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Showing papers on "Pressure gradient published in 1980"


Journal ArticleDOI
TL;DR: In this paper, the natural transition of boundary layers is investigated for a flat plate in a low-speed wind tunnel with free-stream turbulence intensities ranging from 0.3 to 5 per cent.
Abstract: Natural transition of boundary layers is investigated for a flat plate in a low-speed wind tunnel with free-stream turbulence intensities ranging from 0.3 to 5 per cent, and with pressure-gradient ...

727 citations


Journal ArticleDOI
TL;DR: In this paper, an idealized problem has been solved for onedimensional, unsteady, non-isothermal flow of polymer between two parallel plates and the subsequent nonisothermal relaxation following cessation of flow.
Abstract: By using theLeonov viscoelastic constitutive equation, an idealized problem has been solved for onedimensional, unsteady, non-isothermal flow of polymer between two parallel plates and the subsequent non-isothermal relaxation following cessation of flow. Numerical results are presented for the time dependence of the pressure gradient, the gapwise distribution of linear velocity, shear rate, shear stress and normalstress differences, together with the components of birefringence in different planes. Comparison of the present predictions for the pressure gradient with results based upon an “inelastic” model indicate close agreement whereas the corresponding predictions for normal-stress differences are found to be markedly different from those for the “inelastic” case.

141 citations


Journal ArticleDOI
M. L. Booy1
TL;DR: In this paper, a mathematical model for isothermal flow of a Newtonian liquid through corotating twin screw equipment is derived for two different flow regimes: the first regime is completely filled with liquid, and the second regime is partly full.
Abstract: A mathematical model is derived for isothermal flow of a Newtonian liquid through corotating twin screw equipment. Two different flow regimes are studied. In the first, channels of twin screw equipment are completely filled with liquid, generate a pressure gradient, and provide a discharge pressure at the end of the pump. Equations are given for drag flow rate, pressure backflow rate, and flow rate through the nip zone. It is shown how the analysis of single screw pumps can be modified for twin-screw pumps. In the second regime channels are partly full, which is the case with extraction equipment. Equations show how the degree of fill in the equipment changes with flow rate, speed, and dimensions.

109 citations


Journal ArticleDOI
TL;DR: In this article, the authors explored the possibility of steady isothermal or adiabatic flows, driven by a pressure difference between the loop feet, and provided a possible explanation for the cool cores that are sometimes observed in coronal loops.
Abstract: It is now known that the corona is filled with a multitude of loop-like structures. The likelihood of these loops being in static equilibrium is small and so this paper explores the possibility of steady isothermal or adiabatic flows, driven by a pressure difference between the loop feet. For a symmetric loop the flow becomes supersonic at the summit and is then retarded by a shock-wave at some point on the downflowing leg. The effect of adiabatic flow is to lower both pressure and temperature by at least a factor of two and so provide a possible explanation for the cool cores that are sometimes observed in coronal loops.

108 citations


Journal ArticleDOI
TL;DR: In this paper, the nonlinear evolution of the ion pressure gradient driven drift wave instability is investigated through three-dimensional fluid simulations, and anomalous thermal transport produced in the saturated state is reported as a function of the system parameters.
Abstract: The nonlinear evolution of the ion pressure gradient driven drift wave instability is investigated through three-dimensional fluid simulations. The anomalous thermal transport produced in the saturated state is reported as a function of the system parameters.

94 citations


Journal ArticleDOI
01 Jul 1980
TL;DR: In this article, the dynamics of equatorial currents are considered in the light of the wind and current measurement at Gan (0.5°S, 73°E) reported by Knox (Deep-Sea Research, 23, 211-221, 1976).
Abstract: The dynamics of equatorial currents are considered in the light of the wind and current measurement at Gan (0.5°S, 73°E) reported by Knox ( Deep-Sea Research , 23 , 211–221, 1976). For westerly and meridional winds the response of equatorial currents is predominantly local and rapid. It follows that the current reversals observed at Gan are most likely due to changes in the local winds and not to a reflection from the eastern boundary, as was previously suggested. The winds at Gan are predominantly westerly, resulting in downwelling at the equator. The eastward momentum put in by the wind at the surface is advected downward giving subsurface eastward flow. With persistent easterlies (as in the Atlantic and Pacific) there is an undercurrent driven by the eastward pressure gradient force, both because of the direct, down gradient flow and because of the vorticity transported by the associated meridional circulation. It is suggested that the undercurrent that has been observed in the Indian Ocean in the early spring is similarly driven by an eastward pressure force. This pressure gradient is a non-local transient feature generated by the zonal readjustment of mass induced by the relaxation of the winds at the fall monsson transition. This idea is consistent with the presence of the undercurrent in 1973 and its absence in 1974.

92 citations


Journal ArticleDOI
TL;DR: In this paper, the authors used the Hansen and Rattray classification of the Columbia River Estuary at low discharge to estimate the diffusive fraction of the upstream salt flux in reasonable agreement with the observed values, and they also provided reasonable estimates of P and F m for low discharge condition but for high discharge only the estimate of P is reasonable.

92 citations


Journal ArticleDOI
TL;DR: In the present experiment velocity profiles have been measured in and around the region of separated flow, showing a large influence of adverse pressure gradient on the reattaching flow over a rearward-facing step that has not been reported previously.
Abstract: The turbulent, incompressible reattaching flow over a rearward-facing step has been studied by many researchers over the years. One of the principal quantities determined in these experiments has been the distance from the step to the point (or region) where the separated shear layer reattaches to the surface (x(r)). The values for x(r)/h, where h is the step height, have covered a wider range than can reasonably be attributed to experimental technique or inaccuracy. Often the reason for a largely different value of x(r)/h can be attributed to an incompletely developed turbulent layer, or a transitional or laminar boundary layer. However, for the majority of experiments where the boundary layer is believed to be fully developed and turbulent, x(r)/h still varies several step heights; generally, 5 1/2 approximately < x(r)/h approximately < 7 1/2. This observed variation has usually been attributed to such variables as l/h (step length to height, h/delta (step height to initial boundary-layer thickness), R(e)(theta)), or the experimental technique for determining reattachment location. However, there are so many different combinations of variables in the previous experiments that it was not possible to sort out the effects of particular conditions on the location of reattachment. In the present experiment velocity profiles have been measured in and around the region of separated flow. Results show a large influence of adverse pressure gradient on the reattaching flow over a rearward-facing step that has not been reported previously. Further, the many previous experiments for fully developed, turbulent flow in parallel-walled channels have shown a range of reattachment location that has not been explained by differences in initial flow conditions. Although these initial flow conditions might contribute to the observed variation of reattachment location, it appears that the pressure gradient effect can explain most of that variation.

90 citations


Journal ArticleDOI
TL;DR: In this article, a new perspective of the dynamics of a tropical cyclone eye is given in which eye subsidence and the adiabatic warming accompanying it are accounted for directly from the equations of motion.
Abstract: A new perspective of the dynamics of a tropical cyclone eye is given in which eye subsidence and the adiabatic warming accompanying it are accounted for directly from the equations of motion. Subsidence is driven by an adverse, axial gradient of perturbation pressure which is associated principally with the decay and/or radial spread of the tangential wind field with height at those levels of the cyclone where the tangential winds are approximately in gradient wind balance. However, this pressure gradient is almost exactly opposed by the buoyancy force field due to adiabatic warming. This corroborates with observational data. The relationship between the present view of eye dynamics and those of Malkus and Kuo and a recent study by Willoughby is discussed in detail.

77 citations


Journal ArticleDOI
TL;DR: The isothermal flow of a Newtonian liquid in a co-rotating twin screw extruder having screw elements with three tips has been analyzed when the effect of the intermeshing zone on flow can be neglected.
Abstract: The isothermal flow of a Newtonian liquid in a co-rotating twin screw extruder having screw elements with three tips has been analyzed when the effect of the intermeshing zone on flow can be neglected. It was found that values for four dimensionless parameters must be specified in order to obtain a unique relationship between the dimensionless axial pressure gradient and the dimensionless volumetric flow rate. These parameters included the number of screw tips, the helix angle, the ratio of the clearance to the screw radius, and the ratio of the distance between screw centers-to the screw radius Values for the dimensionless throughput and pressure gradient were computed for a range of helix angles at fixed values for all other dimensionless parameters. Shape factors were also computed and it was found that the shape-factor for pressure How is substantially less than that for drag flow. Asymptotic values for both these factors at large values of the channel width (large helix angles) were found to be less than unity.

74 citations


Journal ArticleDOI
TL;DR: A simple analytical dispersion relation that contains the main physical factors affecting an important class of these modes is given in this paper, where the authors also present a model for axisymmetric plasma columns.
Abstract: At finite ratios of the kinetic plasma pressure to the magnetic pressure, the magnetic confinement configurations of axisymmetric plasma columns tend to acquire characteristics that hinder the onset of instabilities driven by the combined effects of magnetic curvature and pressure gradient. A simple analytical dispersion relation that contains the main physical factors affecting an important class of these modes is given.

Journal ArticleDOI
TL;DR: In this paper, the effects of axial pressure gradients on the turbulent diffusion flame of a hydrogen jet issuing into a co-flowing air stream has been extended to include the effect of pressure gradient.
Abstract: Earlier work on the turbulent diffusion flame of a hydrogen jet issuing into a co-flowing air stream has been extended to include the effects of axial pressure gradients Pressure gradients with parameters of − 11 × 10−3, — 041 × 10−3 and +009 × 10−3 were produced by converging and diverging the floor and roof of the working section Laser-Doppler anemometer (LDA) measurements including mean velocities, turbulence intensities and Reynolds stress were made with only the jet seeded so that the measurements are of a turbulent zone average nature Both favourable (negative) and adverse pressure gradients shorten the flame A flame of elliptical cross-section was produced but the distortion is fully accounted for by the free stream strain and the results are presented in pseudo-axisymmetric form For favourable pressure gradient, the mean velocity profiles in the radial direction are closely similar to those found earlier for near-zero pressure gradient For the adverse pressure gradient, the mean

Journal ArticleDOI
TL;DR: In this article, a new balance for direct measurement of skin friction in turbulent boundary layers with severe pressure gradients was described, which was mainly used to investigate the error of the Preston tube in adverse pressure gradient, where the gaps between the floating element and the surrounding wall were filled with a liquid to eliminate disturbing pressure forces on the element.
Abstract: This paper describes a new balance, suitable for direct measurement of skin friction in turbulent boundary layers with severe pressure gradients. The gaps between the floating element and the surrounding wall are filled with a liquid in order to eliminate disturbing pressure forces on the element. The resulting friction forces are measured with piezo-electric transducers with high sensitivity and extremely small element displacement.Skin friction measurements were taken in the turbulent boundary layer of a wind tunnel with circular cross-section at M [les ] 0·25. Severe adverse pressure gradients were generated by means of a step on the wall or, alternatively, by a conical centre body.The new apparatus was mainly used to investigate the error of Preston tubes in adverse pressure gradients. It was necessary to develop a new measuring technique to improve the repeatability of the Preston tube readings.The Preston tube error was found to depend on both the local pressure gradient P = (dp/dx) ν/ρ3τ and on the Preston tube diameter uτd/ν and to be independent of the upstream pressure distribution for the range of parameters covered by the experiments.

Patent
24 Dec 1980
TL;DR: In this paper, a method and means to increase or decrease, on demand, the drag exerted by a fluid on a boundary is described. But the method is not suitable for the case of turbulent flow.
Abstract: Disclosed is a method and means to increase or decrease, on demand, the drag exerted by a fluid on a boundary. The boundary comprises a surface portion of a structure enclosing a moving fluid or may comprise a portion of the outer surface of an object moving through the fluid. Drag is varied by means of a set of piezoelectric sensors and an accompanying set of piezoelectric driver elements arranged in close proximity to one another at the boundary and electrically interconnected so that the pressure exerted by the moving fluid is sensed by one or more sensors and converted to an electrical signal which is then transformed into an electrical drive signal which is applied to one or more driver elements to cause a flexing of the driver element(s) in a predetermined direction so that drag is either reduced by moving the driver(s) away from the fluid or increased by moving the driver(s) towards the fluid. In the case of turbulent flow, drag is decreased by decreasing the pressure gradient in the fluid; that is, the drivers are moved away from the fluid in regions of high pressure and toward the fluid in regions of low pressure. The drag is increased by reversing these motions.

Journal ArticleDOI
TL;DR: In this paper, the authors examined the frequency response of optical fiber hydrophones for the range 100 Hz to 50 kHz and the observed frequency and coil orientation dependence of the pressure sensitivity is explained in terms of an approximate theoretical model.
Abstract: The frequency response of optical fiber hydrophones is examined both theoretically and experimentally. Previous models have considered only either static pressures or high‐frequency (axially constrained) perturbations. In the present study, the acoustic sensitivities for fiber coils (5‐cm‐diam, 10‐m total length) are given for the range 100 Hz to 50 kHz. The observed frequency and coil orientation dependence of the pressure sensitivity is explained in terms of an approximate theoretical model. According to this model the acoustic driving force on the coil is the sum of two terms, a surface pressure and a pressure gradient term, of opposite sign. It is assumed that only the lowest‐order radial mode of vibration leads to a net optical phase shift in the coil. The observed peaks in the pressure sensitivity of the coils are found to be in the vicinity of the resonance frequency for the lowest‐orderadial mode.

Journal ArticleDOI
TL;DR: In this article, the wall static pressure fields beneath tornado-like vortices have been investigated using a large vortex generator especially designed to model tornado cyclone airflow, and the data include both a series of radial profiles across the mean pressure field under a variety of flow conditions, and a detailed investigation of the magnitude of the central pressure as a function of swirl.
Abstract: The wall static pressure fields beneath tornado-like vortices have been investigated using a large vortex generator especially designed to model tornado cyclone airflow. Presented in nondimensional form, the data include both a series of radial profiles across the mean pressure field under a variety of flow conditions, and a detailed investigation of the magnitude of the central pressure as a function of swirl. The profiles clearly show the development of the intense vortical core from the no-swirl state, and the evolution of the core from a one-celled into a two-celled flow. For the experimental range examined, it is found that the greatest pressure deficits and largest pressure gradients (in the mean field) are associated with single-celled vortices. Strong evidence is found for the existence of a dynamically induced downdraft in the two-celled vortex.

Journal ArticleDOI
TL;DR: In this paper, a simple model of the observed phenomena is a sloping plane beach acted upon by cross-shore wind, varying sinusoidally in the longshore direction, and a parabolic equation is found to govern steady state flow, expressing a balance of vorticity tendencies due to cross-isobath flow, curl of bottom stress and any forcing.
Abstract: Observations of currents 12 km south of the Long Island coast show that strong offshore winds could generate considerable longshore nontidal flow well below any surface Ekman drift. A momentum balance calculation in the longshore direction shows a surface level gradient of order 10/sup -6/ to be the proximate cause of the longshore flow. A very simple model of the observed phenomena is a sloping plane beach acted upon by cross-shore wind, varying sinusoidally in the longshore direction. With bottom friction parameterized by a linear law, a parabolic equation is found to govern steady state flow, expressing a balance of vorticity tendencies due to cross-isobath flow, curl of bottom stress and any forcing. Calculated solutions for variable cross-shore wind show a trapped pressure field on the inner shelf which controls the transition between an essentially frictionless momentum balance on the outer shelf to frictionally dominated flow at the shore. Realistic estimates of the parameters entering the theory suggest that the longshore gradients associated with the trapped inner shelf field are of the correct order of magnitude to explain the generation of longshore flow by a system of cross-shore winds.

Journal ArticleDOI
TL;DR: Theoretical consideration is given to two unsteady pipe flows in this paper, where a combined steady and oscillatory shear flow is generated by a pulsatile pressure gradient in a stationary pipe.
Abstract: Theoretical consideration is given to two unsteady pipe flows. In the first, a combined steady and oscillatory shear flow is generated by a pulsatile pressure gradient in a stationary pipe. In the second, the pressure gradient is constant, but the pipe wall executes axial vibrations.

Journal ArticleDOI
TL;DR: In this article, an attempt is made to study the unsteady flow or an incompressible viscous fluid with uniform distribution of dust particles between two parallel plates under an impulsive pressure gradient.
Abstract: In the present investigation, an attempt is made to study the unsteady flow or an incompressible viscous fluid with uniform distribution of dust particles between two parallel plates under an impulsive pressure gradient. Analytical expressions for velocities of the fluid and the dust particles have been obtained. The variation of total fluxes for fluid and dust particles has been discussed. The influence on skin friction has been noticed.

Journal ArticleDOI
TL;DR: The steady state solution for the interaction of an isotropic stellar wind with a homogeneous, isothermal nebular environment is a spherical cavity, filled by unshocked stellar wind, and bounded by a shock as mentioned in this paper.
Abstract: The steady state solution for the interaction of an isotropic stellar wind with a homogeneous, isothermal nebular environment is a spherical cavity, filled by unshocked stellar wind, and bounded by a shock. The radius of the shock is determined by the condition of balance between the ram pressure of the wind and the ambient gas pressure. In this paper we consider the interaction of an isotropic stellar wind with a nebular environment having a pressure gradient. This situation is expected to apply for recently formed stars located at the edge of a dark cloud. The resulting static configurations are ovoid-shaped cavities with the star located near the tip closer to the high-density region. The stellar wind suffers a first shock against the oblique walls of the configuration and is refracted in the form of an annular stream toward the distant tip of the cavity. At this point a second shock occurs when the stream is forced to move away from the star. Upon cooling, this gas radiates with the characteristic parameters of an HH object. This model is applied to HH 1 and found to account satisfactorily for the observations.

Book ChapterDOI
01 Jan 1980
TL;DR: In this paper, GATE measurements from the South Equatorial Current and the upper portion of the Undercurrent at the equator were used to examine the kinetic energy of the mean (21-day time average) motion and of the turbulent motion in both the south equatorial current and the undercurrent.
Abstract: Measurements from GATE enable examination of many terms in the equations for the kinetic energy of the mean (21-day time average) motion and of the turbulent motion in both the South Equatorial Current and the upper portion of the Undercurrent at the equator. Below 20 m depth, the balance in the equation for kinetic energy of turbulent motion is between the rate of production and the rate of dissipation, and leads to estimates of the vertical eddy viscosity, Km, due to turbulence. The largest terms in the equation for the kinetic energy of the mean motion are: 1) the input of energy from the wind, 2) the exchange with the zonal pressure gradient, and 3) the loss to turbulent energy. The rates of exchange of energy with horizontal eddies and meanders are likely significant but estimates of these terms are as yet unavailable.

Journal ArticleDOI
TL;DR: In this article, a two-dimensional numerical hydrodynamic study showed that a Rayleigh-Taylor unstable gradient, which can develop after the bounce of a collapsing stellar core, gives rise to a dramatic, large-scale l 2 overturn of the whole core.
Abstract: A two-dimensional numerical hydrodynamic study shows that a Rayleigh-Taylor unstable gradient, which can develop after the bounce of a collapsing stellar core, gives rise to a dramatic, large-scale l=2 overturn of the whole core. the unstable pressure gradient in these calculations is artificially weak because the equation of state used causes an early bounce at low density. A more dramatic overturn with greater kinetic and neutrino energy release is to be expected with recent equations of state, given sufficient time to reduce diffusively and convectively any transient shock-produced entropy-stabilizing gradients.

Journal ArticleDOI
TL;DR: In this paper, a power-law fluid with a suddenly applied arbitrary time-dependent pressure gradient in a horizontal circular tube is presented, and the momentum equations are solved numerically using a implicit finite-difference technique for the timedependent velocity profiles for both start up and oscillating pressure gradients.
Abstract: Flow of a power-law fluid with a suddenly applied arbitrary time-dependent pressure gradient in a horizontal circular tube is presented. The momentum equations are solved numerically using a implicit finite-difference technique for the time-dependent velocity profiles for both start up and oscillating pressure gradients. Dimensionless curves are presented showing velocity profile development and phase angle variation for a variety of power-law index values.

Journal ArticleDOI
TL;DR: In this article, a generalized extension of the Rabinowitsch-Mooney method for estimating true viscosity in capillary flow is proposed, which essentially involves the estimation of temperature, pressure, shear rate and shear stress under a variety of experimental conditions at a predetermined point in the capillary.
Abstract: Capillary viscometers have been used extensively, because of their simplicity and reliability, to measure the viscosity of fluids over a wide range of shear rates. However, in capillary flow, the shear rate is not uniform throughout the capillary, a pressure gradient is established in the direction of flow, and the temperature of the fluid is nonuniform due to viscous dissipation. In the present work, a general, simple and practical method is proposed for correcting for the effects of pressure variation and viscous dissipation in determining the viscosity of polymer melts at high pressures. The method essentially involves the estimation of temperature, pressure, shear rate, and shear stress under a variety of experimental conditions at a predetermined point in the capillary. As such, it may be considered as a generalized extension of the classical Rabinowitsch-Mooney method for estimating true viscosity in capillary flow.

Journal ArticleDOI
TL;DR: In this paper, numerical solutions to the MHD Falkner-Skan equation and the corresponding heat transfer equation have been obtained on taking into consideration the effects of suction and injection and the pressure gradient parameter β.
Abstract: Numerical solutions to the MHD Falkner-Skan equation and the corresponding heat transfer equation have been obtained on taking into consideration the effects of suction and injection and the pressure gradient parameter β. Velocity and temperature profiles are shown on graphs and the numerical values of the skin friction and the rate of heat transfer are given in the form of tables. It has been observed that an increase inN m (magnetic field parameter) leads to an increase in velocity, skin friction, rate of heat transfer and a fall in temperature. Also an increase in suction leads to a fall in the value of the skin friction and the rate of heat transfer, opposite to the case of injection.

Journal ArticleDOI
TL;DR: In this article, an equilibrium model for smectite-illite reaction in the northern Gulf of Mexico has been proposed, with the shift in the logarithm of the equilibrium coefficient with depth being proportional to the product of the reaction enthalpy and the geothermal gradient.
Abstract: Mixed layer smectite-illite clays comprise a significant fraction of fine-grained clastic sediments in many basins around the world. Abnormally high fluid pressure (geopressure) is associated with parts of these basins. The presence of smectite-illite is a necessary but not sufficient criterion for the existence of geopressure. Smectite reacts with potassium feldspar producing illite, silica, sodium-calcium feldspar, and releasing loosely bound water. Observations in the northern Gulf of Mexico support an equilibrium model for the reaction, the shift in the logarithm of the equilibrium coefficient with depth being proportional to the product of the reaction enthalpy and the geothermal gradient. Reaction enthalpies range from 2,000 to 26,000 cal/mole, highest reaction enthalpies occurring along the south Texas coast, lowest in the Mississippi delta. Abrupt diagenesis-depth profiles are associated with geopressure, gradual reaction with depth associated with near hydro-static fluid pressure gradients. Sediments compact over intervals where the effective pressure increases. Geopressure is associated with porosity increase and effective pressure decrease with depth. The top of the zone of sediment under-compaction coincides with change in sign of the effective pressure gradient from positive to negative. In this interval, fluid pressure increases with depth faster than does the overburden pressure. Very high fluid-pressure gradients are associated with the combination of low shale permeability, high shale porosity, and rapid basement subsidence. Because of the close connection between high fluid-pressure gradient and abrupt conversion of smectite to illite, we conclude that this reaction is responsible for abnormal loss of permeability, probably a result of the finely divided silica hat is produced. End_of_Article - Last_Page 708------------

Journal ArticleDOI
TL;DR: In this paper, a first-order model of the ionopause pressure variations as a function of height and solar-zenith angle was proposed, and the results indicated that both the secular variation and the latitudinal asymmetry may be responsible for the closer bow shock crossings of the Venera 9 andVenera 10 spacecraft in the range from approximately 25 deg to approximately 153 deg.
Abstract: Solar wind plasma and magnetic field data and ionospheric data obtained from the Pioneer Venus orbiter are discussed. The variation in the magnetic field pressure within the magnetic barrier is shown to be similar to that expected for the solar wind pressure variations along an obstacle's boundary when a more realistic approximation of the shape of the ionosphere is included. Simultaneous solar wind pressure, ionospheric pressure, and magnetic barrier pressure data reveal that the ionospheric pressure below the ionopause is approximately equal to the solar wind pressure. The magnetic barrier pressure is found to be equal to approximately 2/3 to 3/4 of both the solar wind pressure and the ionospheric pressure. Estimates of the hot plasma pressure contribution to the total pressure in the magnetic barrier vary from 1/4 to 1/3. Just below the ionopause the ionospheric pressure deviations from the mean ionospheric pressure are significant, especially below approximately 400 km; they appear to be indicative of the adjustment of the ionospheric structure to changeing solar wind conditions. A first-order model of the ionopause pressure variations as a function of height and solar-zenith angle is proposed. Venera 9 and Venera 10 bow shock crossings are then analyzed for solar zenith angles in the range from approximately 25 deg to approximately 153 deg. A comparison of Venera 9 and Venera 10 bow shock crossings with those observed by the Pioneer Venus orbiter suggests that both the secular variation and the latitudinal asymmetry may be responsible for the closer shock crossings of the Venera 9 and Venera 10 spacecraft.

Journal ArticleDOI
TL;DR: In this paper, a linear hydrodynamic equation of motion with linear boundary conditions is obtained to describe the horizontal current, as a function of depth and time, determined by a given history of the wind force and pressure gradient up to that time, at a fixed point in the horizontal plane, in well-mixed water of finite depth.
Abstract: Solutions of a linear hydrodynamic equation of motion with linear boundary conditions are obtained to describe the horizontal current, as a function of depth and time, determined by a given history of the wind force and pressure gradient up to that time, at a fixed point in the horizontal plane, in well-mixed water of finite depth. The bottom friction is assumed to be proportional to the bottom current, with zero bottom current and zero bottom friction considered as limiting cases. The general solution is established as an eigenfunction expansion when the eddy viscosity is given as a positive function of depth. Explicit formulas are worked out for viscosity functions that are constant, exponential, or varying as a power of the height from somewhere below the bottom or above the top of the water. For the latter the limit as the viscosity goes to zero at the bottom or top is considered. Numerical results are presented for viscosities that are constant, exponential, linear, or varying as the 3/4 power.

Journal ArticleDOI
TL;DR: In this paper, data have been obtained on the operation of a deep-channel single-screw extruder, pumping a Newtonian liquid under isothermal, developed flow conditions.
Abstract: Data have been obtained on the operation of a deep-channel single-screw extruder, pumping a Newtonian liquid under isothermal, developed flow conditions. Flow rate, screw speed, and pressure gradient characteristics were measured, and a tracer particle technique was employed to determine channel velocity profiles. The data were required for the testing and development of a computer model for flow in the extruder, which takes into consideration channel curvature. Results confirm the correctness of the computer solutions previously reported.

Journal ArticleDOI
TL;DR: In this article, a one-dimensional numerical solution to the Navier Stokes equation including an initial steady-state wind profile, viscosity, pressure gradient, Lorenz force and the Coriolis force was made in order to study the effect of auroral processes on the neutral atmosphere.
Abstract: Lithium trail neutral wind measurements have been made in the morning dayside auroral oval as a function of altitude. During all four experiments the winds displayed a large altitude shear. In the most extreme case the wind at 135-km altitude was toward the south at 210 m/s, and at 185-km altitude toward the northwest at 170 m/s. A one-dimensional numerical solution to the Navier Stokes equation including an initial steady-state wind profile, viscosity, pressure gradient, Lorenz force and the Coriolis force was made in order to study the effect of auroral processes on the neutral atmosphere. Since electric fields and plasma density were measured, the Lorenz force could be modeled with reasonable accuracy. The pressure gradient was determined in an iterative way as a best fit to the observations. Within the limitations of a one-dimensional model the numerical solution is in reasonable agreement with one of the observations, which is applicable to such a modeling, and indicates that both Lorenz forces and pressure gradients due to auroral processes are required to explain the observation.