Showing papers on "Dynamic pressure published in 1987"
TL;DR: Symmetric finite element formulations are proposed for the primitive-variables form of the Stokes equations and shown to be convergent for any combination of pressure and velocity interpolations as mentioned in this paper.
Abstract: Symmetric finite element formulations are proposed for the primitive-variables form of the Stokes equations and shown to be convergent for any combination of pressure and velocity interpolations. Various boundary conditions, such as pressure, are accommodated.
415 citations
TL;DR: In this article, a simple theoretical procedure is presented for the analysis of a free-free beam which is made from a rigid-perfectly plastic material and subjected to a dynamic pressure pulse.
54 citations
TL;DR: In this article, the authors investigated dynamic active earth pressures against rigid retaining structures with dry cohesionless backfill based on the observations of the shaking table model experiment with different wall movement modes.
50 citations
TL;DR: A review of previous experimental measurements of squeeze film damper (SFD) forces is given in this paper, where the effect of fluid inertia on the pressure fields and forces is found to be significant.
Abstract: A review of previous experimental measurements of squeeze film damper (SFD) forces is given. Measurements by the authors of SFD pressure fields and force coefficients, for circular centered orbits with epsilon = 0.5, are described and compared with computer predictions. For Reynolds numbers over the range 2-6, the effect of fluid inertia on the pressure fields and forces is found to be significant.
47 citations
Patent•
22 Jan 1987
TL;DR: In this paper, a dynamic pressure gas bearing device in a rotational unit was designed such that an operating gas generated by the dynamic pressure groove formed between the fixed shaft and the rotational member is directed into a pressure chamber between the ground and the rotating member.
Abstract: Disclosed is a dynamic pressure gas bearing device in a rotational unit in which a rotational member put on a cantilevered fixed shaft is designed such that an operating gas generated by a dynamic pressure groove formed between the fixed shaft and the rotational member is directed into a pressure chamber between the fixed shaft and the rotational member and supports the rotational member in the thrust direction and that the pressure in the pressure chamber is adjusted by a hole formed in the fixed shaft or the rotational member.
26 citations
TL;DR: In this article, the variation of the average low altitude dayside ionospheric magnetisation with solar wind dynamic pressure was studied using the magnetometer measurements from the Pioneer Venus Orbiter.
Abstract: The variation of the average low altitude dayside ionospheric magnetisation with solar wind dynamic pressure is studied using the magnetometer measurements from the Pioneer Venus Orbiter. The data analysed, includes the first three dayside periapsis passes by the orbiter Passes with even low magnetisation values have been included in the analysis. The results indicate a statistically linear relationship between the ionospheric magnetisation and the solar wind dynamic pressure even below the critical pressure for magnetisation adopted earlier by Phillips et al. (1984). Also similar features in the low altitude magnetic field structure are seen to persist for the whole range of solar wind pressures. These observations point to a continuous rather than time evolving mechanism of generation of ionospheric magnetic fields on Venus.
18 citations
TL;DR: In this article, the steady state flow resistance of face sheets on fully assembled acoustic duct liners is measured by subjecting the liner to a sinusoidal acoustic pressure field at the face sheet surface.
Abstract: Apparatus and method for determining the steady state flow resistance of face sheets on fully assembled acoustic duct liners. Resistance is measured by subjecting the liner to a sinusoidal acoustic pressure field at the face sheet surface. The pressure field is applied through a cylindrical waveguide and is measured by a pressure transducer flush mounted on the inside of the waveguide near the liner face. A second pressure measurement, obtained by a similar transducer positioned further from the face, is combined with the first measurement to calculate the acoustic resistance for the excitation frequency. If the excitation frequency coincides with the resonant frequency of the liner configuration, then no significant pressure exists on the back surface of the liner face sheet. For this condition the root mean square (rms) pressure measured at the face sheet is equated to the static pressure drop used to obtain the steady state flow resistance. The rms velocity of the oscillating pressure wave is calculated from the ratio of the rms pressure to resistance. A repetition of the procedure for several magnitudes of dynamic pressure permits the development of a curve which describes the non-linear characteristics of resistance with changes in velocity. This curve may be equated to a similar curve obtained using steady state flow resistance measurements of the liner in its partially assembled state without a backing surface.
13 citations
01 Oct 1987
TL;DR: A brief review of available research in these areas with a description of work under way at Langley Research Center is given in this paper, where a brief review is given of the available research.
Abstract: Aeroacoustic fatigue is anticipated to control the design of significant portions of the structures of high-speed vehicles. This is due to contemplated long-duration flights at high dynamic pressures and Mach numbers with related high skin temperatures. Fluctuating pressure loads are comparatively small beneath attached turbulent boundary layers, but become important in regions of flow separation such as compression and expansion corners on elevons and rudders. The most intense loads are due to shock/boundary-layer interaction. These flows may occur in the engine-exhaust wall jet and in flows over control surfaces. A brief review is given of available research in these areas with a description of work under way at Langley Research Center.
9 citations
TL;DR: In this paper, a spherical static pressure probe was developed and tested for 3D flow simulations, and the spherical probe was shown to be relatively insensitive to both yaw and turbulence, limiting static pressure errors to less than 5% over a 3D range of incident angles of at least ± 20°.
8 citations
01 Dec 1987
TL;DR: The 40-by-80-foot wind tunnel circuit of the National Full-Scale Aerodynamic Complex (NFAC) has recently undergone major modifications and subsequently completed final acceptance testing as mentioned in this paper.
Abstract: The 40- by 80-foot wind tunnel circuit of the National Full-Scale Aerodynamic Complex (NFAC) has recently undergone major modifications and subsequently completed final acceptance testing. The initial testing and calibration of the wind tunnel are described and in many cases these results are compared with predictions derived from model tests and theoretical analyses. The wind tunnel meets or exceeds essentially all performance objectives. The facility runs smoothly and routinely at its maximum test-section velocity of 300 knots (Mach number = 0.45). An effective cooling air exchange system enables the wind tunnel to operate indefinitely at this maximum power condition. Throughout the operating envelope of the wind tunnel the test-section dynamic pressure is uniform to within + or - 0.5 deg, and the axial component of turbulence is generally less than 0.5 percent. Acoustic measurements indicate that, due to the low noise fans and acoustic treatment in the wind-tunnel circuit and test section, the background noise level in the test section is comparable to other large-scale acoustic wind tunnels in the United States and abroad.
7 citations
19 Oct 1987
TL;DR: In this article, the effects of unsteady (dynamic) and steady (static) pressure waves in a cavity at subsonic Mach numbers through transonic Mach numbers were studied.
Abstract: : In order to study the effects of unsteady (dynamic) and steady (static) pressure waves in a cavity at subsonic Mach numbers through transonic Mach numbers, an experimental test program, using a splitter plate and a generic cavity, was conducted. Since most cavities associated with air vehicles house sensors, equipment, or armament, ogive cylinder models were also fabricated and tested inside the cavity to determine their effect on the static and dynamic pressure measurements on the cavity ceiling and walls. The intent of the experiment was to document the effects on steady and unsteady pressures by varying parameters such as the Mach number, cavity dimensions, blockage, and cavity angle of attack. These results will provide engineers with a technology base to aid in the formulation of design requirements and preliminary designs for future air vehicles requiring external cavities. The value of this research is that it provides a more detailed and extensive data base for engineers to utilize during early stages of air vehicle design requiring the utilization of internal design requiring the utilization of internal cavities. Additional tests are currently being planned which will extend this technology data base even further to include aeroacoustic suppressors, cavity doors, and supersonic Mach number effects.
Patent•
15 Dec 1987
TL;DR: In this article, a sliding plate 4 forms a spiral groove on its slide contact surface for generating a dynamic pressure and the action of the dynamic pressure generating spiral groove 11, which forms a thin film of fluid in a sliding part, causes the sliding plate4 to substantially make a relatively rotating motion with a bearing plate 9 preventing both the plates from coming into solid contact with each other.
Abstract: PURPOSE:To permit a large thrust load to be supported, by forming a groove in either a sliding plate or a bearing plate and generating the dynamic pressure of fluid between two flat surfaces of ceramics which come into slide contact with cach other. CONSTITUTION:A sliding plate 4 forms on its slide contact surface a spiral groove 11 for generating a dynamic pressure. And the action of the dynamic pressure generating spiral groove 11, which forms a thin film of fluid in a sliding part, causes the sliding plate 4 to substantially make a relatively rotating motion with a bearing plate 9 preventing both the plates from coming into solid contact with each other. Since a dynamic pressure is generated in the sliding part as a whole, the bending moment in accordance with the dynamic pressure acts on the sliding plate 4 and the bearing plate 9. A back surface of the bearing plate 9 is supported by an elastic member 8 almost over the whole surface. Accordingly, a large thrust load can be supported by small decreasing a deformation amount of the bearing plate 9 due to the dynamic pressure preventing the thrust load from locally concentrating.
TL;DR: In this paper, the aerodynamic interference between high cooling towers in the atmospheric boundary layer (ABL) and uniform flow has been discussed and the similarity condition of the cooling tower in the ABL, the simulation results of a single tower and some typical tower groups have been provided.
Abstract: Aerodynamic interference between high cooling towers in the atmospheric boundary layer (ABL) and uniform flow has been discussed. For the 1/1000 ABL model set up in the 2.25m low speed wind tunnel at Peking University, the similarity condition of the cooling tower in the ABL, the simulation results of a single tower and some typical tower groups have been provided. Experiments showed that the Circumferential pressure distributions were consistent between the smooth model tower and the prototype tower, and between the rough model tower and the prototype tower with ribs; the two dimensional characteristics in the circumferential pressure distribution were also noticeable around the middle 1/3 part of the tower after nondimensionalization by local dynamic pressure. Results demonstrate that, in the flow with strong turbulence the lift coefficient of the downstream cylinder approaches 0.4. In the flow with weak turbulence, the pressure distribution reflects a strong nonsymmetry, and the lift coefficient or stagnation pressure of the downstream cylinder switches alternately between 1 and 0, where a concentrated vortex rolls up and then sheds toward the front of the downstream cylinder and exerts a decisive influence on the aerodynamic properties of the downstream cylinder.
Patent•
22 Oct 1987
TL;DR: In this article, a servo mechanism is used to adjust the supply pressure of a slide-guide according to the output from a detector for detecting relative inclination between a guide face and a slide face.
Abstract: PURPOSE:To enable face pressure to be constant between a dynamic slip guide and a slide substance by providing a servo mechanism for adjusting the supply pressure of pressurized oil according to output from a detector for detecting relative inclination between a guide face and a slide face. CONSTITUTION:Servo valves 407 and 108 are being supplied with pressurized oil from a hydraulic source on a predetermined supply pressure Ps. The servo valves 407 and 408 feed pressurized oil to static pressure pockets 313-316 through a throttle in proportion to instruction values from servo amplifiers 409 and 410. When a grinder axis head 101 is free from moment, clearances between the land of a static pressure plate 207 and lower portions. Also, a force generated at said faces 205-206 presses dynamic pressure slide guide faces 201-204. When moment has been applied to the grinder axis head 101, this head 101 inclines and the aforementioned clearances give a change. The servo valve 407 and 408, however, work to apply such moment to the grinder axis head 101 as to correct the inclination thereof and the posture of said head 101 returns to an original position.
Patent•
13 Nov 1987
TL;DR: In this article, a pressure pulsation and transient pressure change or a flow change are generated in a main steam pipe and a pressure wave corresponding thereto is propagated in the pipelines 7 and 12.
Abstract: PURPOSE:To enable the variate element of a fluid to be measured with a high reliability by providing a lead piping with a pressure pulsation preventing device having a plurality of communication holes to decrease the effect of a pressure pulsation. CONSTITUTION:Pressure pulsation preventing devices 26 are provided in lead pipings 7 and 12 connected to the high pressure side detector 8 and the low pressure side detector 13 of a flowmeter 14, respectively. Each preventing device 26 is formed with a plurality of thin communication holes 28, 28... in parallel to one another in the longitudinal direction of the device 26 and threadedly connected to the lead piping 7 or 12. Thus, when a pressure pulsation and a transient pressure change or a flow change are generated in a main steam pipe 2, a pressure wave corresponding thereto is propagated in the pipelines 7 and 12. The pressure change due to the pressure wave reaches a plurality of the holes 28 of the preventing devices 26 and the pressure pulsation of a fluid is damped by the restriction effect of the holes 28, 28... to suppress a dynamic pressure propagation. Accordingly, an always stable and accurate flow rate measurement can be conducted.
TL;DR: In this article, the effect of dynamic deformation on bearing dynamic properties and stability is unnegligible for softer bearing materials, and the two cross damping coefficients differ from each other, instead of being equal as predicted by the theory for stationary contours.
Abstract: Reynolds equation and deformation equation are derived in complex form for the dynamic increment of oil film pressure and bearing surface dynamic deformation. The complex amplitudes of dynamic pressure and deformation differentiated with respect to journal motions are solved by numerical methods with iterations between them, and the whirl ratio at stability threshold is found by further iterations, wherefrom the dynamic properties relevant to stability threshold are calculated and from the stability characteristics. It is concluded that the effect of dynamic deformation on bearing dynamic properties and stability is unnegligible for softer bearing materials. It is also shown that the two cross damping coefficients differ from each other, instead of being equal as predicted by the theory for stationary contours.
01 Jan 1987
27 Oct 1987
TL;DR: In this paper, a lumped parameter ballistic model is proposed to determine the velocity of a single projectile in a ballistic model, based on the relationship between the computed parameter, the space mean pressure, and the parameter defining the projectile motion, the pressure acting on the base of the projectile.
Abstract: : A very important factor in determining the projectile acceleration in a lumped parameter ballistic model is the relationship between the computed parameter, the space mean pressure, and the parameter defining the projectile motion, the pressure acting on the base of the projectile. The gradients of pressure and density from the breech to projectile were postulated to depend on the term, projectile acceleration times axial position. The model compared favorably with experimental measurements of downbore to chamber pressure ratios. Keywords: Interior ballistics, Gas gradients.
01 Nov 1987
TL;DR: In this article, the inviscid embedded Newtonian theory was used to predict the effects of nose bluntness, flare geometry, angle of attack and center of gravity position on single-degree-of-freedom oscillatory motions.
Abstract: : The stability of oscillatory motions of vehicles flying at hypersonic Mach numbers is of considerable relevance to their initial design. Methods are needed for quick and accurate predictions of stability and control which are applicable over a wide range of body shapes, angles of attack and flow conditions, without the need to resort to computationally time consuming numerical flow field calculation methods. The purpose of this paper is to present experimental data, obtained over a range of angles of attack, concerning the static and dynamic pitching stability of a wide range of both pointed and blunted axisymmetric shapes including cones and blunted cylinder flares. These data have been obtained from free oscillation experiments at M = 6.85 in a short duration free piston driven hypersonic wind tunnel. Inviscid embedded Newtonian theory, which accounts for the reduced dynamic pressure and lower flow velocity in the embedded flow downstream of the strong bow shock, provides surprisingly good agreement with the experimental data over a wide range of conditions. A particular aspect is the ability of the inviscid embedded Newtonian theory to predict the effects of nose bluntness, flare geometry, angle of attack and centre of gravity position on single-degree-of-freedom oscillatory motions. Comparisons with experimental results show the broad flow features and their effect on static and dynamic stability are well described in regimes not containing flow structural change. However, in some cases discrepancies exist between the predictions and experimental observations and these have been attributed to a variety of viscous flow phenomena involving boundary layer transition and flow separation, including complex lee surface vortical flows.
Patent•
13 Mar 1987
TL;DR: In this article, a tool body is rotated in X, Y, and Z directions while being rotated, and the dynamic pressure generating part 7 generates a dynamic pressure effect, drawing in the atmosphere containing fine powder particles.
Abstract: PURPOSE:To favorably generate a flow of fluid containing fine powder particles on a surface to be machined and carry out highly accurate machining by forming a dynamic pressure generating part which generates a dynamic pressure effect and draws in said fine powder particles together with the atmosphere, by means of the rotation of a tool body. CONSTITUTION:The dynamic pressure generating part 7 of a tool body 1 is opposite to the surface of a workpiece 5 at an interval of 3-20mum, i.e., an interval at which the dynamic pressure generating part 7 can securely generate a dynamic pressure effect, and the tool body 1 is moved in X, Y, and Z directions while being rotated. As the tool body 1 is rotated, its dynamic pressure generating part 7 generates a dynamic pressure effect, drawing in the atmosphere containing fine powder particles 2. Accordingly, due to this flow of the atmosphere, the fine powder particles 2 in the atmosphere favorably polish the part of a workpiece 5 opposite to the dynamic pressure generating part 7.
Patent•
10 Sep 1987
TL;DR: In this paper, the authors present a method to determine the direction of the flow, the static pressure, the dynamic pressure, or the rate of flow using the measured pressure values.
Abstract: Probe for measuring fluid flows, having measurement chambers (1, 2, 3, 5) with rectangular or slot-shaped openings which are essentially arranged along a circular arc or along the periphery of a circle, in which chambers it is possible in each case for dynamic pressures to form under the influence of the flow, and having measuring devices for determining the pressure in the measurement chamber and/or for determining pressure differences between two measurement chambers or pressure-measuring lines in a rear region of each measurement chamber, which are guided out of the probe separately or after being brought together with other pressure-measuring lines of other measurement chambers. A method is specified as to how the measured pressure values or differences in measured pressure values can be used to determine the direction of the flow, the static pressure, the dynamic pressure or the rate of flow.
Patent•
15 Jul 1987
TL;DR: In this paper, a gas passage near a gas inlet was constricted by an action of a nozzle to increase the mass flow of a laser oscillator by constricting the passage near the electrode on the upstream side of the gas.
Abstract: PURPOSE:To increase a mass flow of a laser osicllator by constricting a gas passage near the electrode on the upstream side of the gas so that a gas static pressure near a gas inlet from a high differential pressure blower becomes lower than that near a gas inlet from a turbo-blower CONSTITUTION:A gas passage near a gas inlet 22 near an electrode 8 on upstream side of the gas which is opened to a high differential pressure blower 2 is constricted by an action of a nozzle 7 The degree of that constriction is such that a gas static pressure of that part becomes lower than that near a gas inlet 20 opened to a turbo-blower 1 When a voltage is applied between the electrodes 8 and 11, an initial glow discharge 9 of torch form occurs from the front end of the bar-shaped electrode 8 and a glow discharge is produced in a discharge tube 12 If an internal diameter of the nozzle 7 is changed to be constricted, a static pressure is changed into a dynamic pressure in the vicinity of the gas inlet 21 and the static pressure decreases to increase a laser output rapidly
Patent•
02 Jul 1987
TL;DR: In this paper, a safety standpipe for the protection of distant-heating systems against dynamic pressure loads is proposed, which is usable in all hydraulic networks in which, for example owing to pump failure, dynamic pressure changes occur in the hydraulic system, which lead to inadmissible pressure increases.
Abstract: The invention relates to a safety standpipe for the protection of distant-heating systems against dynamic pressure loads and is usable in all hydraulic networks in which, for example owing to pump failure, dynamic pressure changes occur in the hydraulic system, which lead to inadmissible pressure increases. The aim of the invention consists in proposing a solution, complying with safety regulations, for damping dynamic hydraulic processes which is simple in design and has a high degree of reliability and low technical outlay. The object of the invention is to propose a safety standpipe which, even before the maximum pressure limit is reached, allows defined feeding of the heating medium, operates without feeding to the environment and has a characteristic which is different in the pressure drop than in the pressure rise. According to the invention, the object is achieved in that the standpipe is interrupted and water can escape into a vessel surrounding the standpipe at the points of interruption.
TL;DR: In this article, a pressure dataset with an estimated absolute accuracy of 0.3 hPa and a relative accuracy of about 0.1 hPa was compiled based on pre-and post-experiment laboratory and on biweekly field calibrations.
Abstract: During the ALPEX field program, pressure was measured along three Alpine cross sections. In order to attain high accuracy, pressure sensors had to be protected against the influence of wind-induced dynamic pressure effects and against gravity wave signals. Corrections based on pre- and postexperiment laboratory and on biweekly field calibrations enabled the compilation of a pressure dataset with an estimated absolute accuracy of 0.3 hPa and a relative accuracy of about 0.1 hPa. Time series plots and time-space plots of the data were generated for quality control purposes.
01 Jan 1987
TL;DR: In this article, a nonlinear mathematical model for the transmission of a sinusoidal pressure pulse through an elastic straight tube with circular cross-section is presented. But the model is limited to the case where the transducers are long elastic tubes connecting the point of measurement and the pressure transducer.
Abstract: The present paper describes a nonlinear mathematical model for the pressure-pulse transmission through an elastic straight tube with circular cross-section. The distortion of a sinusoidal pressure pulse in dimensionless form depends on two parameters, the Strouhal number and the Euler number. The analysis is useful to the correction of the errors which enter in the measurement of the dynamic pressure when long elastic tubes connecting the point of measurement and the pressure transducer are used.
Patent•
10 Jun 1987
TL;DR: In this paper, a control valve with the range of the pressure has unequal valve opening pressure and valve closing pressure, which can reduce the system impact and increase the stability being used for a back pressure valve, an overflow valve, etc.
Abstract: The utility model relates to a control valve with range of pressure, which is provided with two stages of slide cores. Namely, the control valve with the range of the pressure is provided with a first stage slide core [2] and a second stage slide core [5]. The control valve with the range of the pressure has unequal valve opening pressure and valve closing pressure. Besides, in the special loop, the control valve with the range of the pressure can reduce the system impact and increases the stability being used for a back pressure valve, an overflow valve, etc. the utility model has the advantages of energy saving, long service life, energy saving and long service life. If the control valve with the range of the pressure is used for the overflow valve of a low-pressure big flow pump in a double-pump speed regulation loop, or used for a load discharging valve in a pressure-holding load-discharging loop, the control valve with the range of the pressure can realize the dynamic pressure holding. When a plurality of cylinders work in positive direction and synchronously or in negative direction and in sequence, a plurality of valves are connected in series or connected in parallel, which can compose the loop having definite logic functions.
TL;DR: In this article, a plexiglass channel-cavity model was inserted within the test section of a wind tunnel and a pressure transducer was mounted along the upstream wall of the cavity and was used to monitor, with the help of an oscilloscope, the pressure fluctuations within the cavity.
Abstract: The pressure oscillations within a two-dimensional, rectangular cavity have been explored. The flow was subsonic and the chord-to-depth ratio of the cavity ranged between 0.25 and 1.25. The experimental setup, comprised a plexiglass channel-cavity model, was inserted within the test section of a wind tunnel. The moveable walls of the cavity were adjusted for various cavity geometries. A pressure transducer was flush mounted along the upstream wall of the cavity and was used to monitor, with the help of an oscilloscope, the pressure fluctuations within the cavity. Within a Strouhal number range of 0.4 - 2.4, periodic pressure fluctuations as high as 50% of the free-stream dynamic pressure were observed. The modulation of the external flow is influenced by the cavity which acts as a simple harmonic oscillator with a certain natural frequency. As the velocity of the external flow is increased gradually, the frequency of the pressure fluctuations experiences step changes, shifting to higher or lower frequency levels. Of the two parameters describing the cavity geometry and their effects on pressure oscillations, the cavity length appears to influence the frequency, and the cavity depth effects the amplitude. The maximum amplitude of the pressure oscillations within the cavity were observed to occur under mode 2 and for a cavity geometry corresponding to a chord-to-depth ratio of about 0.5.
TL;DR: The effect of various ways of approximating velocity-pressure-gradient data on the computation of pressure fields in a grain bin is studied in this paper, where the experimental data are also approximated by a cubic spline.
01 Jan 1987
TL;DR: In this article, the effect of nose shape on two flare stabilized projectiles was studied using a parabolized Navier-Stokes code, and different flow field values of pressure, local Mach number, and dynamic pressure were generated by the two different nose configurations.
Abstract: The effect of nose shape on two flare stabilized projectiles was studied using a Parabolized Navier-Stokes code. Pressure coefficients, forces and moments, skin friction coefficients, and Stanton number calculations are presented for the hemisphere-cylinder-flare and the cone-cylinder-flare configurations. Pitching moment and static margin plots versus flare angles and flare lengths are presented in a parametric study to show aerodynamic stability effects. Distinctly different flow field values of pressure, local Mach number, and dynamic pressure were generated by the two different nose configurations. These flow field values just upstream of the flare will be examined. The code demonstrated its value as a design tool by making a clear distinction between aerodynamically stable characteristics for this variety of nose shapes, flare angles, and flare lengths.