A review on natural convection flow along a vertical flat plate

Volume 3, Issue 1, January 201

CHANGES OF BAETE’S ACCREDITATION MANUAL FOR BACHELOR’S DEGREE PROGRAMS IN ENGINEERING IN BANGLADESH

Accreditation has recognized itself worldwide as the key appliance for quality assurance in engineering education, Beginning with the pioneering efforts of Accreditation Board for Engineering and Technology ABET [14], USA, and countries are approaching under the shade of the Washington Accord [7]. Accreditation includes a two-stage process, self-assessment and peer evaluation; the essential changes are highlighted. In the last two decades, an explosive growth in the number of institutions offering engineering programs has been detected. This unprecedented growth obviously led to several problems with regard to quality of engineering education. In order to ensure the quality of engineering education, the Institution of Engineers, Bangladesh (IEB) to formulate the criteria or standards, by which individual programs in any engineering institution can be evaluated [5]. Bangladesh has engaged a big leap forward in the area of engineering education by becoming a provisional member of the Washington Accord through the Board of Accreditation for Engineering and Technical Education (BAETE) [3]. As per the requirement the Institution of Engineers, Bangladesh (IEB)  has revised the procedures and criteria of accreditation to bring it to international standards. The new procedures and criteria of accreditation came to effect from 1st January 2020. This paper presents the changed part of accreditation of the BAETE.  Article visualizations

Dispersion in Alluvial River

River pollution is the contamination of river water by pollutant being discharged directly or indirectly on it. Depending on the degree of pollutant concentration, subsequent negative environmental effects such as oxygen depletion and severe reductions in water quality may occur which affect the whole environment. River pollution can then cause a serious threat for fresh water and as well as the entire living creatures. Dispersion in natural stream is the ability of a stream to dilute soluble pollutants. Different types of pollution, such as accidental spill of toxic chemicals, industrial waste, intermittent discharge from combined sewer overflows and temperature variations produced by thermal outflows, may generate a cloud whose longitudinal spreading strongly affects the pollutant concentration dynamics. Pollutants discharging form a point source is easier to control where as pollutant discharging from non point sources arehardlycontrollable and may represent severe threat to the river ecosystem. The longitudinal dispersion coefficient is used to describe the change in characteristics of a solute cloud from an initial state of high concentration and low spatial variance to a downstream state of lower concentration and higher spatial variance. Therefore, in order to correctly estimate the degree of pollutionwithin a stream and ensure an efficient and informed management of riverine environments,a reliable estimationof the dispersion withinthe stream is a crucial concern. The objective of my research is to develop a mathematical model for determining the dispersion in alluvial river. In order to achieve the goal, a model has been developed which provides an analytical relation for the prediction of the dispersion coefficient in natural streams, given the planimetric configuration of the river and the relevant hydrodynamic and morphodynamic parameters (i.e., width to depth ratio, the sediment grain size, scaled with the flow depth, the Shields stress). One of the most striking features of alluvial rivers is their tendency to develop regular meandering plan forms. Their geometry is in fact characterized by a sequence of symmetrical curves which amplify over time due to erosion processes at the outer bank and deposition at the inner bank. This planimetric pattern affects both the hydrodynamics of the river and the distribution of bed elevations, as well as its hydraulic response, as the average bed slope is progressively reduced along with the flow cross sections. The flow filed that establishes in meandering rivers has clearly a great relevance on the behavior of the pollutant cloud and hence on the dispersion that drives its microscopic evolution. To develop a dispersion coefficient predicting model, the analytical models of flow field establishing in the cross section of a straightriver [TubinoansColombini, 1992] and of a meandering river [Frascati and Lanzoni, 2013] aredeveloped. The two dimensional mass balance equation governing the dynamics of a pollutant is then solved using asymptoticexpression and Morse and Feshbach[1953] formalism. Finally, using the two dimensional spatial distributions of the concentration, the flow depth and the velocity, the dispersion coefficient are obtained. For straight rivers the cross-sectional velocityand the theoretically predicted dispersion coefficients with the field datacollected by Godfrey and Frederick (1970)in two rivers (Clinch River, Copper Creek). The comparison is reasonably good. The performance of the model is also tested with reference to the predictions provided by the model proposed by Deng (2001). The resultant model is found to give prediction closer to 80% of the experimental data,a much better performance agreement with respect to the model of Deng (2001). The results of the model developed to estimate the dispersion coefficients in meandering river, have been compared with the experimental data available in experimental and referring to six different rivers. Also in this case the agreement between the dispersion coefficient predicted theoretically and those calculated on the basis of tracer tests is quite good and better than that ensured by the other theoretical and empirical predictors available in literatur

ALIGNING ASSESSMENT WITH OUTCOME BASED ASSESSMENT: AN EMPIRICAL STUDY ON UNDERGRADUATE COURSE ON FUNDAMENTALS OF STATISTICS

Since the Institution of Engineers, Bangladesh (IEB) has made Outcome Based Assessment (OBA) compulsory towards program accreditation it has been one of the vital interests of most engineering departments in Bangladesh. When considering the mapping of the Course outcome (CO) to Program Outcomes (PO) implementation of the OBA may not be an easy task. This paper reports the analysis procedure of the CO and PO achievement for an B.Sc. course on Fundamentals of Statistics, a subject, which is part of curriculum of Electrical & Electronics Engineering and Computer Science and Engineering at Eastern University, Bangladesh. As a sum, this paper contributes complete process and an example investigation for Outcome Based Valuation starting from course curriculum progress to its CO-PO achievement based on definite criteria.  Article visualizations

Mathematical catastrophe revisited

Volume 2, Issue 1, January 200

Dispersion in Alluvial River

River pollution is the contamination of river water by pollutant being discharged directly or indirectly on it. Depending on the degree of pollutant concentration, subsequent negative environmental effects such as oxygen depletion and severe reductions in water quality may occur which affect the whole environment. River pollution can then cause a serious threat for fresh water and as well as the entire living creatures. Dispersion in natural stream is the ability of a stream to dilute soluble pollutants. Different types of pollution, such as accidental spill of toxic chemicals, industrial waste, intermittent discharge from combined sewer overflows and temperature variations produced by thermal outflows, may generate a cloud whose longitudinal spreading strongly affects the pollutant concentration dynamics. Pollutants discharging form a point source is easier to control where as pollutant discharging from non point sources arehardlycontrollable and may represent severe threat to the river ecosystem. The longitudinal dispersion coefficient is used to describe the change in characteristics of a solute cloud from an initial state of high concentration and low spatial variance to a downstream state of lower concentration and higher spatial variance. Therefore, in order to correctly estimate the degree of pollutionwithin a stream and ensure an efficient and informed management of riverine environments,a reliable estimationof the dispersion withinthe stream is a crucial concern. The objective of my research is to develop a mathematical model for determining the dispersion in alluvial river. In order to achieve the goal, a model has been developed which provides an analytical relation for the prediction of the dispersion coefficient in natural streams, given the planimetric configuration of the river and the relevant hydrodynamic and morphodynamic parameters (i.e., width to depth ratio, the sediment grain size, scaled with the flow depth, the Shields stress). One of the most striking features of alluvial rivers is their tendency to develop regular meandering plan forms. Their geometry is in fact characterized by a sequence of symmetrical curves which amplify over time due to erosion processes at the outer bank and deposition at the inner bank. This planimetric pattern affects both the hydrodynamics of the river and the distribution of bed elevations, as well as its hydraulic response, as the average bed slope is progressively reduced along with the flow cross sections. The flow filed that establishes in meandering rivers has clearly a great relevance on the behavior of the pollutant cloud and hence on the dispersion that drives its microscopic evolution. To develop a dispersion coefficient predicting model, the analytical models of flow field establishing in the cross section of a straightriver [TubinoansColombini, 1992] and of a meandering river [Frascati and Lanzoni, 2013] aredeveloped. The two dimensional mass balance equation governing the dynamics of a pollutant is then solved using asymptoticexpression and Morse and Feshbach[1953] formalism. Finally, using the two dimensional spatial distributions of the concentration, the flow depth and the velocity, the dispersion coefficient are obtained. For straight rivers the cross-sectional velocityand the theoretically predicted dispersion coefficients with the field datacollected by Godfrey and Frederick (1970)in two rivers (Clinch River, Copper Creek). The comparison is reasonably good. The performance of the model is also tested with reference to the predictions provided by the model proposed by Deng (2001). The resultant model is found to give prediction closer to 80% of the experimental data,a much better performance agreement with respect to the model of Deng (2001). The results of the model developed to estimate the dispersion coefficients in meandering river, have been compared with the experimental data available in experimental and referring to six different rivers. Also in this case the agreement between the dispersion coefficient predicted theoretically and those calculated on the basis of tracer tests is quite good and better than that ensured by the other theoretical and empirical predictors available in literatureLo studio della dinamica di un inquinante convenzionale (e.g., BOD) all’interno di un corso d’acqua naturale richiede la conoscenza del campo di moto e della batimetria che si realizzano nel corso d’acqua stesso, delle modalità di immissione (continua o localizzata, accidentale o sistematica) e delle reazioni chimiche a cui l’inquinante è soggetto. L’obiettivo della presente tesi è quello di caratterizzare la distribuzione spazio-temporale della nuvola di inquinante, in modo da poter valutare i carichi inquinanti e controllare il soddisfacimento, o meno, dei requisiti di legge. In particolare, l’attenzione è stata concentrata sul comportamento dell’inquinante nel cosiddetto campo lontano, ovvero a una distanza dalla sorgente tale per cui l’inquinante si è mescolato verticalmente e trasversalmente, distribuendosi quasi uniformemente sulla sezione. In tali condizioni, ai fini applicativi è sufficiente studiare il comportamento della concentrazione media sulla sezione. Tale comportamento è retto dalla classica equazione dell’avvezione-dispersione la cui soluzione, nel caso di immissione istantanea e localizzata di una determinata massa di sostanza inquinante e tratto di corso d’acqua omogeneo, è data dal classico andamento Gaussiano. La stima del coefficiente di dispersione da utilizzare nella suddetta equazione risulta di fondamentale importanza per una corretta previsione del comportamento spazio-temporale dell’inquinante. La struttura di tale coefficiente, d’altra parte, è strettamente legata al campo di moto che si realizza in un alveo naturale e, in particolare, alle deviazioni rispetto ai valori medi sulla sezione della velocità e della concentrazione. Utilizzando le attuali conoscenza relative al campo di moto in alvei a fondo mobile, nella presente tesi viene derivata una soluzione analitica del coefficiente di dispersione dipendente da parametri in ingresso quali il rapporto larghezza-profondità desumibile dalla geometria della sezione, il diametro dei sedimenti, normalizzato con la profondità della corrente, la pendenza del corso d’acqua. Il problema è inizialmente affrontato nel caso di alveo rettilineo e sezione in equilibrio con il trasporto in cui il fondo varia gradualmente in direzione trasversale. Risulta cos`ı possibile suddividere la generica sezione in una zona centrale, dove la profondità della corrente si mantiene approssimativamente costante, e due regioni di sponda, nelle quali la profondità si riduce gradualmente a zero. Il campo di moto calcolato tendendo conto di questa lenta variazione trasversale del fondo (che consente di semplificare opportunamente l’equazione della quantità di moto), raccordato con quello che si realizza nella regione centrale, unitamente all’equazione del bilancio di massa dell’inquinante, consentono di determinare analiticamente il coefficiente di dispersione. Il passo successivo è stato quello di considerare in caso di alvei alluvionali ad andamento meandriforme. Si tratta di una tipologia di configurazione planimetrica molto comune in natura, caratterizzata da una sequenza più o meno regolare di curve alternate. Sfruttando il fatto che molto spesso la curvatura dell’asse del canale è debole, risulta possibile ottenere una soluzione analitica del campo di moto e della topografia del fondo. Tale soluzione, associata all’equazione del bilancio di massa dell’inquinante riscritta in coordinate curvilinee, opportunamente semplificata sfruttando l’ipotesi di deboli curvature, consente di determinare analiticamente il coefficiente di dispersione. Le stime del coefficiente di dispersione ottenute nei casi di alveo rettilineo e ad andamento meandriforme, sono state infine confrontate con i dati di campo reperibili in letteratura, ottenuti tramite campagne di misura con traccianti. Per entrambe le configurazioni planimetriche analizzate(rettilinea e meandriforme), l’accordo tra coefficienti osservati in campo e i risultati delle previsioni teoriche appare generalmente buono e, comunque, decisamente migliore di quello offerto dalle varie formulazioni semi-empiriche e teoriche attualmente disponibili in letteratur

Natural convection flow from a porous vertical plate in the presence of heat generation

Abstract: Natural convection flow from a porous vertical plate in presence of heat generation have been presented here. The governing boundary layer equations are first transformed into a non dimensional form and the resulting non linear system of partial differential equations are then solved numerically using finite difference method together with Keller-Box scheme. The numerical results of the surface shear stress in terms of skin friction coefficient and the rate of heat transfer in terms of local Nusselt number, velocity as well as temperature profiles are shown graphically and tabular form for a selection of parameters set of consisting of heat generation parameter Q, Prandtl number Pr