Hydraulic Pressure Variations Research Articles

Intrusion and leakage in drinking systems induced by pressure variation

Pathogen intrusion is a phenomenon that can cause a serious pollution problem in drinking systems. The paper describes the entry of external fluids through pipe defects caused by a pressure drop. This situation is especially important during hydraulic pressure variations. Pressure variations that can cause intrusion are analyzed in this paper. Three cases of pressure transients are modeled with the leak located near the transient origin, thus creating a critical scenario to force the intrusion. A combination of the method of characteristics and computational fluid dynamics is implemented in order to quantify the intrusion and leakage volume during the transient event in a pipe. Laboratory procedures provided data for validation of the results. The objective of this paper is to obtain the volume of intrusion and leakage during the pressure variations through defects in pipes. The flow resulting from the intrusion event will be quantified during the transient pressure, noting the potential implications of this event for public health.

Correlation between Sheet Deformation and Hydraulic Pressure Variation during Sheet Hydroforming

In our series of studies, the outflow characteristics of a pressure medium used for a sheet hydroforming process have been investigated. The variation of hydraulic pressure during a square-cup sheet hydroforming process was examined, focusing on correlation with sheet deformation. In the initial stage, the outflow of the pressure medium remained stable because a greater extent of pre-bulging arose around the die shoulder just after the process commenced. When the pre-bulging ceased, the pressure medium was sealed in the chamber. Thus, the hydraulic pressure began to increase rapidly within the chamber, and fell in the flange area. The punch stroke at which the hydraulic pressure in the chamber began to rise was highly dependent on the blank holding force because the height of pre-bulging was determined by this force. When the sheet conformed completely to the die shoulder, the pressure medium was also sealed at the shoulder. Therefore, the hydraulic pressure on the die shoulder as well as in the flange area started to fall. The correlation between the critical punch stroke for fracture and the hydraulic pressure in the flange area was also examined.

Time evolution of hydraulic and electrokinetic parameters around the Nojima fault, Japan, estimated by an electrokinetic method

The Nojima Fault Zone Probe was designed to study the properties and healing processes of the Nojima fault, which is the surface fault rupture of the Hyogo-ken Nanbu earthquake ( M7.2) of 1995 (1995 Kobe earthquake). In this project, water injection experiments were conducted in a borehole of 1800 m depth at the Nojima fault. We set up electrodes around the borehole and observed self-potential variations to investigate the magnitude of electrokinetic and hydraulic parameters around the Nojima fault zone. In the 1997 experiment, self-potential variations were in the range of a few to about 20 mV across 320–450 m electrode dipoles with hydraulic pressure variations from 3.5 to 4 MPa. In the 2000 experiment, self-potential variations were in the range of a few to about 85 mV across 160–260 m electrode dipoles with the hydraulic pressure variations from 3 to 4.5 MPa. In the 2003 experiment, self-potential variations were in the range of a few to about 30 mV across 20–80 m electrode dipoles with hydraulic pressure of 4 MPa. These observed self-potential variations were explained well with an electrokinetic effect due to the underground flow of the injected water. From the observed results, we estimated that the ratio of hydraulic parameters (permeability, porosity, and tortuosity) to electrokinetic parameters (zeta potential and dielectric constant) decreased approximately 40% during eight years after the earthquake. This result suggests that the healing process around the fault zone progress.

Setting time determination of cementitious materials based on measurements of the hydraulic pressure variations

An experimental investigation was carried out to determine the setting time of cement based materials (cement paste, mortar, concrete, etc.). An original method based on measurements of both total lateral pressure and hydraulic pressure has been investigated. An original device has been engineered to measure the pressure kinetics. Just after mixing and filling of the device, a simultaneous drop and an equal value of the both hydraulic and total lateral pressures has been recorded. A definitive cessation of total lateral pressure and negative hydraulic pressures are then observed. The proposed setting time was defined as the elapsed time between the end of mixing and the time at which the hydraulic pressure becomes zero. In addition to the usual W / C parameter, the influence of the vibration and the height of the material tested on the pressure based method were studied. Comparing to other classical methods (Vicat, calorimetry, ultrasonic pulse-echo …), the presented device is efficient with major types of cement based materials (concrete, SCC …) and was able to give a simple and direct information about the mechanical state of the material.

On hiccuping and yawning: why we do it

Common fetal reflexes include hiccuping and yawning. In the second and third trimesters, these reflexes are easily seen, and can be documented in any fetus if ultrasonographic examination is prolonged. If observed in the sagittal plane, the diaphragm may be seen moving caudad with the yawn; a full yawn sequence is characterized by a number of small mouth openings, each with concomitant mild neck extension, just prior to the full yawn, with maximal and prolonged jaw extension and extension of the neck, followed flexion at the end of the reflex, as occurs in children and adults. Similarly, hiccuping is easily seen in the second and third trimester, the sternum suddenly retracting concomitant with caudad diaphragmatic movement, and is commonly observed in an extended ultrasound. I have determined that both of these reflexes occur in the first trimester—documenting hiccuping at 10 weeks, and yawning sequence at 11 weeks, captured on videotape. The fact that these reflexes are present and active in the first trimester likely is not by chance. From an evolutionary biological perspective, such early expression of a reflex suggests that it has a selective advantage. Since all mammals yawn, as do reptiles and birds, the reason must be pan-species. The reflexes are disinhibited in the decerebrate adult. These reflexes may be necessary for the normal development of the airway passages during organogenesis in the first trimester, helping to prevent bronchial and tracheal webs. Bronchial webs may lead to focal adenomatous malformation of the lung. Should a tracheal web occur, the evolutionary fitness for that individual is 0, since the organism would die at birth. Both reflexes would serve to dislodge potential webs from formation through hydraulic pressure variation. Any anatomic anomaly which would interfere with normal flow prenatally (then liquid flow) would predispose towards tracheal webs and neonatal death—as in a neonate who died of asphyxia last year, whom I found at autopsy affected with Treacher Collins syndrome and a tracheal web. Hence, the reason why we yawn and hiccup is simply because we had to do it in the first trimester to assure patent airway development, and postnatlly the reflexes just keep going.

AMADEUS: advanced manipulation for deep underwater sampling

AMADEUS is a dexterous subsea robot hand incorporating force and slip contact sensing, using fluid filled tentacles for fingers. Hydraulic pressure variations in each of three flexible tubes (bellows) in each finger create a bending moment, and consequent motion or increase in contact force during grasping. Such fingers have inherent passive compliance, no moving parts, and are naturally depth pressure-compensated, making them ideal for reliable use in the deep ocean. In addition to the mechanical design, development of the hand has also considered closed loop finger position and force control, coordinated finger motion for grasping, force and slip sensor development/signal processing, and reactive world modeling/planning for supervisory 'blind grasping'. Initially, the application focus is for marine science tasks, but broader roles in offshore oil and gas, salvage, and military use are foreseen.

An analysis of constant-pressure filtration

Up to now, the non-linear partial differential equation of filtration has not been solved, and the variation of hydraulic-pressure, flow rate of liquid and porosity in cake can only be analyzed by means of numerical techniques and compression—permeability simulation. In this paper, an analytical solution of the filtration differential equation, is obtained in the form of error functions. The distribution of hydraulic pressure P L in the cake is discussed. It is shown that P L distribution is affected not only by cake compressibility, but also by operational conditions such as slurry concentration and filtration pressure. In addition, two deliquoring mechanisms are presented—surface filtration and solid cake compression. A parameter β is proposed to stand for the relative contribution of the surface filtration and solid compression to solid—liquid separation.

Paper 11: Variation of Hydraulic Pressure in Annular Space between Guide Vanes and Impeller of a Francis Turbine

One of the main sources of vibration in Francis turbines is thought to be pressure-wave disturbances generated from the impeller and interference impulses between impeller vanes and guide vanes. A theory is developed which explains the occurrence of severe vibrations caused by the elasticity of the water as a resonance phenomenon between the disturbing impulses and normal modes of vibration in the space between the impeller and the guide wheel. The wave propagation in the fluid, which is assumed to be uniform with no steady flow, is thought to satisfy the well-known sound-wave differential equation without any damping effects. The natural frequencies for one- and two-dimensional pressure-wave oscillations are calculated. The calculations, based on prior knowledge of the velocity of sound-wave propagation, show that a simple theory of one-dimensional oscillations interpreted as rotating sound waves in the annular space is sufficient to predict critical speeds of the turbine. Measurements carried out on a laboratory model Francis turbine for a head of 4.5 m and a capacity of about 1.0 m3/s confirmed the presence of free oscillations and indicated the occurrence of a resonance phenomenon in the annular space.

The role of porosity in filtration: VI. New definition of filtration resistance

AbstractThe definition of filtration resistance is re‐examined in view of the new theory (12) of the variation of flow rate with respect to distance through a filter cake. In the new definition it is shown that the filtration resistance depends upon slurry concentration as well as applied pressure. A correction factor modifying the specific filtration resistance previously defined by Ruth (5, 6) is developed.Where the hydraulic pressure variation within a cake is known, methods are presented for calculating the variation of flow rate with respect to distance and the change of filtration resistance in relation to slurry concentration.

Behaviours of Various Kaolin Slurries in Constant Pressure Filtration (about Hongkong Kaolins, "Pink" and "Dark yellow, " and Shinmei Kaolin)

In order to study the filtration characteristics of Kaolin slurries, a number of experiments were conducted in constant-pressure filtration, and measurements of the hydraulic pressure variations within actual filter-cakes at constant-pressure filtration (using air-sealed manometers) and compression permeability experiments (using a consolidometer) were made.The results may be summarized as follows:(i) The Ruth's coefficients K20 obtained from Eqs. (3) and (4) showed deviations of less than 10% from the actual filtration results K20f.(ii) The values of m obtained from Eq. (4) showed good agreement with m′ obtained from Eq. (4′), as revealed in Table 3. Consequently, it may safely be concluded that so far as Kaolin slurries are concerned, experiments in constant pressure filtration besides mere compression tests would be enough to make clear the behaviours thereof.(iii) The specific resistance αf of the constant-pressure-filtration cakes of Kaolin slurries proved to be a function not only of P but also of s and V.(iv) By the direct measurements of liquid pressure distribution in the cakes under constant-pressure filtration, the cake thickness L was observed to be exactly linear with the filtrate volume V, as shown in Fig. 7. m″ obtained from Eq. (10) was nearly equal to m or m′.(v) Liquid pressure distribution as measured by using air-sealed manometers showed closer approximation to Px vs. x′/L curve obtained from Eq. (7′) as shown in Fig. 6-1, rather than Px vs. x/L curve obtained from Eq. (7).