Instantaneous Pressure Changes Research Articles

Physics informed neural networks for fault severity identification of axial piston pumps

Artificial intelligence (AI) has shown great potential in the maintenance stage of industrial manufacturing. However, the existing data-driven methods often lack integration with physics knowledge, leading to the implicit decision-making processes. To overcome this limitation, this study proposes a physics informed neural network for identifying fault severity in axial piston pumps. The method begins by establishing a discharge pressure model that incorporates physics information to describe instantaneous pressure changes. Subsequently, a neural network model is employed to estimate the temporal function of discharge pressure based on observed signals. Moreover, by allowing the learnability of fault-related physics parameters, the discharge pressure model is transformed into a physics informed loss term that guides the learning process. By incorporating the physics informed loss, the proposed method effectively combines observations and physics knowledge, providing explicit physical interpretation to the identified parameters. Additionally, the introduction of volume efficiency establishes a relationship between the physical degradation indicator and fault severity, offering a physical explanation of the identified results. Experimental results on an axial piston pump demonstrate the effectiveness and robustness of the proposed method, particularly in terms of interpretability for fault severity identification.

Production rate of multi-fractured wells modeled with Gaussian pressure transients

This study presents new pressure transient solutions, illustrated with some examples of the vast practical application potential. Gaussian pressure transients (GPT) are derived here to quantify the temporal and spatial propagation of instantaneous pressure changes in porous media, as initiated from cylindrical sources (vertical wells) and planar sources (hydraulic fractures). After solving the scalar pressure field in the reservoir space, and adequately accounting for the interference of the various pressure fronts by mathematical integration and superposition, the resulting pressure gradients solve for the velocity field in the reservoir space. Unique for GPT solutions is that the well rate, unlike in the traditional well-testing equations, does not appear as an input. Applying Darcy's Law, the fluid flux from the reservoir into the well and hydraulic fractures can be directly computed from the GPT solutions. The closed-form production-forecasting model can be implemented either in matrix-coded flow-visualizations of pressure depletion and flow paths for reservoir sections or in grid-less spreadsheet solutions to instantaneously generate production profiles for wells in any type of fluid injection/extraction project (water production, geothermal energy extraction, hydrocarbon production, and fluid disposal wells). Additionally, the Gaussian method also is suitable for physics-based decline curve analysis. The practical examples included in this study are for Eagle Ford shale oil and Marcellus dry gas wells. The hydraulic diffusivities are constrained by the field data, and range between 2.36 x10−10 and 3.48 x10−10 m2 s−1 for the Eagle Ford Formation; for the Marcellus the range is 3.64x10−9 to 5.67x10−8 m2 s−1. The breakthrough solution method of Gaussian pressure transients is placed in the context of past and present modeling approaches for shale plays developed with multi-fractured wells.

Spectral normalization in dual-comb spectroscopy of acetylene using a sealed gas cell and a liquid nitrogen trap

We demonstrate spectral normalization in dual-comb spectroscopy of acetylene using a sealed gas cell and liquid nitrogen trap. The normalized spectra of the P- and R-branches of the ν 1 + ν 3 vibration band of 12 C 2 H 2 were observed at a comb repetition rate of 19.8 MHz. We also observed instantaneous pressure changes inside the cell during the cooling of the liquid nitrogen trap, with different averaging times.

Study of Water Impact and Entry of a Free Falling Wedge Using Computational Fluid Dynamics Simulations

Many offshore constructions and operations involve water impact problems such as water slamming onto a structure or free fall of objects with subsequent water entry and emergence. Wave slamming on semisubmersibles, vertical members of jacket structures, crane operation of a diving bell, and dropping of free fall lifeboats are some notable examples. The slamming and water entry problems lead to large instantaneous impact pressures on the structure, accompanied with complex free surface deformations. These need to be studied in detail in order to obtain a better understanding of the fluid physics involved and develop safe and economical design. Numerical modeling of a free falling body into water involves several complex hydrodynamic features after its free fall such as water entry, submergence into water and resurfacing. The water entry and submergence lead to formation of water jets and air cavities in the water resulting in large impact forces on the object. In order to evaluate the forces and hydrodynamics involved, the numerical model should be able to account for the complex free surface features and the instantaneous pressure changes. The water entry of a free falling wedge into water is studied in this paper using the open source computational fluid dynamics (CFD) model REEF3D. The vertical velocity of the wedge during the process of free fall and water impact are calculated for different cases and the free surface deformations are captured in detail. Numerical results are compared with experimental data and a good agreement is seen.

Continuous assessments of pressure comfort on a train – A field-laboratory comparison

Pressure variations on a train predominantly occur while trains are passing through tunnels. These aerodynamic effects may give rise to aural discomfort in railway passengers. We conducted a field study on the high speed railway track Cologne-Frankfurt/Main as well as a simulation study in our pressure chamber TITAN (DLR-Institute of Aerospace Medicine) with 31 subjects (mean age = 37.7, SD = 12.7; 51.6% male) to investigate pressure comfort for passengers. Continuous assessments of pressure events using sliders and retrospective assessments were acquired. Pressure variations were mostly tolerated. A comparison of field and laboratory setting revealed high congruency of continuous as well as retrospective assessments. A generalized estimating equation model identified pressure change attributes contributing to passengers' discomfort. Beside attributes of instantaneous pressure changes (e.g. high amplitudes, short durations), pressure events of the recent past significantly influenced current discomfort. Design engineers may use these findings to improve train and tunnel design.

Application of an active device for helicopter noise reduction in JAXA

Important issues in noise problems for current helicopters are described. An active tab (AT) was developed as a new active device for noise/vibration reduction under research cooperation between Japan Aerospace Exploration Agency (JAXA) and Kawada Industries, Inc. The wind tunnel test was conducted in order to investigate the effectiveness of the AT on the aeroacoustic characteristics of a helicopter. From the wind tunnel test, the capability of reducing blade vortex interaction (BVI) noise by an AT was verified. A new control law using instantaneous pressure change on a blade during BVI phenomena was introduced and applied to the wind tunnel testing. This new control law shows reasonable controllability for helicopter noise reduction. Furthermore, in order to analyze noise characteristics, the advanced computational fluid dynamics (CFD) code named JAXA_ov3d was developed in JAXA and extended to include CFD–CSD (computational structure dynamics) coupling by using the beam theory for blade deformation.

Middle ear pressure change as a function of body position

To verify and assess immediate middle ear (ME) pressure changes as a function of body position. A prospective clinical trail. Twenty-six adult volunteers having 52 normal, healthy ears had tympanometric ME pressures measured in an upright and recumbent positions. Recordings were obtained immediately after positioning and after 3 minutes. The main outcome measure was the pressure difference between upright and recumbent measurements, that is, positional ME pressure change. All ME pressure recordings were within (-)100 to (+)55 mmH(2)O. An instant and significant (P < .001) pressure elevation was recorded in all ears once position changed from upright to recumbent. The average pressure increment was 19 mmH(2)O. Once a recumbent ear was repositioned upright it demonstrated an immediate pressure drop and regaining the initial ME pressure. Assuming the volume of a normal ME cleft as 8 mL and following Boyle's law, an ME volume alteration of about 17 microL was required to induce such pressure change. Positional pressure changes were within the range of normal daily ME pressure variations. The instantaneous pressure changes and reversibility may be explained by filling and emptying of blood vessels within the ME cleft, following gravity causing an alteration of the aerated volume. Individual differences of pressure change may follow variability of ME cleft volume, its surface, and vessel density.

Pressures Generated Within the Chambers of the MagScrew TAH: An In Vitro Study

Incompetent inflow valves have been reported with clinical pulsatile left ventricular assist devices that use bioprosthetic valves. Suspected as the cause of premature valve failure within these devices, absolute pressures and instantaneous pressure changes were evaluated in the MagScrew total artificial heart (TAH). The MagScrew TAH is a passively filling pulsatile pump which uses a reciprocating magnetic actuating mechanism under various control modes to propel blood into circulation. Both right and left ejection speeds were modulated and optimized at the onset of hydraulic eject. These various speed profiles were evaluated in vitro at 220 beats per minute (bpm), 100% pump fill, mean aortic pressure of 100 mm Hg and mean pulmonary artery pressure of 20 mm Hg. The pressure inside the left and right pump chambers was measured with Millar Mikro-Tip catheter and captured using Power Lab at a rate of 40 kHz. The pump chamber peak pressure, operating with unmodified eject speeds, measured on average 183 mm Hg for the left and 133 mm Hg for the right. Eject speed profiling for both pumps reduced the peak pressure by 10% and 28% for the left and right pump, respectively. Future studies will assess software controlled optimization of the eject speed profiles under any operating condition and how effective it is in vivo.

Response of submarine hydrologic monitoring instruments to formation pressure changes: Theory and application to Nankai advanced CORKs

We describe the response of a compressible submarine hydrologic monitoring instrument to formation pressure changes in low‐diffusivity rock. The measured pressure depends on the frequency of the pressure signal, the hydraulic diffusivity, and the wellbore storage. The Nankai advanced circulation obviation retrofit kits (ACORKs) (offshore Japan) record tide‐induced formation pressure changes with small amplitudes (&lt;10% of seafloor amplitudes) and large phase shifts (&gt;25°). The pressure measurements occur in thick, homogeneous, compressible, low‐permeability sediment, where in situ tidal pressure responses should approximate the seafloor tidal signal. A wellbore storage of 2 × 10−8 m3 Pa−1 can explain many of the observed tidal responses, given the hydraulic diffusivities of the monitored intervals. A reduced permeability around the wellbore of 1000‐fold and a wellbore storage of 10−11 m3 Pa−1 can also reconcile the data. Our analysis suggests that ACORK screens in the Lower Shikoku Basin facies have a critical frequency on the order of 5 × 10−8 Hz (equivalent to a period of 250 days); higher‐frequency formation pressure signals will be distorted in the pressure record. Within the Lower Shikoku Basin facies the time for this monitoring system to record 90% of an instantaneous pressure change is on the order of 10 d. We suggest that the ACORK instrument compliance contributes to, but does not fully explain, the small tidal amplitudes and large phase shifts recorded at the least permeable monitoring intervals.

Relation between wear and tooth width modification in spur gears

In this experimental study, width modification of a spur gear was investigated to fix instantaneous pressure changes along single meshing area on the gear profile. In this gear, variable pressure distribution caused by the single and double teeth meshing and the radius of curvature along the active gear profile was approximately kept constant by maintaining a constant ratio of applied load to the tooth width ( F/ b) on every point. Hence, Hertz pressure distribution along the gear profile was approximately equally achieved. Other factors affecting wear were kept constant during the experiment. The specimen used was made from AISI 4140 steel. Finally, the amount of wear in the teeth profiles between the modified and unmodified gears was compared. And wear depth of modified gear along the meshing area was almost uniform.

PRESSURE GENERATED WITHIN THE CHAMBERS OF THE MAGSCREW TAH

Purpose: Incompetent inflow valves have been reported with clinical pulsatile LVADs that use bioprosthetic valves. Absolute pressures and/or instantaneous pressure changes within these devices have been suspected to cause premature valve failure. The MagScrew total artificial heart (TAH) was evaluated to quantify absolute pump internal pressures and instantaneous pressure changes under different operating conditions. Methods: The MagScrew TAH is a passively filling pulsatile pump which utilizes a reciprocating magnetic actuating mechanism to propel blood into the circulation. Multiple pump eject parameters were varied which yielded various speed profiles. A total of 49 speed profiles were tested for the left eject phase, and 38 speed profiles were tested for the right eject phase. These were evaluated in-vitro under the following operating conditions: 220BPM, 100% pump fill, a mean aortic pressure of 100 mmHg and a mean pulmonary artery pressure of 20 mmHg. The pressure inside the left and right pump chambers was measured with a Millar Mikro-Tip catheter and captured using Power Lab at a rate of 40 kHz. Results: The pump chamber peak pressures operating with unprofiled eject velocity measured 183–226 mmHg for the left and 126–130 mmHg for the right. Eject speed profiling for both pumps reduced the peak pressure by as much as 25 and 30 mmHg for the left and right pump, respectively. Future studies will look into software controlled optimization of the eject speed profiles under any operating condition.

Computational Electrochemistry: The Simulation of Voltammetry under Hydrodynamic Modulation Control

A conceptually simple and numerically efficient approach to the simulation of current/time transients under hydrodynamically modulated conditions is presented. The generality of the method is illustrated by reference to the case of hydrodynamic modulated voltammetry (HMV) within a channel cell device under pressure driven flow control. For the preliminary studies reported here, modulation refers to a stepped change in the pressure between two limits. This change occurs either instantaneously or linearly over a normalized time. The voltammetric response of a simple redox reaction is used to illustrate the predicted influence of the modulation rate on the current flowing within the flow cell. A normalization procedure is proposed to simplify data presentation and shown to be valid for a wide range of experimentally viable conditions. The simulations are also employed to assess how the current response is influenced by the form of the pressure change between two limits. Simulations are presented for cases where an instantaneous pressure change is employed and compared to results where a linear variation in the pressure is used.

Computational electrochemistry: simulation of voltammetry following an instantaneous pressure step within a tubular flow cell

A tubular flow cell under pressure driven control is used to illustrate a numerically efficient approach to the simulation of hydrodynamically stepped current/time transients. A simple redox reaction is used to illustrate the voltammetric response within a tubular cell to an instantaneous pressure change. To simplify the presentation of data, a normalisation method is proposed and shown to be valid for situations in which a pressure step occurs.

Theory for the propagation of tidally induced pore pressure variations in layered subseafloor formations

Tidally induced pore pressure variations below the seafloor depend on the elastic moduli and transport properties of the pore fluid and formation. Hence observations of pore pressure variations, in conjunction with model predictions, can provide important constraints on these formation properties. In this paper, we study the propagation of tidally induced pore pressure variations in a layered poroelastic medium. We derive an analytic solution and use the solution to investigate the effects of various parameters, in particular, the bulk modulus of the formation, the bulk modulus of the pore fluid, and the formation permeability. Specific examples are considered that include the typical continuous depth variation of properties that occurs through normal sediment consolidation and imbedded layers of contrasting properties. Diffusive propagation of tidal pressure variations from the seafloor depends on the hydraulic diffusivity. The depth limit of diffusive propagation scales with the inverse square root of permeability and the period of the signal; for typical fine‐grained marine sediments the depth scale at tidal frequencies is only a few meters. Any internal contrast in elastic properties, due to the presence of free gas for example, can give rise to large instantaneous pressure changes across a layer boundary, which in turn can induce diffusive propagation of signals above and below the interface. Long‐term pressure records from sealed deep‐ocean boreholes that included tidal signals are considered in light of the model results. In Ocean Drilling Project (ODP) Hole 857D on the Juan de Fuca Ridge, the observed attenuation of the seafloor tidal signal to 15% is consistent with the relatively low compressibility of the hydrothermally indurated section intersected by the open part of the borehole and with the high compressibility of the hot formation fluid. In ODP Hole 892B in the Cascadia accretionary prism, the attenuation to 55% and several degree phase lead of the formation tidal signal are probably the result of the open part of the hole being connected to an overlying interval bearing a few percent free gas via a high‐permeability fault zone.

Study of Rotational Noise Reduction for Axial Flow Fan. (Analysis and Estimation of Secondary Fan-Noise Component).

Rotational noise is one of the main sources of noise emitted by a fan. This type of noise has discrete frequency components, and is so severe that many methods have been developed for its reduction. There have been few studies on rotational noise, however, to clarify the generation mechanism and determine concrete methods for noise reduction. In the present study the spacings of the blades were changed and comparisons were made with a fan having equally spaced blades. The discrete frequency components were found to be suppressed in the fan with unequally spaced blades and the noise tended to become white noise if the blade spacing and blade setting angles were properly chosen. The instantaneous pressure change on the shroud due to blade passing was examined since it is closely related to the discrete frequency components of noise. By decomposing the measured pressure change in terms of a Fourier series the characteristics of rotational noise were analyzed and compared with simulation results obtained using a pressure wave model. The prediction of the rotational noise emitted by axial fans with unequally spaced blades is presented and found to agree well with the experimental results.

Effect of regenerator matrix properties on the stirling engine performance.

The engine speed and pressure dependences of performance of the laboratory research Stirling engine MELSE IIIs have been measured for six species of regenerator matrix ; five wire gauses with different mesh numbers and one smonge metal. In addition to the ordinary characteristics such as shaft power, indicated power and thermal input, the flow friction and reheat losses at the regenerator have been determined from the measurements of the instantaneous pressure changes and the heat removed by cooling water, respectively. These two losses related to regenerator matrix properties have been compared with the theoretical ones calculated from fundamental matrix data according to rather simple models. The results indicate that the optimum matrix and geometry of the regenerator can be obtained theoretically.

Laboratory evaluation of an airborne ozone instrument that compensates for altitude/sensitivity effects

One problem encountered in the use of air-quality instrumentation on aircraft is the variation of instrument sensitivity with pressure as the result of altitude changes of the aircraft. Many instruments experience sensitivity changes of as much as a factor of 2 at altitudes of 6 km. Discussed are recent modifications to a chemiluminescent (ethylene) ozone detector that allow the instrument to automatically compensate for pressure/sensitivity effects. The modification provides automated mass flow rate control for both the sample and ethylene gas flows. The flow control systems maintain flow rate to within 15 percent for a 100-torr instantaneous pressure change, and flow rates are returned to the desired set points within 10 s after the pressure change. During simulated altitude changes (300 m/min from mean sea level to 3-km altitude), flow rates were controlled to within 3 percent of the set point. Laboratory data are summarized verifying the operation of the instrument for a pressure range of 760 torr (sea level) to 350 torr (approximately 20,000 ft) and an ozone concentration range from 20 to approximately 700 ppb.

Studies of root function in Zea mays I. Apparatus and methods

An apparatus is described to which the cut end of an excised root may be sealed and the developing root pressure measured by a transducer as a function of time. In addition to measurements of pressure under zero volume flow, flow rates at various applied pressures may also be obtained. By applying an instantaneous pressure change which is just sufficient to terminate flow, the true osmotic driving force within the root can be determined. This provides a measurement of the hydraulic conductivity of the root which is independent of the presence of unstirred layers and of osmotically active species whose reflection coefficients may not be one. The technique also separates the effects which changes in hydraulic conductivity (Lp) and solute flux (Js) exert on volume flow(Jv)

Effect of Pore Water Pressure on Sand Splash

AbstractWe studied the effect of pore‐water pressure and particle‐size distributions on the amount of sand splash and on the instantaneous pressure changes within a packed sand core caused by single water drops falling on the surface. Both splash amounts and pore‐water pressure changes were affected by particle size, pore‐water pressure before drop impact, and by the direction of approach to the pore‐water pressure equilibrium. Pore‐water pressure increases from falling water drops were generally greater when equilibrium pressures were approached directly than when they were approached from minimum pressure. Sand splash was also generally greater when equilibrium pressure was approached directly.

Alveolar pressure response to “top-hat” gas flow or pressure waves in artificial ventilation

Patients and dogs were anaesthetized and paralysed and their airways were exposed to an instantaneous pressure change applied during artificial ventilation. Measurements of respiratory gas flow and volume, and of trachéal, oesophageal and pleural pressures were made. The results presented support the hypothesis that alveolar pressure responds to an instantaneous pressure change in a patient's airway during artificial ventilation by an instantaneous step change of pressure. Methods for measuring oesophageal pressure and for calculating kinetic respiratory resistance and compliance are discussed.