Smooth Water Surface Research Articles

The Growth of Oil Slicks and Their Control By Surface Chemical Agents

A calculation method for predicting the rate at which an oil slick will spread on water can also be used to predict the behavior of a slick that has been treated with a surface chemical collecting agent. Field and laboratory tests show that only a small quantity of the agent is needed to contain a slick for a considerable time. Introduction Highly important in designing an oil pollution control system is a knowledge of the growth rate of the oil slick. This information is particularly necessary if there is an impending spill so that a cleanup strategy can be planned before the spill occurs. This knowledge can also be applied to predict theoretically the behavior of an oil slick that has been treated with a surface chemical agent. A surface chemical agent is a compound that, when applied to the water surface, forms a thin layer that changes the surface tension characteristics of the water-air interface and thereby affects the spreading rate of oil on the water surface When a quantity of oil is added to a smooth water surface that has been treated by one of these compounds, the oil may form a stable circular lens. For such a stable lens to form, it is necessary that the spreading pressure, defined as w, - o, - ow, be negative. (Here w, o, and ow, represent the water-air, oil-air, and oil-water interfacial tensions, respectively.) Garrett and Barger have proposed the application of suitable surface chemical agents to prevent the uncontrolled spread of oil slicks on the open sea. If such slicks are left untreated, they will spread quickly, and on a calm sea several barrels of oil will spread as much as a mile a day. These large, thin oil slicks are very difficult to recover mechanically, but a suitable surface chemical agent applied to the perimeter will drastically affect their growth. If a slick is thicker than the stable lens, its growth decreases and eventually stops when the thickness equals that of the stable lens. If at first the slick is thinner than the stable lens, treating it with the agent mill cause it to shrink until its thickness equals that of the stable lens. For a typical crude oil the stable lens is about 1/2 cm thick, and for a 1,000-bbl spill this would correspond, assuming the slick is circular, to a stable diameter of only about 200 m. Because it is thicker, this slick can be removed by mechanical skimmers more easily than one that is left untreated. The chemicals used to control oil spills must be nontoxic and water insoluble and must have a high spreading pressure. Some chemicals that meet these requirements are the high-molecular-weight water-insoluble alcohols and acids such as steric acid and oleic acid. Additional substances are cited in Ref. 1. To understand how these surface chemical agents affect the spreading of oil on water it is necessary to identify and to understand the forces governing the growth of a slick. In the following sections we shall deal with the important forces, develop a related mathematical model, compare the model predictions with field test results, and predict the effects of surface chemical agents on the growth behavior of an oil slick. Forces Important in the Spreading of Oil Fig. 1 shows a cross-section of the oil-water-air interface of a growing oil slick. It shows that the forces acting on the slick are surface tension, pressure, and viscosity. pressure, and viscosity. JPT P. 781

Atmospheric Neutral Points over Water

The positions of the neutral points of the skylight are computed for the model of a Rayleigh atmosphere and a smooth water surface that reflects light specularly according to the Fresnel law. The Babinet and Brewster points disappear from the principal plane. They appear within a few degrees below the almucantar near the direction of the sun. The Arago point does not disappear from the principal plane but is shifted closer to the horizon.

Effect of Specular Reflection at the Ground on Light Scattered from a Rayleigh Atmosphere

The method of Chandrasekhar is used to compute the parameters that characterize the scattered light leaving the top of a Rayleigh atmosphere. The atmosphere of this model lies above a smooth water surface, which reflects light according to Fresnel’s law. The combined atmosphere and water is called the Fresnel model. The results for the Fresnel model are compared with corresponding results for a second model, which is called the Lambert model, since its ground reflects light according to Lambert’s law. The reflectance at the ground is less than 0.1, if either the solar zenith angle θ0 0.6. The relative difference between the outward fluxes from the tops of the atmospheres of the two models is less than 0.07 if θ0 0.5, but the difference becomes large at small τ1. The maximum degree of polarization and the neutral-point positions at the top of the atmosphere of the Fresnel model are quite different from those of the Lambert model, when the total optical thickness is less than 0.5. The neutral points for the Fresnel model appear outside of the vertical plane through the sun for restricted ranges of both the total normal optical thickness and the solar zenith angle.

Simplified Design for Flume Inlets

The subject of contractions for open channel flow at subcritical velocity is studied. In particular, the design for flume inlets is critically examined. It is suggested that a gradual warped wall transition is unnecessary, and a simplified alternative design is proposed. Hydraulic models verify that the proposed design has low head loss, is scour-free at the entrance, and produces a smooth water surface. The proposed inlet has several advantages compared to the more complicated warped wall design.

The Effect of the Long-wave Reflectivity of Natural Surfaces on Surface Temperature Measurements Using Radiometers

This paper deals with the influence exerted by natural surfaces with non-black body characteristics on surface temperature measurements using the radiation method. The difference between the true surface temperature and the temperature measured with a radiometer in the 8- to 15-μ region (the “radiation temperature”), is computed for smooth and rough water surfaces, and generally found to be below 1C. Spectra of vertical long-wave sky radiation were used for the case of specular reflection of a smooth water surface. The values for hemispherical long-wave sky radiation, necessary in the computation for rough water surfaces, were derived from the vertical spectra by a method developed for this purpose. The computations were verified empirically by measurements taken from a helicopter. The effect of the spectral distribution of reflectivity and long-wave sky radiation is also discussed. It is shown that for the measurement of water surface temperature a radiometer with an 8 to 11- or 12-μ bandpass would be more satisfactory. Furthermore, some “gray” reflectivities (infrared albedo) of natural surfaces for which no spectral reflectivity curves were available to date, have been determined by measurements. The difference between true surface temperature and radiation temperature is computed for gray reflectivities of 2.5, 5.0 and 7.5 per cent.

The influence of albedo radiation on the photodetachment rate for O2−in theDregion

Calculations have been performed to determine the effect of reflected and scattered solar radiation on the photodetachment rate for O2− ions at a height of 65 km. The results are given for surfaces which reflect in accordance with Lambert's law, and for a smooth water surface which reflects in accordance with Fresnel's law. For Lambert surfaces, the detachment rate rises monotonically with increasing solar elevation angle and reaches a peak value when the sun is in the zenith. Upper and lower limits are given for various values of the reflection coefficient. For a reflection coefficient of 0.8 (thick cloud layer, or fresh snow cover), the upper limit on the noontime detachment rate is 1.1 sec−1 and the corresponding lower limit is 0.86 sec−1 (clear day) or 0.74 sec−1 (hazy day). For a reflection coefficient of 0.25 (desert sand), the upper limit is 0.69 sec−1 and the lower limit is 0.57 sec−1 (clear day) or 0.53 sec−1 (hazy day). The detachment rate at 65 km above a smooth water surface, not including the effect of the reflected skylight, rises with increasing solar elevation angle to a peak value of 0.53 sec−1. This value is attained approximately one hour and fifty minutes after sunrise at 65 km.

Local evaporation from a smooth water surface

The evaporation factor (ratio of local evaporation rate to the product of wind speed and deficit of the water-vapor density from its saturation value) was measured for a water surface considered to be hydrodynamically smooth. The evaporation from a section of a smooth water surface was compared with that from a small pan situated upon it. The evaporation factor for the pan located upon a larger water surface was then obtained, and the evaporation factor for the smooth water surface was deduced. It was found to vary with wind speed as expected, but is larger by 25 to 60 per cent than the theoretical factor for a water surface that is hydrodynamically smooth. Possible causes of the discrepancy between experiment and theory are considered.

On the Exchange of Carbon Dioxide between the Atmosphere and the Sea

The physical and chemical processes responsible for exchange of carbon dioxide between the atmosphere and the sea are analyzed. It is shown that the rate of transfer is considerably decreased due to the finite rate of hydration of CO 2 in water. This is the case both for a smooth water surface where molecular diffusion plays a role in the first few hundredths of a millimeter as well as for a rough sea where turbulence extends all the way to the surface. A general agreement is found between the transfer rate deduced in this way and the rate of exchange estimated on the basis of the C 14 /C 12 ratio in the atmosphere and the sea. DOI: 10.1111/j.2153-3490.1960.tb01311.x

On the Exchange of Carbon Dioxide between the Atmosphere and the Sea

The physical and chemical processes responsible for exchange of carbon dioxide between the atmosphere and the sea are analyzed. It is shown that the rate of transfer is considerably decreased due to the finite rate of hydration of CO2 in water. This is the case both for a smooth water surface where molecular diffusion plays a rôle in the first few hundredths of a millimeter as well as for a rough sea where turbulence extends all the way to the surface. A general agreement is found between the transfer rate deduced in this way and the rate of exchange estimated on the basis of the C14/C12 ratio in the atmosphere and the sea.

Review of Theories of Mechanism of Action of Radiation in Treatment of Cancer

There is not much hope for the solution of the problem of the action of radiation on tissues for some years. We know far too little about the physiology and chemistry of the individual cells and their interactions. The immediate action of radiation takes place inside the cell, and how can we expect to find out what happens in it when we know so little about its structure. Radiation, however, has given us a new method of studying changes inside the cells. It is important that we make it clear to ourselves what facts have been established, how these facts can be coordinated with the new theories, and which theories will be of any value to us. There are several theories concerning the action of radiation on tissues and it might be conceived that all must be wrong except, eventually, one. That is not necessary, however, as there are theories for different stages of the action which do not contradict each other but which can be combined very well. It is important, therefore, to consider the theories for each stage separately. Naturally we would like to know the complete chain of actions and are therefore led at first to consider the physical foundation and theories connected with it. All physicists now agree that all radiation used in therapy, except the particles from radioactive substances, consists of electromagnetic waves. That means some kind of vibrations transplanted through space. It is easier to visualize this by thinking of some substance which is set in vibration. Perhaps the simplest picture is a smooth water surface on which a stone is dropped. Several waves start where the stone hits the water and spread out one after the other with a certain constant speed over the surface. The distance from one top to the next is the wavelength. The difference between light and X-rays is simply a difference in wavelengths; the light waves are much longer than the X-rays (about 10,000 times longer). The visible part (light) lies between 3500 and 8000 A., whereas X-rays used in therapy cover the region 0.06 to 1 A. X-rays are harder or more penetrating the shorter the wavelengths; likewise the higher the voltage used, the shorter the wavelength.