1,721,017 research outputs found
Features of flow around the leading edge of a circular cylinder
Full text linkPaper presented to the 10th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Florida, 14-16 July 2014.Axial flow over a circular cylinder is very complex, particularly around the leading edge of the cylinder, comprising separation bubble/cavitation, shear-layer reattachment, etc. Pressure fluctuations in the separation region may induce structural vibrations and generate noise. This paper presents the results of wall pressure measurement and flow visualization done around the cylinder leading edge with blunt, conical and hemispherical noses at Reynolds number (ReD, based on cylinder diameter D) ranging from 1.5 × 103 to 4.2 × 104. The yaw angle is varied from 0° (axial) to 3.5°. Attention has been paid to investigate the effects of nose shape, ReD and on the flow features as well as time-mean pressure coefficient Cp and fluctuating (rms) pressure coefficient Cp . At = 0°, blunt nose engenders longer reattachment length xR, wider bubble width W and shorter transition length xTr, compared with conical and hemispherical noses. Cp and Cp’ are found to be highly sensitive to ReD for hemispherical nose. Blunt nose presents highest Cp’, while hemispherical nose corresponds to the lowest Cp’. With increasing from 0° to 3.5°, Cp declines and Cp’ increases for both blunt and conical noses, while those for hemispherical nose vary less regularly. A slight increase in influences the flow separation with enhanced XR and W, and reduced XTr for all the three noses.cf201
Fluid dynamics around twin cylinders and interactions
Full text linkPaper presented at the 8th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Mauritius, 11-13 July, 2011.Multiple cylindrical structures are widely seen in
engineering. Flow interference between the structures leads to
a very high fluctuating forces, structural vibrations, acoustic
noise, or resonance, which in some cases can trigger failure.
Recently circular pins in various arrays have been using as
fins to enhance the cooling effect. While the enhancement is
directly connected to nature of flow around the pins, no much
is known of physics of flow around the pins. The knowledge
of flow around two cylinders is insightful for understanding
the flow around an array of cylinders/pins. This paper presents
results of an experimental investigation into interactions
between flowing fluid and a cylinder that is neighbored by
another cylinder of the same diameter. Strouhal number (St),
time-mean and fluctuating forces on and flow structures
around the cylinder are investigated while the gap-spacing
ratio T/D is varied from 0.1 to 5 and the attack angle a from
0 to 180 where T is the gap width between the cylinders,
and D is the diameter of a cylinder. A flow visualisation test
was conducted to observe flow structures around the cylinders.
Based on forces, St, flow structures and fluid-cylinder
interaction mechanisms, 19 distinct flow categories in the
ranges of a and T/D are observed, including one quadristable
flow, three tristable flows and four bistable flows. The
quadristable, tristable and bistable flows ensue from
instabilities of the gap flow, shear layers, vortices, separation
bubbles and wakes, engendering a strong jump/drop in forces
and St of the cylinders. Six different interaction mechanisms
are observed, namely interaction between boundary layer and
cylinder, shear layer/wake and cylinder, shear layer and shear
layer, vortex and cylinder, vortex and shear layer, and vortex
and vortex. While the interaction between vortex and cylinder
results in a very high fluctuating drag, that between vortex and
shear layer results in a high fluctuating lift. On the other hand,
the interaction between shear layer/wake and cylinder
suppresses mean and fluctuating forces as well as weakens
flow unsteadiness for stationary cylinders but may cause
violent galloping vibration when the cylinders are elastic. The
interaction between boundary layer and cylinder also may
generate galloping vibrations.mp201
Two-cylinder wake with and without tripwires
No full textPaper presented at the 7th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Turkey, 19-21 July, 2010.This works aims to investigate interference between two tripped cylinders of identical diameter D (= 49 mm), based on measured time-mean drag (CD) and fluctuating drag (CDF) and lift (CLF) at stagger angle a= 0°~ 180° and gap spacing ratio T/D = 0.1 ~ 5, where T is the gap width between the cylinders. Two tripwires, each of 5 mm, were attached on each cylinder at azimuthal angle p = ±30°. Forces on two plain cylinders are also measured and compared with those on tripped cylinders. Flow visualization test was conducted to observe flow structures around the cylinders. CD, CDF and CLF all for the plain cylinders are strong function of a and T/D due tostrong mutual interference between the cylinders, connected to nineteen distinct flow categories including three kinds of tristable flow and five kinds of bistable flow. On the other hand, the tripped cylinders interfere weakly one another, resulting in insignificant variation in forces with a and T/D. Tripwires suppress forces on the cylinders remarkably.ej201
The impact of national culture on the organizational culture: Multinational companies doing businesses in developing countries
No full textAbstract Title: The impact of national culture on the organizational culture: Multinational companies doing businesses in developing countries Level: Final assignment for Master Degree in Business Administration (MBA) Author: Md. Mahbub Alam Supervisor: Dr. Ehsanul Huda Chowdhury Examiner: Dr. Maria Fregidou-Malama Day: 2017- May Aim: The aim of the study is to understand how national culture of Bangladesh is affecting the organizational culture of the multinational firms operating in Bangladesh. To understand the issue, Hofstede’s Cultural Dimensions are regarded as benchmark for analysis. Method: Qualitative study has been conducted whereby both primary and secondary data are used. Hereby, primary data have been gathered from ten employees of Grameen Phone a multinational working in Bangladesh. To collect data, face to face interviews has been conducted using Skype. Results & Conclusions: Finding of the study is the MNCs integration with national culture with the view to sustainable business operation. It has been demonstrated that national culture affects the organizational culture in the form of employee participation, collective working environment, collaborative work efforts, and knowledge sharing through continuous communication. Suggestions for future research: Further investigations on national culture’s impact on organizational culture can be undertaken by making a comparison between MNC and a purely local firm. Additionally, an analysis on a large number of MNCs operating in host country can add value for further researches. Contribution of the thesis: To the theoretical model, this study makes contribution on the ground of understanding how MNC adapt their business with local culture where cultural sensitiveness is high. Managerial implications: MNCs can ensure collaboration, support, and teamwork among employees as part of their attempt to integrate with local culture. This study reveals that local employees can be used as means of cultural carriers by managers which can promptly address the cultural differences to be mitigated. Keywords: Multi-national Corporations (MNCs), National Culture, Organizational Culture, Uncertainty Avoidance, Individualism vs. Collectivism, Power Distance
Extraction of the inherent nature of wind using wavelets
Full text linkPaper presented to the 10th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Florida, 14-16 July 2014.Due to the availability of multi-megawatt wind turbines,
ease of installation and maintenance, economic compatibility
and commercial acceptance, the power of the wind is being
used globally for both grid-connected and off-grid applications.
The power of the wind is intermittently available due to the
fluctuating nature of the wind and hence needs to be understood
well. Therefore, its variability in time and spatial domains was
studied. The present work utilized daily mean values of wind
speed from different meteorological stations spread over the
Kingdom of Saudi Arabia in conjunction with wavelet
transform and fast Fourier transform power spectrum
techniques to understand the dynamic nature of the wind at nine
stations. The study found that wind speed changed by ±0.6 to
±1.6 knots over a long period of about 10 years depending on
the locations. The long-term mean wind speed of 5.6, 8.9, 6.25,
8.1, 6.0, 7.1, 6.0, 8.6 and 7.3 knots were obtained at Abha,
Dhahran, Gizan, Guryat, Hail, Jeddah, Riyadh, Turaif and
Yanbo, respectively. The annual fluctuation in wind speed is
larger (±1.3 to ±3.0 knots) and more regular at Abha, Dhahran,
Guryat and Yanbo, while smaller (±0.7 to ±1.1 knots) and less
regular at Gizan, Hail, Jeddah, Riyad and Turaif, with the
greatest (±3.0) and smallest (±0.7) at Guryat and Gizan,
respectively.dc201
Understanding and controlling the structure of thin polymer films used in photolithography
Full text linkSPATIO-TEMPORAL LEARNING OF VESSEL TRAJECTORIES FROM AIS DATA USING MULTI-MODAL CLUSTERING AND PHYSICS-INFORMED FORECASTING
No full textIn recent years, vessel accidents have surged alongside increased maritime traffic, with collisions, often from human error, emerging as a primary concern. Enhancing navigators' situational awareness by predicting neighboring vessels' movements is essential to facilitate proactive collision avoidance. However, to effectively mitigate these risks, prediction models must deliver outputs that are not only accurate but also timely. This thesis addresses the shortcomings of existing approaches by formulating and investigating novel methodologies to produce accurate, computationally efficient, and physically consistent trajectory predictions across scenarios and geographic contexts.
The work begins with clustering-based strategies for future location prediction, addressing the heterogeneity and multi-modality of vessel mobility patterns. To this end, we propose a framework incorporating engineered features representing vessel behavior and environmental conditions. This improves the performance and interpretability of spatial predictions over traditional autocorrelation-based methods.
To improve fidelity to trajectories, we introduce a Physics-Informed Neural Network (PINN) solution that integrates kinematic constraints into deep learning. The model uses a discretized finite difference loss function based on Euler's first-order and Heun's second-order methods, ensuring output accuracy and physical consistency.
Further, we develop a transformer-based architecture that jointly forecasts future trajectories of both target and nearby vessels. This approach enables dynamic collision risk assessment through interaction-aware trajectory modeling, offering a comprehensive framework for maritime traffic safety, focusing on crowded waterways.
Collectively, these contributions advance the state-of-the-art in vessel trajectory prediction by integrating clustering, deep learning, and physics-informed modeling under a common purpose. Experiments and evaluation across diverse maritime contexts demonstrate significant improvement in predictive capability, robustness, and operational relevance. These findings lay a methodological foundation for next-generation decision-support systems, with potential implications for traffic management, regulatory compliance, and autonomous vessel operations
Characterization of Cartilage-Like Spheroids via Safranin-O Staining and Digital Densitometry
No full textThe kotwali thana central cooperative association (KTCCA): a study on sustainability of two-tier cooperative system
No full textThis thesis is submitted in partial fulfillment of the requirements for the degree of Masters of Arts in Governance and Development, 2006.Cataloged from PDF version of thesis.Includes bibliographical references (page 53 - 55).Md. Mahbub-ul-AlamM. Governance and Developmen
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