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Magnetohydrodynamic Flows in Pipe and Boundary Layer With Heat Transfer

Thesis Info

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Author

Sufian Munawar

Program

PhD

Institute

Quaid-I-Azam University

City

Islamabad

Province

Islamabad.

Country

Pakistan

Thesis Completing Year

2013

Thesis Completion Status

Completed

Subject

Mathemaics

Language

English

Link

http://prr.hec.gov.pk/jspui/bitstream/123456789/2588/1/2612S.pdf

Added

2021-02-17 19:49:13

Modified

2024-03-24 20:25:49

ARI ID

1676726598307

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In a viscous flow the viscosity effects are prominent only in a thin region near the solid boundary, namely, the boundary-layer or the thin shear layer. Since the start of the last century the study of boundary layer flows has been identified as a self- standing field of research in the area of fluid dynamics. The theory of boundary-layer has greatly helped the scientists and engineers towards the understanding of flow and heat transfer phenomenon in viscous flows. Despite the continuous research of scholars the understanding of three dimensional boundary-layers is still a demanding area of research. Three dimensional boundary-layer momentum equations are more complicated in comparison to the two dimensional ones but still there is a class of flows which are three dimensional with less complicated equation. Such flows are commonly known as axisymmetric flows. Axisymmetric flows occur inside/outside the pipes, over blunt bodies and in rotating disk systems. In this dissertation, we aim to examine various flow situations of multi- dimensional boundary-layer flows of axisymmetric nature. The impact of surface expansion/contraction and rotation has been investigated on the internal boundary- layer flow inside a pipe of uniform cross-section. The effects of surface stretching, rotation and oscillation on momentum and thermal transport in the external boundary- layer have been considered in the flow near a solid cylinder. The stagnation point flow has also been studied in rotating disk boundary-layer flow. Furthermore the effects of magnetohydrodynamic (MHD), suction/injection and unsteadiness have also been investigated in some cases. The calculation of skin friction coefficient and the coefficient of heat transfer has been the major study. Analytic and (or) numerical solutions have been obtained in all cases, however, the preference has been given to the analytic solution. Homotopy analysis method has been used for analytic solution and for numerical computations the shooting technique or the finite difference schemes have been applied. The accuracy and validity of these solutions have been proved in detail either by calculating the residual errors or through comparison with authentic results or both. The analysis reveals that both the momentum and energy transport strongly depend upon the curvature of cylinder. As compared to the flat plate case the coefficient of skin friction and heat transfer are bigger in magnitude for a cylinder of large curvature. For efficient cooling the dissipation effects are recommended to be minimized. Furthermore, the fluids of high Prandtl number are observed to be serving as good coolant.
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رسائل و جرائد

شعر و ادب کو پروان چڑھانے میں ادبی شخصیتوں کا اپنا مقام و مرتبہ ہے یہ کیسے ہو سکتا تھا کہ رسائل و جرائد اور اخبارات ان سے پیچھے رہتے خطہ سیالکوٹ کے مقامی رسائل و جرائد اور اخبارات ادب کی ترقی کے لیے ماضی سے اہم خدمات سر انجام دیتے چلے آرہے ہیں۔ان میں ’’نوائے سماج‘‘،’’ندائے سیالکوٹ‘‘،’’ہمدرد پاکستان‘‘ ،’’محنت کش‘‘ اور ’’شبنم‘‘ اہم رسائل و جرائد میں شمار ہوتے ہیں۔ان رسائل و جرائد اور اخبارات کے باقاعدہ ادبی ایڈیشن بھی شائع ہوتے رہے ہیں۔

          سیالکوٹ کے اخبارات کی موجودہ صف میں ’’صدائے شہر‘‘ ،’’نوائے شمال‘‘ اور ’’اخبار سیالکوٹ‘‘ نمایاں اخبارات ہیں۔رسائل و جرائد کی فہرست میں ’’مرے کالج میگزین ‘‘،’’مفکر‘‘،’’کاوش‘‘، ’’افق‘‘،’’محورِحیات ‘‘، ’’اقدار‘‘، ’’ادراک‘‘، ’’انتخاب‘‘، ’’کیہان‘‘، ’’یدبیضا‘‘، ’’گجر‘‘، ’’کرائیڈن‘‘، اور’’سٹی میگ‘‘آج بھی ادبی خدمات میں اہم کردار ادا کر رہے ہیں۔

          ’’گجر‘‘ ،’’انتخاب‘‘،’’ید بیضا‘‘ تاب اسلم کے شعور و فکر کا نچوڑ ہیں ان تینوں رسائل وجرائد کو تاب اسلم بڑی عرق ریزی سے ادبی دنیا کے سامنے پیش کرتے رہے ہیں۔ان ادبی رسائل نے بہت سے نئے لکھنے والوں کی راہنمائی کا فریضہ سر انجام دیا ہے۔تاب اسلم کے ان جرائد کو نہ صرف سیالکوٹ بلکہ برصغیر پاک و ہند کے نامور ادبا و شعرا ،ناقدین اور محققین کا قلمی تعاون حاصل رہا۔سیالکوٹ کے اہم ادبی رسائل و جرائد کے تعارف کے لیے تفصیل پیش کی جاتی ہے۔

۱۔       مر ے کالج میگزین :

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Pandemic Impact on the Travels and Tourism Sector of Nepal

The travel and tours enterprise were badly affected due to pandemics. In the aftermath of high restrictions on human movement, travel-based entrepreneurs were highly impacted due to lockdown. Due to pandemic, highly impacted into earning-saving, lack of supportive working conditions, lower self-capacity, and lack of recovery budget and policies, the travel and tours-based entrepreneurs were highly impacted. The study reflected the impact of pandemics on travel and tours, major constraints, and a possible way forward to sustaining. The research explores what are the major existing practices of sustaining travel and tours entrepreneurs during pandemics, what factors can contribute to building bounce-back capacities of travel and tours entrepreneurs’ sustainability. Above forty-four, snowball-based sampling was done from major travel and tours entrepreneurs, Pokhara-Nepal. A structure-based open-ended questionnaire, key informant interviews, and in-person-based discussion were applied in the method of study. Used the content analysis along with a recap of the research question, undertake bracketing to identify biases, operationalize variables with develop a coding, and code the data with undertaking analysis while qualitative analysis, and multiple regression facilitated on quantitative analysis to finalize the discussion. The study reflects that self-saving, social support, state and financial institutions recovery support, social behavior and change communication, full vaccination practices, and self-accountable tourist behavior are highly expectable conditions to the sustainability of travel and torus entrepreneurship in the learning area. The study concludes that self-saving capacity can contribute to bounce-back capacity for every entrepreneur. Social support and socioeconomic recovery packages were also contributing to sustaining travel and tours in the study area. Self-saving condition and capacity is higher bounce back capacity compared to non-saved entrepreneurs in the study area. Social support, socioeconomic recovery practices, and recovery packages from state and financial institutions were not at the higher level as expected.

Synthesis of Polyaniline Composites and Their Applications

Conducting polymers represent an important class of functional organic materials for next-generation electronic and optical devices. Advances in nanotechnology allow for the fabrication of various conducting polymer nanomaterials composites synthesis with the different methods. Conducting polymer nanomaterials composites featuring high surface area, small dimensions, and exhibit unique physical and chemical properties therefore they have been widely used for various purposes such as, they can be used as photocatalyst The present research work is divided in to two parts. First part of thesis deals with the synthesis of three different series of Polyaniline (PANI) composites in which two are Zr-Co-substituted nickel ferrite with formula (NiFe1.2 Zr0.4 Co0.4 O4) and (NiFe Zr0.5 Co0.5 O4), one with MnAl-substituted multiferroics with formula (BiAl0.3Mn0.3Fe0.4O3). The synthesis of composites of Polyaniline (PANI) is carried out with the variation of nanoparticles amount (12.5, 25, 37.5, and 50% w/w). These composites are characterized by different techniques such as Fourier Transform Infrared Spectroscopy (FTIR), X-ray diffraction (XRD), UV/Visible, X-ray photoelectron spectrometry (XPS), and scanning electron microscopy (SEM). The structure of PANI/nanomatrials composites was confirmed by XRD analysis while surface morphology was investigated by SEM analysis. The FTIR spectroscopy is used to identify their functional groups present in PANI/NPs composites and the shifting of the peaks has been found towards higher wave number side which exhibits the interaction between the polymer and the nanoparticles in synthesized photocatalyst. In UV/ Vis study blue shift has been found which give the information about the interaction between ferric ions of nanomaterial with nitrogen atom of PANI, shortening in the conjugation length, and coordinating complex formation. The XPS analysis has been carried out to determine oxidation states of the elements present in the synthesized composites materials. In the second part these synthesized PANI/NPs are used as photocatatlyst against toxic dyes such as Methylene Blue (MB) and Methyl Orange (MO). These synthetic dyes are most widely used in textile and leather tanning industries. These dyes are highly colored, toxic, and carcinogenic in nature. These effluents released from the textile and leather tanning industries containing 1mg/L of dye are enough to impart color to the water thus making it unpotable for daily use. The technology used to treat dyes is based on physical, chemical, and biological methods. Precipitation, coagulation, filtration, floatation, electrochemical degradation, and advanced oxidation techniques are considered as chemical methods. Adsorption, reverse osmosis, and ultrafiltration are treated as physical methods. Photochemical irradiation of toxic dyes in presence of a photocatalyst is one of the alternative methods developed recently. Theses composites are then used for the photoelectric degradation of methylene blue and methylene orange from aqueous media under UV light. Effect of reaction time, NPs concentration and the kinetics is studied. It has been found that the degradation of methylene blue and methylene orange increase with the increase in nanoparticles concentration in the composite material. This degradation rate has been found to be low for methylene blue which is cationic dye as compare to the methylene orange. The photoelectric degradation for both dyes is also examined under the similar conditions of UV light by pure PANI and nanoparticles. The degradation rate has been found very low because recombination of electron-holes occurs in pure PANI and pure nanomaterial very comfortably as compare to composites in which it is strictly prohibited. The NPs amount present in the composite shows remarkable influence on the degradation efficiency. Through several groups of univariate experiments, the optimum PANI/ NPs composite dosage of the photolysis process is found to be 0.2g at 40ml of 10-5M solution of both dyes. The photolysis process is relatively fast at the initial stage up to 30 minutes and later it become slow, moreover the degradation of both dyes is in accordance with the first-order kinetic equation.