doppler Anemometry (LDA) for Re=10⁵. For the unsteady incident velocity, longitudinal freestream oscillations have been studied numerically, since experimental study of an unsteady freestream is challenging. In this regard, the streamwise freestream velocity and pitch angle of incidence oscillated with the same frequency in a wide range of phase differences. Changing the phase difference caused variation of the results, including significantly augmented and dramatically damped dynamic stall loads, both increasing and decreasing trends for vortex growth time during phase increase and shifted location of the maximum loads. The results showed strong dependency on the velocity and acceleration of the freestream during dynamic stall and the dynamic stall characteristics differed significantly from those of the steady freestream states. The results also demonstrated consistent trends regardless of the airfoil shape and the Reynolds number while Re=10⁵ and 10⁶. The vortex study presented here not only provides information about the unsteady aerodynamic forces, but also knowledge regarding airfoil noise generation and distributed flow for downstream objects beyond wind turbine applications.

A new method, Computational Acoustic Beamforming, is proposed in this thesis. This novel numerical sound source localization methodology combines the advantages of the Computational Fluid Dynamics (CFD) simulation and experimental acoustic beamforming, which enable this method to take directivity of sound source emission into account while maintaining a relatively low cost. This method can also aid the optimization of beamforming algorithm and microphone array design. In addition, it makes sound source prediction of large structures in the low frequency range possible. Three modules, CFD, Computational Aeroacoustics (CAA) and acoustic beamforming, are incorporated in this proposed method. This thesis adopts an open source commercial software OpenFOAM for the flow field simulation with the Improved Delayed Detached Eddy Simulation (IDDES) turbulence model. The CAA calculation is conducted by an in-house code using impermeable Ffowcs-Williams and Hawkings (FW-H) equation for static sound source. The acoustic beamforming is performed by an in-house Delay and Sum (DAS) beamformer code with several different microphone array designs. Each module has been validated with currently available experimental data and numerical results. A flow over NACA 0012 airfoil case was chosen as a demonstration case for the new method. The aerodynamics and aeroacoustics results are shown and compared with the experimental measurements. A relatively good agreement has been achieved which gives the confidence of using this newly proposed method in sound source localization applications.

The total worldwide base of installed wind energy peak capacity reached 94 GW by the end of 2007, including 1846 MW in Canada. Wind turbine systems are being installed throughout Canada and often in mountains and cold weather regions, due to their high wind energy potential. Harsh cold weather climates, involving turbulence, gusts, icing and lightning strikes in these regions, affect wind turbine performance. Ice accretion and irregular shedding during turbine operation lead to load imbalances, often causing the turbine to shut off. They create excessive turbine vibration and may change the natural frequency of blades as well as promote higher fatigue loads and increase the bending moment of blades. Icing also affects the tower structure by increasing stresses, due to increased loads from ice accretion. This can lead to structural failures, especially when coupled to strong wind loads. Icing also affects the reliability of anemometers, thereby leading to inaccurate wind speed measurements and resulting in resource estimation errors. Icing issues can directly impact personnel safety, due to falling and projected ice. It is therefore important to expand research on wind turbines operating in cold climate areas. This study presents an experimental investigation including three important fundamental aspects: 1) heat transfer characteristics of the airfoil with and without liquid water content (LWC) at varying angles of attack; 2) energy losses of wind energy while a wind turbine is operating under icing conditions; and 3) aerodynamic characteristics of an airfoil during a simulated icing event. A turbine scale model with curved 3-D blades and a DC generator is tested in a large refrigerated wind tunnel, where ice formation is simulated by spraying water droplets. A NACA 63421 airfoil is used to study the characteristics of aerodynamics and convective heat transfer. The current, voltage, rotation of the DC generator and temperature distribution along the airfoil, which are used to calculate heat transfer coefficients, are measured using a Data Acquisition (DAQ) system and recorded with LabVIEW software. The drag, lift and moment of the airfoil are measured by a force balance system to obtain the aerodynamics of an iced airfoil. This research also quantifies the power loss under various icing conditions. The data obtained can be used to valid numerical data method to predict heat transfer characteristics while wind turbine blades worked in cold climate regions.

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