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 …

I and i

The American Society for Testing and Materials (ASTM) is an independent organization devoted to the development of standards.

American Society for Testing and Materials

There is a special reason for reviewing this book at this time: it is the 50th edition of a compendium that is known and used frequently in most chemical and physical laboratories in many parts of the world. Surely, a publication that has been published for 56 years, withstanding the vagaries of science in this century, must have had something to offer. There is another reason: while the book is a standard fixture in most chemical and physical laboratories, including those in medical centers, it is not as frequently seen in the laboratories of physician's offices (those either in solo or group practice). I believe that the Handbook can be useful in those laboratories. One of the reasons, among others, is that the various basic items of information it offers may be helpful in new tests, either physical or chemical, which are continuously being published. The basic information may relate

Handbook of Chemistry and Physics

Annual Energy Outlook 2008 With Projections to 2030

An efficient ghost-cell immersed boundary method (GCIBM) for simulating turbulent flows in complex geometries is presented. A boundary condition is enforced through a ghost cell method. The reconstruction procedure allows systematic development of numerical schemes for treating the immersed boundary while preserving the overall second-order accuracy of the base solver. Both Dirichlet and Neumann boundary conditions can be treated. The current ghost cell treatment is both suitable for staggered and non-staggered Cartesian grids. The accuracy of the current method is validated using flow past a circular cylinder and large eddy simulation of turbulent flow over a wavy surface. Numerical results are compared with experimental data and boundary-fitted grid results. The method is further extended to an existing ocean model (MITGCM) to simulate geophysical flow over a three-dimensional bump. The method is easily implemented as evidenced by our use of several existing codes.

A Ghost-Cell Immersed Boundary Method for Flow in Complex Geometry

Mimicking the humpback whale: An aerodynamic perspective

One of the major flow phenomena associated with low Reynolds number flow is the formation of separation bubbles on an airfoil’s surface. NACA4415 airfoil is commonly used in wind turbines and UAV applications. The stall characteristics are gradual compared to thin airfoils. The primary criterion set for this work is the capture of laminar separation bubble. Flow is simulated for a Reynolds number of 120,000. The numerical analysis carried out shows the advantages and disadvantages of a few turbulence models. The turbulence models tested were: one equation Spallart Allmars (S-A), two equation SST K-ω, three equation Intermittency (γ) SST, k-kl-ω and finally, the four equation transition γ-Reθ SST. However, the variation in flow physics differs between these turbulence models. Procedure to establish the accuracy of the simulation, in accord with previous experimental results, has been discussed in detail.

/pdf/turbulence-model-selection-for-low-reynolds-number-flows-4dgszau1o3.pdf

Turbulence Model Selection for Low Reynolds Number Flows

The usage of natural gas in internal combustion engines involves various difficulties, like weak lean-burn ability, low flame speed and ignitability, which demand deep studies for its usage in IC engines. For compressed natural gas (CNG) in SI engines, there is an engine efficiency sacrifice at low loads and high levels of hydrocarbon (HC) and carbon monoxide (CO) emissions which cannot be solved without using after-treatment equipment. This equipment, however, is very expensive. Therefore, an additional fuel can enhance the characteristics of the combustion of natural gas, which can be added in the intake charge. Hydrogen is an effective gas for enhancing the flame rate regarding combustion in an SI-CNG engine, in addition to increasing engine stability. Small amounts of hydrogen improve performance and reduce exhaust emissions. Thus, a number of investigators have carried out research studies on SI engines with different ratios of HCNG. This paper is comprehensive overview of CNG, H 2 and HCNG blends. The main topics discussed consist of the combustion fundamentals of natural gas, hydrogen and hydrogen-natural gas mixture. Natural gas and hydrogen usage as fuels and their characteristics have been analysed. The storage of hydrogen and HCNG is still challenging researchers and, therefore, their storage has been taken into consideration. Moreover, a comprehensive review has been performed of HCNG blends in order to understand the effect of hydrogen enriched CNG on performance and the emissions of SI engines. The combustion characteristics of HCNG engines are strongly dependent on the conditions of the engine. The air-fuel ratio, the time of injection, the compression ratio and speed play a major role in blending HCNG in an SI engine and have been discussed in this article.

HCNG fueled spark-ignition (SI) engine with its effects on performance and emissions

https://cyberleninka.org/article/n/659749.pdf

Flapping wing micro-aerial-vehicle: Kinematics, membranes, and flapping mechanisms of ornithopter and insect flight

Diesel engines produce high emissions of smoke, particulate matter and nitrogen oxide. The challenge now is to decrease exhaust emissions without making any major changes on their mechanical configuration. Therefore, adding hydrogen becomes a natural choice to enhance the performance and emissions of diesel engines. This paper offers an overview of the effect of hydrogen additional to the diesel engine. The overall finding from the review suggests that the air–fuel ratio, engine speed, and engine load play a key role in the performance and emission of diesel engines with hydrogen enrichment. The brake thermal efficiency (BTE), brake power output, brake means effective pressure (BMEP), and specific energy consumption (SEC) are dependent on the operating conditions of the engine when adding the hydrogen. It is also found that increasing the percentage of hydrogen will affect emissions, so that the reduction in unburned hydrocarbon (HC), carbon monoxide (CO), carbon dioxide (CO2), particulate matter (PM), and smoke are observed when adding the hydrogen. However, nitrogen oxide (NOx) is increased when enriching H2, but this increase in NOx can be controlled by numerous injections, exhaust gas recirculation (EGR) or water injection as well as exhaust after-treatment as has been discussed in this paper.

/pdf/a-review-of-the-effect-of-hydrogen-addition-on-the-3sp1h0m1e1.pdf

Kamarul Arifin Ahmad

Papers

Mimicking the humpback whale: An aerodynamic perspective

Turbulence Model Selection for Low Reynolds Number Flows

HCNG fueled spark-ignition (SI) engine with its effects on performance and emissions

Flapping wing micro-aerial-vehicle: Kinematics, membranes, and flapping mechanisms of ornithopter and insect flight

A review of the effect of hydrogen addition on the performance and emissions of the compression - ignition engine