Showing papers on "Dynamic pressure published in 2006"

Instantaneous pressure and material acceleration measurements using a four-exposure PIV system

Abstract: This paper describes a non-intrusive technique for measuring the instantaneous spatial pressure distribution over a sample area in a flow field. A four-exposure PIV system is used for measuring the distribution of material acceleration by comparing the velocity of the same group of particles at different times and then integrating it to obtain the pressure distribution. Exposing both cameras to the same particle field at the same time and cross-correlating the images enables precision matching of the two fields of view. Application of local image deformation correction to velocity vectors measured by the two cameras reduces the error due to relative misalignment and image distortion to about 0.01 pixels in synthetic images. An omni-directional virtual boundary integration scheme is introduced to integrate the acceleration while minimizing the effect of the local random errors in acceleration. Further improvements are achieved by iterations to correct the pressure along the boundary. Typically 3–5 iterations are sufficient for reducing the incremental mean pressure change in each iteration to less than 0.1% of the dynamic pressure. Validation tests of the principles of the technique using synthetic images of rotating and stagnation point flows show that the standard deviation of the measured pressure from the exact value is about 1.0%. This system is used to measure the instantaneous pressure and acceleration distributions of a 2D cavity turbulent flow field and sample results are presented.

Wall Pressure and Shear Stress Spectra from Direct Simulations of Channel Flow

Abstract: Wall pressure and shear stress spectra from direct numerical simulations of turbulent plane channel flow are presented in this paper. Simulations have been carried out at a series of Reynolds numbers up to Re? = 1440, which corresponds to Re = 6:92 x 10(4) based on channel width and centerline velocity. Single-point and two-point statistics for velocity, pressure, and their derivatives have been collected, including velocity moments up to fourth order.§ The results have been used to study the Reynolds number dependence of wall pressure and shear stress spectra. It is found that the point spectrum of wall pressure collapses for Re? ? 360 under a mixed scaling for frequencies lower than the peak frequency of the frequency-weighted spectrum, and under viscous scaling for frequencies higher than the peak. Point spectra of wall shear stress components are found to collapse for Re? ? 360 under viscous scaling. The normalized mean square wall pressure increases linearly with the logarithm of Reynolds number. The rms wall shear stresses also increase with Reynolds number over the present range, but suggest some leveling off at high Reynolds number.

Modeling the size and shape of Saturn's magnetopause with variable dynamic pressure

Abstract: [1] The location and shape of a planetary magnetopause is principally determined by the dynamic pressure, Dp, of the solar wind, the orientation of the planet's magnetic dipole with respect to the solar wind flow, and by the distribution of stresses inside the magnetosphere. The magnetospheres of Saturn and Jupiter have strong internal plasma sources compared to the solar wind source and also rotate rapidly, causing an equatorial inflation of the magnetosphere and consequently the magnetopause. Empirical studies using Voyager and Pioneer data concluded that the kronian magnetopause was Earth-like in terms of its dynamics (Slavin et al., 1985) as revealed by how the position of the magnetopause varies with dynamic pressure. In this paper we present a new pressure-dependent model of Saturn's magnetopause, using the functional form proposed by Shue et al. (1997). To establish the pressure-dependence, we also use a new technique for fitting a pressure-dependent model in the absence of simultaneous upstream pressure measurements. Using a Newtonian form of the pressure balance across the magnetopause boundary and using model rather than minimum variance normals, we estimate the solar wind dynamic pressure at each crossing. By iteratively fitting our model to magnetopause crossings observed by the Cassini and Voyager spacecraft, in parallel with the pressure balance, we obtain a model which is self-consistent with the dynamic pressure estimates obtained. We find a model whose size varies as ∼Dp−1/4.3 and whose flaring decreases with increasing dynamic pressure. This is interpreted in terms of a different distribution of fields and particles stresses which has more in common with the jovian magnetosphere compared with the terrestrial situation. We compare our model with the existing models of the magnetopause and highlight the very different geometries. We find our results are consistent with recent MHD modeling of Saturn's magnetosphere (Hansen et al., 2005).

Flame structure and burning speed of jp-10 air mixtures

Abstract: The burning speed and flame structure of Jet Propellant (JP)-10 fuel-air mixtures have been studied using two similar constant volumes: a cylindrical vessel with end windows and a spherical chamber. Both vessels are equipped with a central ignition, pressure transducer for measuring pressure rise during combustion process and ionization probes for monitoring flame arrival time. Both spherical and cylindrical chambers can be heated up to 500 K. The spherical vessel can withstand 425 atm pressures while the maximum allowable pressure for cylindrical chamber is 50 atm due to the two windows at end caps. A thermodynamic model has been developed to calculate burning speed using dynamic pressure rise in the spherical vessel. The model considers a central burned gas core of variable temperature surrounded by a preheat zone, an unburned gas shell with uniform temperature and a thermal boundary layer at the wall. The model also includes losses associated with thermal radiation from burned gas to the wall ...

Impact of ULF oscillations in solar wind dynamic pressure on the outer radiation belt electrons

Abstract: [1] This work addresses radial transport of outer radiation belt electrons due to ULF disturbances of geomagnetic field. A new approach to calculating inductive electric field is developed and implemented using a dynamical model of the storm-time geomagnetic field. The approach is used to analyze the effects associated with solar wind dynamic pressure (Pdyn). It is found that Pdyn produces large-scale electric fields with maximum intensity at noon and midnight local time. Derived fields are used in test particle calculations of relativistic electron dynamics. The results show that even moderate oscillations of Pdyn typical for quiet-time magnetosphere can result in rapid electron scattering across the drift shells, which identifies Pdyn as one of the primary mechanisms of radial transport in the belt. Calculations show that electron motion is inconsistent with radial diffusion, and hence a more detailed description is required for accurate predictions of electron fluxes in the belt.

Magnetopause energy and mass transfer: results from a global MHD simulation

Abstract: . We use the global MHD model GUMICS-4 to investigate the energy and mass transfer through the magnetopause and towards the closed magnetic field as a response to the interplanetary magnetic field (IMF) clock angle θ=arctan (BY/BZ), IMF magnitude, and solar wind dynamic pressure. We find that the mass and energy transfer at the magnetopause are different both in spatial characteristics and in response to changes in the solar wind parameters. The energy transfer follows best the sin2 (θ/2) dependence, although there is more energy transfer after large energy input, and the reconnection line follows the IMF rotation with a delay. There is no clear clock angle dependence in the net mass transfer through the magnetopause, but the mass transfer through the dayside magnetopause and towards the closed field occurs preferably for northward IMF. The energy transfer occurs through areas at the magnetopause that are perpendicular to the subsolar reconnection line. In contrast, the mass transfer occurs consistently along the reconnection line, both through the magnetopause and towards the closed field. Both the energy and mass transfer are enhanced in response to increased solar wind dynamic pressure, while increasing the IMF magnitude does not affect the transfer quantities as much.

Simulation of a rigid plate hit by a cylindrical hemi-spherical tip-ended soft impactor

Abstract: This work is concerned with the dynamic impact response simulations of a soft model bird projectile striking a flat rigid panel. A hemi-spherical cylindrical tip-ended soft material was adopted to model a bird traveling with an incident velocity of 116, 197 and 253 m/s. The constitutive modeling of the soft impactor was studied. The diameter and the length of the impactor were 11.4 and 22.8 cm, respectively, and the weight of the impactor was 1.8 kg (i.e. 4 lb). Based on J. S. Wilbeck’s AFML-TR-77-134’s report, the material properties of the soft impactor was modeled to be similar to the properties of a real bird and the shear strength of the bird was neglected. The non-linear finite element code – LS-DYNA was used in this study to analyze the problem numerically. Three different formulation approaches, i.e. the Lagrangian (LAG), Eulerian (EUL) and the Arbitrary Lagrangian Eulerian (ALE) methods, were adopted in the present numerical analysis. Simulated dynamic pressure at the center of impact surface was computed based on three methods proposed. Simulated dynamic pressure versus time relationships were compared with Wilbeck’s test result and also checked against the stable stagnation pressure for the present study. Good results were found with the use of the coupled-field ALE method to obtain the dynamic pressure evolution after impact initiated and also the stable stagnation pressure. The results based on the LAG and EUL methods were reported to be less accurate.

Statistical study of effect of solar wind dynamic pressure enhancements on dawn-to-dusk ring current asymmetry

Abstract: [1]In this paper, we statistically investigate the effect of solar wind dynamic pressure enhancements on the dawn-to-dusk ring current asymmetry by examining disturbances of the ASY-H index and low-latitude and midlatitude ground asymmetric perturbations in the north-south (H) component of the geomagnetic field during 186 events occurring from 1 June 2003 to 30 September 2004. Both storm time and nonstorm time events are included. It is found that a pressure enhancement further intensifies the ring current asymmetry provided that the ring current is already asymmetric at the time of the onset of the pressure enhancement. This effect strongly depends on the IMF B z conditions prior to the pressure enhancement. Generally, for negative IMF B z , pressure enhancements further increase the ring current asymmetry. This effect also depends on the strength of the pressure enhancement. Under the same IMF B z conditions, the stronger the pressure enhancement is, the stronger the intensification of the asymmetric ring current is. The IMF B z conditions during a pressure enhancement play a similar role to that of the IMF B z preconditioning. The results further show that midlatitude H perturbations around the local noon or midnight region as well as the ASY-H index often include significant contribution from field-aligned currents, e.g., the region 1 (R1) or region 2 (R2) currents or the substorm current wedge. Citation:Shi, Y., E. Zesta, L. R. Lyons, K. Yumoto, and K. Kitamura (2006), Statistical study of effect of solar wind dynamic pressure enhancements on dawn-to-dusk ring current asymmetry,J. Geophys. Res.,111, A10216, doi:10.1029/2005JA011532.

The influence of pool geometry and induced flow patterns in rock scour by high-velocity plunging jets

Abstract: The dissipation of energy of flood discharges from water releasing structures of dams is often done by plunging jets diffusing in water and impacting on the riverbed downstream. The construction of expensive concrete structures for energy dissipation can be avoided but the assessment of the scour evolution is mandatory for dam safety. The scour growth rate and shape depend on the riverbed geology. The geometry of scour may influence the turbulent flow pattern in the pool, the dynamic loadings acting on the rock interface, and the pressures propagating inside rock joints. Up to present, dynamic impact pressures at the pool bottom have been investigated mainly in pools with flat bottom and are therefore described as function of the pool depth and the characteristics of the jets only. To approach the conditions found in practice, non-flat plunge pools and turbulent two-phase jets are investigated in this research work. This fundamental investigation focuses on the interaction between the development of plunging jets in the water and the geometry of the plunge pool. The influence of laterally confining jet diffusion is investigated by means of experimental work in near prototype conditions, in terms of jet velocities and air entrainment in the pool. Different pool geometries typical of prototype conditions are tested and compared with a reference pool with flat bottom. Pressure measurements at the jet outlet, at the pool bottom and inside a closed-end fissure are presented. The main emphasis of the text is on the analysis and the description of physical processes. The integration of the findings in existing scour estimation models is discussed. The thickening of the water cushion downstream, artificially or by scour, is investigated for fully controlled jet issuance conditions. The dissipation of jet energy is estimated based on measurements of mean impact pressures and is compared with results from an analytical model. The developed model features jet diffusion in limited-depth pools and is tentatively applied to turbulent two-phase jets. Agreement is good in the early stages of scour and in deep flat pools. For pool depths about the jet core development length (i.e. transitional pools), analytical estimates are quite sensitive to the initial assumptions on the centreline velocity decay, dimensions of the impinging zone and pool aeration. The findings highlight the limitations of existing empirical laws in representing the diffusion of turbulent two-phase jets in pools with flat bottom. Turbulent impact pressures are also investigated for increasing pool depths. Based on an evaluation of high-order statistical moments and autocorrelation functions of pressure fluctuations at stagnation, jet development conditions at impact are distinguished in core and developed impact conditions. Core impact conditions are typical of shallow pools and generate negatively asymmetric distributions at stagnation. The end of core development is associated with highly intermittent flow conditions, with important pressure fluctuations (high kurtosis). For developed impact conditions, pressure fluctuations at stagnation are positively asymmetric. A Gaussian distribution fits satisfactorily the data, save for extreme high and low (cumulated) probabilities. Air-water measurements are carried out at selected points in pools with at bottom. They allow describing the behaviour of air bubbles before, at, and aside stagnation. Void fraction estimates close to the entry of rock fissures show that air bubbles reduce in size under the influence of the high-pressure gradient at stagnation. The characteristic dimensions of the air bubbles close to the bottom are small compared to typical entry dimensions of rock fissures. The investigations conducted in pools with flat bottom are used as a reference scenario in the investigation of plunge pools with more realistic geometries. The experimental results show that mean impact pressures at the pool bottom are lower in laterally confined pools than in equivalent pools with flat bottom. The length of core development can be reduced, depending on the degree of confinement and pool depth. Enhanced pool turbulence is described by power spectra density and probabilistic distribution functions of impact pressures. It is concluded that the flow currents created by deflection of the jet on the lateral boundaries of the pool may interfere with the development of the jet, generate additional dissipation in the water column and hinder the propagation in depth of air bubbles in the pool. For shallow and transitional laterally confined pools, pressure fluctuations may have more energy than in corresponding pools with flat bottom. Power spectra of pressure fluctuations have higher energy content in the intermediate frequency range (e.g. 10 a 100 Hz). Extreme positive pressures increase. In terms of scour, there is a trade-off relatively to flat pools: there is hardly core impact and persistent hydro-fracturing (because mean impact pressures are lower), but fracturing may occur if high low-persistence pressure peaks are generated inside rock fissures (by transients due to enhanced impact pressure fluctuations). For deep laterally confined pools, the energy of pressure fluctuations is lower than in pools with flat bottom. Extreme positive pressures are similar, but increase in relative terms to the total energy of pressure fluctuations. Negative extreme pressures are lower. The most relevant flow features in laterally confined pools are identified using direct observations of flow patterns and in-depth analysis of the characteristics of turbulent pressures at impact. Large-scale pool flow features like surface oscillations, shear eddies and air-water ejections are described. The evolution of geometry-induced flow patterns and dynamic loading with scour development, for variable width of confinement and pool depth, are presented for four typical scour scenarios. The role of the deflected upward currents and shear eddies in the dissipation process depends on the degree of confinement, jet velocity and pool depth. The closer they are to the plunging jet, the higher is the dissipation of energy before impact. Recirculation currents may enhance jet development by either pushing upward currents into the jet. The dynamic pressure measurements performed inside closed-end fissures allow concluding that the dynamic response of rock fissures varies with the turbulent character of impact pressures at the rock interface. It is shown that the dimensions of the entry of the fissure play an important role in filtering turbulent pressure fluctuations in the transition from the pool into the fissure: the larger the dimensions, the lower are the frequencies filtered out. It is observed that the energy of pressure fluctuations inside the fissure is always higher than at the entry, for all pool configurations tested. The energy of pressure fluctuations inside rock fissures is lower in narrow confined pools for transition and deep pools, but higher in shallow pools, compared with equivalent pools with flat bottom. This is also valid for positive extreme pressures. Negative extreme pressures are generally lower. Amplification of pressure peaks is observed inside a closed-end fissure for both shallow and deep pools; it depends of the degree of jet development, i.e. of relative pool depth, pool geometry and jet turbulent characteristics (and, indirectly, of the amount of entrained air reaching the bottom of the pool). Therefore, transient pressure peaks generated inside fissures are a potential agent of scour in laterally confined pools, from shallow to deep. Amplification occurs due to the development of transient flows inside the fissure, that may include column separation. The occurrence of resonance inside fissures is investigated numerically. Multiple resonant harmonics are replicated solving numerically the waterhammer equations inside the fissure with the hydraulic impedance method. A probabilistic-based event analysis is developed to correlate the probability, persistence, duration and energy content of extreme pressure pulses. It is shown that pulses with high extreme (cumulated) probabilities have low persistence and high energy content. The concept of relevant probability is outlined, allowing for the selection of pressure events that should effectively be considered for the propagation of rock fissures or for the dynamic uplift of rock blocks. The role of extreme pressure events in the scouring processes of crack propagation and block displacement is discussed. In conclusion, the experimental investigation of jet diffusion in pools with flat bottom and laterally confined pools shows the importance of pool flow patterns in the definition of impact pressures and transient pressures inside rock fissures. It provides detailed information on hydrodynamic processes involved in rock scour, as well as several contributions to engineering practice, in terms of jet issuance conditions, empirical relationships for impact pressures and recommendations for the design of pre-excavated pools.

System for monitoring anemobaroclinometric parameters for aircraft

Abstract: The invention concerns a system for monitoring anemobaroclinometric parameters in an aircraft, comprising a primary detection circuit (1) including at least one measuring channel (10), said measuring channel comprising: a device for measuring a static air pressure (13, 14); a device for measuring a side-slip angle of the aircraft; a device for measuring (15) a dynamic pressure, a total temperature and an angle of attack of the aircraft; and a data processing device (12) adapted to determine anemobaroclinometric parameters based on the measurements of static pressure, side-slip angle, dynamic pressure, total temperature and angle of attack; at least one laser anemometer (50) for measuring a true speed parameter of the aircraft.

Boundary Conditions for a Divergence Free Velocity-Pressure Formulation of the Incompressible Navier-Stokes Equations

Abstract: Boundary Conditions for a Divergence Free Velocity-Pressure Formulation of the Incompressible Navier-Stokes Equations

Boundary Layer Transition on the High Lift T106A Low-Pressure Turbine Blade With an Oscillating Downstream Pressure Field

Abstract: This paper presents the results of an experimental study of the interaction between the suction surface boundary layer of a cascade of LP turbine blades and a fluctuating downstream potential field. A linear cascade equipped with a set of T106 LP turbine blades was subjected to a periodic variation of the downstream pressure field by means of a moving bar system at low-speed conditions. Measurements were taken in the suction surface boundary layer using 2D Laser Doppler Anemometry, flush mounted unsteady pressure transducers and surface shear stress sensors. The Reynolds number, based on the chord and exit conditions, was 1.6×105 . The measurements revealed that the magnitudes of the suction surface pressure variations induced by the oscillating downstream pressure field, just downstream of the suction peak, were approximately equal to those measured in earlier studies involving upstream wakes. These pressure field oscillations induced a periodic variation of the transition onset location in the boundary layer. Two turbulence levels were investigated. At a low level of inlet freestream turbulence of 0.5%, a separation bubble formed on the rear part of the suction surface. Unsteady measurements of the surface pressure revealed the presence of high frequency oscillations occurring near the start of the pressure recovery region. The amplitude of these fluctuations was of the order of 7–8% of exit dynamic pressure, and inspection of the velocity field revealed the presence of Kelvin-Helmholtz type shear layer vortices in the separated free shear layer. The frequency of these shear layer vortices was approximately one order of magnitude greater than the frequency of the downstream passing bars. At a higher inlet freestream turbulence level of 4.0%, which is more representative of real engine environments, separation was prevented by an earlier onset of transition. Oscillations were still observed in suction surface shear stress measurements at a frequency matching the period of the downstream bar, indicating a continued influence on the boundary layer from the oscillating pressure field. However, the shear layer vortices seen in the lower turbulence intensity case were not so clearly observed and the maximum amplitude of suction surface pressure fluctuations was reduced.Copyright © 2006 by ASME

Effect of change in large and fast solar wind dynamic pressure on geosynchronous magnetic field

Abstract: We present a comparison of changes in large and sharp solar wind dynamic pressure, observed by several spacecraft, with fast disturbances in the magnetospheric magnetic field, measured by the geosynchronous satellites. More than 260 changes in solar wind pressure during the period 1996–2003 are selected for this study. Large statistics show that an increase (a decrease) in dynamic pressure always results in an increase (a decrease) in the magnitude of geosynchronous magnetic field. The amplitude of response to the geomagnetic field strongly depends on the location of observer relative to the noon meridian, the value of pressure before disturbance, and the change in amplitude of pressure.

Multiple pressure regime control to minimize RH excursions during transients

Abstract: A control system for a fuel cell stack that controls the relative humidity of the cathode outlet gas during stack power transients to provide better cathode outlet gas relative humidity control by reducing the dynamic pressure range and thus the dynamic cathode outlet gas relative humidity range. In one embodiment, the control system uses a first narrower cathode pressure range based on stack current density during stack power transients to provide better cathode outlet gas relative humidity control, and uses a second wider cathode pressure range based on stack current density during low current density and steady-state current density to improve system efficiency by decreasing compressor parasitics.

Analysis of basic processes inside the keyhole during deep penetration Nd-YAG cw laser welding

Abstract: During laser welding, the keyhole is generated by the recoil pressure induced by the evaporation processes occurring mainly on the front keyhole wall (KW). In order to characterize the evaporation process, we have measured this recoil pressure by using a plume deflection technique, where the plume generated for static conditions (i. e. with no sample displacement) is deflected by a transverse side gas jet. From the measurement of the plume deflection angle, the recoil pressure can be determined as a function of incident intensity and sample material. From these data one can estimate the pressure generated on the front KW, during laser welding. Therefore, the corresponding dynamic pressure exerted by the vapor plume expansion on the rear KW, in contact with the melt pool, can be also estimated. These pressures appear to be in close agreement with those generated by an additional side jet that has been used in previous experiments, for stabilizing the observed melt pool oscillations or fluctuations.

A Novel Approach for Dynamic Pressure Transducer Based Pipeline Leak Detection

Abstract: A novel sensor-based approach for leak detection of oil pipeline is proposed. The approach uses piezoelectric sensor in dynamic pressure transducer. The key to the detection algorithm is the use of the characteristic of piezoelectric sensor: when there are no changes in the pressure, the signal output is zero. Assume the dynamic pressure wave applied to the sensor is symmetry, then the total energy in a period of time is approximately zero, so that, after leak occurred, the total energy in a period of time will greatly deviate from zero. Using a dimensionless variable called sequential energy percentage, the leakage signal becomes distinct and can be easily extracted. Test results are reported to demonstrate the effectiveness of the proposed approach.

Air blower for range hood

Abstract: PROBLEM TO BE SOLVED: To prevent the attachment and accumulation of oil and dust by not disposing a pressure detecting portion and a rotation detecting portion in the main flow of air, and to obtain a desired air volume by normally operating the pressure detecting portion and the rotation detecting portion, to solve problems in controlling the air volume in an air blower of a range hood and the like where a wind velocity sensor, a dynamic pressure sensor and a static pressure sensor converting the air volume as voltage signals are disposed in the main flow of the air, and thus it is difficult to normally operate the sensors bacause of oil and dust included in the air and it is difficult to control the desired air volume. SOLUTION: A pressure hole 15 and a rotational frequency detector 18 are disposed at a back side of a main plate 6a at an inner side with respect to an outside diameter projection face of a centrifugal fan 6. As the pressure hole 15 and the rotational frequency detector 18 measuring an internal pressure of a fan case 3 are disposed at the back side of the main plate 6a of the centrifugal fan 6 at the inner side with respect to the outside diameter projection face of the centrifugal fan 6, the operation not directly affected by the airflow can be performed. COPYRIGHT: (C)2008,JPO&INPIT

Flutter of High-Speed Civil Transport Flexible Semispan Model: Time Frequency Analysis

Abstract: Time/frequency analysis of fluctuations measured by pressure taps and strain gauges in the experimental studies of the flexible semispan model of a high-speed civil transport wing configuration is performed. The interest is in determining the coupling between the aerodynamic loads and structural motions that led to the hard flutter conditions and loss of the model. The results show that, away from the hard flutter point, the aerodynamic loads at all pressure taps near the wing tip and the structural motions contained the same frequency components. On the other hand, in the flow conditions leading to the hard flutter, the frequency content of the pressure fluctuations near the leading and trailing edges varied significantly. This led to contribution to the structural motions over two frequency ranges. The ratio of these ranges was near 2:1, which suggests the possibility of nonlinear structural coupling.

Dynamic pressure probe and method for measuring high temp jet dynamic pressure by the probe

Abstract: The invention discloses a dynamic pressure measuring probe and a method for measuring high temperature jet dynamic pressure by this probe And it comprises a water cooled conical pressure probe and pressure sensor, where the water cooled conical pressure probe comprises outer tube whose head is made with sampling hole and whose center is provided with water-air isolating tube, the interacvity of the water-air isolating tube is formed with an airflow channel and a cooling water channel is formed between the water-air isolating tube and outer tube, the tail end of the outer tube is connected with the pressure sensor, the sensing surface of the pressure sensor corresponds to the airflow channel, and the pressure sensor is connected in turn with amplifier and signal collection system by signal lines And the invention reduces inlet water pressure requirements and reduces measuring cost, and can conveniently and quickly obtain dynamic pressure distribution on jet cross section, largely reducing measuring time

Spindle motor having dynamic pressure fluid bearing

Abstract: A spindle motor ( 51 ) is composed of a rotor section ( 12 ) a stator section ( 14 ) and a thrust dynamic pressure fluid bearing and a radial dynamic pressure fluid bearing for sustaining the rotor section ( 12 ) to be rotatable freely with respect to the stator section ( 14 ) by employing lubrication fluid ( 20 ), wherein the thrust dynamic pressure fluid bearing is provided with first and second thrust dynamic pressure fluid bearing sections (SB 1 , SB 2 ) each generating a dynamic pressure in a direction opposite to each other, and wherein the lubrication fluid ( 20 ) is filled in a filling section (M) as a prescribed gap provided between the rotor section ( 12 ) and the stator section ( 14 ), and wherein the filling section (M) is constituted by a first filling section (M 1 ) that links one end section ( 6 ) opened to the outside, the second thrust dynamic pressure fluid bearing section (SB 2 ), the first thrust dynamic pressure fluid bearing section (SB 1 ) and the radial dynamic pressure fluid bearing (RB 1 , RB 2 ) in order and a second filling section (M 2 ) that links a point allocated between the second and first thrust dynamic pressure fluid bearing sections (SB 2 , SB 1 ) and another point allocated between the first thrust dynamic pressure fluid bearing section (SB 1 ) and the radial dynamic pressure fluid bearing (RB 1 ) in the first filling section (M 1 ).

Applying the Local Dynamic Similarity Model and CFD for the Study of Cross-Ventilation

Abstract: The Local Dynamic Similarity Model (LDSM) is a ventilation model for predicting the discharge coefficient and the inflow angle at the opening of a cross-ventilated building. This model requires a dynamic pressure generated by the wind velocity component tangential to the opening in addition to wind pressure. Also, total pressure, wind pressure, static pressure, room pressure and inflow velocity components are needed for model validation. Under cross-ventilation, it is rather difficult to measure these parameters, especially the total pressure and the velocity components at the opening, as the inflow angle is not known a priori. Therefore, an alternative was sought. This study applied a CFD method to determine the required parameters as a way of using the local dynamic similarity model. The CFD method had been validated with experimental results before the CFD data was used for LDSM. Good agreement was obtained between CFD and LDSM. Consequently the LDSM was also verified by CFD and it was viable t...

Methods, systems and apparatus for measuring acoustic pressure

Abstract: A hydrophone (10) for immersion in a liquid body defining a pressure is disclosed The hydrophone (10) includes a sensor (11) for providing an electrical signal indicative of the pressure; and a transducer (12) electrically connected to the sensor (11). The transducer (12) acts upon a fibre optic cable (15) so as to convert the electrical signal into a corresponding optical output signal for transmission within the fibre optic cable (15). The liquid body defines a depth-dependent static pressure and a dynamic pressure and the sensor (11) provides an electrical signal having a first component indicative of the static pressure and a second component indicative of the dynamic pressure. A filter (16) is electrically connected to the sensor (11) so as to receive (he electrical signal, filter out the first component, and output to the transducer (12) a uttered electrical signal indicative of substantially only the second component.