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Home > A Parametric Study of Flow Field and Heat Transfer Between Squeezing Disks

A Parametric Study of Flow Field and Heat Transfer Between Squeezing Disks

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Author

Khan, Aamir

Program

PhD

Institute

University of Engineering and Technology

City

Peshawar

Province

KPK

Country

Pakistan

Thesis Completing Year

2019

Thesis Completion Status

Completed

Subject

Fluid Dynamics

Language

English

Link

http://prr.hec.gov.pk/jspui/bitstream/123456789/10802/1/Aamir%20Khan_Fluid%20Dynamics_2019_UET_Peshawar_PRR.pdf

Added

2021-02-17 19:49:13

Modified

2024-03-24 20:25:49

ARI ID

1676725403077

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Squeeze flow is a simple and extremely useful rheological technique by which a fluid is squeezed between the gap of two parallel bodies (Disks) under the action of a normal force. In general, one of the bodies is held fixed and the other body moves toward it. If used in a steady shearing mode, certain properties such as shear modulus can be de duced. However, squeeze flow is more frequently used to find the dynamic properties such as storage and loss modulus of viscoelastic materials. Commercially available rheometre devices like piezoelectric axial vibromter which is used to measure these properties, are only capable for a frequency range between 10 to 400Hz. The squeeze flow is generated between the disks gap can be varied between 20 to 200µm for a required sample volume 100µL. This allows for the measurements on a fluid with viscosity range 1 to 200 mPas. This device seems to be very promising; however, the volume of liquid required is too large and the viscosity that can be measured is too low to satisfy a number of industrial needs. It seems apparent that a device capable of measuring fluid properties into kHz range and measuring fluid’s properties into kHz range, operating on sub-µL volume and sub-µm gap is yet to be developed - a challenging task. The friction between the fluid and disks surface creates heat which modifies the fluid viscosity and velocity distribution. This temperature gradient plays a pivotal role in designs of high energy devices. A large number of physical phenomena involve natural convection, which are enhanced and driven by internal heat generation. The effect of internal heat generation is especially pronounced for low Prandtl number i.e metal fluids. The friction between fluid and disks surface also creates electric charges which flow with fluid flow. The motion of theses charges eventually creates a magnetic field in fluid domain. This magnetic field controls change in viscosity due to temperature gradient. According to Lenz’s law, motion of a conductor through a magnetic field, Lorentz force acts on fluid and modifies its motion, which makes the theory highly non-linear. The main purpose of this research is to gain a better understanding of the behavior of fluid flow and heat transfer between squeezing disks. The constitutive expression of un steady Newtonian fluid is employed in the mathematical formulation to model the flow between the circular space of porous and contracting disks. The expressions for fluid torque and magneto-hydrodynamic pressure gradient which the fluid exerts on disks are derived. The Soret and Dufour effects due to concentration and temperature gradients are investigated. It is depicted through graphs and numerical results that increase in Soret number and inertial forces increases the rate of heat flux and decreases mass flux. The effect of centrifugal and Coriolis forces due to the rotation of disks is also studied in detail and shown that increasing the rotational speed of the upper disk increases rate of heat transfer. For the very first time in literature, the Navier-Stokes equations of viscous fluid along with energy and concentration equations are investigated under the influence of variable magnetic field. The conservation equations with three dimensional Maxwell’s equations are taken into account and concluded that the fluid axial velocity and temperature in crease with increase in the axial component of magnetic field. The fluid’s pressure and torque on upper disk is also gaining strength as the azimuthal and axial component of magnetic field are increasing. Different flow regimes corresponding to disks rotations in same and opposite directions are found in radial and azimuthal velocity distribution. As viscosity and thermal conductivity changes with alteration in a magnetic field, there fore magnetic field dependent viscosity and magnetic field dependent thermosolutal con vection are investigated for the first time in fluid dynamics. During analysis, it has been observed that an increase in viscosity decreases the strength of azimuthal and axial com ponents of magnetic field. It is also observed that heat and mass coefficient are increasing the function of the rotational Reynolds number. An error analysis is conducted in this thesis to ensure the reliability of the analysis for the remaining minimal errors. The analysis is performed using 40th-order approxima tions. In the case of flexible disks, the self-esteem equations are solved using Parametric Continuation Method and the Homotopy Analysis Method (HAM) with an appropriate initial estimates and auxiliary parameters to compile an algorithm with accelerated and assured convergence. The validity and accuracy of HAM results is proved by comparison of the HAM solutions with numerical solver package BVP4c.
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محمد نظام الدین

محمد نظام الدین
ابھی قلم یہیں تک پہنچا تھاکہ ڈاکٹر محمد نظام الدین کے انتقال کی خبر حیدآباد سے ملی۔ مرحوم عرصہ تک عثمانیہ یونیورسٹی حیدآباد میں فارسی کے پروفیسر اوردائرۃ المعارف کے ڈائرکٹر رہے اوراس حیثیت سے انھوں نے اسلامی علوم وفنون کی بڑی قابل قدر خدمات انجام دیں۔وہ پروفیسر براؤن کے خاص شاگرد تھے اور عربی وفارسی کے نامور اساتذہ اور فضلاء کی اس پرانی نسل سے تعلق رکھتے تھے جو اب آفتابِ لب بام ہے۔ستربرس کے لگ بھگ عمر ہوگی۔لیکن اس عالم میں بھی علمی کام کرتے رہتے تھے۔چنانچہ ابھی چندماہ ہوئے انھوں نے دوکتابیں سلوک الملوک فضل بن روز بن نبھان اورجوامع الحکایات از عوفی آڈٹ کرکے شائع کی تھیں۔علمی اورتحقیقی کمالات کے علاوہ بڑے مہذب شائستہ اورخدا ترس انسان تھے۔اﷲ تعالیٰ انہیں مغفرت و بخشش کی نعمتوں سے سرفراز فرمائے ۔آمین۔
[دسمبر ۱۹۶۸ء]

 

فیوض الحرمین کے دو اردو تراجم کا تقابلی جائزہ

Fayyuz-ul-Herman is the book of Shah Waliullah. In which he describes the circumstances of the two years he spent in Macca and Madina. This book is in Arabic and there are two translations in Urdu. The name of the first Translation is Saadat e Konin. The second translation's name is Mushahidat o Maaraf. This article has a comparative study of both the merits and the shortcomings are described.

Characterization of Antimicrobial Compounds Producing Lactic Acid Bacteria from Domestic Mammals and Their Application As Probiotic or Food Preservative

Foodborne pathogens are a major threat to human health and the food industry. These bacteria cause spoilage of food and diseases on consumption. Moreover, the emergence of antibiotic resistance in clinically important strains of bacteria has led to the search for alternative solutions. Lactic Acid Bacteria (LAB) are well known for their antagonistic potential against closely related microbial species. The antagonistic activity is strain specific. LAB and their inhibitory compounds are gaining attention as they are declared GRAS status by FDA and have been utilized as probiotics and substitute of food preservatives. LAB are cosmopolitan and are found in dairy fermented products, soil and intestine. Previous studies were based on their isolation from dairy products but intestinal microbiota of domestic mammals is a less explored area. Our current study was focused on isolation and characterization of LAB strain from intestinal microbiota with antagonistic activity against important clinical and foodborne pathogens. The probiotic properties of LAB strains were also analyzed. We explored their metabolites as food preservative and determine physiochemical characteristics of the active component. Moreover, we also tried to partially purify the active component and determine its influence on the cell wall of pathogen and detection of the bacteriocin encoding gene in one of the potent strain. Finally prophylactic potential of most prominent strain using Listeria monocytogenes infection model in mouse. A total of sixty three (63) strains were isolated from the intestine of 7 domestic mammals. Out of which 48 trains presented acid production property and were considered lactic acid bacteria. Out of 48 only 22 strains could exhibit antimicrobial activity against both gram positive and negative bacteria. The indicator strains used in the study include Staphylococcus aureus, Clostridium perfringens, Listeria monocytogenes, Escherichia coli, Salmonella enteritidis, Pseudomonas aeruginosa, Klebsiella pneumoniae and Proteus mirabilis. Six strains were selected on the basis of high antagonistic potential presented against at least one gram positive and one gram negative target strain used in the study. The selected strains were identified on the basis of 16S rRNA gene sequencing and accession number was obtained from NCBI Genebank. They are identified as Lactobacillus brevis MF179529, Enterococcus ratti MF183967, Enterococcus sp. MH734728, () Enterococcus sp. MH734729, Enterococcus durans MF179526, Pediococcus sp. MH734727. These strains were initially named as H, R, A, C, O, P respectively. Probiotic potential of the strains was evaluated on the basis of tolerance to NaCl (1-8%), bile salt (0.5-2%), pH (2-6), temperatures (35-50%), antibiotic resistance and non-hemolytic nature towards RBCs. Our results indicated that 6 strains had probiotic potential and were safe for utilization as food preservative. Among all strain Lactobacillus brevis MF179529 exhibited higher probiotic potential being resistant to grow at pH2, 50°C temperature, 3% bile salt and non-hemolytic nature. Furthermore, it exhibited 85% hydrophobicity and 69% antibiotic sensitivity making it the most promising probiotic candidate. To analyze the potential of the active component of CFS (Cell Free Supernatant) of selected strain against selected pathogen tests were performed. The comparison of growth kinetics of foodborne pathogens (L. monocytogenes, C. perfringens, S. enteritidis and E. coli) in the presence of 20% CFS of our six LAB strains showed inhibition of pathogen in food products. Our LAB strains produced active metabolites in growth medium and their CFS was effective against selected foodborne pathogens and is recommended for further studies for its use as food preservative. Inhibitory activity among strains varied but CFS of Enterococcus ratti MF183967 was appeared to be more active against L. monocytogenes. The oral administration of Lactobacillus brevis MF179529 provides the protective effect to the Listeria monocytogenes infected in mice. L. brevis MF179529 reduces L. monocytogenes load in liver, spleen and intestine and also maintain intestinal microbial equilibrium. Further studies are needed to best understand the mechanisms by which this microorganism promotes resistance against infectious diseases. Chemical nature of CFS was determined by treatment with enzymes, surfactant, pH and temperatures. The results indicate the proteinaceous nature of the active compounds as their activity diminished after treatment with protinase K and pepsin. CFS of all strain remained active at pH4-10, their inhibitory activity remained stable up to 100°C. SDS-PAGE analysis of the partially purified fraction of CFS of E. ratti MF183967 indicated the presence of two peptide bands of 20 and 30KDa, out of which 20KDa showed antimicrobial activity against Methicillin resistant Staphylococcus aureus (MRSA). Mode of action of the active component of E. ratti on the cell wall of MRSA revealed its rupturing that was observed under scanning electron microscope (SEM). Presence of enterocin coding genes entp and entL50A also strengthen the production of enterocin like inhibitory substance, by E. ratti MF183967 and that is applicable in food preservation. It is concluded that our six strains possess high inhibitory potential against spoilage and clinical pathogens. E. ratti MF183967 produce 20KDa peptide which is responsible for antimicrobial activity against MRSA. Presence of enterocin coding genes entp and entL50A also strengthen the production of enterocin like inhibitory substance, by E. ratti MF183967. In addition, L. brevis MF179529 ingestion has health promoting capacities and a good candidate to be employed as a probiotic against listeria infection.