Journal of Engineering and Technological Sciences
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Formerly known as:
ITB Journal of Engineering Science (2007 – 2012)
Proceedings ITB on Engineering Science (2003 - 2007)
Proceedings ITB (1961 - 2002)
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Comparison Study of Flow in a Compound Channel: Experimental and Numerical Method Using Large Eddy Simulation SDS-2DH Model
Nugroho, Eka Oktariyanto;
Ikeda, Syunsuke
Journal of Engineering and Technological Sciences Vol 39, No 2 (2007)
Publisher : ITB Journal Publisher, LPPM ITB
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DOI: 10.5614/itbj.eng.sci.2007.39.2.1
Flow modeling in a compound channel is a complex matter. Indeed, due to the smaller velocities in the floodplains than in the main channel, shear layers develop at the interfaces between two stage channels, and a momentum transfer corresponding to this shear layer affects the channel conveyance. Since a compound channel is characterized by a deep main channel flanked by relatively shallow flood plains, the interaction between the faster fluid velocities in the main channel and the slower moving flow on the floodplains causes shear stresses at their interface which significantly distort flow and boundary shear stress patterns. The distortion implies that flow field in rivers is highly non homogeneous turbulent, which lateral transport of fluid momentum and suspended sediment are influenced by the characteristics of flow in rivers. The nature of mechanism of lateral transport needs to be understood for the design of river engineering schemes that rely upon realistic flow. Furthermore, the flows in river are also almost turbulent. This means that the fluid motion is highly random, unsteady, and three -dimensional. Due to these complexities, the flow cannot be properly predicted by using approximate analytical solutions to the governing equations of motion. With the complexity of the problems, the solution of turbulent is simplified with mathematics equation. The momentum transfer due to turbulent exchanges is then studied experimentally and numerically. Experimental data is obtained by using ElectroMagnetic Velocimetry and Wave Height Gauge. The Large Eddy Simulation Sub Depth Scale (LES SDS)-2 Dimensional Horizontal (2DH) Model is used to solve the turbulent problem. Successive Over Relaxation (SOR) method is employed to solve the numerical computation based ob finite difference discretization. The model has been applied to the compound channel with smooth roughness. Some organized large eddies were found in the boundary between main channel and flood channel. At this boundary the transverse velocity profile exhibits a steep gradient, which induces significant mass and momentum exchange, acts as a source of vorticity, and generates high Reynolds stresses. The Large Eddy Simulation SDS-2DH model enables to predict quite successfully the wavelength of some observed vortices. The estimated vortex wavelengths agree again with the measurements and the theoretical predictions. The present model is proven to be a useful tool for engineering applications, as it can simulate the dynamic development of large eddies.
Experimental Study of an Aluminum-Polysilicon Thermopile for Implementation of Airflow Sensor on Silicon Chip
Subandi, Ayub;
Idris, Irman;
Ahmad, Adang Suwandi
Journal of Engineering and Technological Sciences Vol 39, No 2 (2007)
Publisher : ITB Journal Publisher, LPPM ITB
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DOI: 10.5614/itbj.eng.sci.2007.39.2.2
A multi-directional airflow sensor has been realized. The essential part of the considered sensor is a thermopile configuration, which enables the measurement of flow speed and flow direction. The thermopile is a series arrangement of eight thermocouples. A thermocouple converts a difference in temperature into an electrical signal, by means of the Seebeck effect . The thermocouples are made of aluminum-N-type polysilicon junctions. The incoming flow is heated and the degree of heat transfer by convection to the flow, depends on the speed of the flow; the faster the flow the smaller the heat transfer, which leads to a smaller (Seebeck) output voltage of the thermopiles. After signal conditioning - i.e., filtering and amplification by means of an amplification system - the electrical output signals of the thermopiles are further signal-processed by applying analog-to-digital signal conversion, so that finally the flow speed and the flow direction can be properly displayed on a computer screen. The measured values of the Seebeck coefficient or thermopower (S) were in the range of: 0.43 to 0.68 mV/K which are in good agreement with the values found in the literature: 0.5 to 0.7 mV/K. Moreover, it was found that the flow speed Uï¥ is proportional to the reciprocal value of the square of the output voltage of the outgoing thermopile.
Utilizing Shear Factor Model and Adding Viscosity Term in Improving a Two-Dimensional Model of Fluid Flow in Non Uniform Porous Media
Bindar, Yazid;
Makertihartha, IGBN;
Supardan, M. Dani;
Buchori, Luqman
Journal of Engineering and Technological Sciences Vol 39, No 2 (2007)
Publisher : ITB Journal Publisher, LPPM ITB
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DOI: 10.5614/itbj.eng.sci.2007.39.2.3
In a packed bed catalytic reactor, the fluid flow phenomena are very complicated because the fluid and solid particle interactions dissipate the energy. The governing equations were developed in the forms of specific models. The shear factor model was introduced in the momentum equation for covering the effect of flow and solid interactions in porous media.  A two dimensional numerical solution for this kind of flow has been constructed using the finite volume method. The porous media porosity was treated as non-uniform distribution in the radial direction. Experimentally, the axial velocity profiles produce the trend of having global maximum and minimum peaks at distance very close to the wall. This trend is also accurately picked up by the numerical result. A more comprehensive shear factor formulation results a better velocity prediction than other correlations do. Our derivation on the presence of porous media leads to an additional viscosity term. The effect of this additional viscosity term was investigated numerically. It is found that the additional viscosity term improves the velocity prediction for the case of higher ratio between tube and particle diameters