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46 results on '"Darmawan, Steven"'

1. Aerodynamic Analysis of the Rear Spoiler of Hatchback Vehicles Using SST K-ω Turbulence Model

Author

Kuwito, Andre, Darmawan, Steven, Tanujaya, Harto, Chaari, Fakher, Series Editor, Gherardini, Francesco, Series Editor, Ivanov, Vitalii, Series Editor, Haddar, Mohamed, Series Editor, Cavas-Martínez, Francisco, Editorial Board Member, di Mare, Francesca, Editorial Board Member, Kwon, Young W., Editorial Board Member, Trojanowska, Justyna, Editorial Board Member, Xu, Jinyang, Editorial Board Member, Irwansyah, editor, Iqbal, Mohd., editor, Huzni, Syifaul, editor, and Akhyar, editor

Published
2024
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2. Design and Analysis of Automatic Fish Dryer Prototype

Author

Raynaldo, Kevin, Andrianto, Richie, Darmawan, Steven, Cavas-Martínez, Francisco, Series Editor, Chaari, Fakher, Series Editor, Gherardini, Francesco, Series Editor, Haddar, Mohamed, Series Editor, Ivanov, Vitalii, Series Editor, Kwon, Young W., Series Editor, Trojanowska, Justyna, Series Editor, di Mare, Francesca, Series Editor, and Akhyar, editor

Published
2021
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8. CFD analysis of flow around AF1300a cylinder model at Reynolds number variation.

Author

Yorkie, Janssen Paolo, Darmawan, Steven, and Tanujaya, Harto

Subjects
*REYNOLDS number, *AERODYNAMICS, *ENGINEERING design, *FLUTTER (Aerodynamics), *AERODYNAMICS of buildings
Abstract

Aerodynamics are fundamental to the daily lives of us living primarily in a gaseous environment we call air. It can be observed in many daily things such as piping, vehicles, and buildings. Aerodynamics can play a crucial part in safety or efficiency of an object. Design engineers must include aerodynamic calculation into consideration, especially if it includes safety, such as buildings, bridges, and other important structures. Cylinder is one of many geometries profile that can represent specific flows which occurs on such applications. Design engineers now have the option of using a CFD software to aid them through the process of engineering. This software takes almost all parameters into account and calculate them according to the user choice of subject. This research is aimed to investigate the flow around cylinder model using CFD method of AF1300a. The simulation is done using ANSYS CFD software, at 5 different speeds (1,39 m/s, 2,78 m/s, 4,17 m/s, 5,56 m/s, and 12,5 m/s) with 3 different mesh smoothing options (low, medium, and high smoothing) which results in different number of nodes and elements of the mesh. The result shows medium and high smoothing mesh to have similar output in pressure area, and velocity area. So medium mesh smoothing is enough for the next research as the optimal mesh smoothing option. The results of this research will be used for future research on vehicles aerodynamics. [ABSTRACT FROM AUTHOR]

Published
2023
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9. Effect of differences in condensation temperature on condenser performance in distillation machines for HDPE plastic waste.

Author

Paskalis, Ryan, Tanujaya, Harto, and Darmawan, Steven

Subjects
MACHINE performance, WATER temperature, CONDENSATION, PLASTIC recycling, TEMPERATURE, PLASTIC scrap
Abstract

Plastics are one of the biggest waste in the world and are difficult to recycle. One of the methods used to recycle plastics is by a distillation machine. Condensor is one part of the distillation machine that is used to condense liquid vapor from the plastic burning process. There are three variables used to investigate the performance of the condenser, namely heat released, condensation rate, and condenser efficiency. Consideration in using temperature difference for analysis is developed in this study. The temperature difference is obtained based on the cooling water temperatur used. Extrapolation is used to get the outlet temperature of the cooling water. Five variations of cooling water temperature were used in this study to get the temperature difference, namely 10 oC, 15 oC, 23 oC, 27 oC, and 30 oC. The temperature difference obtained is based on the cooling water temperature, namely 20 oC, 26,6 oC, 35,4 oC, 53 oC, 64 oC. The result shows that from the temperature 20 oC to 64 oC, there is an increase in heat released from 83,72 kJ/s to 267,904 kJ/s, the condenssation rate and condenser efficiency are also increased from 0,468 kg/s to 1,499 kg/s and 12,369 % to 39,582 %. [ABSTRACT FROM AUTHOR]

Published
2023
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10. Decision making using simple additive weighting and weighted product method for selection of underground mining method.

Author

Balusa, Bhanu Chander, Subbarayalu, Venkatraman, Janvekar, Ayub Ahmed, Rangaswamy, Manoj Kumar, Mahanta, Tapan K., and Darmawan, Steven

Subjects
DECISION making, MINES & mineral resources, STATISTICAL decision making, MULTIPLE criteria decision making
Abstract

Making a decision is one of the crucial tasks for choosing the best optimal solution for various problems related to the decision making. Decision can be made easily for the problems with one or two input criteria and many choices/alternatives as solution. Whereas, it's very difficult to take the decision for the problems with more than two input criteria and many choices/alternative as solution. This type of problems can be solved with Multi-Criteria Decision-Making (MCDM) approaches. There are many MCDM approaches in the field of decision making research. This study considers two efficient MCDM approaches namely Simple Additive Weighting (SAW) method and Weighted Product Method (WPM) to solve the multi criteria decision making problems. These two MCDM approaches are implemented for underground mining method selection problem for the Indian metal mine X as a case study. For the specified mine SAW and WPM provides the Room and Pillar as a suitable mining method for extraction of the minerals. [ABSTRACT FROM AUTHOR]

Published
2023
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40. CFD INVESTIGATION OF FLOW OVER A BACKWARD-FACING STEP USING AN RNG k-ε TURBULENCE MODEL.

Author

Darmawan, Steven and Tanujaya, Harto

Subjects
MATHEMATICAL models of turbulence, NUMERICAL analysis
Abstract

Backward-facing step (BFS) is a benchmarked geometry for visualizing recirculation flow and validating turbulence models. Nowadays, numerical analysis with the CFD method has became more popular and has stimulated research involving CFD without avoiding the experimental method. In this paper, flow over a BFS was numerically investigated with an RNG k-ε turbulence model to predict recirculating flow. BFS geometry refers to the geometry proposed by Kasagi & Matsunaga; it is three-dimensional, with inlet Re = 5.540. The paper aims to investigate the performance of the RNG k-ε turbulence model over a BFS. Two important parameters were analayzed: the performance of the RNG k-ε on the recirculation zone and on the reattachment length. Recirculation flow is presented by the x-velocity for Y = 17.4 mm and Y = 34.9 mm. In these Y-section, the RNG k-ε is compared to the STD k-ε and both models show the recirculation flow occurred from X = 0 mm to about X = 200 mm. The following results were obtained. The RNG k-ε predicted a slightly higher x-velocity component than that predicted by the STD k-ε. This result shows that the RNG k-ε turbulence model is suitable for predicting recirculation flow on the BFS. The reattachment length was measured by non-dimensional X/h to the x-velocity component with the RNG k-ε turbulence model. The analyzed data were taken from X/h = 4.5 to X/h = 10, on the x-velocity component from Y = 17.4 mm. The reattachment point was achieved at X/h = 7.22, close to that achieved by Kasagi & Matsunaga of X/h = 6.51. [ABSTRACT FROM AUTHOR]

Published
2019
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45. Inverse-Turbulent Prandtl Number Effects on Reynolds Numbers of RNG k-ε Turbulence Model on Cylindrical-Curved Pipe

Author

Budiarso, Siswantara, Ahmad Indra, Darmawan, Steven, and Tanujaya, Harto

Abstract

Inverse-turbulent Prandtl number (α) is one of important parameters on RNG k-ε turbulence model which represent the cascade energy of the flow, which occur in cylindrical curved-pipe. Although many research has been done, turbulent flow in curved pipe is still a challanging problem. The range of α of the basic RNG k-ε turbulence model described by Yakhot and Orszag (1986) with range 1-1.3929 has to be more specific on Reynolds number (Re) and geometry. However, since the viscosity is sensitive to velocity and temperature, the reference of α is needed on specific range of Reynolds number. This paper is aimed to gain optimum inverse-turbulent Prandtl number of the flow in curved pipe with upper and lower Re which simulated numerically with CFD. The Re at the inlet side were; Re = 13000 and Re = 63800 on cylindrical curved-pipe with r/D of 1.607.The inverse-turbulent Prandtl number (α) were varied to 1, 1.1, 1.2, 1.3. The curved pipe was an cylindrical air pipe with 43mm inlet diameter. The computational grid that is used for CFD numerical simulation with CFDSOF®, hexagonal-surface fitted consist of 139440 cells. CFD simulation done with inverse-turbulent Prandtl number α varies by 1, 1.1, 1.2, dan 1.3. The wall is assumed to zero-roughness. The CFD simulation generated several results; at Re 13000, the value of α did not affect the turbulent parameter which also confirmed the basic therory of RNG k-ε turbulence model that the minimum Re of α is 2.5 x 104. At Re = 63800, the use of α of 1.1 shows more turbulent flow domination on molecular flow. Lower eddy dissipation by 1.67%, increasing turbulent kinetic energy by 2.2%, and Effective viscosity increase by 4.7% compared to α = 1. Therefore, the use of α 1.1 is the most suitable value to be used to represent turbulent flow in curved pipe with RNG k-ε turbulence model with Re 63800 and r/D 1.607 among others value that have discussed in this paper.

Published
2015
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46. Effect of cutting speed on temperature cutting tools and surface roughness of AISI 4340 steel

Author

Lubis, Sobron M., Darmawan, Steven, and and, Adianto

Abstract

During the machining process, a few cutting parameters are implemented such as cutting speed, depth of cut, and feeding speed. Variation of cutting speed beside affect the result of machining also could affect the rise of temperature during the machining process. In this study, carbide and ceramic cutting tool was used to see the comparison of temperature growth between two different tools. Tool temperature was estimated by simultaneous temperature measurement using K-type thermocouple and a digital thermometer to measure on tool temperature. Experiments were carried out in dry machining using workpiece material of AISI 4340 alloy steel. A DNMG 150404HQ CVD-coated carbide insert and the ceramic insert was used during the turning process. The result of the experiment show The highest measured temperature value on carbide cutting tool was 114degC at 240 m / min cutting speed while the lowest temperature value was 87.8degC at 160 m / min cutting speed. While on the ceramic cutting tool the highest measured temperature value is 52,5degC at 240 m / min cutting speed and lowest is 47,5degC at cutting speed 160 m / min

Published
2019

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