Showing papers on "Dynamic pressure published in 2010"

A new form of Saturn's magnetopause using a dynamic pressure balance model, based on in situ, multi-instrument Cassini measurements

Abstract: The shape and location of a planetary magnetopause can be determined by balancing the solar wind dynamic pressure with the magnetic and thermal pressures found inside the boundary. Previous studies have found the kronian magnetosphere to show rigidity (like that of Earth) as well as compressibility (like that of Jupiter) in terms of its dynamics. In this paper we expand on previous work and present a new model of Saturn's magnetopause. Using a Newtonian form of the pressure balance equation, we estimate the solar wind dynamic pressure at each magnetopause crossing by the Cassini spacecraft between Saturn Orbit Insertion in June 2004 and January 2006. We build on previous findings by including an improved estimate for the solar wind thermal pressure and include low-energy particle pressures from the Cassini plasma spectrometer's electron spectrometer and high-energy particle pressures from the Cassini magnetospheric imaging instrument. Our improved model has a size-pressure dependence described by a power law D-P(-1/5.0 +/- 0.8). This exponent is consistent with that derived from numerical magnetohydrodynamic simulations.

Solar wind driving of magnetospheric ULF waves: Field line resonances driven by dynamic pressure fluctuations

Abstract: [1] Several observational studies suggest that solar wind dynamic pressure fluctuations can drive magnetospheric ultralow‐frequency (ULF) waves on the dayside. To investigate this causal relationship, we present results from Lyon‐Fedder‐Mobarry (LFM) global, three‐dimensional magnetohydrodynamic (MHD) simulations of the solar wind–magnetosphere interaction. These simulations are driven with synthetic solar wind input conditions where idealized ULF dynamic pressure fluctuations are embedded in the upstream solar wind. In three of the simulations, a monochromatic, sinusoidal ULF oscillation is introduced into the solar wind dynamic pressure time series. In the fourth simulation, a continuum of ULF fluctuations over the 0–50 mHz frequency band is introduced into the solar wind dynamic pressure time series. In this numerical experiment, the idealized solar wind input conditions allow us to study only the effect of a fluctuating solar wind dynamic pressure, while holding all of the other solar wind driving parameters constant. We show that the monochromatic solar wind dynamic pressure fluctuations drive toroidal mode field line resonances (FLRs) on the dayside at locations where the upstream driving frequency matches a local field line eigenfrequency. In addition, we show that the continuum of upstream solar wind dynamic pressure fluctuations drives a continuous spectrum of toroidal mode FLRs on the dayside. The characteristics of the simulated FLRs agree well with FLR observations, including a phase reversal radially across a peak in wave power, a change in the sense of polarization across the noon meridian, and a net flux of energy into the ionosphere.

Analysis of a turbulent buoyant confined jet modeled using realizable k–ɛ model

Abstract: Through this paper, analyses of components of the unheated/heated turbulent confined jet are introduced and some models to describe them are developed Turbulence realizable k–ɛ model is used to model the turbulence of this problem Numerical simulations of 2D axisymmetric vertical hot water confined jet into a cylindrical tank have been done Solutions are obtained for unsteady flow while velocity, pressure, temperature and turbulence distributions inside the water tank are analyzed For seeking verification, an experiment was conducted for measuring of the temperature of the same system, and comparison between the measured and simulated temperature shows a good agreement Using the simulated results, some models are developed to describe axial velocity, centerline velocity, radial velocity, dynamic pressure, mass flux, momentum flux and buoyancy flux for both unheated (non-buoyant) and heated (buoyant) jet Finally, the dynamics of the heated jet in terms of the plume function which is a universal quantity and the source parameter are studied and therefore the maximum velocity can be predicted theoretically

Periodic plasma escape from the mass-loaded Kronian magnetosphere

Abstract: [1] We use a single‐fluid global MHD model to study the solar wind control of large‐ scale mass loading and plasma release phenomena in the Kronian magnetosphere. We show that, at high solar wind dynamic pressure, the loss of plasma in the magnetotail is continuous. At medium dynamic pressure, plasmoids are pinched off periodically along an X‐line in the postmidnight sector through a cascade of helical reconnection. Plasmoids have a magnetic topology of a helical flux rope with its ends anchoring in the polar regions of Saturn. With decreasing dynamic pressure, the repetition period of plasmoids gradually increases. A higher mass‐loading rate or a higher axial tilt of Saturn makes the repetition period longer. At low dynamic pressure, the release of plasmoids becomes quasi‐periodic or chaotic. The pressure control of the repetition period is very similar to the behavior of a dripping faucet. The mass and volume of the closed magnetosphere are smaller at lower dynamic pressures because of a relatively longer X‐line. In our simulations, large‐scale plasmoids are responsible for less than 8% of the total mass loss, and the rest of the plasma is lost via cross‐field diffusion or other small‐scale mechanisms.

Effects of Injector Recess and Chamber Pressure on Combustion Characteristics of Liquid–Liquid Swirl Coaxial Injectors

Abstract: Combustion characteristics such as combustion performance and combustion stability have been studied experimentally using a small liquid rocket thrust chamber with 19 liquid–liquid swirl coaxial injectors. Data were obtained from static pressure, temperature, and dynamic pressure sensors installed in propellant manifolds and the combustion chamber. While changing the recess length of the injector, characteristic velocity and pressure fluctuation data were collected and analyzed. In addition, chamber pressure was varied between 42 and 54 bar, which covers the sub- and supercritical pressures of oxygen. The results show that the longer recess length generally promotes combustion performance and the spray interaction between injectors in the multielement combustor increases the characteristic velocity. When the chamber pressure is above the critical pressure of oxygen, the recess length scarcely affects the pressure fluctuation. However, when the chamber pressure is below the critical pressure, the shift fro...

Flow Force Analysis of a Variable Force Solenoid Valve for Automatic Transmissions

Abstract: Three-dimensional numerical simulations were carried out to investigate the flow dynamic behavior and pressure characteristics of a variable force solenoid (VFS) valve used in automatic transmissions. To visualize the dynamic movement of the spool, a moving mesh with dynamic layering meshes for varying boundary conditions was employed. Relevant experiment was performed to validate the simulations. The VFS valve was characterized by determining the variation in the equivalent orifice area with the spool displacement. The pressure sensitivity was found to be precisely controlled by the relation between the depth and the area of the notch in the range of the characteristic length of the valve. The results of model C, which takes into account both seal leakage and notches, indicate that there are linear pressure sensitivities in the range of the valve overlap and that there are smooth pressure control characteristics in the range of the two notches. The VFS valve with a spool was shown to have an unavoidable and unique hysteresis, which is caused by the nonlinear electromagnetic forces at the end of strokes of the spool and by the friction forces in the valve overlap. The effects of varying the oil temperature on the pressure sensitivity curves and the seal leakage flow rates were also examined.

Influence of hot plasma pressure on the global structure of Saturn’s magnetodisk

Abstract: Using a model of force balance in Saturn's disk-like magnetosphere, we show that variations in hot plasma pressure can change the magnetic field configuration. This effect changes (i) the location of the magnetopause, even at fixed solar wind dynamic pressure, and (ii) the magnetic mapping between ionosphere and disk. The model uses equatorial observations as a boundary condition-we test its predictions over a wide latitude range by comparison with a Cassini high-inclination orbit of magnetic field and hot plasma pressure data. We find reasonable agreement over time scales larger than the period of Saturn kilometric radiation (also known as the camshaft period).

Real-Time Pressure and Flow Dynamics Due to Boom Section and Individual Nozzle Control on Agricultural Sprayers

Abstract: Most modern spray controllers when coupled with a differential global positioning system (DGPS) receiver can provide automatic section or swath (boom section or nozzle) control capabilities that minimize overlap and application into undesirable areas. This technology can improve application accuracy of pesticides and fertilizers, thereby reducing the number of inputs while promoting environmental stewardship. However, dynamic system response for sprayer boom operation, which includes cycling or using auto-swath technology, has not been investigated. Therefore, a study was conducted to develop a methodology and subsequently perform experiments to evaluate tip pressure and system flow variations on a typical agricultural sprayer equipped with a controller that provided both boom section and nozzle control. To quantify flow dynamics during boom section or nozzle control, a testing protocol was established that included three simulation patterns under both flow compensation and no-compensation modes achieved via the spray controller. Overall system flow rate and nozzle tip pressure at ten boom locations were recorded and analyzed to quantify pressure and flow variations. Results indicated that the test methodology generated sufficient data to analyze nozzle tip pressure and system flow rate changes. The tip pressure for the compensated section control tests varied between 6.7% and 20.0%, which equated to an increase of 3.7% to 10.6% in tip flow rate. The pressure stabilization time when turning boom sections and nozzles off approached 25.2 s but only approached 15.6 s when turning them back on for the flow compensation tests. Although extended periods were required for the tip pressure to stabilize, the system flow rate typically stabilized in less than 7 s. The tip flow rate was consistently higher (up to 10.6%) than the target flow rate, indicating that system flow did not truly represent tip flow during section control. The no-compensation tests exhibited tip pressure increases up to 35.7% during boom and nozzle control, which equated to an 18.2% increase in tip flow. Therefore, flow compensation over no-compensation had better control of tip flow rate. A consistent difference existed in dynamic pressure response between boom section and nozzle control. Increased tip pressure and delayed pressure stabilization times indicated that application variability can occur when manually turning sections on and off or implementing auto-swath technology, but further testing is needed to better understand the effect on application accuracy of agricultural sprayers.

Elastohydrodynamic lubrication analysis of a compliant journal bearing considering static and dynamic deformations of the bearing-liner

Abstract: In this article, the effect of both static and dynamic deformations of the bearing liner on the dynamic performance characteristics and stability of a water-lubricated, rubber-lined journal bearing operating under small harmonic vibrations is theoretically investigated. To take into account the dynamic deformations of the bearing liner, the first-order perturbation technique is used to determine the eight dynamic coefficients for a given excitation frequency value. The static and dynamic deformation of the fluid/bearing-liner interface is assumed to be proportional to the steady-state and dynamic fluid-film pressures. It was found that the dynamic properties and stability of the compliant finite-length journal bearing are affected by surface coatings from soft materials. It was also shown that when dynamic deformations are considered in the calculations, the dynamic coefficients depend on the excitation frequency, especially for higher values of this parameter. Moreover, the two cross-damping coefficients...

Exhaust of Underexpanded Jets from Finite Reservoirs

Abstract: We examine the response of an underexpanded jet to a depleting, nite reservoir with experiments and simulations. An open-ended shock tube facility with variable reservoir length is used to obtain images of nitrogen and helium jet structures at successive instances during the blowdown from initial pressure ratios of up to 250. The reservoir and ambient pressures are simultaneously measured to obtain the instantaneous pressure ratio. We estimate the time-scales for jet formation and reservoir depletion as a function of the specic heat ratio of the gas and the initial pressure ratio. The jet structure formation time-scale is found to become approximately independent of pressure ratio for ratios greater than 50. In the present work, no evidence of time-dependence in the Mach disk shock location is observed for rates of pressure decrease associated with isentropic blowdown of a nite reservoir while the pressure ratio is greater than 15. The shock location in the nitereservoir jet can be calculated from an existing empirical t to innite-reserv oir jet data evaluated at the instantaneous reservoir pressure. For pressure ratios below 15, however, the present data deviate from a compilation of data for innite-reserv oir jets. A new t is obtained to data in the lower pressure regime. The self-similarity of the jet structure is quantied and departure from similarity is noted to begin at pressure ratios lower than about 15, approximately the same ratio which limits existing empirical ts.

Influence of Hot Plasma Pressure on the Global Structure of Saturn's Magnetodisk

Abstract: Using a model of force balance in Saturn's disk-like magnetosphere, we show that variations in hot plasma pressure can change the magnetic field configuration. This effect changes (i) the location of the magnetopause, even at fixed solar wind dynamic pressure, and (ii) the magnetic mapping between ionosphere and disk. The model uses equatorial observations as a boundary condition-we test its predictions over a wide latitude range by comparison with a Cassini high-inclination orbit of magnetic field and hot plasma pressure data. We find reasonable agreement over time scales larger than the period of Saturn kilometric radiation (also known as the camshaft period).

Magnetospheric modes and solar wind energy coupling efficiency

Abstract: [1] Using observations and two different global MHD simulations, we demonstrate that the solar wind speed controls the magnetospheric response such that the higher the speed, the more dynamic and irregular is the magnetospheric response For similar level of driving solar wind electric field, the magnetospheric modes can be organized in terms of speed: Low speed produces steady convection events, intermediate speeds result in periodic sawtooth oscillations, and high speeds drive large geomagnetic storms We show that the control parameter of energy transfer and coupling is the electric field along the large-scale X line We demonstrate using global MHD simulations that for slowly varying interplanetary magnetic field (IMF), the reconnection line is tilted approximately by an angle θ/2, where θ is the IMF clock angle Then, for clock angles away from northward, the magnetospheric energy entry and response scale with the electric field along the reconnection line (EPAR), rather than the traditionally used EY If we define the energy coupling efficiency as response/EPAR, we can show it to be independent of the IMF clock angle and only weakly dependent on the solar wind dynamic pressure These results demonstrate the ability of the localized reconnection line to control the energy input through the entire magnetopause

New method for investigating the dynamic pressure behavior of compression garment

Abstract: Purpose – The paper aims to develop a system and measuring method for investigating the dynamic pressure behavior of compression garments.Design/methodology/approach – The dynamic pressure behavior measurement, realized by use of the self‐designed system, is a direct measuring method, which is based on a rigid hemisphere with five pressure sensors distributed on its surface. The dynamic pressure is measured over time under the process of fabric 3D deformation. The pressure distributions at the basic five sites are accepted as the measuring results. The dynamic stiffness index can be calculated from dynamic pressure profile and 3D deformation of compression garments.Findings – The measuring system records the pressure‐time curve and pressure‐deformation curve. The dynamic pressure stiffness index expresses the change in pressure owing to the change in elongation of compression fabrics. The pressure measuring system and the index provide much information in the field of compression garment assessment.Resear...

Modeling, Dynamic Simulation, and Controller Design for an Air-breathing Combustion System

Abstract: A novel, high-fidelity, low-order model is developed for an air-breathing combustion system designed for supersonic flight with a subsonic combustor. Individual components – intake, combustor, exhaust nozzle – are modeled with detailed models obtained from CFD, quasi-1D, or isentropic analysis, as the case may be. The components are then interlinked by a low-order global model that captures the physics of the interaction between the intake and the subsonic combustor. Disturbances due to bulk mode acoustics in the combustion chamber and due to turbulent interactions in the intake diffuser and the combustor are modeled, and a detailed model of the fuel supply system is also included. Dynamic simulations are performed with fuel flow rate and exhaust nozzle throat area as the two inputs. The terminal shock location in the intake duct is quantified in terms of the intake backpressure margin, called P4margin. An innovative controller is designed to take the system from 2.1 Mach, 1.4 km altitude to cruise at 3.0 Mach, 14.5 km. The primary requirement of the controller is to regulate the fuel flow to the combustor so that adequate thrust is available at all flight conditions, while maintaining a tight control on P4margin (intake shock location). Limits on fuel-air ratio, peak combustor temperature, fuel flow rate, and throat area actuator limits are also required to be satisfied. Only intake backpressure, P4, is assumed to be measurable. Separate PID controllers for fuel flow rate and throat area, with P4margin as the commanded variable, are designed at several operating points on the acceleration and cruise segments of the flight. A control allocation scheme is used to divide the control effort between the fuel flow rate and throat area channels. An outer guidance loop using Dynamic Inversion (DI) as a rapid prototyping tool commands Mach number and computes the desired thrust. An intermediate stage maps this computed thrust to a P4margin command using a single-valued static map. The PID gains and the static maps are scheduled with dynamic pressure during acceleration and angle of attack in the cruise phase. A separate PID controller is designed for the fuel supply system. Various components of the controller are individually tested extensively. Finally, a composite closed-loop simulation is successfully carried out taking the system through the acceleration phase to the desired cruise condition with a smooth switching between the acceleration and cruise segments.

Fluid dynamic pressure bearing device, spindle motor and disk drive apparatus

Abstract: A bearing mechanism includes a shaft, a sleeve portion, a thrust portion, and a cover portion. Lubricating oil is arranged in a communicating channel in the sleeve portion, a thrust gap between the sleeve portion and the thrust portion, and a tapered gap between an outside surface of the thrust portion and the cover portion. A lower end opening of the communicating channel is defined in an outer circumferential portion of a lower surface of the sleeve portion radially outward of the thrust gap. A radially outermost portion of the thrust portion is arranged either tangent to a wall surface of the communicating channel or closer to a central axis than the wall surface. The tapered gap is arranged closer to the central axis than a radially outermost point of the wall surface. The outer circumferential portion and the cover portion define a guide gap therebetween.

Outside pressurized type dynamic and static pressure gas lubricating and sealing device

Abstract: The invention discloses an outside pressurized type dynamic and static pressure gas lubricating and sealing device, which comprises a moving ring (5) and a seal static ring (11), wherein the moving ring (5) is fixed on a moving ring seat (1) and rotates along with a spindle, and the seal static ring (11) is fixed on a seal cavity (2) and a seal end cover (12); channels (9) for introducing outsidepressurized gas from outside are arranged in the seal static ring (11), and the channels (9) of certain numbers are distributed in the seal static ring (11) along circumference; throttle devices (8) are arranged in the channels (9), and pressure equalizing troughs (7) of certain depth are arranged at the outlets of the channels (9); various dynamic pressure troughs (6) having dynamic pressure effects are formed on the end face of the moving ring (5) or the seal static ring (11), and the inside and outside of the pressure equalizing troughs (7) are provided with seal dams not communicated withthe pressure equalizing troughs; and on-line monitoring is realized by adjusting the pressure of the outside pressurized gas. The pressurized type dynamic and static pressure gas lubricating and sealing device greatly lowers resistance moment and power consumption and improves the phenomenon that the traditional end face seal abrasion is severe.

Solar wind driving of magnetospheric ULF waves: Field line resonances driven by dynamic pressure fluctuations

Abstract: Several observational studies suggest that solar wind dynamic pressure fluctuations can drive magnetospheric ultra-low frequency (ULF) waves on the dayside. To investigate this causal relationship, we present results from Lyon-Fedder-Mobarry (LFM) global, three-dimensional magnetohydrodynamic (MHD) simulations of the solar wind-magnetosphere interaction. These simulations are driven with synthetic solar wind input conditions, where idealized ULF dynamic pressure fluctuations are embedded in the upstream solar wind. In three of the simulations, a monochromatic, sinusoidal ULF oscillation is introduced into the solar wind dynamic pressure time series. In the fourth simulation, a continuum of ULF fluctuations over the 0-50 mHz frequency band is introduced into the solar wind dynamic pressure time series. In this numerical experiment, the idealized solar wind input conditions allow us to study only the effect of a fluctuating solar wind dynamic pressure, while holding all of the other solar wind driving parameters constant. We show that the monochromatic solar wind dynamic pressure fluctuations drive toroidal mode field line resonances (FLRs) on the dayside, at locations where the upstream driving frequency matches a local field line eigenfrequency. In addition, we show that the continuum of upstream solar wind dynamic pressure fluctuations drives a continuous spectrum of toroidal mode FLRs on the dayside. The characteristics of the simulated FLRs agree well with FLR observations, including a phase reversal radially across a peak in wave power, a change in the sense of polarization across the noon meridian, and a net flux of energy into the ionosphere.

Breaking Wave Impact Pressure on a Vertical Wall

Abstract: Offshore and coastal structures experience wave impact loads particularly due to breaking waves throughout its design period. In the present paper, an experimental program has been devised to improve our perceptive of the physics and the characteristics of impact pressures due to breaking waves on a vertical wall. The salient features of the study such as model details, breaking wave simulation, the impact and dynamic pressure variation along the depth of the wall are presented. The maximum impact pressure magnitude is found to be of the order of ten times that of the non-breaking dynamic pressure and it always occurred above the still water level for different intensities of breaking waves considered. The minimum pressure rise time is observed to be 0.235 ms.

Flow and Dipole Source Evaluation of a Generic SUV

Abstract: Accurately predicting both average flow quantities and acoustic sources at the front window of today's ground vehicles are still a considerable challenge to automotive companies worldwide. One of the most important aspects in terms of obtaining not only trustworthy results but also the most tedious one and therefore perhaps overlooked, is the control and outcome of the mesh generation process. Generating unstructured volume meshes suitable for large eddy simulations with high level representation of geometrical details is both a time consuming and an extremely computer demanding activity. This work investigates two different mesh generation processes with its main aim to evaluate their outcome with respect to the prediction of the two dominating dipole sources in a temporal form of the Curle's equation. Only a handful of papers exists that report a high level representation of the vehicle geometry and the aim of predicting the fluctuating exterior noise sources. To the author's knowledge no studies have been conducted in which both these source terms are evaluated quantitatively against measurements. The current paper investigates the degree to which the amplitude of these two source terms can be predicted by using the traditional law-of-the-wall and hex-dominant meshes with isotropic resolution boxes for a detailed ground vehicle geometry. For this purpose, the unstructured segregated commercial FLUENT finite volume method code is used. The flow field is treated as incompressible and the Smagorinsky-Lilly model is used to compute the subgrid stresses. Mean flow quantities are measured with a 14 hole probe for 14 rakes downstream of the side mirror. The dynamic pressure sensors are distributed at 16 different positions over the side window to capture the fluctuating pressure signals. All measurements in this work were conducted at Ford's acoustic wind tunnel in Cologne. All three simulations accurately predict the velocity magnitude closest to the window and downstream of the mirror head recirculation zone. Some variations in the size and shape of this recirculation zone are found between the different meshes, most probably caused by differences in the detachment of the mirror head boundary layer. The Strouhal number of the shortest simulation was computed from the fundamental frequency of the drag force coefficient. The computed Strouhal number agrees well with the corresponding results from similar objects and gives an indication of an acceptable simulation time. The dynamic pressure sensors at 16 different locations at the vehicle side window were also used to capture the levels of the two dipole source terms. These results are compared with the three simulations. With the exception of three positions, at least one of the three simulations accurately captures the levels of both source terms up to about 1000 Hz. The three positions with less agreement as compared with measurements were found to be in regions sensitive to small changes in the local flow direction. [DOI: 10.1115/1.4001340]

Gas Turbine Single Annular Combustor Sector: Combustion Dynamics

Abstract: This paper investigates the combustion dynamics of a single cup gas turbine combustor sector, a swirl-stabilized burner with dilution and cooling air holes. The burner was fueled by natural gas and was operated at one atmospheric pressure with various air inlet temperatures, air pressure drops, and air–fuel ratios. Acoustic emissions as functions of operating conditions were measured. Chemiluminescence imaging with a high-speed CCD camera and simultaneous dynamic pressure measurements has been used to characterize the combustor’s behavior. Imaging of the combustion energy release rate has provided an insight on the flame structure and its interaction with the dilution air jets. The combustion dynamics were correlated well with the heat release rate in the primary zone or in the dilution air jet region. Two low-frequency combustion dynamics modes (fuel-rich combustor domes with frequency around 420Hz, and fuel-lean combustor domes with frequency around 280 Hz) were identified by a dynamic microphone, dynamic pressure transducers, and a high-speed CCD camera. A two-dimensional distribution of the heat release rate dynamics (amplitude and phase angle) reveals different combustion dynamics driving mechanisms for fuel-lean and fuel rich modes. The acoustic emissions for the fuel-lean combustion mode correlated well with the energy release rate dynamics of the swirling jet inside the combustor dome. The acoustic emissions for the fuel-rich mode were associated with the unsteady chemical energy release rate from interactions between the dilution air jets and the fuel-rich mixture convected from the combustor dome.

Application of charged particle beams of TWAC-ITEP accelerator for diagnostics of high dynamic pressure processes

Abstract: The 800 MeV proton radiography facility for high dynamic pressure research in condensed matter has been commissioned at the Terrawatt Accelerator of Institute of Theoretical and Experimental Physics (TWAC-ITEP) in Moscow. Spatial resolution of the facility measured in static experiments with a variety of test objects was found to be 0.30±0.01 mm in current experimental arrangement. First dynamic experiments on the observation of a shock loading of steel surface and a propagation of the detonation wave in a high explosive charge were conducted. Good quantitative agreement of density profiles reconstructed from obtained radiographic images with theoretical and simulated data showed the capabilities of high energy ion beam radiography as an excellent tool for bulk density measurements in high dynamic pressure studies.

Method for manufacturing hydrodynamic bearing and rotating shaft

Abstract: The invention provides a manufacturing method of dynamic pressure bearing, which comprises the following steps: an obturator is provided, the surface of the obturator is convexly provided with a plurality of protrusions; the obturator is arranged in the central position of a hollow bearing mould, and a hollow cavity in the bearing mould is filled with the mode of encapsulation molding to form an embryo of the dynamic pressure bearing; the obturator is removed from the embryo of the dynamic pressure bearing through the mode of catalytically degreasing; binder in the embryo of the dynamic pressure bearing is removed; the embryo of the dynamic pressure bearing is sintered; finally, the dynamic pressure bearing is formed. The dynamic pressure bearing integrally forms the dynamic pressure bearing and a dynamic pressure groove through the method of encapsulation molding, and removes micro-molecular gases which is decomposed from the obturator by using the method of catalytically degreasing,thereby preventing the embryo of dynamic pressure bearing from generating defects as deformation, bending or fracture, etc., improving the mass production capability and the dimensional precision of the dynamic pressure bearing. The invention also provides a manufacturing method of a dynamic pressure rotating shaft.

Aircraft dynamic pressure estimation system and method

Abstract: Methods and apparatus are provided for estimating aircraft dynamic pressure. The load on the flight control surface actuator that is coupled to a flight control surface is measured. An estimate of the aircraft dynamic pressure is calculated from the measured load.

Disk drive device improved in anti-vibration characteristic

Abstract: A disk drive device includes a rotating body, a fluid dynamic bearing unit that rotatably supports the rotating body, and a drive unit. The fluid dynamic bearing unit has: a lubricant holding portion in which lubricant is held; a first thrust dynamic pressure groove with which a first thrust dynamic pressure generating portion for generating the dynamic pressure in the pump-in direction, which is oriented toward the inside of the lubricant holding portion, is structured; and a second thrust dynamic pressure groove with which a second thrust dynamic pressure generating portion for generating at least the dynamic pressure in the pump-out direction, is structured. The first thrust dynamic pressure generating portion and the second thrust dynamic pressure generating portion have dynamic pressure generation characteristics in which, when the rotating body is biased in the rotational axis direction from the state where the rotating body is floating in the lubricant, the sum of the changes in the dynamic pressure in the pump-out direction is larger than that of the changes in the dynamic pressure in the pump-in direction.

An empirical relationship between coronal mass ejection initial speed and solar wind dynamic pressure

Abstract: [1] Interplanetary shocks that precede coronal mass ejections (CMEs) are mainly responsible for sudden impulses, which are characterized by a simple step-like increase in the horizontal H component. Such a magnetic field change has been explained as a compression of the magnetosphere by the passage of a sudden increase in the solar wind dynamic pressure. Strong compression of the dayside magnetopause could cause geosynchronous satellites to be exposed to solar wind environments where large fluctuations of the interplanetary magnetic field and highly energetic particles are present. In this study, we chose 26 event pairs consisting of a type II burst/CME occurring in conjunction with a sudden commencement/sudden impulse (SC/SI) whose solar wind, and Earth magnetic field data are available. We then investigated relationships among three physical properties (kinetic energy, directional parameter, and speed) of near-Sun CMEs, solar wind dynamic pressure, and SC/SI amplitude. As a result, we found that (1) the CME speed is more highly correlated with SC/SI amplitude than its kinetic energy and direction parameter; (2) by adopting the empirical relationship between solar wind dynamic pressure and amplitude of symmetric H (a steplike increase in the horizontal H component at low latitude), we could derive an empirical formula for the relationship between solar wind dynamic pressure near the Earth and the CME speed; (3) the CME speed has a linear relationship with the difference of magnetopause locations derived by using the model of Shue et al. (1998) at the subsolar point before and after the shock arrivals; (4) a fast CME greater than 1600 km s−1 could be a driver of the magnetopause crossing of a spacecraft at geosynchronous orbit. Our results show that the CME speed is an important parameter for early prediction of geosynchronous magnetopause crossing.

Monitoring of velocity and pressure fields within an axial turbine

Abstract: In the framework of the consortium of R&D on hydraulic machines launched by the LAMH (Hydraulic Machines Laboratory of Laval University) in November 2007, a five holes unsteady pressure probe using embedded pressure sensors has been developed. Such probe allows us to obtain the unsteady static pressure, total pressure and the three flow velocity components. This paper aims to present this new five holes unsteady pressure probe, used and results for a propeller turbine.

Dynamic pressure as a measure of gas turbine engine (GTE) performance

Abstract: Utilizing in situ dynamic pressure measurement is a promising novel approach with applications for both control and condition monitoring of gas turbine-based propulsion systems. The dynamic pressure created by rotating components within the engine presents a unique opportunity for controlling the operation of the engine and for evaluating the condition of a specific component through interpretation of the dynamic pressure signal. Preliminary bench-top experiments are conducted with dc axial fans for measuring fan RPM, blade condition, surge and dynamic temperature variation. Also, a method, based on standing wave physics, is presented for measuring the dynamic temperature simultaneously with the dynamic pressure. These tests are implemented in order to demonstrate the versatility of dynamic pressure-based diagnostics for monitoring several different parameters, and two physical quantities, dynamic pressure and dynamic temperature, with a single sensor. In this work, the development of a dynamic pressure sensor based on micro-electro-mechanical system technology for in situ gas turbine engine condition monitoring is presented. The dynamic pressure sensor performance is evaluated on two different gas turbine engines, one having a fan and the other without.

Extraction method for pipeline leakage feature based on dynamic pressure signal

Abstract: A dynamic pressure transmitter for the long-distance oil and gas transmission pipeline was designed.The dynamic pressure transmitter can directly measure the dynamic change of pipeline pressure.In the pipeline leakage detection,the dynamic pressure transmitter has higher sensitivity than the general pressure transmitter to obtain the dynamic pressure signal along the pipeline.Then the detected signal was decomposed into a sum of finite intrinsic mode functions(IMF) by empirical mode decomposition(EMD).The normalized kurtosis value of the main IMF components was analyzed,and the eigenvectors of the detected signal could be extracted.The application examples show that the features of the signals resulted from pipeline leakage or operations of pump and valve can be extracted by the signal analysis method.