villages in Indonesia, deemed as remote areas, still did not have access to the national grid electricity. To resolve this issue, the use of independent power plants is an appropriate solution. The use of a pico-scale Turgo turbine, which is an independent power plant, is recommended in Indonesia due to its mini-, micro-, and pico-scale water energy potential of 19 GW. As the Turgo turbine is intended for use in remote areas, the use of local materials, e.g., coconut shells, is proposed as the bucket material. From static compressive strength tests revealed that the maximum pressure points a coconut shell proportional to the water pressure with a potential power of 3300 W. The size of a coconut shell spoon, which is not uniform, can be overcome by its curvature angle. The curvature angle represents the relative angle of the incoming and outgoing jets, while this is a represents of the depth and length of the spoon. Thus, to ensure the performance of the Turgo turbine under maximum conditions, the curvature angle of the coconut shell spoon is ~90°. Moreover, the total efficiency of the turbine is 34.94%, with a possibility of reaching higher values.

The geography of Indonesia renders it difficult to connect many areas to the national electricity grid. To overcome these problems, people need to be able to generate their own electricity. Pico hydro has been proven to be a cost-effective solution for electrification. The Turgo turbine is known for its reliability and strength, and it can perform efficiently with a range of flows. The Turgo's blade consists of an inlet and outlet trail with a curve that joins them. The curve in this study will be made from a simple circle arc to improve manufacturability. Three blades were designed using a basic calculation derived from the velocity triangles, with each blade having a different circle radius. The Computational Fluid Dynamics (CFD) method is used to determine the stream flow through the blade at a level of detail that cannot be obtained using other methods. The boundary conditions used in the study include 2.7 meters of head and a 21 l/s flow rate, a steady-state homogenous multiphase, and the turbulent models used SST k-ω. The result shows that the Turgo turbine with a 60 mm arc radius generated 477.7 Watts and has an efficiency of 85.97%, the highest when compared to the other two blades that used 50 mm and 55 mm arc radii, respectively.

The nozzle in a crossflow turbine is important because it accelerates the flow of the inlet and directs it to the runner at an angle relative to entrance angle (β1), which is used to obtain the maximum efficiency value. The β1 value must match the angle of the runner's outer blade considering the transfer of water from stationary to the rotating coordinates. To obtain the desired β1 value, the design of the nozzle is essential. In this study, 6-DoF simulations were conducted to find the best nozzle geometry. The incoming flow angles (λ) of the nozzle ranged from 50° to 90°. A study without a proper nozzle design was also conducted to compare the results. The results showed that a nozzle geometry of λ = 50° yielded the highest efficiency (60.6%). This study shows that the design of the nozzle in a crossflow turbine significantly affects its performance.

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The computational fluid dynamics (CFD) method is a method often used in predicting the performance and flow field of turbine because it is cheap and fast. The accuracy of CFD method is influenced by several aspects: boundary conditions, discretization of space and time method, and the use of turbulence models. For turbulence model, there is no clarity of the most accurate model, especially in the pico hydro type propeller. Therefore, this study compared three turbulent models based on Reynolds Average Navier-Stokes (RANS) two equations to predicts the performance of a pico hydro propeller turbine: standard k-ε, Group Normalization (RNG) k-ε, and Shear Stress Transport (SST) k-ω. This study used a three-dimensional simulation method, transient, and six-degree of freedom features. The Grid Convergency index (GCI) and Time-step Independence Index (TCI) were used to verify the simulation results. From the results, the CFD results were similar to the experiment results (valid). Furthermore, there was different prediction of performance due to differences in the turbulence model but not too high. Based on this, for prediction of performance pico hydro propeller turbine, the standard k-ε turbulence model was recommended for use. However, for study flow field, RNG k-ε and SST k-ω were recommended because they were not over-predicted in the dissipation rate calculation.

Breastshot waterwheel are considered as one of solutions for electrification in remote areas in Indonesia. Since it has low investment and maintenance costs, as well as an uncomplicated manufacturing process. Analytically, the optimum performance of this turbine occurs at the ratio of tangential velocity of wheel with the upstream velocity of water is 0.25-0.35 and numerically simulated the best efficiency is 62%. However, there is no experimental study for 16 blades of breastshot waterwheel in pico scale in actual river condition. The experiment is carried out in actual conditions with a discharge of 0.09708 m 3 /s and head 0.26 m. Based on results, the highest mechanical efficiency occurs at the ratio of tangential velocity of wheel with the upstream velocity of water is 0.83, while for electrical efficiency it was found at the 0.95. for U / C compared to the reference, the results are quite far from optimal and for efficiency the result is slightly lower at 45%.

Batik waste can increase water characteristics, such as turbidity, color and total suspended solids (TSS). Thus, an efficient technique for separating Batik from the liquid to decrease these characteristics is needed. The aim of the current study was to understand the results of flotation using electrolysis and to investigate the bubble characteristics that influence the results of the flotation of Batik waste. Flotation studies have been conducted using electrolysis to produce bubbles to separate batik synthetic dye from the liquid. Research conducted with 316L stainless steel electrodes, inside a 100 cm tall acrylic pipe with an inner diameter of 8.4 cm and a voltage variation of 10, 15 and 20 V. Batik waste was mixed with distilled water. Commercial alum powder [aluminum sulfate, Al 2 (SO 4 ) 3 .14H 2 O, that is 17% Al 2 O 3 ] as the reagent was added to coagulate Batik waste in a ratio of 1 gram per 10 ml of Batik waste. The results showed that flotation of Batik waste can be used to separate Batik waste with the addition of alum. Alum was shown to be capable of acting as a collector in this type of waste separation. The results showed that flotation using electrolysis could be an effective method for reducing turbidity, color and TSS.

Automobile aerodynamic studies are typically undertaken to improve safety and increase fuel efficiency as well as to find new innovation in automobile technology to deal with the problem of energy crisis and global warming. Some car companies have the objective to develop control solutions that enable to reduce the aerodynamic drag of vehicle and significant modification progress is still possible by reducing the mass, rolling friction or aerodynamic drag. Some flow control method provides the possibility to modify the flow separation to reduce the development of the swirling structures around the vehicle. In this study, a family van is modeled with a modified form of Ahmed's body by changing the orientation of the flow from its original form (modified/reversed Ahmed body). This model is equipped with a suction on the rear side to comprehensively examine the pressure field modifications that occur. The investigation combines computational and experimental work. Computational approach used a commercial software with standard kepsilon flow turbulence model, and the objectives was to determine the characteristics of the flow field and aerodynamic drag reduction that occurred in the test model. Experimental approach used load cell in order to validate the aerodynamic drag reduction obtained by computational approach. The results show that the application of a suction in the rear part of the van model give the effect of reducing the wake and the vortex formation. Futhermore, aerodynamic drag reduction close to 13.86% for the computational approach and 16.32% for the experimental have been obtained. Abstrak Modifikasi Struktur Aliran pada Model Kendaraan Van dengan Kontrol Aliran Hisapan untuk MengurangiHambatan Aerodinamika. Studi aerodinamika kendaraan biasanya berkaitan dengan keselamatan dan peningkatan efisiensi bahan bakar serta penemuan inovasi baru dalam teknologi kendaraan untuk mengatasi masalah krisis energi dan pemanasan global. Beberapa perusahaan mobil memiliki tujuan untuk mengembangkan solusi kontrol yang memungkinkan pengurangan hambatan aerodinamika kendaraan seiring dengan kemajuan modifikasi kendaraan yang masih dapat dilakukan dengan cara mengurangi massa, rolling friction atau hambatan aerodinamika. Beberapa metode kontrol aliran memberikan kemungkinan dalam memodifikasi pemisahan aliran untuk mengurangi terbentuknya swirling structure di sekitar kendaraan. Dalam studi ini, sebuah kendaraan keluarga dimodelkan dengan memodifikasi Ahmed body dengan mengubah orientasi aliran dari bentuk aslinya (modifikasi Ahmed body/reversed Ahmed body). Model ini dilengkapi dengan hisapan pada sisi belakang untuk memeriksa secara komprehensif perubahan medan tekanan yang terjadi. Penelitian dilakukan dengan pendekatan komputasi dan eksperimental. Pendekatan komputasi menggunakan perangkat lunak komersial dengan model turbulensi aliran k-epsilon standar dan bertujuan untuk mengetahui karakteristik medan aliran dan pengurangan hambatan aerodinamika yang terjadi pada model uji. Pendekatan eksperimental mengg...