The interaction between oscillating-grid turbulence and a sediment layer

The critical conditions for incipient sediment motion induced by oscillating-grid generated turbulence interacting with a sloping sediment layer were investigated experimentally. Near-spherical monodisperse sediments were used throughout with relative densities of 1.2 and 2.5 and mean diameters(d)ranging between 80 and 1087 μm. Interaction characteristics were analysed in terms of the critical Shields parameter θc, defined using the peak root mean square (r.m.s) horizontal velocity component in the near-bed region. Bed slope effects on θc were investigated by tilting the bed (and the grid) at angles between 0 and the repose limit. In all cases, the grid was aligned to be parallel to the bed surface, so that the oscillation direction is always normal to bed surface. The measured values of θc on a horizontal bed were comparable to the values reported in the traditional Shields diagram with θc seen to increase monotonically for hydraulically smooth bedforms and to be approximately constant for hydraulically rough bedforms. To account for bed slope effects, the measured values of θc were compared with a force-balance model based on the conditions for incipient grain motion on a sloping bed. For hydraulically smooth bedforms, where the bed roughness is small compared to the boundary-layer depth, the model was derived to account for how viscous stresses act to damp the drag and lift forces acting on the near surface sediment. For hydraulically rough bedforms, where this viscous-damping effect is not present, the model assumes the standard approach with the drag and lift forces scaling with the square of the near-bed (inviscid)velocity scale. In both cases the model predicts the bedforms to become more mobile as the bed slope is increased. However, the damping effect of the viscous sublayer acts as a stabilizing influenced for hydraulically smooth bedforms, to reduce the rate at which the bed mobility increases with bed slope. The measured values of θc in the hydraulically rough bedforms were in agreement with the trends predicted by this model. However, measured θc in smooth bed cases were lower than predicted, and fall on the hydraulically rough trend when bed slope is < 20. When the bed slope reaches the repose limit, θc falls between the smooth-bed and rough-bed cases. Measurements of sediment trajectories due to the turbulence interacting with the bed were obtained, for a range of impact conditions. Observations of the sediment trajectories during the interaction show the individual sediment grains to be predominantly displaced in a circular 'splash'. Data showed that the ‘splash’ feature and particle entrainment within the turbulence structure was within one eddy turnover time

Grain size analysis of surface fluvial sediments in rivers in Kelantan, Malaysia

Grain size spectrum and textural parameters for the fluvial sediment bed in seven tropical rivers of Kelantan, Malaysia are presented in this article. The samples were collected from six tributaries to the main Sungai Kelantan spanning approximately 248 km stretch of water streams. Sand or gravel dominated river was identified for each river using the sediment composition analysis. Textural pattern shows complicated profiles of mean size and no consistent decreasing grain size and gradation parameter were observed towards the downstream flow. Most of the samples fall under the category of either very poorly sorted or poorly sorted and has very platykurtic kurtosis distributions. CM diagram (C=one percentile in microns and M = median grain size in microns) suggested that the deposition of fine-grained sediment for samples with median grain size d50 <1 mm are either by rolling, rolling and saltation or saltation and suspension

Application of Vortex Control Principle at Pump Intake

Vortex flow in a pump intake could affect a pump operation significantly if not treated appropriately. Many researches have been conducted to determine the best control method for vortex flow in pump sumps so that the pump lifespan can be maximized. In this study, a vortex control principle designed to minimize the impact of submerged vortex flow in pump sump on major pump components is presented. This principle employs a device called the plate type floor splitter which serves the function of eliminating vortices formed on the sump floor and reduces the intensity of swirling motion in the intake flow. A pump sump model was built to carry out the study by installing a floor splitter plate sample under the pump suction inlet and the corresponding parameters used to quantify the swirl intensity known as the swirl angle was measured. Procedures for the measurement were conducted based on ANSI/HI 9.8-2018 standard. A numerical simulation was performed to study the flow in a full-scale pump sump. The results showed that the installation of floor splitter plate can eliminate vortices efficiently and reduce swirl angle significantly. However, optimization of floor splitter design is needed to achieve a reduction effect that can reduce swirl angles to an acceptable value of lower than 5° according to ANSI/HI 9.8-2018 standard

Vortex measurement at bell-shaped pump inlet using particle image velocimetry

The vortex formed at the pump intake is known to be the main factor affecting the performance of a pump and it contributes directly to the increase of energy consumption. This study was aimed at obtaining an in-depth visualization and identifying the characteristics of the vortices generated by the installation of a bell-shaped suction inlet in a pump-induced flow using particle image velocimetry (PIV). A complementary metal-oxide semiconductor (CMOS) camera was used to capture images of the illuminated bubbles in a sump pump model. The PIV images were analysed using PIVlab, which provided representations of the 2-D plane velocities and vorticities around the inlet of the pump. The measurements were taken at four different planes that were coaxial with the bell circumference below the bell inlet. The results showed that the diameter of the vortex structure became smaller as it approached the bell inlet. Higher values of vorticity were observed within the vortex core, which conformed to the characteristics of a vortex formation. The velocity profiles exhibited the proportionality of the velocity against the radius of the vortex, which categorized this as a forced vortex. The findings from the study will be utilized by the Department of Irrigation and Drainage (DID) Malaysia to develop remedial measures for problems related to the formation of vortices in sump pumps

Vital Conditions to Remove Pollutants from Synthetic Wastewater Using Malaysian Ganoderma lucidum

Mycoremediation, a fungal-based technology, has seen tremendous growth as an effective alternative to treat industrial wastewater due to its ability to oxidise pollutant loadings. Considering the non-toxic properties and high potential degradation performance of Ganoderma lucidum, this research aims to study the performance of a Malaysian G. lucidum strain, the effect of agitation speed, and different carbon-to-nitrogen (C/N) ratio concentrations of synthetic wastewater in degrading chemical oxygen demand (COD) and ammonia. Different agitation speeds (25 rpm, 50 rpm and 100 rpm) and C/N ratios (C10N1, C13.3N1 and C16.7N1) were chosen as parameters to be analysed in this study. The best degradation of COD and ammonia with a percentage removal in the range of 95% to 100% within 30 h of treatment. ANOVA analysis was done using the response surface methodology to verify the obtained results, and it was found that mycoremediation using 100 rpm agitation provided the best results, removing more than 95% of COD and ammonia from synthetic wastewater. The microscopic analysis also showed that the structure of G. lucidum changed after wastewater treatment. This result proved that the Malaysian G. lucidum strain has a good potential in treating synthetic domestic wastewater, especially with high organic content, as a naturally sustainable bioremediation system

The relation of neighbouring land use type and sedimentary characteristics of fluvial sediments in tropical rivers

This study investigates the relationship between land use types and sedimentary characteristics of fluvial bed at three rivers in Selangor, Malaysia; namely Sungai Tengi, Selangor and Langat. The diversity in population density and land development at the adjacent river banks gives associated dominant land use type as forest, agriculture and urban for Tengi, Selangor and Langat, respectively. Field sampling was conducted at consistent spatial locations for Tengi and Selangor, whereas for Langat, the bed sediment was taken at non-uniform spatial points due to limited access. Statistical analysis of the sediment bed mixture shows that forest dominated land gives finer bed sediment size at 650 μm. Correlation analysis proved that there is a relationship between types of land use with the mean sediment size. No distinctive correlation can be observed for sorting, skewness and kurtosis of the sediment with the types of land use

The application of open FOAM in modelling flow for vegetated channel

Vegetation plays an important role in the hydrodynamic behaviour of an open channel flow. This study attempted to investigate the flow characteristics of an emergent vegetated channel using Open-source Operations and Manipulation (OpenFOAM). InterFoam is an OpenFOAM solver used to model this simulation. It is one of the methods available to model free-flow surface flow. Results for flow velocity profile can be generated using ParaView software. This study used a constant inlet velocity of 0.0417 m/s. There are two sets of models including model L8 with a solid volume fraction (SVF) of 8% using 9 rigid dowels, and model 4S with SVF of 4% using 17 dowels within a 1.2 m2 study area. Dowels in L8 are arranged in linear formation compared to the 4S model in a staggered arrangement. The study found that in model 4S, the stem-scale vortices are developed individually after each dowel due to sparse staggered vegetation. Meanwhile, model 8L suggests oppositely the vortex is cramped from the closeness of the dowels. The shear layer is formed as the flow enters the vegetation patch at upstream and the instability causes the shear layer vortices between inside and outside the vegetation region. Both models agreed that as the flow moves downstream the vortices are greater and make the streamwise velocity region become slower. The vertical velocity profile acknowledges the shear layer patch-scale vortices have a greater influence on the flow of both models. The magnitude of turbulence intensity in lateral directions is bigger in model 4S than in model 8L. The influence of vortices shed by upstream cylinders has an increasing impact on the irregular shedding behaviour of downstream cylinders as plant density increases. In general, the TKE values of the Model 4S are higher than those of the Model 8L. Regardless of the solid volume percentage difference, the vegetation pattern between linear and staggered has an effect on the flow. Computational Fluid Dynamic (CFD) is indeed capable to solve complex hydrodynamic characteristic

Kesedaran dan kelakuan pelajar prasiswazah terhadap aktiviti plagiat dalam penulisan akademik

Makalah ini membincangkan tahap kesedaran dan kelakuan pelajar prasiswazah di universiti terhadap aktiviti plagiat dalam penulisan akademik. Objektif kajian adalah untuk menilai pengetahuan dan pemahaman pelajar mengenai plagiat, termasuk jenis-jenis plagiat yang biasa dilakukan oleh pelajar, tahap keseriusan dan kekerapan perlakuan setiap jenis plagiat. Metodologi yang digunakan ialah pendekatan kuantitatif dengan menggunakan kaedah tinjauan. Instrumen yang digunakan ialah soal selidik yang mempunyai tiga bahagian. Responden kajian terdiri daripada pelajar prasiswazah, dari tahun pertama hingga tahun akhir pengajian di sebuah institusi pengajian tinggi awam di Malaysia dengan menggunakan persampelan rawak mudah. Dapatan kajian menunjukkan, hampir 80% para pelajar prasiswazah mempunyai kesedaran dan mengetahui implikasi aktiviti plagiat, namun begitu mereka mengaku masih melakukan plagiat dalam penulisan akademik. Dapatan dominan menunjukkan empat jenis plagiat dalam takrif serius iaitu pencurian, penyalinan kata demi kata, penulisan hantu dan plagiat lain, manakala aktiviti plagiat seperti parafrasa palsu, parafrasa gelap dan kitar semula dianggap tidak serius kerana mendapat maklum balas yang rendah daripada pelajar. Signifikan kajian ini ialah, dapat membantu pihak universiti untuk mengadakan kursus-kursus penulisan akademik yang beretika supaya peratus plagiat dalam kalangan pelajar dapat dikurangkan seterusnya dapat mengelakkan hal ini daripada berlaku

Evaluation of coastal hydrodynamic performance using statistical analysis at the Kelantan coast, Malaysia

Coastal zones are vulnerable to the effects of nature and man, as well as being physically volatile. The interaction of hydrodynamic conditions in coastal areas is a complex phenomenon. Considering the characteristics in this specific area, understanding its hydrodynamic behaviour should be obviously clarified. Thus, the hydrodynamic characteristics for Kelantan coast had been simulated using a numerical software of MIKE 21 Hydrodynamic FM. To assess the performance of the model, a combination of time series analysis and statistical evaluation were carried out against two weeks of observed data. Time series analysis shows a good agreement with the field measurements for both magnitude and phase. Statistical analysis using Root Mean Squared Errors (RMSE) and Regression analysis (R2) for current speed and water level were analysed. The results indicate that the RMSE for current speed are 8.97% and 8.00% for ADCP 1 and ADCP 2, respectively while the RMSE for water level is 8.89 %. Through the regression analysis, the output indicates that the numerical model is in a good performance as the R2 ranged from 0.72 to 0.9. Both time series and statistical approach were successfully utilised in the hydrodynamic model to determine the performance of the coastal hydrodynamic characteristics in Kelantan’s coastline. The output model can provide important information, especially on the coastal management and land-use planning for the developers, planners and state authority

Pharmaceutical compounds in Malaysian urban domestic wastewater

The emerging contaminants (ECs) is detected at trace concentration in the discharge of sewage treatment plant (STP) to the water bodies indicate incomplete removal during the treatment process. The presence of the ECs in the water has a potential impact on the ecological and human health associated with long-term ingestion of the mixture ECs compounds, and this includes the development of resistance in pathogenic bacteria, aquatic toxicity, genotoxicity, and endocrine disruption. In this study, we investigate the presence of ECs and review the occurrence of mainly of four pharmaceutical active compounds belonging to the group of non-steroidal anti-inflammatory drugs (NSAIDs) in influent and effluent of the STP. The target analytes (ibuprofen (IBU), diclofenac (DIC), ketoprofen (KET), and naproxen (NAP)) are extracted from the wastewater using the solid-phase extraction (SPE) followed by the identification and quantification using gas chromatography-mass spectrometry (GC-MS). The GC-MS detection was improved by the derivatisation technique using N-Methyl-N-(trimethylsilyl)trifluoroacetamide (MSTFA) and an internal standard of Ibuprofen-D3 used as the internal standard. The targeted analytes were detected in both influent and effluent wastewater in the range 5.04±5.9 to 37.4±28.4 μg/L with removal efficiency between 11 - 86% using the current activated sludge treatment process in the STP. This concentration of compounds shows inadequate current treatment techniques to eliminate the emerging contaminants in the wastewater