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Currently available methods for interpreting data from unconfined aquifers are based on analytical solutions which restrict attention to flow in the saturated zone and account for drainage of water from the unsaturated zone through a source term. The parameter, specific yield (Sy), is assumed to dictate the total quantity of water that is derivable through the desaturation process. It is commonly assumed that flow in the unsaturated zone has little effect on flow in the saturated zone and therefore that all the drainable water is instantly delivered at the water table as it declines in response to pumping. In a model proposed in 1954, Boulton empirically assumed that the drainable water associated with Sy is released gradually at the water table as an exponential function of time. This concept of Boulton is similar to the notion of first‐order kinetics frequently used to handle chemical transformations. Boulton's model is considered by some to have no physical basis. Numerical experiments performed on sand columns with reasonable properties suggest that vertical drainage of water at the water table due to a falling water table is a time‐dependent process which is mathematically more complex than a simple exponential relation. Although Boulton did not provide a rational physical explanation, his exponential assumption has some merit in that it implicitly provides for a time dependent drainage process which seems to occur in the unsaturated zone. However, the simple exponential approximation is not adequate to account for what is seemingly a complex process. It appears that a physically comprehensive model of radial flow in an unconfined aquifer will combine time‐dependent drainage from above the water table with vertical components of flow in the saturated zone. An additional assumption frequently made is that the well can be treated as a line source. Results from numerical experiments suggest that caution is in order before neglecting effects of well‐bore storage in interpreting data from tests on unconfined aquifers.

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Considered herein is the initial-value problem for the generalized periodic Camassa-Holm equation which is related to the Camassa-Holm equation and the Hunter-Saxton equation. Sufficient conditions guaranteeing the development of breaking waves in finite time are demonstrated. On the other hand, the existence of strong permanent waves is established with certain initial profiles depending on the linear dispersive parameter in a range of the Sobolev spaces. Moreover, the admissible global weak solution in the energy space is obtained.

In order to effectively remove mercury from raw natural gas, a preparation method of columnar sulfur-impregnated activated petroleum coke was proposed and mercury adsorption experiments were conducted under simulated natural gas processing operating conditions. The physicochemical properties of the adsorbents were discussed with the aid of characterization methods, including nitrogen adsorption/desorption and scanning electron microscopy (SEM) analysis, ultimate analysis, X-ray photoelectron spectroscopy (XPS) analysis, and thermalgravimetric (TG) analysis. The influence of different preparation procedures, KOH activation, sulfur impregnation, and the modification temperature, space velocity, and inlet Hg 0 concentration on mercury adsorption performance were investigated in a fixed bed reactor. The better preparation procedure of the adsorbent of columnar sulfurimpregnated activated petroleum coke was suggested by following the order of KOH activation, columnar shaping, and sulfur impregnation. Proper space velocity and inlet concentrations of Hg 0 can effectively improve mercury removal. The results showed that, compared with raw petroleum coke, the mercury removal efficiency of KOH activated petroleum coke increased by 20% and its specific surface area reached more than 1300 m 2 /g. After both KOH activation and sulfur impregnation, the bulk sulfur content reached more than 10 atom %, surface oxygen functional groups reached more than 24 atom %, and nonoxidized sulfur forms reached more than 8 atom %, which were most beneficial for mercury removal. It was found that the bonding of the short-chain S molecules to carbon matrix was fairly stable. Sulfur impregnation dominated the Hg 0 removal and the rich micropores were conducive to more sulfur loading and more active sites for mercury adsorption. The adsorbed mercury species of HgS and HgO were attributed to the surface nonoxidative sulfur forms and oxygen functional groups based on the temperature-programmed-desorption (TPD) and XPS results. Kinetic studies indicated that both external mass transfer and chemisorption played a more important role in mercury adsorption than intraparticle diffusion.

As a new modification method, mechanochemistry features the remarkable advantages of simple operation process, low energy consumption, easy chemical modification, and suitability for industrialization. In this work, the coal-fired byproduct fly ash was modified by a mechanical–chemical method through omnidirectional planetary ball mill. The effect of the mechanical–chemical modification process parameters on the performance of mercury removal and physicochemical properties of the fly ash and the relationship between the mercury removal efficiency and the physicochemical properties were studied. The experimental results showed that, under the condition of single mechanical ball milling, the mercury removal efficiency of fly ash (FA) was slightly higher than that of raw FA. After being modified by NaBr, the mercury removal efficiency of FA increased considerably with the increase of ball milling time and speed and decreased with the increase of the size of the grinding ball. However, it was no longer significantly improved with further increasing the ball milling time and speed owing to the limited unburned carbon content in FA. The best modification process parameters were determined from the ball milling time of 1 h, the ball milling speed of 400 rpm, and the ball size of 5 mm. The characterization results showed that there was no big difference in physical properties of FA between various mechanical–chemical modification processes. However, the content of carbonyl and carboxyl/ester groups and C–Br covalent groups on modified FA demonstrated a key role in promoting mercury removal performance. The contents of carbonyl and carboxyl/ester groups and C–Br covalent groups were positively proportional to the mercury removal rate, and they were consumed during mercury adsorption. The results confirmed that the improvement of mercury removal efficiency of modified FA was dominated mainly by the surface chemical properties. Compared with the carbonyl and carboxyl/ester groups, the C–Br covalent group was the major chemisorption site of Hg0.

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Body-fitted and embedded mesh techniques are combined to obtain accurate external aerodynamic solutions for realistic car geometries with minimal user intervention. The key idea is to mesh with typical body-fitted RANS grids the external shape of the vehicle, which is smooth and requires detailed physical modeling. The underhood and undercarriage are treated as embedded surfaces. The flow in this region is massively separated, requiring LES runs and isotropic grids. This makes it a suitable candidate for embedded grids. Comparisons with body-fitted and experimental data for a typical car show that this approach can yield drag predictions with an error less than 5%. Thus, the present approach reduces turnaround times for complete car geometries to 1-2 days, without compromising accuracy. I. INTRODUCTION With the advent of robust, accurate flow solvers and abundant, pervasive computer resources, the task of defining quickly a flow domain and the required boundary conditions has become a key bottleneck for numerical simulations. For external vehicle aerodynamics, the car industry at present is contemplating turnaround times of 1-2 days for arbitrary configurations. For so-called body fitted grids, the surface definition must be watertight , and any kind of geometrical singularity, as well as small angles, should be avoided in order to generate a mesh of high quality. This typically presents no problems for the main 'shape' of the car (the part visible to a streetside observer), but can be difficult to obtain in such a short time for the underhood and undercarriage of a typical car or truck. Experience indicates that even with sophisticated software toolkits, manual cleanup in most cases takes several days for a complete car. An alternative is to use grids that are not body-conforming, and simply 'embed' the triangulations of the wetted surfaces of the structures in them. Techniques of this kind are also known as immersed, embedded, fictitious domain or Cartesian methods. The treatment of points in the vicinity of the embedded CSD triangulations or CSD bodies is modified in such a way that the required kinetic or kinematic boundary conditions are properly