Papers by mohamed sukri mat ali
The comfort state of office building’s occupants is crucial since its related to the worker’s pro... more The comfort state of office building’s occupants is crucial since its related to the worker’s productivity. This comfort temperature of people from tropical climate might be different from temperate climate area. This study aimed to investigate thermal comfort and adaptive behaviour of occupants in office buildings with different ventilation modes: air-conditioned, mixed-mode, and free running. On February and March 2015, approximately 400 responses has been obtained through field surveys in three office buildings Bandung, Indonesia. The results has shown quite different comfort range between occupants in three ventilation modes: 24.7 oC, 26.3 oC, and 27.5 oC operative comfort temperature for FR, CL, and MM accordingly.
Article history: Received 12 October 2018 Received in revised form 4 December 2018 Accepted 13 Ja... more Article history: Received 12 October 2018 Received in revised form 4 December 2018 Accepted 13 January 2019 Available online 5 February 2019 Airfoil Leading Edge noise is generated due to impingement of turbulent structures on the airfoil surface. The rod-airfoil configuration is a benchmark configuration for the Leading edge noise and their noise calculation by computer simulation has peen progressively investigated to acceptable compare with the experiment. This paper presents the noise results finding between two distinct simulation models and their comparison with the experimental results. The two simulation models are Large-eddy simulation (LES) and the Delayed Detached-Eddy simulation (DDES). The DES can provide good noise results with the correct number of meshing grids with shorter timespan if compared to the LES. This study proposes to use DDES results for further rodairfoil noise analysis.
This study aims to explore the role of street trees in a tropical city. The outdoor field measure... more This study aims to explore the role of street trees in a tropical city. The outdoor field measurements of roadside trees are carried out at two streets with different tree densities at two major cities, Kuala Lumpur and Petaling Jaya of Malaysia. The results of variation pattern of air and globe temperature are presented. To further analyse the thermal environment, thermal images are captured and mean radiant temperature (MRT) are estimated to compare between all cases.
The goal of this paper is to investigate the performance of an active suspension system via linea... more The goal of this paper is to investigate the performance of an active suspension system via linear quadratic regulator (LQR) control and proportional–derivative–integral (PID) control. This project presents the mathematical models of the two degrees of freedom of a quarter-car active suspension system. This project introduces the design of a controller performance used for an active suspension system. The equations of motion of the quarter-car active suspension system model are developed. In the passive suspension system, there are huge oscillations or vibrations that occur in the suspension system. This phenomenon will lead to uncomfortable ride among the passengers or the driver. Besides, it takes longer time to reduce the vibration. Therefore, a good controller design must be able to reduce the vibration and produce a fast settling time. This project is focused on designing a controller for active suspension system by using MATLAB and Simulink software for both PID and LQR contro...
Chemical engineering transactions, 2017
Wind power is a clean energy source and alternative to the non-renewable type of energy sources. ... more Wind power is a clean energy source and alternative to the non-renewable type of energy sources. One of the challenges in utilizing wind energy is to efficiently harvest the wind energy into a usable electrical power, especially in the regions with low wind speed. This study aims to assess the possibility of harvesting wind energy by using the concept of flow induced vibration of a bluff body. A thin flat plate is introduced downstream of the cylinder as a simple but effective passive wind control. Three conditions have been tested to evaluate its effects on wind energy harvesting: isolated cylinder, flat plate with vibrating cylinder and cylinder with vibrating flat plate. The wind-body interaction is simulated using mesh motion technique available in OpenFOAM, an open source code for Computational Fluid Dynamics, while the harvested energy is calculated based on the work done by the single degree of freedom (SDOF) vibrating body. The study found that the vibrating cylinder with fl...
ARPN journal of engineering and applied sciences, 2015
The aerodynamics problems of train commonly come when the flow pass through train body. The incre... more The aerodynamics problems of train commonly come when the flow pass through train body. The increasing speed of train to achieve highly technology demands has led to increase the forces and moments and increase sensitivity of train stability and may cause the train to overturn. In this paper, two prisms arranged in tandem represent a simplified model of high speed train are performed at different yaw angle ranging from 0° to 90° by using the unsteady Reynolds-Averaged Navier Stokes (URANS) equation combined with k-? SST turbulence model. The Reynolds number is 3.14x105 based on height of the train and the free stream velocity. The aerodynamic quantities such as the side force, lift force and drag force coefficient show a similar trend where the forces increase with the yaw angle until a certain critical yaw angle before start to decrease till the yaw angle of 90°. The flow structure around the train under the effect of crosswind is visualized. The vorticiticy start to form from the ...
International Journal of Rail Transportation, 2018
In this article, simulations of crosswinds over a rectangular prism with two types of train nose ... more In this article, simulations of crosswinds over a rectangular prism with two types of train nose shapes (i.e. blunt and ellipse) that are running on flat ground case are discussed. The incident flow angle is varied from 0°to 90°. The flow around the train is solved using the incompressible form of the unsteady Reynolds Navier-Stokes (URANS) equations combined with the Shear-Stress-Transport k À ω turbulence model. The Reynolds number used, based on the height of the train is 3.7 × 10 5. Two distinctive flow regimes appear which represent a slender body behaviour at a smaller range of incident flow angles (below 45°) and bluff body behaviour at a much higher range of incident flow angles (above 45°). The safety guidelines for train's operation suggested that both the train's nose geometry and the wind speed condition are the two major factors that limit the maximum allowable speed for a particular train to be travelling.
Sustainability, 2020
As a Malay Agricultural Settlement established in 1900, Kampung Baru which is located in Kuala Lu... more As a Malay Agricultural Settlement established in 1900, Kampung Baru which is located in Kuala Lumpur, has become a subject of prolonged national interests in terms of economic, social, environment, and political issues along with the pressure of modern and future development. This study investigated the urban morphological impact of Kampung Baru on the intensity of urban heat island (UHI) by developing a smart geodatabase for urban climatic mapping. The database provided baseline data which was crucial to unveil the spatiotemporal characteristics of UHI in Kampung Baru. Determination of the urban heat island intensity (UHII) in Kampung Baru was carried out through two approaches, mobile and fixed measurements. In a period of six days, the mobile measurement was conducted within the target area at night using a motorcycle equipped with the temperature and relative humidity data logger while the fixed measurement was conducted using the similar equipment installed at a school buildin...
Journal of Wind Engineering and Industrial Aerodynamics, 2018
Sheltering of buildings has a significant impact on the total drag of an urban surface. This stud... more Sheltering of buildings has a significant impact on the total drag of an urban surface. This study performs large eddy simulations (LESs) of flows over vertical random arrays (comprised of buildings with height variability) in staggered layout to estimate the drag coefficient, C D. The vertical random arrays are configured in several frontal area densities, λ F (ratio of buildings' frontal area to total surface area) ranging from 0.09 to 0.81. The sheltering effect is parameterized using the individual building's wind pressure coefficient, C p(t) normalized with that of the isolated building, C p(iso). The ratio C p(t) /C p(iso) is well correlated with the target building's frontal area density, λ f(t). Subsequently, the relationship between C p(t) and λ f(t) is expressed using power law equations for three building categories based on the height-to-width ratio, α p(t) : tall (2.64 α p(t) 3.76), medium-rise (1.32 α p(t) 2.00), and low-rise (0.36 α p(t) 0.84). Based on the C p(t) , an equation of the C D is formulated, yielding the following outcomes. Firstly, the predicted C D values are mostly within 10% of the previous experimental results. Secondly, a semi-empirical model is derived, whereby the predicted C D values are generally consistent for various vertical random arrays.
International Journal of Vehicle Noise and Vibration, 2018
Interior noise of a production car is a total contribution mainly from engine, tyres and aerodyna... more Interior noise of a production car is a total contribution mainly from engine, tyres and aerodynamics. At high speed, wind noise can dominate the total interior noise. Wind noise is associated with the unsteadiness of the flow. For most production cars, A-pillar and side view mirror are the regions where the highly separated and turbulent flows are observed. This study quantifies the wind noise contribution from A-pillar and side view mirror with respect to the interior noise of a generic realistic model, DrivAer. The noise sources are obtained numerically from the flow-structure interactions based on the unsteady Reynolds averaged Navier stokes (URANS) while the noise propagation is estimated using Curle's equation of Lighthill acoustic analogy. The sound pressure frequency spectrum of the interior noise is obtained by considering the sound transmission loss from the side glass by using the mass law for transmission loss. The study found that the noise from the A-pillar is higher than the noise from the side view mirror in the whole frequency range. Near the end of the A-pillar component contributes the highest radiated noise level with up to 20 dB louder than that at the front part of the A-pillar.
E3S Web of Conferences, 2019
Immense information and details observation of flow physics inside a draining tank can be achieve... more 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 divided 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, di...
Journal of Wind Engineering and Industrial Aerodynamics, 2018
The phenomenon of flow-induced vibration (FIV) over a square cylinder at Reynolds numbers, Re ¼ (... more The phenomenon of flow-induced vibration (FIV) over a square cylinder at Reynolds numbers, Re ¼ (3.6-12.5  10 3) is numerically studied. This current study provides a detailed explanation of the behaviour of transverse motion of square cylinder with the mass damping ratio, m Ã ζ ¼ 2.48. The computation of FIV is conducted by numerical simulation based on the Unsteady Reynolds Navier-Stokes (URANS) flow field using OpenFOAM software. The first part of the numerical simulation consists of an isolated square cylinder to validate the solution with previous studies. The computation of FIV with a total number of cells, N ¼ 101,662 have shown a comparable pattern of amplitude curve. The coexistence of vortex-induced vibration (VIV) and galloping is observed for a single isolated cylinder. A downstream flat plate is introduced in the second part of the work. Different gaps separation between the cylinder and flat plate (0.1 ⩽G/D ⩽ 3) are simulated. Based on the amplitude curve against reduced velocities 4 ⩽ U R ⩽ 20, four regimes are identified. According to the power estimation, the optimum gap separation is G/D ¼ 0.1. The harnessed power is higher than a single isolated square cylinder while preserving the robustness for the remote harvesting purpose.
IOP Conference Series: Materials Science and Engineering, 2017
Accurate simulation of liquids draining is a challenging task. It involves two phases flow, i.e. ... more Accurate simulation of liquids draining is a challenging task. It involves two phases flow, i.e. liquid and air. In this study draining a liquid from a cylindrical tank is numerically simulated using OpenFOAM. OpenFOAM is an open source CFD package and it becomes increasingly popular among the academician and also industries. Comparisons with theoretical and results from previous published data confirmed that OpenFOAM is able to simulate the liquids draining very well. This is done using the gas-liquid interface solver available in the standard library of OpenFOAM. Additionally, this study also able to explain the physics flow of the draining tank.
2016 IEEE International Conference on Automatic Control and Intelligent Systems (I2CACIS), 2016
The research presented in this paper is carried out to investigate the performance of a suspensio... more The research presented in this paper is carried out to investigate the performance of a suspension systems either an active or passive type. Controllers that are used in this study are proposed fuzzy logic controller and proportional integral derivative controller as a benchmarking comparison. The simulations in this research have been carried out using Simulink of MATLAB. The parameters in the simulation model for the suspension system under study include car body mass, wheel mass, spring and damping elements of shock absorber, and tire. The block model of the suspension system has been designed to represent the equation of motion of the sedan car suspension system. The road disturbance for the active suspension system is modelled in two different ways, namely, unit step input signal and sine wave input signal. The simulation results indicate that fuzzy logic control of an active car suspension system has better performance compared to the passive system.
Procedia Engineering, 2016
This study applied a Reynolds Averaged Navier-Stokes (RANS) approach with Renormalization Group (... more This study applied a Reynolds Averaged Navier-Stokes (RANS) approach with Renormalization Group (RNG) k-turbulence model on a simplified cubical array with uniform height arranged in square layout to study the effect of different opening position on wind-induced ventilation performance in urban area. Nine different cross opening configurations located on both leeward and windward façade are tested. The velocity distribution inside the building is observed as well as the ventilation rate for all cases. The result shows that openings located in the upper part of windward wall allows higher flow rate while openings positioned near the floor exhibits the lowest.
Jurnal Teknologi, 2016
Ocean Thermal Energy Conversion (OTEC) is a promising renewable energy technology with the concep... more 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 lo...
Jurnal Teknologi, 2016
Wind flow in the urban boundary layer is influenced by both large- and small-scale surface roughn... more 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.
Building and Environment, 2016
Thermal comfort is one of the most important factors for satisfying occupants within indoor envir... more Thermal comfort is one of the most important factors for satisfying occupants within indoor environments, especially in regions that experience warm summer seasons, and analyses of thermal comfort and occupant behaviour are critical for the effective implementation of energy saving programs. This paper presents the results of studies on the thermal comfort and adaptive behaviour of occupants in university buildings with free running (FR) and cooling (CL) mode offices in Fukuoka, Japan. Both thermal measurements and thermal comfort surveys were conducted during the summer season. The mean thermal sensation vote (TSV) in FR and CL modes was 0.7 and À0.1, respectively. These data show that occupants in FR mode offices felt slightly warmer than those in CL mode offices, where occupants typically reported feeling neutral. The mean comfort temperature for both cases, as estimated by using the Griffiths method, was 26.6 C. For personal clothing, we found that the use of clothing insulation was inversely proportional to the outdoor temperature. The adaptive behaviours of occupants were found to be more active in FR mode offices compared to those in CL mode offices, which were more passive. This indicates that amenable thermal conditions were present in the air conditioning (A/C)-controlled indoor environments where occupants expressed no wish to make changes.
Aerospace Science and Technology, 2016
Abstract The effect of placing a wedge in the wake of a square cylinder (side length D) at a Reyn... more Abstract The effect of placing a wedge in the wake of a square cylinder (side length D) at a Reynolds number of 22,000 is numerically investigated. In particular, the effect of the wedge on aerodynamic noise is observed along with its effect on the flow field. Wedge base height (h) and its gap distance (G) downstream of the cylinder are systematically varied. Flow simulations are carried out using an unsteady RANS model employing the k – ω SST turbulence model, whereas the calculation of aerodynamic noise radiated from the flow is solved using Curle's equation. A special correction technique is applied to consider spanwise effects on noise production and validation is provided using new aeroacoustic data for a square cylinder in cross-flow. It is found that the flow behavior can be divided into two main regimes (regime I and regime II), with a linking transition regime. For regime I, the generated sound is lower than that of the isolated square cylinder case. The thinnest wedge produced the best sound reduction (11.79 dB) when the wedge is placed at G = 2 D . For regime II, the calculated sound level is higher than the case of an isolated square cylinder. This is because the sound emitted from both bodies have about the same magnitude and are in phase. For this case, the maximum increase of sound pressure is 6.24 dB, when the medium wedge is at G = 2.5 D .
Energy Procedia, 2015
In a typical urban area where buildings are built in a cluster with random spacing, the distribut... more In a typical urban area where buildings are built in a cluster with random spacing, the distribution of the wind pressure on a building is influenced by interference effects from neighbouring buildings, which could ultimately affect the wind-induced ventilation across the building. Large-eddy simulations (LESs) were conducted for six cases of staggered random arrays with various packing densities (λp). In addition, the heterogeneity of a typical urban surface was represented by buildings of different heights. Each type of building had a different aspect ratio αp (the ratio of the front area to the planar area of the building), which ranged between 0.84 (low-rise building) and 3.76 (high-rise building). The LES results showed that high-rise buildings (i.e. αp ≥ 3.0) were less obstructed from the approaching flow because they had higher aspect ratios than the low-rise buildings (i.e. αp ≤ 2.64). This was also because of their positions immediately behind the low-rise buildings. In dense arrays (i.e. λp ≥ 0.250), the pressure drag was dominated by high-rise buildings by up to 55%. These findings will be beneficial in a study of the mean pressure distribution of clustered buildings. Although the results of this study were exclusive to random staggered arrays, they are an important addition to the existing literature on the study of wind-induced ventilation in urban areas.
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Papers by mohamed sukri mat ali