Maximum Cp Research Articles

Experimental Optimization of the SG6043 Airfoil for Horizontal Axis Wind Turbines Using Schmitz Equations

This study presents the experimental optimization of the SG6043 airfoil for horizontal axis wind turbines (HAWTs) using the Schmitz equation, focusing on enhancing power output and elucidating the surface flow structure. Two blade models, M1 (conventional) and M2 (optimized), were designed and tested at rotational speeds of 400 rpm and 600 rpm across a range of tip speed ratios (TSR). The M2 model, optimized using Schmitz equations, demonstrated significantly improved performance compared to the M1 model at both rotational speeds. At 400 rpm, the maximum power coefficient (CP) for M1 was 0.274, while M2 reached 0.419, indicating a 52.91% improvement. At 600 rpm, M1 achieved a maximum CP of 0.293, whereas M2 attained 0.458, representing a 56.31% enhancement. The M2 model also showed superior performance at higher TSRs, with the highest percentage increase in CP recorded at 4.9 TSR, reaching 574.54%. Additionally, dynamic surface oil-flow visualization experiments were conducted to examine flow behavior on the blade surfaces. Results indicated better flow attachment in the M2 blade due to its optimized twist angle and chord length, particularly in the mid-section, leading to delayed flow separation. The reattachment observed on the suction side of the M2 model, following the laminar separation bubble (LSB), which was absent in the M1, contributed to its higher aerodynamic efficiency and overall power performance. These findings confirm that the optimized SG6043 airfoil design, guided by Schmitz equations, offers significant improvements in HAWT performance, particularly under varying operational conditions.

Unveiling the Effects of Phosphorus on the Mineral Nutrient Content and Quality of Alfalfa (Medicago sativa L.) in Acidic Soils

Alfalfa (Medicago sativa L.) grown in acidic soils is often affected by phosphorus (P) deficiency, which results in reduced mineral nutrient content and forage quality. In this context, the effects of phosphorus (P) fertiliser remain unclear. In this study, we analysed the effects of P application on mineral nutrient content and forage quality in aluminium (Al)-sensitive (Longzhong) and Al-tolerant (Trifecta) alfalfa cultivars cultivated in two acidic soil environments. Mineral nutrient content and quality were affected by genotype, soil type, and P treatment concentration (p < 0.001). In limestone soil, for Longzhong and Trifecta, the optimal potassium (K), calcium (Ca), and magnesium (Mg) contents as well as crude protein content (CP) and ether extract (EE) values were observed at 20 mg P kg−1, that of the P content was observed at 40 mg P kg−1, and the minimum neutral detergent fibre (NDF) acid detergent lignin (ADL) values were observed at 40 mg P kg−1. In yellow soil, the maximum K, Ca, Mg, and P contents in Longzhong and Trifecta were observed at 40 mg P kg−1, whereas the maximum CP, EE, and ADL values were observed at 20 mg P kg−1. Our study provides an empirically based framework for optimising alfalfa fertilisation programmes in acidic soils.

A numerical investigation of a new horizontal wind turbine performance for rural use

In this paper, a new configuration of a horizontal axis wind turbine with three blades for domestic electricity production on farms was numerically simulated. Three configurations were tested numerically: a standard single-blade wind turbine (STWT), a single wind turbine (SWT), and a tandem three-blade wind turbine (TWT) for rural use. For the tandem wind turbine, the effects of pitch angle and the distance between the blades were also investigated. The Gambit and Fluent 19.2 codes were, respectively, used to generate different meshes and determine various parameters. The resolution of the averaged Navier–Stokes equations (RANS) using a finite volume method was conducted. The k–[Formula: see text] realizable two-equation model was chosen for turbulence calculation. The obtained results showed that the maximum power coefficient (Cp) was 0.444 for one of the tandem configurations (TWT), compared to the conventional blade (STWT). The maximum Cp obtained in this study is slightly greater than the experimental results found in the literature. It has also been observed that the flow on these new turbines exhibits a complex phenomenon on both surfaces.

Design, optimization and analysis of a modified Savonius hydro-kinetic turbine (MSHT) with curved winglet and straight blade

The pico-scale power generation in remote locations is now very promising due to small-scale power requirements. The major challenge is harnessing the same from the run-off river streams or canals that have low free-stream flow-speed (less than 1 m/s). Savonius hydro-kinetic turbine can self-start in such flow streams, but it exhibits poor efficiency. This study proposes a novel airfoil-shaped curved winglet that can enhance the functionality of this turbine. The popular semi-circular blade is replaced with a hybrid blade profile consisting of a curved winglet at the front-edge, which is tore out from NACA 63415 airfoil, followed by a straight blade section up to the trailing edge, thereby resulting in a modified Savonius hydro-kinetic turbine. The curved winglet minimizes negative torque effect on the rotor, while the long straight edge offers a greater moment-arm and gap-flow. The research is performed in two stages. In the first stage, three different models of the turbine with various combinations of blade overlapping, side clearance, and winglet offset are designed. Transient Computational Fluid Dynamics (CFD) simulations are run to assess and compare the model performances under different low flow-speeds. Taguchi optimization is then performed to obtain a combination of best design and operating conditions for higher performance. In the second stage, two more design variables of the winglet, namely winglet arc angle and cut-out arc section are introduced on the previous best model and detail analysis is done to further improve the turbine performance. Finally, the two best models are compared to obtain important performance insights of the turbine. Results show that winglet parameters with best cut-out arc section and offset improve performance more than the performance with traditional overlapping or side clearance design considerations. The maximum Cp and CT of 0.36 and 0.75 are obtained for the best model at the best winglet arc angle (a1) of 30° for flow-speed 0.4 m/s, and TSR 0.7 with combinations of 20 % blade overlapping, 6.14 % side clearance, and 15 mm winglet offset. The performance parameters of the turbine is also compared with the existing modified Savonius-turbine designs to emphasize the essential improvement of the current design.

Enhancing Savonius Rotor Performance With Zigzag Surface Investigated at Drag Force, Pressure, and Flow Visualization Analysis

Savonius, a type of vertical-axis wind turbine, is a small-scale energy conversion device suitable for low wind speeds, such as those characteristic of Indonesian wind speeds, yet has low efficiency. Savonius is a drag-type turbine. Drag force on the surface is affected by roughness or wavyness. The purpose of this study is to analyze the impact of applying wavy (zigzag) variations to the concave surface of Savonius blades on their performance. This was achieved by the use of 3D computational fluid dynamics simulation at TSR 0.6 with a velocity inlet of 5 m/s. The model was semicircular, zigzag on the concave surface on semicircular with t = 0.75, t = 0.25, and t = 1 mm. The result of this study's CD maximum is 1,817 at the zigzag model with t = 1 and CD avrg =1.24. The average drag coefficient increased by 14 percent compared to the conventional semicircular rotor. The maximum Cp value is also found at t = 1 mm, which is 0.315. The power coefficient increased by 29 percent compared to the conventional semicircular rotor. The total pressure on the blade shows the highest model with t = 1 mm at the same angle of attack (α = 30). Zigzag on the concave surface affects blade pressure, which improves the performance of the Savonius rotor.

Coefficient of power of Indonesian traditional wind-pump blade model

Indonesia has wind energy potential as a renewable energy resource which is currently being developed intensively. Salt farmers have used it with wind-pump as part of the traditional salt-making process. They have the ability to manufacture, operate and maintain the Indonesian traditional wind-pump. The aim of the experiment was to find out characteristic of windmill of the traditional wind-pump. The characteristics was expressed with relation of coefficient of power (Cp) and the tip speed ratio (tsr). The ratio of the wind mill model was 1: 2.5. The wind mill model consisted of four blades and 80 cm diameter. The experiment was done in a wind tunnel with wind speed of 5 m/s. The adjustable shaft load was electric machine. In the experiment, the wind speed range was 5.7 up to 6.3 m/s and shaft speed was 42.3 up to 387.4 rpm. The experiment resulted minimum and maximum tsr and Cp were 0.295 up to 2.705 and 2.623 up to 11.073, respectively. The experiment found out relationship of Cp and tsr in an equation Cp = -3.248 tsr2 + 12.29 tsr – 1.007. The equation showed that the traditional windmill model has maximum Cp of 10.62 at the tsr of 1.89.

CFD Modeling of a Pitching Airfoil for the Estimation of the Performance Curve in an H‐Rotor Vertical Axis Wind Turbine

In this work, the performance curve of a straight‐bladed vertical axis wind turbine (VAWT) is estimated through a CFD two‐dimensional modeling of a single airfoil under unsteady pitching motion. A typical URANS approach, with a k‐ω SST turbulence model and UDF functionalities, has been employed to simulate a fixed airfoil under variable inlet conditions. Induction factors are previously computed using a simple stream tube model (SSTM) in an iterative process. Frequencies and amplitudes of the pitching motion are modified to simulate the operative range of tip‐speed ratios (TSRs) for the wind turbine. The obtained results have been compared with experimental curves of a 0.5 solidity turbine measured in a wind tunnel. The experimental results of the wind‐tunnel turbine provide a maximum Cp value of 0.22 at a TSR = 3.1, while the numerical procedure estimates a value of 0.33, also at TSR = 3.1. Despite of the discrepancy, due to the 2D assumptions in the simulation, the procedure makes reliable and more accurate estimations than traditional analytical models with steady coefficients. This alternative methodology significantly reduces the computational cost. Moreover, these nonrotating simulations allow more robust and practical routines that can be easily implemented in optimization algorithms for the design of VAWTs.

Local SAR management strategies to use two-channel RF shimming for fetal MRI at 3 T.

This study evaluates the imaging performance of two-channel RF-shimming for fetal MRI at 3 T using four different local specific absorption rate (SAR) management strategies. Due to the ambiguity of safe local SAR levels for fetal MRI, local SAR limits for RF shimming were determined based on either each individual's own SAR levels in standard imaging mode (CP mode) or the maximum SAR level observed across seven pregnant body models in CP mode. Local SAR was constrained either indirectly by further constraining the whole-body SAR (wbSAR) or directly by using subject-specific local SAR models. Each strategy was evaluated by the improvement of the transmit field efficiency (average |B1 + |) and nonuniformity (|B1 + | variation) inside the fetus compared with CP mode for the same wbSAR. Constraining wbSAR when using RF shimming decreases B1 + efficiency inside the fetus compared with CP mode (by 12%-30% on average), making it inefficient for SAR management. Using subject-specific models with SAR limits based on each individual's own CP mode SAR value, B1 + efficiency and nonuniformity are improved on average by 6% and 13% across seven pregnant models. In contrast, using SAR limits based on maximum CP mode SAR values across seven models, B1 + efficiency and nonuniformity are improved by 13% and 25%, compared with the best achievable improvement without SAR constraints: 15% and 26%. Two-channel RF-shimming can safely and significantly improve the transmit field inside the fetus when subject-specific models are used with local SAR limits based on maximum CP mode SAR levels in the pregnant population.

Impact of Blade and Solidity on the Performance of H-Darrieus Hydrokinetic Turbines by CFD Simulation

Purpose: In the present work, the 2D design of H-Darrieus turbines with a diameter of 900 mm and NACA blades 0018, 0025, 2415, and 4415 has been carried out for the solidity values of 0,5; 1 and 1,5. In order to know its maximum performance. Method/design/approach: The 2D simulations were developed with the ANSYS® FLUENT package in the transient state, varying the angular velocity (ω) for a peak velocity ratio (TSR) of 1 to 7 and the SST K-ω turbulence model, for a constant water flow rate of 1 m/s. This in order to know the results of the torque (Nm) generated and thus calculate the power coefficient (Cp). Results and conclusion: The NACA 0018 blade reached a power coefficient of 0,604 for a solidity of 0,5, followed by NACA 2415 blade at the same solidity with a maximum Cp of 0,594. On the other hand, the NACA 0025 blade for solidity of 1 reached a maximum Cp value of 0,570, while the NACA 4415 profile with a solidity of 1,5 obtained a maximum value of 0.495. Research implications: These results of maximum Cp values were given in a TSR range of 2 to 4 with a mean value of 3,5 for NACA profiles 0018 and 2415. Thus, evidencing the behavior of this type of turbine reaching maximum values to then begin to decrease. Originality/value: The present work contributes to the understanding of the impact of geometrical parameters on the operating coefficient of H-Darrieus.

Design modification and performance prediction of ellipsoid cross-flow hydrokinetic turbine

In this study, an ellipsoid-shaped cross-flow hydrokinetic (ECFHKT) has been selected for the study. The performance of the ECFHKT was investigated for different design parameters, namely the number of blades, blade angle and blade length. The performance of ECFHKT was evaluated in terms of coefficient of torque (Ct) and coefficient of power (Cp) with respect to different tip speed ratios (TSR) by considering different flow velocities in the range of 0.5 m/s to 3.0 m/s, experimentally and numerically. Further, the Flow behavior across the ECFHKT was analyzed and discussed through pressure contour, velocity contour and velocity vector. It was found that design parameters play a vital role in enhancing the performance of the rotor and self-starting capabilities. For this analysis, the maximum Ct and Cp were obtained as 1.08 and 0.267, respectively. Further, It was observed that the ECFHKT performed well both in low and high flow conditions within a narrow range of tip speed ratio.

Influence of Nano Additives on Performance, Combustion, and Emission Characteristics of Diesel Engine using Tamarind Oil Methyl Ester-Diesel Fuel Blends

Hazardous emissions majorly NOx and the poor performance of alternative fuels (biodiesel/its blends) are global concerns, as fossil fuel depletion and rising energy prices encourage researchers to rely on alternative energy sources with the addition of nano additives in the recent decade. The current experimental study investigates the performance, combustion, and emission characteristics of biodiesel-diesel mixtures dispersed with titanium dioxide (TiO2) as a fuel additive on a 1-cylinder diesel engine. TiO2 was dispersed in a Tamarind Oil Methyl Ester (TOME)-diesel blend (B20) in three concentrations of 40, 80, and 120 ppm via ultrasonication in the presence of QPAN80 surfactant to enhance the stability of the prepared fuel sample. A ratio of 1:4 TiO2:QPAN80 was found to produce the highest stability and homogeneity which is evidenced by the characterization of TiO2. The engine tests revealed that the greatest decrement in BSFC, CO, HC, and NOx was observed as 15.2%, 15.2%, 11.10%, and 9.06%, and the maximum BTE, HRR,and CP were improved by 9.76%, 50.32 J/degree, and 50.32 bar for the B20T80 blend correlated with B20 blend. Thus, the inclusion of TiO2 nano additives improved overall engine performance and decreased emissions of CI engines significantly.

Modelling the effects of boundary proximity on a tidal rotor using the actuator line method

For a turbine in unconstrained flow, the maximum power coefficient (CP ) is limited to 16/27 of the undisturbedkinetic energy flux through the rotor area according to work attributed to Betz, Lanchester, and Joukowsky [1].This maximum, often referred to as the Betz limit, occurs when the rotor presents the optimum resistance tothe incoming flow, imparting enough force to generate power without overly choking the flow through the rotor.However, in the context of tidal stream energy, the flow is often constrained by the seabed and the free surfacechanging the balance of optimal rotor resistance. Thus, the limit for maximum power extraction is modifiedto the form first presented by Garrett and Cummins, CP = (16/27)(1 − B)−2 [2]. The factor B, known as theblockage ratio, represents the fraction of the channel cross-section occupied by the rotor swept area, and allowsrotors operating in confined conditions to theoretically exceed the Betz limit. Subsequent theoretical work byNishino and Willden extended this model to demonstrate that constructive interference effects between closelyspaced turbines in a co-planar fence can allow efficiency increases above the Betz limit, even in an infinitely widechannel where the global blockage ratio is negligible [3]. This phenomenon, attributed to the concept of localblockage, defined as the ratio of rotor swept area to the surrounding flow passage area, has been observed byseveral studies both experimentally, and numerically using actuator disk and blade element momentum methods[4, 5, 6]. However, neither the experimental nor the numerical studies provided detail on unsteady loading effectsstemming from azimuthal variations in the flow field caused by anisotropy in the local blockage, such as whenthe rotor is not centred in the flow passage. In this study, a single tidal rotor is simulated using the actuatorline model embedded in a Reynolds-Averaged Navier-Stokes solver with varying degrees of anisotropic blockageimposed by proximity to a non-deformable upper boundary. The investigation is carried out in the contextof the Supergen ORE Unsteady Tidal Turbine Benchmarking Project using a 1.6 m rotor in a computationaldomain equivalent to the towing tank dimensions at the Qinetiq Haslar facility in which the turbine was testedexperimentally [7]. The discrete blade representation and unsteady nature of the actuator line method allowsinvestigation of variations in loads and the importance of boundary proximity by extracting the spanwise loaddistributions and local flow parameters at different positions around the azimuth. The effects of two differenttip-loss correction models on the spanwise force distributions and overall loads are investigated. Analysis of theintegrated rotor loads shows potential for an increase in the maximum CP of ∼1% with changing proximity tothe upper boundary without any detriment to the power-to-thrust ratio. However, anisotropy in the local flowpassage can result in azimuthally varying blade forces, introducing an additional source of fatigue loading tothe rotor and drive train.

Computational study of the effect of building height on the performance of roof-mounted VAWT

The power of a Vertical Axis Wind Turbine (VAWT) placed at the frontal corner of a roof-top of a building is significantly higher compared to the same turbine in a uniform wind without a surrounding building. Due to the importance of this configuration's benefits, it is crucial to study its effect for different building heights. To investigate the impact of building height on the power performance of VAWTs, three buildings with heights of 30.48 m (100 ft), 60.96 m (200 ft), and 91.44 m (300 ft) are considered. A two-blade Darrieus-type VAWT is placed on the roof-top, with the wind flow directed straight towards the corner of the building. Computational Fluid Dynamics (CFD) is utilized to simulate the entire flow over the building and the rotating turbine. Different atmospheric boundary wind velocity profiles are considered. Firstly, the same velocity profile is applied to all three buildings, with taller buildings experiencing higher velocities. Secondly, three distinct velocity profiles are used over the buildings, ensuring that the wind velocity at the middle of the turbine for each case remains at 9.3 m/s. The results demonstrate that placing the VAWT on the roof-top of a 30.48 m (100 ft) building increases the maximum Power Coefficient (CP) by 36% compared to the turbine operating in a uniform flow. Moreover, in the case of one velocity profile applied to buildings with different heights, it was observed that the maximum CP increased by 84% for a building with a height of 91.44 m compared to the turbine operating in uniform flow. On the other hand, in the second scenario with three different velocity profiles over the buildings, it was found that the maximum CP increased by 18% and 22% when the turbine was placed in the 60.96 m and 91.44 m buildings, respectively, compared to the 30.48 m building.

Evaluation of Regional Elevation and Blade Density Effects on the Efficiency of a 1-kW Wind Turbine for Operation in Low-Wind Counties in Iran

This research investigates the effect of blade density and elevation above sea level on the startup time (Ts) and power coefficient (Cp) of a 1-kW two-bladed wind turbine. The study uses three Iranian hardwoods as the blade material and four counties of Iran with low wind speeds and different elevations as the case studies. The BW-3 airfoil is considered as the blade profile. A multi-objective optimization process with the aid of the differential evolution (DE) algorithm is utilized to specify the chord length and twist angle. The findings demonstrate that, while the maximum Cp of the optimal blades designed with all three types of wood is high and equal to 0.48, the average Ts of the optimal blades designed with oak and hornbeam wood is 84% and 108% higher than that of alder wood, respectively. It is also observed that, while raising the elevation to 2250 m decreases the Cp by only 2.5%, the ideal blade designed to work at sea level could not manage to start rotating at a height of 1607 m and above. Finally, an improvement in the Ts and Cp was observed by performing optimization based on the local atmospheric conditions associated with the incrementing blade chord length at high elevations.

Wind tunnel test and numerical analysis of wooden-bladed Darrieus wind rotor at low wind speed conditions

The present study aims to conduct wind tunnel tests and numerical analyses to comprehensively assess the performance of wooden-bladed Darrieus wind rotors, specifically focusing on their behavior at low wind speeds. Limited investigation exists on the aerodynamic behavior of wooden-bladed Darrieus wind rotors under low wind speed conditions, necessitating comprehensive analysis to understand their performance characteristics and address this research gap. The present study is undertaken to address this gap. In addition, the paper also presents airfoil and blade material selection and fabrication of the rotor. The study is conducted on the NACA 0018 airfoil profile of the blades at low wind speeds of 4 and 6 m/s, commonly encountered in urban areas. The wind tunnel tests measure various rotor performance parameters such as the Static torque coefficient (Cts) and Power coefficient (Cp). At the same time, numerical simulations are used to study the flow behavior around the rotor blades. The Cts of the rotor is calculated at 12 different azimuthal positions between 0° to 360°. The Cp of the rotor is calculated at different tip speed ratios (λ). The present rotor exhibited maximum Cts of 0.64 and 0.66 and maximum Cp of 0.132 (at λ = 1.26) and 0.141 (at λ = 1.29) for 4 m/s and 6 m/s, respectively. Finally, it can conclude that the constructed wooden Darrieus rotor is working positively at low wind speeds, and the results may be used to develop wooden wind turbines for small-scale power generation.

Experimental investigation of solidity and blade profile effects on H-Darrieus wind rotor: Performance and self-starting analysis

The present study investigates the impact of rotor solidity and blade profile on the self-starting characteristics and performance of H-Darrieus wind rotors (H-rotors) through subsonic wind tunnel experiments. Three symmetrical (NACA 0018) and three unsymmetrical (NREL S823) H-rotors were analyzed to determine the coefficient of static torque (Cts) and coefficient of power (Cp) across three solidities (σ = 0.25, 0.3, and 0.35) and two free stream wind speeds (Uf = 6 and 8 m/s). The findings revealed that the NREL S823-bladed H-rotor outperformed the NACA 0018-bladed H-rotor, displaying 13% and 11% higher Cts values at σ = 0.25 (Uf = 6 and 8 m/s), 9% and 9% at σ = 0.3 (Uf = 6 and 8 m/s), and 13% and 11% at σ = 0.35 (Uf = 6 and 8 m/s). The NREL S823-bladed H-rotor achieved a maximum Cp of 0.197 at σ = 0.3 and Uf = 8 m/s, which is 6% higher than the maximum Cp obtained by the NACA 0018-bladed H-rotor. Furthermore, the trend of maximum Cp values for both H-rotors followed the order of Cp, max σ = 0.25 < Cp, max σ = 0.3 > Cp, max σ = 0.35. Based on the experimental findings, it is inferred that the NREL S823-bladed H-rotor with a solidity of 0.3 is suitable for small-scale wind turbines.

Optimal utilization of hydrokinetic energy resources through performance improvement of the darrieus turbine using concave and flat blocking plates

Energy extraction from renewable sources like hydrokinetic energy from the flowing water of rivers and canals is one of the affordable and clean energy generation technique. The current work is carried out towards performance enhancement of the Darrieus hydrokinetic turbine for open water channel utilization application. The investigation has been done using the flat and concave shape of blocking plate. Both blocking plates have been analyzed for different sizes as well as location at the upstream side of the turbine. The obtained results are reported after considering appropriate velocity correction. The blocking plates with projected width of 76 mm, 89 mm, 101 mm, 127 mm, 152 mm, and 203 mm are selected for the investigation. It is observed that 101 mm (Width Ratio, WR=0.36) with concave blocking plate provides maximum Cp of 0.245 at 0.99 TSR. Also, the optimum region is found between 0.143 and 0.286 Distance Ratio (DR) from the top corner of the acrylic plate. The concave blocking plate enhance the performance more compared to flat blocking plate. The conclusion is made that, the performance with flat blocking plate with optimized width and location improve the power coefficient by 10.92% and that of concave blocking plate by 18.45%.

Performance investigation on blade arc angle and blade shape factor of a Savonius hydrokinetic turbine using artificial neural network

ABSTRACT Hydrokinetic turbines can generate electricity in remote rural locations using the kinetic energy of nearby rivers or canals. The Savonius hydrokinetic turbine (SHKT) is the easiest to design and manufacture. Optimization of blade shape factor (p/q) and blade arc angle (Φ) can contribute significantly to enhancing the efficiency of a turbine. The present work proposes a time-saving and reliable method to design an optimized SHKT by using a blend of experimentally validated 3D computational fluid dynamics (CFD) simulations and Artificial Neural Network (ANN). To optimize the turbine blade, the turbine performance needs to be analyzed for a number of values of blade parameters selected at very small intervals. Performing so many CFD simulations is a costly task. Application of an ANN tool trained using a smaller number of CFD results should significantly curtail the costs while maintaining reliability as well. The power coefficient (Cp) of SHKT was obtained using CFD simulations for some selected sets of Φ and p/q. These results were used to train the ANN by creating a parametric map between the input parameters viz. Φ, p/q, and the output parameter Cp. The trained ANN tool was further used to predict the turbine’s performance for sets of input parameters varying at very small intervals. The blade with p/q of 0.2 and Φ of 148° provides a maximum Cp of 0.209 at a TSR of 0.8. This optimal blade was 10.5% more efficient than the standard semicircular blade.

Valorisation of aquaculture sludge into microbial protein using bioreactor with an optimised nutrients

The present study was conducted to optimise the nutrients used for producing high nutritional biofloc in bioreactor utilising aquaculture waste. Full Factorial design (23) of independent variables such as sludge quantity (20 and 30 gL−1), carbon nitrogen ratio (15:1 and 20:1) and bioflocculant (cationic starch) doses (30 and 60 ppm) were used for optimisation. The percentage of crude protein and crude lipid in biofloc was shown to be significantly influenced by the interaction between carbon nitrogen ratio and bioflocculant dose (BC) as well as the interaction between sludge quantity, carbon nitrogen ratio, and bioflocculant dose (ABC) (p < 0.05). The floc volume of biofloc was shown to be significantly influenced by the interaction between carbon nitrogen ratio and bioflocculant dose (BC) (p < 0.05). The optimised parameters were 30 gL−1 of sludge, a carbon nitrogen ratio of 20:1, and 30 ppm of cationic starch, which resulted in a maximum CP of 27.09%, a maximum CL of 4.36%, and a maximum floc volume of 132 mL L−1. Principal component analysis (PCA) resulted in a 2 principal components (PC 1, nutritional factors which decides the nutritional composition of biofloc and PC 2, nitrification factors which are needed for biofloc formation) that explained 85% of total data variation. This study found the production of nutritive biofloc in a bioreactor using aquaculture waste with optimised nutrients.

Performance of Savonius Turbines with Tubercles Inspired by Humpback Whales

Recent studies found that tubercles had been integrated into various applications beyond nature to enhance performance. Therefore, the present work investigates the performance of a Savonius turbine with various tubercle configurations at a wind speed of 7 m/s which corresponds to a Reynolds number of 148,000. The Savonius turbines with tubercle features were initially designed and inspired by the distribution of tubercles on the flippers of humpback whales. However, only the models with the best performance were chosen for fabrication and tested in the wind tunnel. The new turbine designs have 33% of the blade without tubercles, with turbine model 1 (D1) having a large tubercle beginning in the midspan and tapering towards the endplates, while turbine model 2 (D3) applies the 33% without tubercles in the midspan of the blade. The results demonstrated that turbine model 1 had the highest maximum Cp of 0.19 at the tip speed ratio of 0.78 and indicated that the spanwise location of tubercles in which it is integrated into the turbine is a significant geometric arrangement to improve the performance. The new turbine models designed with tubercles performed significantly better than the baseline model, with 46.15% and 23.08% improvements, respectively. The flow visualization for both models with tubercle configurations showed smaller wake sizes that represent reduced drag and eventually produced higher performance in comparison with the baseline. The results provide insights into the implementation of the tubercles concept on a Savonius turbine with a low aspect ratio.