scholarly journals Investigating H and Z geomagnetic component disturbance field in the mid-latitude

2016 ◽  
Vol 11 (5) ◽  
pp. 66-70
Author(s):  
F N Okeke ◽  
E C Okoro ◽  
E B I Ugwu
Keyword(s):  
Disturbance Field

The Influence of Wake–Wake Interactions on Loss Fluctuations of a Downstream Axial Compressor Blade Row

1998 ◽  
Vol 120 (4) ◽  
pp. 695-704 ◽  
Author(s):  
G. J. Walker ◽  
J. D. Hughes ◽  
I. Ko¨hler ◽  
W. J. Solomon
Keyword(s):  
Free Stream ◽  
Guide Vane ◽  
Axial Compressor ◽  
Inlet Guide Vane ◽  
Viscous Losses ◽  
Wake Interaction ◽  
Blade Row ◽  
Wake Interactions ◽  
Periodic Fluctuations ◽  
Disturbance Field

The interaction between wakes of an adjacent rotor–stator or stator–rotor blade row pair in an axial turbomachine is known to produce regular spatial variations in both the time-mean and unsteady flow fields in a frame relative to the upstream member of the pair. This paper examines the influence of such changes in the free-stream disturbance field on the viscous losses of a following blade row. Hot-wire measurements are carried out downstream of the outlet stator in a 1.5-stage axial compressor having equal blade numbers in the inlet guide vane (IGV) and stator rows. Clocking of the IGV row is used to vary the disturbance field experienced by the stator blades; the influence on stator wake properties is evaluated. The magnitude of periodic fluctuations in ensemble-averaged stator wake thickness is significantly influenced by IGV wake-rotor wake interaction effects. The changes in time-mean stator losses appear marginal.

scholarly journals Equatorial Ionospheric Disturbance Field-Aligned Plasma Drifts Observed by C/NOFS

2018 ◽  
Vol 123 (5) ◽  
pp. 4192-4201 ◽  
Author(s):  
Ruilong Zhang ◽  
Libo Liu ◽  
N. Balan ◽  
Huijun Le ◽  
Yiding Chen ◽  
...  
Keyword(s):  
Ionospheric Disturbance ◽  
Plasma Drifts ◽  
Disturbance Field

The Quasi-Cylinder of Specified Thickness and Shell Loading in Supersonic Flow

1960 ◽  
Vol 11 (4) ◽  
pp. 387-395
Author(s):  
H. Portnoy
Keyword(s):  
Supersonic Flow ◽  
Shell Thickness ◽  
Operational Calculus ◽  
Wave Drag ◽  
Small Disturbance ◽  
Characteristic Cone ◽  
Present Solution ◽  
The Mean ◽  
Disturbance Field ◽  
General Method

SummaryThe methods of the operational calculus are used to obtain a linear approximation to the shape of the mean camber surface of a quasi-cylinder in a supersonic flow in terms of its shell thickness and loading distributions. The analysis deals with a generalised quasi-cylinder; that is one which, although lying close to a mean cylinder, need not possess axial symmetry. The quasi-cylinder is also permitted to be within the small disturbance field of other separate components, e.g. a centre-body. Because the linearised theory is inadmissable for internal duct flows close to and beyond the first reflected characteristic cone, the present solution is likewise invalid close to and beyond the position where this characteristic meets the mean cylinder. The work given here enables the camber shapes of “ring-wings”, which have been used theoretically to reduce or even nullify the wave-drag of a central slender-body, to be found. An example illustrates the general method.

Structure of Acoustic Radiation from an Artificially Excited Supersonic Boundary Layer

2005 ◽  
Vol 4 (3) ◽  
pp. 353-362
Author(s):  
Nickolay V. Semionov ◽  
Alexander D. Kosinov
Keyword(s):  
Boundary Layer ◽  
Free Stream ◽  
Acoustic Radiation ◽  
Supersonic Boundary Layer ◽  
Local Source ◽  
Hot Wire ◽  
Supersonic Wind Tunnel ◽  
Local Disturbance ◽  
Wave Characteristics ◽  
Disturbance Field

An experimental study of the controlled disturbance field, introduced into the free stream with the help of the local source of disturbances, was carried out. The controlled disturbances were excited in the supersonic boundary layer by using a local disturbance generator designed based on the amount of discharge in the chamber in the plate. This process was accompanied by radiation of controlled disturbances into the free stream. This radiation from the system “discharge-boundary layer” was used as controlled disturbances in the free stream. The acoustic nature of the radiation was obtained. The levels, wave characteristics and modes of the artificial fluctuations have been obtained by hot-wire measurements in the free stream of the supersonic wind tunnel at a Mach number of 2.

scholarly journals Aspects of the current system producing magnetic disturbance

1935 ◽  
Vol 152 (876) ◽  
pp. 277-298 ◽  
Author(s):  
J. M. Stagg ◽  
George Clarke Simpson
Keyword(s):  
Magnetic Field ◽  
Field Component ◽  
Daily Variation ◽  
Current System ◽  
Diurnal Variations ◽  
Magnetic Disturbance ◽  
Earth’S Magnetic Field ◽  
Normal Behaviour ◽  
Transition Zones ◽  
Disturbance Field

1—If N, E. and Z (vertical) are the three rectangular components of the earth's magnetic field, a study of the behaviour of the changes ΔN, ΔE, and ΔZ produced in them by a perturbing field gives information about the corresponding changes in this field and therefore in the overhead current system to which the field is due. In this enquiry ΔN, ΔE, ΔZ will be regarded as departures for 60-minute intervals from an undisturbed condition which is taken to be the corresponding departure on quiet days. It will be understood that this procedure assumes that the effect of disturbance on the earth’s field is to overlay quiet conditions by an additional system of forces. Average diurnal variations on both quiet, q , and disturbed, d , days were therefore formed for N, E, and Z, starting from the published hourly values of the primary horizontal elements H and D where necessary. With the two sets of variations converted into departures from their respective means, difference departures Δ d — Δ q for N, E, and Z were formed hour-by-hour to give 24 disturbance field component vectors. This was done for the seasons separately and the year as a whole for each of the observatories in Table I. In discussing the average features of regular disturbance there are advantages in using as extensive series of data as possible. Even when the five internationally selected d and q days per month are used, as in the present enquiry, exceptional isolated disturbances may obscure normal behaviour. This is especially true when the study concerns stations representing transition zones in the phenomena of disturbance. The inclusion of Fort Rae, the British Polar Year station in N. W. Canada, will, however, be seen to be fully warranted, not because of the scale of disturbance there but because of its instructive position on the polar side of the line over which the current system producing the main features of the regular daily variation of disturbance is mainly concentrated.

scholarly journals Tropical Cyclone Initialization with a Spherical High-Order Filter and an Idealized Three-Dimensional Bogus Vortex

2010 ◽  
Vol 138 (4) ◽  
pp. 1344-1367 ◽  
Author(s):  
In-Hyuk Kwon ◽  
Hyeong-Bin Cheong
Keyword(s):  
Tropical Cyclone ◽  
Three Dimensional ◽  
Analysis Data ◽  
High Order ◽  
Positive Anomaly ◽  
Order Filter ◽  
Intensity Prediction ◽  
Tangential Wind ◽  
Tropical Cyclone Initialization ◽  
Disturbance Field

Abstract A tropical cyclone initialization method with an idealized three-dimensional bogus vortex of an analytic empirical formula is presented for the track and intensity prediction. The procedure in the new method consists of four steps: the separation of the disturbance from the analysis, determination of the tropical cyclone domain, generation of symmetric bogus vortex, and merging of it with the analysis data. When separating the disturbance field, an efficient spherical high-order filter with the double-Fourier series is used whose cutoff scale can be adjusted with ease to the horizontal scale of the tropical cyclone of interest. The tropical cyclone domain is determined from the streamfunction field instead of the velocities. The axisymmetric vortex to replace the poorly resolved tropical cyclone in the analysis is designed in terms of analytic empirical functions with a careful treatment of the upper-layer flows as well as the secondary circulations. The geopotential of the vortex is given in such a way that the negative anomaly in the lower layer is changed into positive anomaly above the prescribed pressure level, which depends on the intensity of the tropical cyclone. The geopotential is then used to calculate the tangential wind and temperature using the gradient wind balance and the hydrostatic balance, respectively. The inflow and outflow in the tropical cyclone are constructed to resemble closely the observed or simulated structures under the constraint of mass balance. The bogus vortex is merged with the disturbance field with the use of matching principle so that it is not affected except near the boundary of tropical cyclone domain. The humidity of the analysis is modified to be very close to the saturation in the lower layers near the tropical cyclone center. The balanced bogus vortex of the present study is completely specified on the basis of four parameters from the Regional Specialized Meteorological Center (RSMC) report and the additional two parameters, which are derived from the analysis data. The initialization method was applied to the track and the intensity (in terms of central pressure) prediction of the TCs observed in the western North Pacific Ocean and East China Sea in 2007 with the use of the Weather Research and Forecasting (WRF) model. No significant initial jump or abrupt change was seen in either momentum or surface pressure during the time integration, thus indicating a proper tropical cyclone initialization. Relative to the results without the tropical cyclone initialization and the forecast results of RSMC Tokyo, the present method presented a great improvement in both the track and intensity prediction.

Magnetic disturbance field compensation of a geomagnetic vector measuring instrument

2017 ◽  
Vol 13 (3) ◽  
pp. 356-361 ◽  
Author(s):  
Zhongyan Liu ◽  
Qi Zhang ◽  
Mengchun Pan ◽  
Feng Guan ◽  
Chengbiao Wan ◽  
...  
Keyword(s):  
Magnetic Disturbance ◽  
Measuring Instrument ◽  
Disturbance Field
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