Aerodynamic Sensitivity Analysis for a Wind Turbine Airfoil in an Air-Particle Two-Phase Flow

In this paper, the Navier-Stokes equations coupled with a Lagrangian discrete phase model are described to simulate the air-particle flows over the S809 airfoil of the Phase VI blade, the NH6MW25 airfoil of a 6 MW wind turbine blade and the NACA0012 airfoil. The simulation results demonstrate that, in an attached flow, the slight performance degradation is caused by the boundary layer momentum loss. After flow separation, the performance degradation becomes significant and is dominated by a more extensive separation due to particles, since the aerodynamic coefficient increments and the moving distance of separation point present similar variation trends with increasing angle of attack. Unlike the NACA0012 airfoil, a most particle-sensitive angle of attack is found in the light stall region for a wind turbine airfoil, at which the lift decrement and the drag increment reach their peak values. For the S809 airfoil, the most sensitive angle of attack is about 3° higher than that for the maximum lift-to-drag ratio. Hence, the aerodynamic performance of a wind turbine is very susceptible to particles. Based on the most sensitive angles of attack, the more sensitive scope of angles of attack of a blade airfoil and the more sensitive range of rotor tip speed ratios are predicted sequentially. The present study clarifies the principles for the performance degradation of a wind turbine airfoil due to particles and the conclusions are useful for the wind turbine design reducing the particle influences

Numerical Study on the Power Efficiency and Flow Characteristics of a New Type of Wind Energy Collection Device

The increased velocity (Invelox) wind turbine system is a novel wind energy collection device. This system can collect and accelerate the air flow through a funnel and a Venturi tube. However, the efficiency of this system is relatively low under some wind directions. To improve the aerodynamic performance of Invelox, a straight-through layout with a windshield was proposed. The flow field of the improved design was studied by applying Computational Fluid Dynamics (CFD) and was compared with that in the original configuration. Numerical results show that when the Invelox exit is facing the incoming wind, the ratio of the average velocity inside the Venturi tube to the incoming wind speed, i.e., the speed ratio, will drop sharply, and even the airflow will push back. The improved layout can eliminate the sensitivity of incoming wind direction to aerodynamic characteristics. The windshield can effectively reduce the interference of incoming air to the outlet air, making the speed ratio increase by about 42%. Different wind profiles in the atmospheric boundary layer are used in the boundary of the flow domain as the incoming flow wind. With the increase in the wind profile index, the speed ratio of the Invelox system will gradually decrease

Rumen Bacteria Abundance and Fermentation Profile during Subacute Ruminal Acidosis and Its Modulation by <i>Aspergillus oryzae</i> Culture in RUSITEC System

This study aimed at characterizing changes in rumen bacteria abundance and fermentation profiles by artificial saliva (AS) pH, and at evaluating the potential modulatory role of Aspergillus oryzae culture (AOC) in a rumen simulation technique (RUSITEC) system. The treatment included high AS pH (pH 6.8) or low AS pH (pH 5.5) according to the McDougall’s method, and low AS pH was sustained by changing the composition of the AS (NaHCO3 from 9.8 to 1.96 g/L, Na2HPO4 from 9.3 to 1.86 g/L). In low AS pH condition, the diets contained either 0% AOC, 1.25% AOC, or 2.5% AOC. Therefore, there are four treatments: (1) high AS pH, 0% AOC (HASP); (2) low AS pH, 0% AOC (AOC0); (3) low AS pH, 1.25% AOC (AOC1); (4) low AS pH, 2.5% AOC (AOC2), respectively. The experimental diets were supplemented with 16 g basic diets with the forage to concentrate ratio of 40:60. The experiments were conducted two independent 13 days, with 9 days adaption periods and 4 days sample collection. The results showed that low AS pH decreased the degradabilites of dry matter (DM), organic matter (OM), crude protein (CP), neutral detergent fiber (NDF), and acid detergent fiber (ADF) (p Ruminococcus albus (p p = 0.026) and tended to increase the molar proportion of butyrate (p = 0.086) and the ratio of acetate to propionate (p = 0.088). The abundances of phylum Firmicutes (p = 0.065) and Proteobacteria (p = 0.063) tended to be greater in low AS pH group than high AS pH group. Low AS pH increased the abundance of phylum Actinobacteria (p = 0.002) compared to the high AS pH and decreased the abundances of phylum Spirochaetes (p = 0.032). Compared with the high AS pH, low AS pH increased the abundances of Prevotella (p = 0.003), Pseudoscardovia (p = 0.001), Mitsuokella (p = 0.005), and Dialister (p = 0.047), and decreased the abundances of Olivibacter (p = 0.026), Ruminobacter (p = 0.025), Treponema (p = 0.037), and Sphaerochaeta (p = 0.027) at genus level. Under a severe SARA in RUSITEC, supplementation of 2.5% AOC increased OM degradability, the copy numbers of Selenomonas ruminantium and Fibrobacter succinogenes. These findings indicate that the reduction AS pH at 5.5 caused a strong shift in bacterial composition in rumen. In addition, the addition of AOC in diets increased the growth rate of certain rumen bacteria that digest fiber or utilize lactate under SARA condition in RUSITEC system

Rumen Bacteria Abundance and Fermentation Profile during Subacute Ruminal Acidosis and Its Modulation by Aspergillus oryzae Culture in RUSITEC System

This study aimed at characterizing changes in rumen bacteria abundance and fermentation profiles by artificial saliva (AS) pH, and at evaluating the potential modulatory role of Aspergillus oryzae culture (AOC) in a rumen simulation technique (RUSITEC) system. The treatment included high AS pH (pH 6.8) or low AS pH (pH 5.5) according to the McDougall&rsquo;s method, and low AS pH was sustained by changing the composition of the AS (NaHCO3 from 9.8 to 1.96 g/L, Na2HPO4 from 9.3 to 1.86 g/L). In low AS pH condition, the diets contained either 0% AOC, 1.25% AOC, or 2.5% AOC. Therefore, there are four treatments: (1) high AS pH, 0% AOC (HASP); (2) low AS pH, 0% AOC (AOC0); (3) low AS pH, 1.25% AOC (AOC1); (4) low AS pH, 2.5% AOC (AOC2), respectively. The experimental diets were supplemented with 16 g basic diets with the forage to concentrate ratio of 40:60. The experiments were conducted two independent 13 days, with 9 days adaption periods and 4 days sample collection. The results showed that low AS pH decreased the degradabilites of dry matter (DM), organic matter (OM), crude protein (CP), neutral detergent fiber (NDF), and acid detergent fiber (ADF) (p &lt; 0.05), which occurred due to a decreased abundance of fibrolytic Ruminococcus albus (p &lt; 0.001). The total concentration of volatile fatty acid (VFA) and proportion of propionate were decreased in the low AS pH (p = 0.026) and tended to increase the molar proportion of butyrate (p = 0.086) and the ratio of acetate to propionate (p = 0.088). The abundances of phylum Firmicutes (p = 0.065) and Proteobacteria (p = 0.063) tended to be greater in low AS pH group than high AS pH group. Low AS pH increased the abundance of phylum Actinobacteria (p = 0.002) compared to the high AS pH and decreased the abundances of phylum Spirochaetes (p = 0.032). Compared with the high AS pH, low AS pH increased the abundances of Prevotella (p = 0.003), Pseudoscardovia (p = 0.001), Mitsuokella (p = 0.005), and Dialister (p = 0.047), and decreased the abundances of Olivibacter (p = 0.026), Ruminobacter (p = 0.025), Treponema (p = 0.037), and Sphaerochaeta (p = 0.027) at genus level. Under a severe SARA in RUSITEC, supplementation of 2.5% AOC increased OM degradability, the copy numbers of Selenomonas ruminantium and Fibrobacter succinogenes. These findings indicate that the reduction AS pH at 5.5 caused a strong shift in bacterial composition in rumen. In addition, the addition of AOC in diets increased the growth rate of certain rumen bacteria that digest fiber or utilize lactate under SARA condition in RUSITEC system

Application of a Gas-Kinetic BGK Scheme in Thermal Protection System Analysis for Hypersonic Vehicles

One major problem in the development of hypersonic vehicles is severe aerodynamic heating; thus, the implementation of a thermal protection system is required. A numerical investigation on the reduction of aerodynamic heating using different thermal protection systems is conducted using a novel gas-kinetic BGK scheme. This method adopts a different solution strategy from the conventional computational fluid dynamics technique, and has shown a lot of benefits in the simulation of hypersonic flows. To be specific, it is established based on solving the Boltzmann equation, and the obtained gas distribution function is used to reconstruct the macroscopic solution of the flow field. Within the finite volume framework, the present BGK scheme is specially designed for the evaluation of numerical fluxes across the cell interface. Two typical thermal protection systems are investigated by using spikes and opposing jets, separately. Both their effectiveness and mechanisms to protect the body surface from heating are analyzed. The predicted distributions of pressure and heat flux, and the unique flow characteristics brought by spikes of different shapes or opposing jets of different total pressure ratios all verify the reliability and accuracy of the BGK scheme in the thermal protection system analysis

Improved vibration-based energy harvesting by annular mass configuration of piezoelectric circular diaphragms

Vibration-based energy harvesting using piezoelectric circular diaphragms (PCDs) has drawn many attentions in the recent decades, in which a structure with the central mass (C-mass) configuration was widely employed. In this work, we propose a new configuration with the annular proof mass (A-mass) where an improved energy harvesting is promised. Combining the numerical analysis using the circuit-coupled piezoelectric simulation and experimental validation using the even-width annular the PCDs via modifying the mass configurations as well as the parameters piv1 and piv2 which indicates the ratio between the inner boundary radius and the piezoelectric ceramic radius and the ratio between outer boundary radius and the substrate radius, respectively. The impedance-matched output power of full-electrode PCDs was also collected with varying structural parameters and some distinct improvement was measured on certain structural parameters. The power increases from 14.1mW to 19.0mW after changing the configuration of samples from C-mass to A-mass with the same parameters (piv1, piv2)=(0.16,0.9), showing the considerable improvement in energy harvesting by using A-mass configuration

Preparation of Whole-Cut Plant-Based Pork Meat and Its Quality Evaluation with Animal Meat

Low-moisture (20~40%) and high-moisture (40~80%) textured vegetable proteins (TVPs) can be used as important components of plant-based lean meat, while plant-based fat can be characterized by the formation of gels from polysaccharides, proteins, etc. In this study, three kinds of whole-cut plant-based pork (PBP) were prepared based on the mixed gel system, which were from low-moisture TVP, high-moisture TVP, and their mixtures. The comparisons of these products with commercially available plant-based pork (C-PBP1 and C-PBP2) and animal pork meat (APM) were studied in terms of appearance, taste, and nutritional qualities. Results showed the color changes of PBPs after frying were similar to that of APM. The addition of high-moisture TVP would significantly improve hardness (3751.96~7297.21 g), springiness (0.84~0.89%), and chewiness (3162.44~6466.94 g) while also reducing the viscosity (3.89~10.56 g) of products. It was found that the use of high-moisture TVP led to a significant increase in water-holding capacity (WHC) from 150.25% to 161.01% compared with low-moisture TVP; however, oil-holding capacity (OHC) was reduced from 166.34% to 164.79%. Moreover, essential amino acids (EAAs), the essential amino acids index (EAAI), and biological value (BV) were significantly increased from 272.68 mg/g, 105.52, and 103.32 to 362.65 mg/g, 141.34, and 142.36, respectively, though in vitro protein digestibility (IVPD) reduced from 51.67% to 43.68% due to the high-moisture TVP. Thus, the high-moisture TVP could help to improve the appearance, textural properties, WHC, and nutritional qualities of PBPs compared to animal meat, which was also better than low-moisture TVP. These findings should be useful for the application of TVP and gels in plant-based pork products to improve the taste and nutritional qualities