Buoyancy


A well known example of capillary-buoyancy equilibrium is the experiment in which a number of glass tubes of varying diameter are placed into a tray of water. The water level rises up the tubes, reaching its highest point in the narrowest of the tubes. The same observation would be made if the fluids in the system were oil and water rather than air and water.  [c.120]

Capillary - buoyancy equilibrium  [c.122]

Once the liberated gas has overcome a critical gas saturation in the pores, below which it is immobile in the reservoir, it can either migrate to the crest of the reservoir under the influence of buoyancy forces, or move toward the producing wells under the influence of the hydrodynamic forces caused by the low pressure created at the producing well. In order to make use of the high compressibility of the gas, it is preferable that the gas forms a secondary gas cap and contributes to the drive energy. This can be encouraged by reducing the pressure sink at the producing wells (which means less production per  [c.186]

The consequences of undetected corrosion in a bulk carrier are particularly serious with the vertical side shell frame end brackets posing the greatest risk. General corrosion of face plates and web plates of the end brackets, possibly compounded by grooving corrosion at weld toes, will weaken the frame to the point of failure if not detected. The problem is progressive and failure can be rapid since neighbouring frames are likely to fail through the imposition of transferred loads. Loss of the support given by these frames is liable to result in horizontal fractures in the side shell plating at the hinge formed with either tire topside tank or the hopper tank. The ingress of sea water followed by the consequent sloshing effect can cause further degradation of the hull structure. In cases where corrosion has weakened the inner bottom structure or the transverse bulkhead structure the combined loading of cargo and seawater can result in progressive flooding and the buoyancy of the ship will be threatened. If this sequence of events takes place in the Nol forward hold the effects are particularly serious and the loss of the ship can occur within minutes.  [c.1048]

Princen and co-workers have treated the more general case where w is too small or y too large to give a cylindrical profile [86] (see also Refs. 87 and 88). In such cases, however, a correction may be needed for buoyancy and Coriolis effects [89] it is best to work under conditions such that Eq. 11-35 applies. The method has been used successfully for the measurement of interfacial tensions of 0.001 dyn/cm or lower [90, 91].  [c.31]

The supporting medium was water at 298 K (p = 0.99727), and the density of latex is 1.2049 g cm . The latex particles had an average radius of 2.12 x 10 mm hence, their effective mass corrected for buoyancy is their volume times the density difference Ap between latex and the supporting medium, water  [c.75]

The table which follows gives the values of k (buoyancy reduction factor), which is the correction necessary because of the buoyant effect of the air upon the object weighed the table is computed for air with the density of 0.0012 m is the weight in grams of the object when weighed in air weight of object reduced to in vacuo = m + m/1000.  [c.157]

Density of object weighed Buoyancy reduction factor, k  [c.157]

Density of object weighed Buoyancy reduction factor, k  [c.158]

With gravimetric methods, the magnitude of the buoyancy correction should be assessed. Particular attention must be paid to the adsorbent temperature because of the unavoidable gap between the sample and the balance case (cf. Section 6.2).  [c.284]

Calibrating a balance, however, does not eliminate ah sources of determinate error. Due to the buoyancy of air, an object s weight in air is always lighter than its weight in vacuum. If there is a difference between the density of the object being weighed and the density of the weights used to calibrate the balance, then a correction to the object s weight must be made. An object s true weight in vacuo, Wy, is related to its weight in air, Wa, by the equation  [c.105]

The buoyancy correction for a solid is small, and frequently ignored. It may be significant, however, for liquids and gases of low density. This is particularly important when calibrating glassware. For example, a volumetric pipet is calibrated by carefully filling the pipet with water to its calibration mark, dispensing the water into a tared beaker and determining the mass of water transferred. After correcting for the buoyancy of air, the density of water is used to calculate the volume of water dispensed by the pipet.  [c.105]

If the buoyancy correction is ignored, the pipet s volume is reported as  [c.106]

To ensure that S eas is determined accurately, we calibrate the equipment or instrument used to obtain the signal. Balances are calibrated using standard weights. When necessary, we can also correct for the buoyancy of air. Volumetric glassware can be calibrated by measuring the mass of water contained or delivered and using the density of water to calculate the true volume. Most instruments have calibration standards suggested by the manufacturer.  [c.130]

In calibrating a 10-mL pipet, a measured volume of water was transferred to a tared flask and weighed, yielding a mass of 9.9814 g. (a) Calculate, with and without correcting for buoyancy, the volume of water delivered by the pipet. Assume that the density of water is 0.99707 g/cm and that the density of the weights is 8.40 g/cm. (b) What are the absolute and relative errors introduced by failing to account for the effect of buoyancy Is this a significant source of determinate error for the calibration of a pipet Explain.  [c.131]

Is the failure to correct for buoyancy a constant or proportional source of determinate error  [c.131]

What is the minimum density of a substance necessary to keep the buoyancy correction to less than 0.01% when using brass calibration weights with a density of 8.40 g/cm  [c.131]

To ensure that S ,ea is determined accurately, we calibrate the equipment or instrument used to obtain the signal. Balances are calibrated using standard weights. When necessary, we can also correct for the buoyancy of air. Volumetric glassware can be calibrated by measuring the mass of water contained or delivered and using the density of water to calculate the true volume. Most instruments have calibration standards suggested by the manufacturer.  [c.811]

Bunsen-Roscoe law Bunte salt Bunte salts Bunte s salt Bunyavirus Buoyancy  [c.136]

Under the appropriate conditions, the acoustic force on a bubble can be used to balance against its buoyancy, hoi ding the single bubble isolated in the Hquid by acoustic levitation. This permits examination of the dynamic characteristics of the bubble can in considerable detail, from both a theoretical and an experimental perspective. Such a bubble is typically quite small, compared to an acoustic wavelength (eg, at 20 kH2, the resonance size is approximately 150 p.m). It was recentiy discovered for rather specialized but easily obtainable conditions, that a single, stable, oscillating gas bubble can be forced into such large ampHtude pulsations that it produces sonoluminescence emissions on each (and every) acoustic cycle (31,32). This phenomenon is called single-bubble sonoluminescence, and has received considerable recent attention (17,18,33,34).  [c.259]

Buoyant Effect of Air. Weighing operations performed m vacuo are not affected by buoyancy forces. An object in air, however, is subject to a buoyancy force that is equal and opposite to the gravitational force on the mass of air the object displaces (10). If the equal arm balance of Figure 1 is in balance with a test weight of mass, in one pan, and material of mass, m, in the other, m = m if they have the same density. If the densities are different, then the buoyancy forces acting on each pan affect the result. Taking moments about the center pivot point gives  [c.331]

Buoyancy has no effect in weighing material of the same density as the test weight (used for direct comparison, or used to caHbrate the balance), or in proportioning materials of approximately the same density. In general, the recipes used in proportioning are derived empirically, and account for the effects of buoyancy. Buoyancy effects can be significant when the absolute mass must be known accurately, eg, in a laboratory environment, and corrections can be made using equation 5. In industrial and commercial weighing, the effect of buoyancy is generally not considered. Note that variations in air density, eg, due to variations in temperature, can also have a slight effect on weighing repeatabiHty.  [c.331]

Physical Properties. Mechanical properties are given in Table 4. Bast and leaf fibers are stronger (higher tensile strength and modulus of elasticity) but lower in elongation (extensibiUty) than cotton. Vegetable fibers are stiffer but less tough than synthetic fibers. Kapok and coir are relatively low in strength kapok is known for its buoyancy.  [c.359]

Variable-Area Flow Meters. In variable-head flow meters, the pressure differential varies with flow rate across a constant restriction. In variable-area meters, the differential is maintained constant and the restriction area allowed to change in proportion to the flow rate. A variable-area meter is thus essentially a form of variable orifice. In its most common form, a variable-area meter consists of a tapered tube mounted vertically and containing a float that is free to move in the tube. When flow is introduced into the small diameter bottom end, the float rises to a point of dynamic equiHbrium at which the pressure differential across the float balances the weight of the float less its buoyancy. The shape and weight of the float, the relative diameters of tube and float, and the variation of the tube diameter with elevation all determine the performance characteristics of the meter for a specific set of fluid conditions. A ball float in a conical constant-taper glass tube is the most common design it is widely used in the measurement of low flow rates at essentially constant viscosity. The flow rate is normally deterrnined visually by float position relative to an etched scale on the side of the tube. Such a meter is simple and inexpensive but, with care in manufacture and caHbration, can provide rea dings accurate to within several percent of full-scale flow for either Hquid or gas.  [c.61]

The basic concepts of a gas-fluidized bed are illustrated in Figure 1. Gas velocity in fluidized beds is normally expressed as a superficial velocity, U, the gas velocity through the vessel assuming that the vessel is empty. At a low gas velocity, the soHds do not move. This constitutes a packed bed. As the gas velocity is increased, the pressure drop increases until the drag plus the buoyancy forces on the particle overcome its weight and any interparticle forces. At this point, the bed is said to be minimally fluidized, and this gas velocity is termed the minimum fluidization velocity, The bed expands slightly at this condition, and the particles are free to move about (Fig. lb). As the velocity is increased further, bubbles can form. The soHds movement is more turbulent, and the bed expands to accommodate the volume of the bubbles.  [c.69]

Equations 3 to 7 indicate the method by which terminal velocity may be calculated. Erom a hydrodynamic force balance that considers gravity, buoyancy, and drag, but neglects interparticle forces, the single particle terminal velocity is  [c.71]

The different fluidized-bed regimes are a function of gas velocity. At a low gas velocity, the soHds are in a packed-bed or fixed-bed state. As the gas velocity is increased, the drag and buoyancy forces eventually overcome the weight of the particles and interparticle forces, and the particles are completely supported by the gas. This is the particulate regime. At minimum fluidization, particles display minimal motion, and the bed is slightly expanded. The bubbling regime, the beginning of aggregative fluidization, occurs when the gas velocity is increased. Bubbling occurs immediately after minimum fluidization for Group B particles, but there is a gas-velocity range of bubble-free expansion for Group A particles which results from interparticle forces. Poor contacting of gas with soHds is a potential problem in the bubbling regime unless bubble size is kept small.  [c.73]

Transport Disengaging Height. When the drag and buoyancy forces exerted by the gas on a particle exceed the gravitational and interparticle forces at the surface of the bed, particles ate thrown into the freeboard. The ejected particles can be coarser and more numerous than the saturation carrying capacity of the gas, and some coarse particles and clusters of fines particles fall back into the bed. Some particles also coUect near the wall and fall back into the fluidized bed.  [c.79]

Free Flows Jets, Wakes, and Plumes. When a smoothly flowing stream is disturbed by inserting a soHd body or by injecting additional fluid, the disturbance is confined to a narrow region downstream of the initial point. When the disturbance is caused by the injection of a fluid at high velocity, the disturbed region is called a jet. When the velocity is lower than that in the main stream, the disturbance is termed a wake. The term plume is usually appbed to a case in which an additional effect, such as buoyancy, plays a significant role and for which the turbulence characteristics of the main stream play the deciding role in its spread.  [c.93]

Mass and heat transport within the jet foUow the same general pattern as does momentum transport. For gases it is found experimentally that the thermal or concentration jet spreads somewhat faster and decays more rapidly than does the momentum jet. All can be described by the turbulent equations of motion and useful results can be obtained by using eddy diffusivities, which are nearly constant across the jet but decay with time (distance downstream). AH of the jets are gradually swallowed up ia the surrounding fluid. The concentration jet, because of its association with a particular chemical species, remains identifiable longest, even though its behavior becomes completely dominated by the surrounding fluid. An important example of such a concentration jet is the plume, as might be released from a smokestack or vent. Except right at the source, the behavior of the plume is dominated by its buoyancy and/or the turbulence of the fluid iato which it is injected. Figure 8 describes several of the plume patterns that can be obtained as they are affected by the temperature gradient ia the surrounding air. The quantitative description of the dispersion of such plumes, especially their ground-level concentration, is stiH imperfectly developed and one must usually resort to empirical correlations. Where the effects of buoyancy are subordinate to the effects of wind velocity, useful results for dispersion over complex terrain or around stmctures can be obtained by wind tunnel experiments using scale models.  [c.94]

Buoyancy. The low density, closed-ceUed nature of many ceUular polymers coupled with their moisture resistance and low cost resulted in their immediate acceptance for buoyancy in boats and floating stmctures such as docks and buoys. Since each ceU in the foam is a separate flotation member, these materials caimot be destroyed by a single puncture.  [c.416]

Separations. Foams have important uses in separations, both physical and chemical (51,52). These processes take advantage of several different properties of foams. The buoyancy and mechanical rigidity of foam is exploited to physically separate some materials. The large volume of vapor in a foam can be exploited to filter gases. The large surface area of a foam can also be exploited in the separation of chemicals with different surface activities.  [c.431]

Displacers. Displacer level switches are suitable for clean and dirty fluids and are used principally to control sump pumps where shifting specific gravity, turbulent surface, and foam are common problems. Displacer(s) are suspended from a range spring coimected to a stem and attraction sleeve. With change in level the spring senses the change in buoyancy causing the stem and attraction sleeve to move within a nonmagnetic enclosing tube. When the attraction sleeve enters the field of the magnet the switch mechanism is actuated. The enclosing tube totally isolates the switch mechanism from process (Fig. 4). A magnetic coupling exists between the attraction sleeve and switch mechanism. Units can be mounted in the vessel top or externally mounted in a separate cage piped to the vessel.  [c.208]

Buoyancy. Buoyancy level controllers are used to control a process having continuous flow through the vessel. The primary appHcation is in reactors, feedwater heaters, deaerators, and similar processes having boiling and turbulent conditions. A hoUow cylinder (displacer) is suspended from a range spring or torque tube. Change in level causes a change in buoyancy which creates a force—balance shift which is transmitted through a metallic seal into the control housing (Fig. 5). Level change causes the controller to increase or decrease the output signal to a proportional control valve. The valve is opened or closed to control flow through the vessel, thus maintaining level within a predeterrnined span. Units are available with a pneumatic 21—103 kPa (3—15 psi) or electronic (4—20 m A d-c) output. Spans are available from 36 to 305 cm. Mounting arrangements include top, side, and external cage with selections of process connection size, style, and materials.  [c.208]

In a reservoir at initial conditions, an equilibrium exists between buoyancy forces and capillary forces. These forces determine the initial distribution of fluids, and hence the volumes of fluid in place. An understanding of the relationship between these forces is useful in calculating volumetries, and in explaining the difference between free water level (FWL) and oil-water contact (OWC) introduced in the last section.  [c.120]

As well as preventing liquid carry over in the gas phase, gas carry undef must also be prevented in the liquid phase. Gas bubbles entrained in the liquid phase must be given the opportunity (or residence time) to escape to the gas phase under buoyancy forces.  [c.245]

This method is smiple but experimentally more cumbersome than the volumetric method and involves the use of a vacuum microbalance or beam balance [22], The solid is suspended from one ann of a balance and its increase in weight when adsorption occurs is measured directly. The dead space calculation is thereby avoided entirely but a buoyancy correction is required to obtain accurate data. Nowadays this method is rarely used.  [c.1877]

Finally, it needs to be noted that the pressures involved in the BET range for nitrogen, from 10 to 200Torr with the actual figures depending on the system, whilst making for experimental convenience, limit the scope of routine nitrogen determination to specific surfaces in excess of 1 m g" this is because of the magnitude of the correction for the gas remaining unadsorbed in the dead space" in the volumetric method, and of the buoyancy correction in the gravimetric technique.  [c.72]

If a 1-kg stainless weight (m = 1, OOOg, = 8,000 kg/m ) is added to one pan of the balance in Figure 1, and material with a density of 1,000 kg/m is added to the other until equiHbrium is reached, the amount of the material needed is 1001.05 g, using equation 5. Thus, it takes 1001.05 g of this material to counterbalance 1,000 g of stainless steel, because of the buoyancy effects on the dissimilar volumes.  [c.331]

Drop Diameter. In extraction equipment, drops are initially formed at distributor no22les in some types of plate column the drops are repeatedly formed at the perforations on each plate. Under such conditions, the diameter is determined primarily by the balance between interfacial forces and buoyancy forces at the orifice or perforation. For an ideal drop detaching as a hemisphere from a circular orifice of diameter and then becoming spherical  [c.69]

The first commercial appHcation of olefin fibers was for automobile seat covers in the late 1940s. These fibers, made from low density polyethylene (LDPE) by melt extmsion, were not very successful. They lacked dimensional stabiUty, abrasion resistance, resiUence, and light stabiUty. The success of olefin fibers began when high density polyethylene (HDPE) was introduced in the late 1950s. Yams made from this highly crystalline, linear polyethylene have higher tenacity than yams made from the less crystalline, branched form (LDPE) (see Olefin POLYMERS). Markets were developed for HDPE fiber in marine rope where water resistance and buoyancy are important. However, the fibers also possess a low melting point, lack resiUence, and have poor light stabihty. These traits caused the polyethylene fibers to have limited appHcations.  [c.312]

Because of high buoyancy and frequently large si2e, gas bubbles rising in a Hquid can deviate greatly from spherical shapes. Figure 6 illustrates the behavior observed. In pure Hquids small bubbles rise faster than would be predicted from the drag correlations developed for soHd spheres because internal circulation permits a higher fluid velocity at the surface and less drag than for the corresponding soHd. Very large bubbles rise much more slowly than do undeformed spheres of the same volume. This is caused by deformation to a shape of large frontal area but small thickness. Very small bubbles obey Stokes law for soHd (immobile) surfaces. This behavior is reflected also in the mass-transfer coefficients for such bubbles, which are lower than would be  [c.92]

The combination of stmctural strength and flotation has stimulated the design of pleasure boats using a foamed-in-place polyurethane between thin skins of high tensUe strength (231). Other ceUular polymers that have been used in considerable quantities for buoyancy appHcations are those produced from polyethylene, poly(vinyl chloride), and certain types of mbber. The susceptibUity of polystyrene foams to attack by certain petroleum products that are likely to come in contact with boats led to the development of foams from copolymers of styrene and acrylonitrUe which are resistant to these materials  [c.416]

Fig. 5. Buoyancy level controller. Courtesy of Magnetrol International, Inc. Fig. 5. Buoyancy level controller. Courtesy of Magnetrol International, Inc.

See pages that mention the term Buoyancy : [c.112]    [c.474]    [c.136]    [c.287]   
Industrial ventilation design guidebook (2001) -- [ c.224 , c.1419 ]