ORCID Profile
0000-0001-6411-9965
Current Organisation
Universiti Teknologi Malaysia - Kampus Antarabangsa
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Publisher: SAGE Publications
Date: 17-03-2020
Abstract: This study investigates the control performance of a structural building system during a seismic scenario using an adaptive nonsingular terminal sliding mode control. To realize the structural integrity of a building, it is necessary to equip the building with a structural control device. This research is focused on a hybrid control device that has excellent characteristics of passive and active control devices and implemented in a three degree-of-freedom system. The system, actuator, and controllers are designed by using the mathematical model developed in MATLAB/Simulink. The input excitation to the structure is taken from the El Centro earthquake that occurred in the 1940s with a magnitude of 6.9 M w and the Southern Sumatra earthquake that occurred in 2007 with a magnitude of 8.4 M w . Adaptive nonsingular terminal sliding mode control is the new proposed control strategy to be applied in structural control field is investigated in terms of controller performance in suppressing the vibrations, and then, compared with sliding mode control and fuzzy logic controller strategies. Sliding mode control is chosen to be compared with adaptive nonsingular terminal sliding mode control because of its advantages of robust performance, whereas fuzzy logic controller is chosen because of its intelligent control base. The effectiveness of the proposed controllers is evaluated based on the displacement response, performance indices, and the probability of building damage. The results have shown that the new proposed controller, an adaptive nonsingular terminal sliding mode control, reduced vibrations better and has superior performance compared with fuzzy logic controller and sliding mode control.
Publisher: Elsevier BV
Date: 11-2015
Publisher: Institute of Advanced Engineering and Science
Date: 05-2018
DOI: 10.11591/IJEECS.V10.I2.PP537-544
Abstract: span lang="EN-US" This paper presents the modelling and simulation of controllers for controlling the position of two degree of freedom (2 DOF) mass spring d er system. Proportional integral (PI), fuzzy logic controller (FLC) and sliding mode controller (SMC) are design to minimize the vibration of the system that represent as building structure towards earthquake. A structural building is simulate based on real earthquake occur in El Centro on May 1940. The algorithm for building structure, actuator and controller is derived. Matlab/Simulink is used to analyze the performance of controllers towards the vibration building structure. At the end of the study the time response for two story building for uncontrolled and controlled system is present. Besides, the result for limitation voltage for each controller is also analyse to determine the maximum voltage consume for the system. The simulation results show the comparison of the controllers’ performance in suppressing the building vibration. From performance analysis, SMC provides better performance compared to PI and FLC based on structural vibration reduction. /span
Publisher: IEEE
Date: 10-2018
Publisher: EDP Sciences
Date: 2017
Publisher: IOP Publishing
Date: 10-2016
Publisher: Trans Tech Publications, Ltd.
Date: 06-2014
DOI: 10.4028/WWW.SCIENTIFIC.NET/AMM.554.696
Abstract: Wind-induced ventilation is widely acknowledged as one of the best approaches for inducing natural ventilation. Computational fluid dynamics (CFD) technique is gaining popularity among researchers as an alternative for experimental methods to investigate the behavior of wind-driven ventilation in building. In this present paper, Reynolds averaged Navier-Stokes equation (RANS) k-ε model approach is considered to simulate the airflow on a simplified cubic building with an opening on a single façade. Preliminary simulation using models from previous experiment indicates the reliability of OpenFOAM, the open source software that will be used in this study. The results obtained in this study will better define options for our future study which aims to explore how different buildings arrays modify the airflow inside and around a naturally ventilated building.
Publisher: SAGE Publications
Date: 22-05-2017
Abstract: The prospect of harvesting energy from flow-induced vibration using an elastic square cylinder with a detached flat plate is experimentally investigated. The feasibility of flow-induced vibration to supply an adequate base excitation for micro-scale electrical power generation is assessed through a series of wind tunnel tests. The current test model of a single square cylinder is verified through a comparable pattern of vibration litude response with previous experimental study and two-dimensional numerical simulations based on the unsteady Reynolds averaged Navier–Stokes (URANS). In addition, a downstream flat plate is included in the wake of the square cylinder to study the effects of wake interference upon flow-induced vibration. A downstream flat plate is introduced as the passive vibration control to enhance the magnitude of flow-induced vibration and simultaneously increases the prospect of harvesting energy from the airflow. The study is conducted by varying the gap separation between the square cylinder and flat plate for 0.1≤ G/ D ≤3. The highest peak litude is observed for the gap G/ D = 1.2 with y rms / D = 0.46 at U R = 17, which is expected to harvest ten times more energy than the single square cylinder. The high litude vibration response is sustained within a relatively broader range of lock-in synchronization. Meanwhile, for G/ D = 2 the vibration is suppressed, which leads to a lower magnitude of harvested energy. Contrarily, the litude response pattern for G/ D = 3 is in agreement with the single square cylinder. Hence, the flat plate has no significance to the wake interference of the square cylinder when the gap separation is beyond 3 D.
Publisher: IEEE
Date: 10-2016
Publisher: EDP Sciences
Date: 2019
DOI: 10.1051/E3SCONF/20199502009
Abstract: Immense information and details observation of flow physics inside a draining tank can be achieved by adopting reliable numerical simulations. Yet the accuracy of numerical results has been always debatable and it is mainly affected by the grid convergence error and computational modeling approaches. Hence, this study is ided into two stages. In the first stage, this paper determines a systematic method of refining a computational grid for a liquid draining inside a tank using OpenFOAM software. The sensitivity of the computed flow field on different mesh resolutions is also examined. In order to study the effect of grid dependency, three different grid refinements are investigated: fine, medium and coarse grids. By using a form of Richardson extrapolation and Grid Convergence Index (GCI), the level of grid independence is attained. In this paper, a monotonic convergence criteria is reached when the fine grid has the GCI value below 10% for each parameter. In the second stage, different computational modeling approaches (DNS, RANS k-ε, RANS k-ω and LES turbulence models) are investigated using the finer grid from the first stage. The results for the draining time and flow visualization of the generation of an air-core are in a good agreement with the available published data. The Direct Numerical Simulation (DNS) seems most reasonably satisfactory for VOF studies relating air-core compared to other different turbulence modeling approaches.
Publisher: Elsevier BV
Date: 08-2016
Publisher: Elsevier BV
Date: 04-2018
Publisher: IOP Publishing
Date: 08-2017
Publisher: Trans Tech Publications, Ltd.
Date: 04-2014
DOI: 10.4028/WWW.SCIENTIFIC.NET/AMM.548-549.1795
Abstract: A proper setting of boundary conditions is a standard upon which simulation results are justified. This study is specifically designed to simulate airflow over a repeating unit of simplified urban models with the application of periodic boundary condition. Similar setting of boundary conditions is used for all models which are of square layout with 25% packing density. The models are constructed with such that the initial velocity field is uniform throughout its internal domain. The results show that different domain heights of 4 h and 5 h ( h as the building height) do not affect the spatial averaging of velocity profiles. In terms of the number of grids per building height, a finer meshing of 32 grids produce more accurate results of velocities and turbulence intensities compared with those of 25 grids when validated against the previous direct numerical simulation (DNS) data. Nevertheless, these criteria depend upon longer averaging period for better estimation of flow statistics. The boundary condition setting used in this preliminary study is nevertheless capable of producing current results comparable to past data although future works should focus on optimizing the important criteria in a simulation such as domain height, grid numbers, and averaging time.
Publisher: Springer Science and Business Media LLC
Date: 13-06-2019
Publisher: Informa UK Limited
Date: 10-01-2018
Publisher: Elsevier BV
Date: 2016
Publisher: Elsevier BV
Date: 11-2016
Publisher: Elsevier BV
Date: 09-2018
Publisher: Informa UK Limited
Date: 10-03-2020
Publisher: Springer Science and Business Media LLC
Date: 30-11-2014
Publisher: Elsevier BV
Date: 09-2017
Publisher: Penerbit UTM Press
Date: 28-08-2016
DOI: 10.11113/JT.V78.5161
Abstract: Wind flow in the urban boundary layer is influenced by both large- and small-scale surface roughness. In this study, Reynolds-averaged Navier-Stokes simulations using the renormalisation group (RNG) k-ε model were performed to study the wind flow in square arrays with small-scale roughness elements at the front and back of cubical obstacles at packing densities of 25.0% and 30.9%. The presence of small-scale roughness reduces streamwise velocity but increases turbulent kinetic energy. Moreover, small vortices are formed within the canopy because of small-scale roughness. The generated streamwise velocity profiles are similar at packing densities of 25.0% and 30.9%, but the drag coefficient is higher in the latter case. In brief, the impact of small-scale roughness on urban wind flow is considerable. The results of this study can contribute to future research on wind flow, particularly in the urban environment.
Publisher: Akademia Baru Publishing
Date: 25-03-2020
Publisher: MDPI AG
Date: 15-04-2022
DOI: 10.3390/SU14084779
Abstract: Rapid population growth and urbanization contribute to an ever-increasing global energy demand, of which the building sector accounts for one-third. The increasing average height and density of buildings escalate the need for vertical transportation, expanding elevator usage and energy needs. This phenomenon accounts for a significant amount of the total building energy use, necessitating a study of elevator system energy consumption. This study aimed to analyze the energy consumption and carbon emissions of elevator systems in low- and high-rise buildings towards energy-efficient estimations. A comprehensive analysis was performed based on a hybrid approach of measurement and calculation using a formula and reference values derived from previous studies. Four buildings were selected and thoroughly studied, representing the low- and high-rise categories. Data were collected based on on-site s ling and observation, as well as information from the building management offices. The mechanical parameters of the elevator system in each building and operational factors in terms of speed, number of trips, load, travel distance, and time were studied. In this analysis, the energy consumption calculation was performed according to International Standard ISO 25745. Annual carbon emissions were calculated in accordance with the USA EPA and IPCC guidelines. The elevator energy efficiency class was determined based on daily energy consumption. It was found from this study that the annual energy consumption of an elevator system is positively correlated to an elevator’s daily energy consumption. The annual carbon emissions of the elevator systems are dependent on increasing annual energy consumption, which is also connected to building height indirectly. The low-rise buildings showed better energy efficiency compared to the high-rise buildings due to lower travel distance, less trips, and fewer floors. The annual number of trips, travel distances, and energy consumption had an effect on the energy efficiency of the elevator systems in this study.
Publisher: Springer Science and Business Media LLC
Date: 16-03-2018
Publisher: Penerbit UTM Press
Date: 04-11-2018
Abstract: Accurate numerical simulation of liquid draining is important to study the physics fluid flow. However, liquid draining involves multiphase and rotational flows, where numerical simulation is expensive to accurately recreate these flow behaviors. The accuracy of numerical results has been also debatable and it is mainly affected by the computational modeling approaches. Therefore, this study evaluates different computational modelling approaches such as DNS, RANS k-ε, RANS k-ω and LES turbulence models. The results for the draining time and flow visualization of the generation of an air-core are in a good agreement with the available published data. The Direct Numerical Simulation (DNS) seems most reasonably satisfactory for VOF studies relating air-core compared to other different turbulence modeling approaches.
Publisher: Bentham Science Publishers Ltd.
Date: 18-10-2013
DOI: 10.2174/1874155X01307010048
Abstract: Bluff body is a simple but a central shape for many engineering applications. The geometry shape of the bluff body characterises the behaviour of the flow over the bluff body, where a more complex flow structure is found near downstream. Shear layer separation is mainly responsible for the periodic global phenomena, that includes the generation of sound. The magnitude of the aerodynamically generated sound is dominated by the fluctuations of aerodynamics forces, i.e., drag and lift. The study also shows that the sound pressure field is shaped by the aeolian tones that is related strongly to the lift fluctuations of the bluff body. Amplitude and frequency of the fluctuating lift change naturally with the shape of a particular bluff body. Triangular cylinder exhibits the largest sound pressure level (41.9 dB) followed by ellipse and circular shapes. Square cylinder emits the lowest sound pressure level (36.7 dB). This corresponds to the longest downstream vortex formation length at which for a square cylinder the long vortex formation length provides space for more vortex to dissipate.
Publisher: Elsevier BV
Date: 2016
Publisher: IEEE
Date: 12-2017
Publisher: IOP Publishing
Date: 10-2016
Publisher: Trans Tech Publications, Ltd.
Date: 10-2014
DOI: 10.4028/WWW.SCIENTIFIC.NET/AMM.629.426
Abstract: Flow structure over bluff bodies is more complex in wake. The wake is characterized by the unsteady behavior of the flow, large scale turbulent structure and strong recirculation region. For the case of high speed train, wake can be observed at the gap between the coaches and also on the rear coach. Wakes formation of high speed train are generated by free shear layer that is originated from the flow separation due to the sudden change in geometry. RANS and LES turbulent models are used in this paper to stimulate the formation of wakes and behavior of the flow over a simplified high speed train model. This model consists of two coaches with the gap between them is 0.5D. A total of four simulations have been made to study the effect of computational domain size and grid resolution on wake profiles of a simplified high speed train. The result shows that the computational domain can be reduced by decreasing the ground distance to 1.5D without affecting the magnitude of the wake profile. Both RANS and LES can capture the formation of the wake, but LES requires further grid refinement as the results between the two grid resolutions are grid dependent.
Publisher: Penerbit UTM Press
Date: 31-10-2016
DOI: 10.11113/.V78.8741
Abstract: Ocean Thermal Energy Conversion (OTEC) is a promising renewable energy technology with the concept to harness the energy stored at the surface seawater (SSW) and the cold deep seawater (DSW). The operation is based on the Rankine cycle, and involves at a minimum temperature difference of 20 K of the SSW and DSW to generate electricity. This research focuses on the economic efficiency of different working fluids used in the OTEC Rankine cycle. The various working fluids include ammonia, ammonia-water mixture (0.9), propane, R22, R32, R134a, R143a, and R410a. Most of the existing commercial OTEC systems use ammonia as the working medium despite its toxic nature. This study shows that the ammonia-water mixture still gives the best results in terms of heat transfer characteristics because of its greater transport properties and stability compared to other fluids. However, fluids such as propane and R32 can also be used as a substitute for ammonia-water mixture despite having slightly lower efficiency, because they are non-toxic and safer towards the environment. The same developmental model was used to present the proposed modified OTEC Rankine cycle, which shows a 4% increase in thermal cycle efficiency. This study reveals economically efficient and environmentally friendly working fluids.
Location: Malaysia
No related grants have been discovered for Sheikh Ahmad Zaki Shaikh Salim.