A low Reynolds number wind turbine blade model based on the S809 airfoil was tested in a subsonic wind tunnel to study the structural vibration of the blade under dynamic pitching maneuvers. Piezoelectric-based synthe...A low Reynolds number wind turbine blade model based on the S809 airfoil was tested in a subsonic wind tunnel to study the structural vibration of the blade under dynamic pitching maneuvers. Piezoelectric-based synthetic jet actuators were embedded inside the blade and activated with a synthetic jet momentum coefficient, Cμ of 2.30 × 10-3. Structural vibration was quantified for a range of unsteady angles undergoing “pitch up and down” and “sinusoidal pitch” maneuvers at a Reynolds number of 5.28 × 104. The blade tip deflection amplitude and frequency were acquired utilizing a pair of strain gauges mounted at the root of the model. Using active flow control vibration reduction was more effective during the pitch up portion of the blade motion cycle compared to the pitch down portion. This effect is due to dynamic stall, where a leading edge vortex is shed during the pitch up motion and contributes to higher lift compared to static angles of attack and lower lift when the blade is pitched down. Dynamic stall was measured with phase-locked stereoscopic particle image velocimetry (SPIV), where global mean flow measurements reveal a shift in location and reduction in the size of a recirculating flow structure near the suction surface of the blade during the pitch up motion compared to the pitch down.展开更多
Motivated by the 2022 worldwide Monkeypox(MPox)outbreak,a compartmental model is proposed to predict the evolution of the disease.Numerous models have been proposed for infectious diseases so far,although the number o...Motivated by the 2022 worldwide Monkeypox(MPox)outbreak,a compartmental model is proposed to predict the evolution of the disease.Numerous models have been proposed for infectious diseases so far,although the number of variables makes it difficult to establish causation relations between individual factors and transmission rates.In order to evaluate the reaction of susceptible people to avoid infection during the outbreak,the rate of transmission is modeled through a unique phenomenological probabilistic approach,allowing the expression of the rate of generation of new cases in terms of two charac-teristics of the susceptible group:the frequency of sexual encounters and the probability of transmission given that there is a sexual encounter.Transmission rates are obtained and compared for the U.S.and several other countries.Results show reductions of up to 71%in the transmissibility parameter,which may be combined with variations in the frequency of sexual encounters(obtained through behavioral research)to determine the changes in the probability of transmission during an outbreak in a much more convenient way than current alternatives.This framework presents a valuable tool to health authorities in the understanding of future sexually transmissible disease outbreaks.展开更多
文摘A low Reynolds number wind turbine blade model based on the S809 airfoil was tested in a subsonic wind tunnel to study the structural vibration of the blade under dynamic pitching maneuvers. Piezoelectric-based synthetic jet actuators were embedded inside the blade and activated with a synthetic jet momentum coefficient, Cμ of 2.30 × 10-3. Structural vibration was quantified for a range of unsteady angles undergoing “pitch up and down” and “sinusoidal pitch” maneuvers at a Reynolds number of 5.28 × 104. The blade tip deflection amplitude and frequency were acquired utilizing a pair of strain gauges mounted at the root of the model. Using active flow control vibration reduction was more effective during the pitch up portion of the blade motion cycle compared to the pitch down portion. This effect is due to dynamic stall, where a leading edge vortex is shed during the pitch up motion and contributes to higher lift compared to static angles of attack and lower lift when the blade is pitched down. Dynamic stall was measured with phase-locked stereoscopic particle image velocimetry (SPIV), where global mean flow measurements reveal a shift in location and reduction in the size of a recirculating flow structure near the suction surface of the blade during the pitch up motion compared to the pitch down.
文摘Motivated by the 2022 worldwide Monkeypox(MPox)outbreak,a compartmental model is proposed to predict the evolution of the disease.Numerous models have been proposed for infectious diseases so far,although the number of variables makes it difficult to establish causation relations between individual factors and transmission rates.In order to evaluate the reaction of susceptible people to avoid infection during the outbreak,the rate of transmission is modeled through a unique phenomenological probabilistic approach,allowing the expression of the rate of generation of new cases in terms of two charac-teristics of the susceptible group:the frequency of sexual encounters and the probability of transmission given that there is a sexual encounter.Transmission rates are obtained and compared for the U.S.and several other countries.Results show reductions of up to 71%in the transmissibility parameter,which may be combined with variations in the frequency of sexual encounters(obtained through behavioral research)to determine the changes in the probability of transmission during an outbreak in a much more convenient way than current alternatives.This framework presents a valuable tool to health authorities in the understanding of future sexually transmissible disease outbreaks.
