Hassan M. Badr

Bio: Hassan M. Badr is an academic researcher from King Fahd University of Petroleum and Minerals. The author has contributed to research in topics: Reynolds number & Nusselt number. The author has an hindex of 29, co-authored 113 publications receiving 2522 citations. Previous affiliations of Hassan M. Badr include University of Western Ontario.

Time-dependent viscous flow past an impulsively started rotating and translating circular cylinder

Abstract: A numerical study is made of the development with time of the two-dimensional flow of a viscous, incompressible fluid around a circular cylinder which suddenly starts rotating about its axis with constant angular velocity and translating at right angles to this axis with constant speed. The governing partial differential equations in two space variables and time are reduced to sets of time-dependent equations in one space variable by means of Fourier analysis. By truncating the Fourier series to a finite number of terms, a finite set of differential equations is solved to give an approximation to the theoretical flow. The solutions are obtained by numerical methods. Results are given for the initial development with time of the asymmetrical wake at the rear of the cylinder at Reynolds numbers R [ges ] 200, based on the diameter of cylinder, and at small rotation rates. The detailed results show the formation of a Karman vortex street. The time development of this separated flow is compared in detail at R = 200 with recent experimental results. The details of the formation and movement of the vortices behind the cylinder and the velocity profiles in several locations are virtually identical in the experimental and theoretical studies. The variations with time of the lift, drag and moment exerted by the fluid on the cylinder are determined both by calculations and by means of approximate analytical expressions. The agreement between these results at small times is excellent.

Unsteady flow past a rotating circular cylinder at reynolds numbers 103 and 104

Abstract: The unsteady flow past a circular cylinder which starts translating and rotating impulsively from rest in a viscous fluid is investigated both theoretically and experimentally in the Reynolds number range 103 [les ] R [les ] 104 and for rotational to translational surface speed ratios between 0.5 and 3. The theoretical study is based on numerical solutions of the two-dimensional unsteady Navier–Stokes equations while the experimental investigation is based on visualization of the flow using very fine suspended particles. The object of the study is to examine the effect of increase of rotation on the flow structure. There is excellent agreement between the numerical and experimental results for all speed ratios considered, except in the case of the highest rotation rate. Here three-dimensional effects become more pronounced in the experiments and the laminar flow breaks down, while the calculated flow starts to approach a steady state. For lower rotation rates a periodic structure of vortex evolution and shedding develops in the calculations which is repeated exactly as time advances. Another feature of the calculations is the discrepancy in the lift and drag forces at high Reynolds numbers resulting from solving the boundary-layer limit of the equations of motion rather than the full Navier–Stokes equations. Typical results are given for selected values of the Reynolds number and rotation rate.

A review of recent developments in carbon capture utilizing oxy‐fuel combustion in conventional and ion transport membrane systems

Abstract: Fossil fuels provide a significant fraction of the global energy resources, and this is likely to remain so for several decades. Carbon dioxide (CO2) emissions have been correlated with climate change, and carbon capture is essential to enable the continuing use of fossil fuels while reducing the emissions of CO2 into the atmosphere thereby mitigating global climate changes. Among the proposed methods of CO2 capture, oxyfuel combustion technology provides a promising option, which is applicable to power generation systems. This technology is based on combustion with pure oxygen (O2) instead of air, resulting in flue gas that consists mainly of CO2 and water (H2O), that latter can be separated easily via condensation, while removing other contaminants leaving pure CO2 for storage. However, fuel combustion in pure O2 results in intolerably high combustion temperatures. In order to provide the dilution effect of the absent nitrogen (N2) and to moderate the furnace/combustor temperatures, part of the flue gas is recycled back into the combustion chamber. An efficient source of O2 is required to make oxy-combustion a competitive CO2 capture technology. Conventional O2 production utilizing the cryogenic distillation process is energetically expensive. Ceramic membranes made from mixed ion-electronic conducting oxides have received increasing attention because of their potential to mitigate the cost of O2 production, thus helping to promote these clean energy technologies. Some effort has also been expended in using these membranes to improve the performance of the O2 separation processes by combining air separation and high-temperature oxidation into a single chamber. This paper provides a review of the performance of combustors utilizing oxy-fuel combustion process, materials utilized in ion-transport membranes and the integration of such reactors in power cycles. The review is focused on carbon capture potential, developments of oxyfuel applications and O2 separation and combustion in membrane reactors. The recent developments in oxyfuel power cycles are discussed focusing on the main concepts of manipulating exergy flows within each cycle and the reported thermal efficiencies. Copyright © 2010 John Wiley & Sons, Ltd.

Laminar combined convection from a horizontal cylinder—Parallel and contra flow regimes

Abstract: The laminar combined convection heat transfer from an isothermal horizontal circular cylinder is studied for the two cases when the forced flow is directed either vertically upward (parallel flow) or vertically downward (contra flow). The investigation is based on the solution of the full vorticity transport equation together with the stream function and energy equations. The velocity and thermal boundary layers are developed in time until reaching steady conditions. The variations of vorticity and Nusselt number are obtained over all the cylinder surface including the zone beyond the separation point. The predicted values of the average Nusselt number are compared with the available experimental data and the agreement is satisfactory. The streamline and isotherm patterns are plotted for several cases to show some of the flow field characteristics.

Steady and unsteady flow past a rotating circular cylinder at low Reynolds numbers

Abstract: Results of calculations of the steady and unsteady flows past a circular cylinder which is rotating with constant angular velocity and translating with constant linear velocity are presented. The motion is assumed to be two-dimensional and to be governed by the Navier-Stokes equations for incompressible fluids. For the unsteady flow, the cylinder is started impulsively from rest and it is found that for low Reynolds numbers the flow approaches a steady state after a large enough time. Detailed results are given for the development of the flow with time for Reynolds numbers 5 and 20 based on the diameter of the cylinder. For comparison purposes the corresponding steady flow problem has been solved. The calculated values of the steady-state lift, drag and moment coefficients from the two methods are found to be in good agreement. Notable, however, are the discrepancies between these results and other recent numerical solutions to the steady-state Navier-Stokes equations. Some unsteady results are also given for the higher Reynolds numbers of 60, 100 and 200. In these cases the flow does not tend to be a steady state but develops a periodic pattern of vortex shedding.

I and i

Abstract: There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality. Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

Carbon capture and storage (CCS): the way forward

Abstract: Carbon capture and storage (CCS) is broadly recognised as having the potential to play a key role in meeting climate change targets, delivering low carbon heat and power, decarbonising industry and, more recently, its ability to facilitate the net removal of CO2 from the atmosphere. However, despite this broad consensus and its technical maturity, CCS has not yet been deployed on a scale commensurate with the ambitions articulated a decade ago. Thus, in this paper we review the current state-of-the-art of CO2 capture, transport, utilisation and storage from a multi-scale perspective, moving from the global to molecular scales. In light of the COP21 commitments to limit warming to less than 2 °C, we extend the remit of this study to include the key negative emissions technologies (NETs) of bioenergy with CCS (BECCS), and direct air capture (DAC). Cognisant of the non-technical barriers to deploying CCS, we reflect on recent experience from the UK's CCS commercialisation programme and consider the commercial and political barriers to the large-scale deployment of CCS. In all areas, we focus on identifying and clearly articulating the key research challenges that could usefully be addressed in the coming decade.

Review of recent advances in carbon dioxide separation and capture

Abstract: This review provides a comprehensive assessment of recently improved carbon dioxide (CO2) separation and capture systems, used in power plants and other industrial processes. Different approaches for CO2 capture are pre-combustion, post-combustion capture, and oxy-combustion systems, which are reviewed, along with their advantages and disadvantages. New technologies and prospective “breakthrough technologies”, for instance: novel solvents, sorbents, and membranes for gas separation are examined. Other technologies including chemical looping technology (reaction between metal oxides and fuels, creating metal particles, carbon dioxide, and water vapor) and cryogenic separation processes (based on different phase change temperatures for various gases to separate them) are reviewed as well. Furthermore, the major CO2 separation technologies, such as absorption (using a liquid solvent to absorb the CO2), adsorption (using solid materials with surface affinity to CO2 molecules), and membranes (using a thin film to selectively permeate gases) are extensively discussed, though issues and technologies related to CO2 transport and storage are not considered in this paper.

Applied Combustion Diagnostics

Abstract: The editors have assembled a world-class group of contributors who address the questions the combustion diagnostic community faces. They are chemists who identify the species to be measured and the interfering substances that may be present; physicists, who push the limits of laser spectroscopy and laser devices and who conceive suitable measuremen