Journal articles: 'Meridional shape'

1

Wang, Yan, Quanlin Dong, and Yulian Zhang. "Meridional shape design and the internal flow investigation of centrifugal impeller." Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 231, no. 23 (August 30, 2016): 4319–30. http://dx.doi.org/10.1177/0954406216667407.

Full text

Abstract:

This paper describes an inverse design method for calculating the shape of meridional plane of centrifugal impeller. This design method permits the shroud and hub contours to be indirectly calculated by medial axis contour and constraint equations. The design process is computationally inexpensive and can conveniently modify the shroud and hub shapes as the design’s demand. Based on this design method, new constraint equations are used for a new shape design of meridional plane that lead to a uniform velocity distribution in the inlet of impeller. Numerical simulations are employed to investigate the fluid flows of centrifugal fan. After validation of the numerical strategy, the pressure and velocity distributions in centrifugal fan are illustrated. The numerical results show that the inlet performance is improved and the velocity distribution is more uniform. Furthermore, in order to understand the flow mechanism inside the centrifugal fan, the secondary flow in the blade passage and velocity distribution at the shroud and hub have been carried out a detailed investigation and study.

APA, Harvard, Vancouver, ISO, and other styles

2

Ragen, Sarah, Kyle C. Armour, LuAnne Thompson, Andrew Shao, and David Darr. "The Role of Atlantic Basin Geometry in Meridional Overturning Circulation." Journal of Physical Oceanography 52, no. 3 (March 2022): 475–92. http://dx.doi.org/10.1175/jpo-d-21-0036.1.

Full text

Abstract:

Abstract We present idealized simulations to explore how the shape of eastern and western continental boundaries along the Atlantic Ocean influences the Atlantic meridional overturning circulation (AMOC). We use a state-of-the art ocean–sea ice model (MOM6 and SIS2) with idealized, zonally symmetric surface forcing and a range of idealized continental configurations with a large, Pacific-like basin and a small, Atlantic-like basin. We perform simulations with five coastline geometries along the Atlantic-like basin that range from coastlines that are straight to coastlines that are shaped like the coasts of the American and African continents. Changing the Atlantic basin coastline shape influences AMOC strength in a manner distinct from simply increasing basin width: widening the basin while maintaining straight coastlines leads to a 10-Sv (1 Sv ≡ 106 m3 s−1) increase in AMOC strength, whereas widening the basin with the geometry of the American and African continents leads to a 6-Sv increase in AMOC strength, despite both cases representing the same average basin-width increase relative to a control case. The structure of AMOC changes are different between these two cases as well: a more realistic basin geometry results in a shoaled AMOC while widening the basin with straight boundaries deepens AMOC. We test the influence of the shape of the both boundaries independently and find that AMOC is more sensitive to the American coastline while the African coastline impacts the abyssal circulation. We also find that AMOC strength and depth scales well with basin-scale meridional density difference, even with different Atlantic basin geometries, illuminating a robust physical link between AMOC and the North Atlantic western boundary density gradient.

APA, Harvard, Vancouver, ISO, and other styles

3

Miyauchi, Sunao, Hironori Horiguchi, Jun-ichirou Fukutomi, and Akihiro Takahashi. "K-1102 Optimization of Meridional Shape Design of Pump Impeller." Proceedings of the JSME annual meeting II.01.1 (2001): 25–26. http://dx.doi.org/10.1299/jsmemecjo.ii.01.1.0_25.

Full text

APA, Harvard, Vancouver, ISO, and other styles

4

Chen, Xin, Linlin Cao, Peng Yan, Peng Wu, and Dazhuan Wu. "Effect of meridional shape on performance of axial-flow fan." Journal of Mechanical Science and Technology 31, no. 11 (November 2017): 5141–51. http://dx.doi.org/10.1007/s12206-017-1008-1.

Full text

APA, Harvard, Vancouver, ISO, and other styles

5

Talon, Suzanne, Georges Michaud, and Alain Vincent. "On meridional Circulation in Stars." Symposium - International Astronomical Union 198 (2000): 498–99. http://dx.doi.org/10.1017/s0074180900167154.

Full text

Abstract:

Even though the existence of meridional currents in stars has been known for quite a long time (Eddington 1925, Vogt 1925), its exact structure as well as its influence on stellar evolution is still unclear. Some authors concentrated on finding the exact shape of meridional circulation in a rotating star, while others tried to model its effect on the chemical distribution in the interior. In all studies performed so far however, meridional circulation is considered in an asymptotic regime in which the advection of entropy by the meridional currents is supposed to balance exactly the source term of the non-zero radiative flux divergence. Other terms could however be added to that asymptotic regime which could turn out to dominate the transport of chemicals. We wish to present here preliminary results of 3D numerical simulation attempted to tackle this problem.

APA, Harvard, Vancouver, ISO, and other styles

6

Miyauchi, Sunao, Hironori Horiguchi, Jun-ichirou Fukutomi, and Akihiro Takahashi. "Optimization of Meridional Flow Channel Design of Pump Impeller." International Journal of Rotating Machinery 10, no. 2 (2004): 115–19. http://dx.doi.org/10.1155/s1023621x04000120.

Full text

Abstract:

The meridional flow channel design of a pump impeller affects its performance. However, since so many design parameters exist, a new design method is proposed in which a meridional and blade-to-blade flow channel is designed by the parallel use of the circulation distribution provided by the designer. Thus, an optimization method was used to design an axis-symmetrical meridional flow channel from the circulation distribution. In addition, the inverse design method proposed by Zangeneh et al. (1996) was employed to design a three-dimensional blade-to-blade flow channel from the circulation distribution and the optimized meridional shape. In this article, a few design examples and these Computational Fluid Dynamics (CFD) validations are also given.

APA, Harvard, Vancouver, ISO, and other styles

7

Kim, Sung, Young-Seok Choi, Kyoung-Yong Lee, and Jun-Ho Kim. "Design Optimization of Mixed-flow Pump in a Fixed Meridional Shape." International Journal of Fluid Machinery and Systems 4, no. 1 (March 31, 2011): 14–24. http://dx.doi.org/10.5293/ijfms.2011.4.1.014.

Full text

APA, Harvard, Vancouver, ISO, and other styles

8

Kvasha, Yu A., and N. A. Zinevych. "On the effect of the meridional contour shape on the power characteristics of a centrifugal compressor wheel." Technical mechanics 2020, no. 3 (October 15, 2020): 12–17. http://dx.doi.org/10.15407/itm2020.03.012.

Full text

Abstract:

This work is concerned with the development of approaches to the optimal aerodynamic design of centrifugal compressor wheels, which is due to the use of centrifugal stages in compressors of modern aircraft gas turbine engines and power plants. The aim of this work is a computational study of the effect of the meridional contour shape of a centrifugal compressor wheel on its power characteristics. The basic method is a numerical simulation of 3D turbulent gas flows in centrifugal wheels on the basis of the complete averaged Navier¬–Stokes equations and a two-parameter turbulence model. The computational study features: varying the shape of the hub and tip part of the meridional contour over a wide range, formulating quality criteria as the mean integral values of the wheel power characteristics over the operating range of the air flow rate through the wheel, and a systematic scan of the independent variable range at points that form a uniformly distributed sequence. As a result of multiparameter calculations, it was shown that in the case of a flow without separation in the blade channels of a wheel with a given starting shape of the meridional contour, varying that shape has an insignificant effect on the wheel power characteristics. It is pointed out that in similar cases it seems to be advisable to aerodynamically improve centrifugal wheels by varying the shape of their blades in the circumferential direction rather than in the meridional plane. This conclusion was made using rather a “coarse” computational grid, which, however, retains the sensitivity of the computed results to a variation in the centrifugal wheel geometry. On the whole, this work clarifies ways of further aerodynamic improvement of centrifugal compressor impellers in cases where the starting centrifugal wheel is a well-designed wheel with a flow without separation in the blade channels. The results obtained may be used in the aerodynamic optimization of centrifugal stages of aircraft gas turbine engines.

APA, Harvard, Vancouver, ISO, and other styles

9

Lutsko, Nicholas J., and Isaac M. Held. "The Response of an Idealized Atmosphere to Orographic Forcing: Zonal versus Meridional Propagation." Journal of the Atmospheric Sciences 73, no. 9 (August 26, 2016): 3701–18. http://dx.doi.org/10.1175/jas-d-16-0021.1.

Full text

Abstract:

Abstract A dry atmospheric general circulation model is forced with large-scale, Gaussian orography in an attempt to isolate a regime in which the model responds linearly to orographic forcing and then to study the departures from linearity as the orography is increased in amplitude. In contrast to previous results, which emphasized the meridional propagation of orographically forced stationary waves, using the standard Held–Suarez (H–S) control climate, it is found that the linear regime is characterized by a meridionally trapped, zonally propagating wave. Meridionally trapped waves of this kind have been seen in other contexts, where they have been termed “circumglobal waves.” As the height of the orography is increased, the circumglobal wave coexists with a meridionally propagating wave and for large-enough heights the meridionally propagating wave dominates the response. A barotropic model on a sphere reproduces this trapped wave in the linear regime and also reproduces the transition to meridional propagation with increasing amplitude. However, mean-flow modification by the stationary waves is very different in the two models, making it difficult to argue that the transitions have the same causes. When adding asymmetry across the equator to the H–S control climate and placing the orography in the cooler hemisphere, it becomes harder to generate trapped waves in the GCM and the trapping becomes sensitive to the shape of the orography. The barotropic model overestimates the trapping in this case. These results suggest that an improved understanding of the role of circumglobal waves will be needed to understand the stationary wave field and its sensitivity to the changes in the zonal-mean climate.

APA, Harvard, Vancouver, ISO, and other styles

10

Biggs, James D. "Meridional Compression of Radio Pulsar Beams." International Astronomical Union Colloquium 128 (1992): 22–25. http://dx.doi.org/10.1017/s0002731600154691.

Full text

Abstract:

AbstractWe have studied the radio pulsar emission beam assuming a) a magnetic dipole field geometry and b) that the beam geometry is defined by the field lines that are not contained within the light cylinder. In general, the beam is compressed in the meridional direction. When the magnetic and rotation axes are aligned the beam is circular and as, the angle between these axes increases, the ratio of meridional to longitudinal dimension decreases monotonically to the minimum value 0.62 when the axes are orthogonal. This beam shape is thus consistent with that inferred from the study of circular polarization in average pulse profiles by Radhakrishnan and Rankin. Evidence for meridional compression is also found in the extensive observational study of Lyne and Manchester (1988).The beam evolution was determined using this data set, the beamwidth being found proportional to P–1/2, where P is the pulsar period. This relation implies that the more rapidly rotating pulsars should have larger beams, and this should aid in their detection. The more numerous, slower pulsars should have somewhat smaller beams than previously determined. This implies that the pulsar birthrate is probably close to the highest current estimates (1 in 25yr).

APA, Harvard, Vancouver, ISO, and other styles

11

Szwed, Aleksander. "Yield Criterion for Concrete Formed From the Deviatoric and Meridional Shape Functions." IOP Conference Series: Materials Science and Engineering 661 (November 20, 2019): 012048. http://dx.doi.org/10.1088/1757-899x/661/1/012048.

Full text

APA, Harvard, Vancouver, ISO, and other styles

12

Rüdiger, G., and I. Tuominen. "Λ-effect, Meridional Flow and the Differential Solar Rotation." International Astronomical Union Colloquium 130 (1991): 172–77. http://dx.doi.org/10.1017/s0252921100079586.

Full text

Abstract:

AbstractRotation laws for the solar convection zone are produced by the Λ-effect in rotating anisotropic turbulence fields. In this paper we use the structure of the turbulence parameters introduced by Rüdiger and Kichatinov (1990), based on a simplified turbulence model. When we neglect the meridional circulation, for small inverse Rossby numbers the angular velocity isolines are spherical, while for increasing inverse Rossby number they approach more and more the helioseismologically derived shape. This simple picture becomes more complicated if the meridional circulation is allowed to act as an angular momentum transporter.

APA, Harvard, Vancouver, ISO, and other styles

13

Elger, D. F., D. M. Blackketter, R. S. Budwig, and K. H. Johansen. "The Influence of Shape on the Stresses in Model Abdominal Aortic Aneurysms." Journal of Biomechanical Engineering 118, no. 3 (August 1, 1996): 326–32. http://dx.doi.org/10.1115/1.2796014.

Full text

Abstract:

Presence of a small abdominal aortic aneurysm (AAA) often presents a difficult clinical dilemma—a reparative operation with its inherent risks versus monitoring the growth of the aneurysm, with the accompanying risk of rupture. The risk of rupture is conventionally believed to be a function of the AAA bulge diameter. In this work, we hypothesized that the risk of rupture depends on AAA shape. Because rupture is inevitably linked to stress, membrane theory was used to predict the stresses in the walls of an idealized AAA, using a model which was axisymmetric and fusiform, with the ends merged into straight open-ended tubes. When the stresses for many different shapes of model AAAs were examined, a number of conclusions became evident: (i) maximum hoop stress typically exceeded maximum meridional stress by a factor of 2 to 3 (ii) the shape of an AAA had a small effect on the meridional stresses and a rather dramatic effect on the hoop stresses, (iii) maximum stress typically occurred near the inflection point of a curve drawn coincident with the AAA wall, and (iv) the maximum stress was a function—not of the bulge diameter—but of the curvatures (i.e. shape) of the AAA wall. This last result suggested that rupture probability should be based on wall curvatures, not on AAA bulge diameter, Because curvatures are not much harder to measure than bulge diameter, this concept may be useful in a clinical setting in order to improve prediction of the likelihood of AAA rupture.

APA, Harvard, Vancouver, ISO, and other styles

14

Sijp, Willem P., Jonathan M. Gregory, Remi Tailleux, and Paul Spence. "The Key Role of the Western Boundary in Linking the AMOC Strength to the North–South Pressure Gradient." Journal of Physical Oceanography 42, no. 4 (April 1, 2012): 628–43. http://dx.doi.org/10.1175/jpo-d-11-0113.1.

Full text

Abstract:

Abstract A key idea in the study of the Atlantic meridional overturning circulation (AMOC) is that its strength is proportional to the meridional density gradient or, more precisely, to the strength of the meridional pressure gradient. A physical basis that would indicate how to estimate the relevant meridional pressure gradient locally from the density distribution in numerical ocean models to test such an idea has been lacking however. Recently, studies of ocean energetics have suggested that the AMOC is driven by the release of available potential energy (APE) into kinetic energy (KE) and that such a conversion takes place primarily in the deep western boundary currents. In this paper, the authors develop an analytical description linking the western boundary current circulation below the interface separating the North Atlantic Deep Water (NADW) and Antarctic Intermediate Water (AAIW) to the shape of this interface. The simple analytical model also shows how available potential energy is converted into kinetic energy at each location and that the strength of the transport within the western boundary current is proportional to the local meridional pressure gradient at low latitudes. The present results suggest, therefore, that the conversion rate of potential energy may provide the necessary physical basis for linking the strength of the AMOC to the meridional pressure gradient and that this could be achieved by a detailed study of the APE to KE conversion in the western boundary current.

APA, Harvard, Vancouver, ISO, and other styles

15

Buchanan-Smith, Hannah M., and David W. Heeley. "Anisotropic Axes in Orientation Perception are Not Retinotopically Mapped." Perception 22, no. 12 (December 1993): 1389–402. http://dx.doi.org/10.1068/p221389.

Full text

Abstract:

The effect of the posture of an observer on the pattern of meridional anisotropy for orientation acuity was examined. Orientation acuity was estimated for the two principal and for one oblique axis with three bodily postures: normal vertical sitting, vertical sitting with the head rotated to 45° from vertical, and prone. The test stimuli were sine-wave gratings covering a range of two octaves of spatial frequency, thin lines, and step edges. Acuity estimates were obtained by two different psychophysical procedures: a single-interval two-alternative forced choice, and a two-interval two-alternative forced choice. Both experimental procedures revealed a strong interaction between the shape of the function that describes the meridional variation of orientation acuity and the posture of the observer. The data are incompatible with models of the oblique effect in orientation perception that are based on a meridional anisotropy in neural properties early in the visual hierarchy.

APA, Harvard, Vancouver, ISO, and other styles

16

Struthers, H., G. E. Bodeker, J. Austin, S. Bekki, I. Cionni, M. Dameris, M. A. Giorgetta, et al. "An evaluation of the simulation of the edge of the Antarctic vortex by chemistry-climate models." Atmospheric Chemistry and Physics Discussions 8, no. 6 (December 1, 2008): 20155–92. http://dx.doi.org/10.5194/acpd-8-20155-2008.

Full text

Abstract:

Abstract. The dynamical barrier to meridional mixing at the edge of the Antarctic spring stratospheric vortex is examined. Diagnostics are presented which demonstrate the link between the shape of the meridional mixing barrier at the edge of the vortex and the meridional gradients in total column ozone across the vortex edge. Results derived from reanalysis and measurement data sets are compared with equivalent diagnostics from five coupled chemistry-climate models to test how well the models capture the interaction between the dynamical structure of the stratospheric vortex and the chemical processes occurring within the vortex. Results show that the accuracy of the simulation of the dynamical vortex edge varies widely amongst the models studied here. This affects the ability of the models to simulate the large observed meridional gradients in total column ozone. Three of the models in this study simulated the inner edge of the vortex to be more than 7° closer to the pole than observed. This is expected to have important implications for how well these models simulate the extent of severe springtime ozone loss that occurs within the Antarctic vortex.

APA, Harvard, Vancouver, ISO, and other styles

17

Zangeneh, M. "Inviscid-Viscous Interaction Method for Three-Dimensional Inverse Design of Centrifugal Impellers." Journal of Turbomachinery 116, no. 2 (April 1, 1994): 280–90. http://dx.doi.org/10.1115/1.2928362.

Full text

Abstract:

A three-dimensional design method for the design of the blade geometry of centrifugal compressor impellers is presented. In this method the blade shape is computed for a specified circulation distribution, normal (or tangential) thickness distribution, and meridional geometry. As the blade shapes are computed by using an inviscid slip (or flow tangency) condition, the viscous effects are introduced indirectly by using a viscous/inviscid procedure. The three-dimensional Navier–Stokes solver developed by Dawes is used as the viscous method. Two different approaches are described for incorporating the viscous effects into the inviscid design method. One method is based on the introduction of an aerodynamic blockage distribution throughout the meridional geometry, while in the other approach a vorticity term directly related to the entropy gradients in the machine is introduced. The method is applied to redesign the blade geometry of Eckardt’s 30 deg backswept impeller as well as a generic high pressure ratio (transonic) impeller. The results indicate that the entropy gradient approach can fairly accurately represent the viscous effects in the machine.

APA, Harvard, Vancouver, ISO, and other styles

18

VANLAERE, W., G. LAGAE, R. VAN IMPE, J. BELIS, and D. DELINCÉ. "EARLY YIELDING OF LIQUID-FILLED CONICAL SHELLS." International Journal of Modern Physics B 22, no. 31n32 (December 30, 2008): 6224–29. http://dx.doi.org/10.1142/s0217979208051832.

Full text

Abstract:

In liquid-filled conical shells, the combination of compressive meridional stresses and tensile hoop stresses can lead to instability. The present design rule for these structures is verified in this contribution by means of numerical simulations. Large axisymmetric imperfections are detrimental and may lead to failure by plastic buckling. For these shapes the design rule may be unconservative. The realism of the proposed shape deviations is questioned. However, partially or completely axisymmetric weld depressions can't be excluded from the simulations. This means that an elaborated study is needed and that the design rule must be checked even further.

APA, Harvard, Vancouver, ISO, and other styles

19

Martelli, F., and V. Michelassi. "Using Viscous Calculations in Pump Design." Journal of Fluids Engineering 112, no. 3 (September 1, 1990): 272–80. http://dx.doi.org/10.1115/1.2909400.

Full text

Abstract:

A viscous computer code for designing the meridional channels of high-performance pumps is presented. An averaging technique is used to reduce the three-dimensional flow to a two-dimensional model. The code, based upon an implicit finite difference method for steady two-dimensional incompressible flows, was validated in complex flow geometries prior to application in the design analysis of an actual pump. Viscous effects are taken into account by two different turbulence models. The Navier-Stokes solver is used in conjunction with a standard blade-to-blade calculation by means of an automatic graphic procedure that exchanges geometric and flowfield data. Various meridional shape solutions are presented and discussed in relation to physical evidence.

APA, Harvard, Vancouver, ISO, and other styles

20

Bing, Hao, Shuliang Cao, Lei Tan, and Baoshan Zhu. "Effects of meridional flow passage shape on hydraulic performance of mixed-flow pump impellers." Chinese Journal of Mechanical Engineering 26, no. 3 (May 2013): 469–75. http://dx.doi.org/10.3901/cjme.2013.03.469.

Full text

APA, Harvard, Vancouver, ISO, and other styles

21

Pei, Ji, Wenjie Wang, and Shouqi Yuan. "Multi-point optimization on meridional shape of a centrifugal pump impeller for performance improvement." Journal of Mechanical Science and Technology 30, no. 11 (November 2016): 4949–60. http://dx.doi.org/10.1007/s12206-016-1015-7.

Full text

APA, Harvard, Vancouver, ISO, and other styles

22

Hoang, Thi Hong Minh, Viet Anh Truong, Ujjwal Shrestha, and Young-Do Choi. "Optimization of the Meridional Plane Shape Design Parameters in a Screw Centrifugal Pump Impeller." KSFM Journal of Fluid Machinery 24, no. 4 (August 31, 2021): 15–25. http://dx.doi.org/10.5293/kfma.2021.24.4.015.

Full text

APA, Harvard, Vancouver, ISO, and other styles

23

Sime, Louise C., David P. Stevens, Karen J. Heywood, and Kevin I. C. Oliver. "A Decomposition of the Atlantic Meridional Overturning." Journal of Physical Oceanography 36, no. 12 (December 1, 2006): 2253–70. http://dx.doi.org/10.1175/jpo2974.1.

Full text

Abstract:

Abstract A decomposition of meridional overturning circulation (MOC) cells into geostrophic vertical shears, Ekman, and bottom pressure–dependent (or external mode) circulation components is presented. The decomposition requires the following information: 1) a density profile wherever bathymetry changes to construct the vertical shears component, 2) the zonal-mean zonal wind stress for the Ekman component, and 3) the mean depth-independent velocity information over each isobath to construct the external mode. The decomposition is applied to the third-generation Hadley Centre Coupled Ocean–Atmosphere General Circulation Model (HadCM3) to determine the meridional variability of these individual components within the Atlantic Ocean. The external mode component is shown to be extremely important where western boundary currents impinge on topography, and also in the area of the overflows. The Sverdrup balance explains the shape of the external mode MOC component to first order, but the time variability of the external mode exhibits only a very weak dependence on the wind stress curl. Thus, the Sverdrup balance cannot be used to determine the external mode changes when examining temporal change in the MOC. The vertical shears component allows the time-mean and the time-variable upper North Atlantic MOC cell to be deduced at 25°S and 50°N. A stronger dependency on the external mode and Ekman components between 8° and 35°N and in the regions of the overflows means that hydrographic sections need to be supplemented by bottom pressure and wind stress information at these latitudes. At the decadal time scale, variability in Ekman transport is less important than that in geostrophic shears. In the Southern Hemisphere the vertical shears component is dominant at all time scales, suggesting that hydrographic sections alone may be suitable for deducing change in the MOC at these latitudes.

APA, Harvard, Vancouver, ISO, and other styles

24

Kim, Sung, Yong-In Kim, Jin-Hyuk Kim, and Young-Seok Choi. "Three-objective optimization of a mixed-flow pump impeller for improved suction performance and efficiency." Advances in Mechanical Engineering 11, no. 12 (December 2019): 168781401989896. http://dx.doi.org/10.1177/1687814019898969.

Full text

Abstract:

In this article, design optimization was carried out to improve the suction performance and efficiency of a mixed-flow pump impeller. Commercial computational fluid dynamics code and a response surface method were used in the optimization to design a mixed-flow pump impeller. When it comes to a mixed-flow pump, the two main research objectives namely efficiency and suction performance tend to contradict. It is very important that the design technology improves the suction performance while maintaining high efficiency. Meridional plane and vane plane development variables were defined in the design of the impeller. The meridional plane expresses the shapes and sizes of the blades, while the vane plane development describes the impeller inlet and outlet angles as well as the blade angle distribution. The blade angle distribution of the impeller was designed using the traditional method by which inlet and outlet angles are connected smoothly. The surface response method was applied to the design variables of the impeller inlet part in this design optimization because they influence the performance of the mixed-flow pump. Objective functions were set to satisfy the total head at the design flow rate as well as to improve efficiency and suction performance. Design variables of the impeller inlet part of the mixed-flow pump and the changes in performance were analyzed in order to produce the optimal shape. The performance of the optimally designed shape was verified by numerical analysis, and the reliability of the test result was checked by comparative analysis against the reference model.

APA, Harvard, Vancouver, ISO, and other styles

25

Waterman, Stephanie, and Brian J. Hoskins. "Eddy Shape, Orientation, Propagation, and Mean Flow Feedback in Western Boundary Current Jets." Journal of Physical Oceanography 43, no. 8 (August 1, 2013): 1666–90. http://dx.doi.org/10.1175/jpo-d-12-0152.1.

Full text

Abstract:

Abstract This manuscript revisits a study of eddy–mean flow interactions in an idealized model of a western boundary current extension jet using properties of the horizontal velocity correlation tensor to diagnose characteristics of average eddy shape, orientation, propagation, and mean flow feedback. These eddy characteristics are then used to provide a new description of the eddy–mean flow interactions observed in terms of different ingredients of the eddy motion. The diagnostics show patterns in average eddy shape, orientation, and propagation that are consistent with the signatures of jet instability in the upstream region and wave radiation in the downstream region. Together they give a feedback onto the mean flow that gives the downstream character of the jet and drives the jet's recirculation gyres. A breakdown of the eddy forcing into contributions from individual terms confirms the expected role of cross-jet gradients in meridional eddy tilt in stabilizing the jet to its barotropic instability; however, it also reveals important roles played by the along-jet evolution of eddy zonal–meridional elongation. It is the mean flow forcing derived from these patterns that acts to strengthen and extend the jet downstream and forces the time-mean recirculation gyres. This understanding of the dependence of mean flow forcing on eddy structural properties suggests that failure to adequately resolve eddy elongation could underlie the weakened jet strength, extent, and changed recirculation structure seen in this idealized model for reduced spatial resolutions. Further, it may suggest new ideas for the parameterization of this forcing.

APA, Harvard, Vancouver, ISO, and other styles

26

Pimm, A. J., S. D. Garvey, and R. J. Drew. "Shape and cost analysis of pressurized fabric structures for subsea compressed air energy storage." Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 225, no. 5 (April 28, 2011): 1027–43. http://dx.doi.org/10.1177/0954406211399506.

Full text

Abstract:

In this article, three different methods are presented for finding the deformed shape of pressurized fabric structures underwater. The methods are used here to analyse the shape and cost of ‘energy bags’, inflatable bags that can be anchored to the seabed and used for subsea compressed air energy storage. First, a system of coupled ordinary differential equations is derived which can be solved to find the shape of an inextensible axisymmetric membrane. Then finite-element analysis (FEA) of an axisymmetric natural shape bag is carried out using cable elements, giving the deformed shape of an extensible axisymmetric membrane. Finally, a full three-dimensional FEA is presented which includes cable and membrane elements. A simple optimization is also used to minimize the cost per unit of energy stored in an axisymmetric natural shape energy bag, and it is shown that if only materials costs are taken into account, the cost of surface is approximately equal to the cost of meridional reinforcement in the optimum-sized bag.

APA, Harvard, Vancouver, ISO, and other styles

27

Lu, Yeming, Xiaofang Wang, and Rong Xie. "Derivation of the Mathematical Approach to the Radial Pump’s Meridional Channel Design Based on the Controlment of the Medial Axis." Mathematical Problems in Engineering 2017 (2017): 1–15. http://dx.doi.org/10.1155/2017/7027016.

Full text

Abstract:

The meridional channel is the base for designing the radial pumps, and a new design approach is proposed here. Different from the previous studies, research here tries to establish the design model simply controlled with the radial coordinate. With the combination of a series of mathematical equations, the new design approach can shape the meridional contours directly by using the initial design variables. As for the mathematical constraint in the new design approach, it was presented in two forms, and each form had its corresponding solution. For the first form (Constraint I), the midpoints of the design points on the hub and shroud contours were thought to be located on the medial axis, and the PSO algorithm was adopted to search for the suitable results. Continually, to accelerate the design process, the second form (Constraint II) to simplify the mathematical constraint was added, and the explicit mathematical expressions calculating the coordinates on the hub and shroud contours were deduced. Finally, to check out the feasibility of the design approach in engineering, it was applied to redesign some typical meridional channels proposed by previous studies, and, through comparative analysis, the effectiveness of the new approach was evaluated and demonstrated.

APA, Harvard, Vancouver, ISO, and other styles

28

Guo, Ming, and Young-Do Choi. "Optimum Design on the Meridional Shape of a Multistage Centrifugal Pump Impeller for Performance Improvement." KSFM Journal of Fluid Machinery 22, no. 3 (June 30, 2019): 41–48. http://dx.doi.org/10.5293/kfma.2019.22.3.041.

Full text

APA, Harvard, Vancouver, ISO, and other styles

29

Hayashi, Yuki, and Kaoru Sato. "Formation of Two-Dimensional Circulation in Response to Unsteady Wave Forcing in the Middle Atmosphere." Journal of the Atmospheric Sciences 75, no. 1 (January 2018): 125–42. http://dx.doi.org/10.1175/jas-d-16-0374.1.

Full text

Abstract:

In previous studies, a steady-state assumption has been frequently used for the analysis of wave-induced meridional circulation. In general, however, the wave forcing is not constant and thus induced circulation can vary in time. Thus, to understand such transient behaviors, time evolutions of a slow variable describing balanced flows and two fast variables describing gravity waves and flows that are slaved to balanced flows are investigated. A Boussinesq equation system is used to examine zonal-mean flow responses to unsteady zonally uniform forcing. Green’s function is used to analytically obtain the evolution of meridional circulation. Responses to zonal wave forcing are mainly examined although responses to a diabatic heating and to wave forcing are discussed in brief. For forcing with a step function shape in time, gravity waves are radiated as a transient response. The time needed to form the circulation depends on the aspect ratio (i.e., latitudinal to vertical lengths) of wave forcing, which determines the group velocity of gravity waves. When the forcing time scale is longer than the inertial period, the response does not include gravity wave radiation and mainly involves a meridional circulation, which is similar to the solution for steady forcing. The two-celled meridional circulation describes the early stage response to the forcing and can be used to examine how the wave forcing is distributed to zonal wind acceleration and Coriolis torque. It is shown that the distribution depends on the aspect ratio of the forcing.

APA, Harvard, Vancouver, ISO, and other styles

30

Meunier, N., and A. M. Lagrange. "Radial-velocity variations due to meridional flows in the Sun and solar-type stars: impact on exoplanet detectability." Astronomy & Astrophysics 638 (June 2020): A54. http://dx.doi.org/10.1051/0004-6361/201937354.

Full text

Abstract:

Context. Stellar variability due to magnetic activity and flows at different spatial scales strongly impacts radial velocities. This variability is seen as oscillations, granulation, supergranulation, and meridional flows. The effect of this latter process is currently poorly known but could affect exoplanet detectability. Aims. We aim to quantify the amplitude of the meridional flow integrated over the disc and its temporal variability, first for the Sun, as seen with different inclinations, and then for other solar-type stars. We then want to compare these amplitudes with low-mass exoplanetary amplitudes in radial velocity. Methods. We used long time series (covering two 11-yr cycles) of solar latitudinal meridional circulation to reconstruct its integrated contribution and study its properties. We then used scaling laws from hydrodynamical simulations relating the amplitude of the meridional flow variability with stellar mass and rotation rate to estimate the typical amplitude expected for other solar-type stars. Results. We find typical rms of the order of 0.5–0.7 m s−1 (edge-on) and 1.2–1.7 m s−1 (pole-on) for the Sun (peak-to-peak amplitudes are typically 1–1.4 m s−1 and 2.3–3.3 m s−1 resp.), with a minimal jitter for an inclination of 45–55°. This signal is significant compared to other stellar activity contributions and is much larger than the radial-velocity signal of the Earth. The variability is strongly related to the activity cycle, with maximum flows during the descending phase of the cycle, and possible variability on timescales lower than the cycle period. Extension to other solar-type stars shows that the variability due to meridional flows is dominated by the amplitude of the cycle of those stars (compared with mass and rotation rate), and that the peak-to-peak amplitudes can reach 4 m s−1 for the most variable stars when seen pole-on. The meridional flow contribution sometimes represents a high fraction of the convective blueshift inhibition signal, especially for quiet, low-mass stars. For fast-rotating stars, the presence of multi-cellular patterns should significantly decrease the meridional flow contribution to the radial-velocity signal. Conclusions. Our study shows that these meridional flows could be critical for exoplanet detection. Low inclinations are more impacted than edge-on configurations, but these latter still exhibit significant variability. Meridional flows also degrade the correlation between radial velocities due to convective blueshift inhibition and chromospheric activity indicators. This will make the correction from this signal challenging for stars with no multi-cellular patterns, such as the Sun for example, although there may be some configurations for which the line shape variations may be used if the precision is sufficient.

APA, Harvard, Vancouver, ISO, and other styles

31

Bouras, B., F. Karagiannis, P. Chaviaropoulos, and K. D. Papailiou. "Arbitrary Blade Section Design Based on Viscous Considerations. Blade Optimization." Journal of Fluids Engineering 118, no. 2 (June 1, 1996): 364–69. http://dx.doi.org/10.1115/1.2817387.

Full text

Abstract:

A blade design and optimization procedure is presented in this work, which is based on viscous flow considerations. This procedure concerns the design of optimum rotating arbitrary compressible high subsonic compressor and turbine blade shapes. It takes into account the effects of wall curvature and Coriolis force on turbulence, while it allows the variation of stream surface radius, along which the blade shape is placed, as well as streamtube width, with meridional distance. In order to establish the inverse part of the viscous optimization procedure, aspects such as laminar stability, transition, optimum deceleration and, more generally, the behaviour of compressible attached and separated shear layers are discussed. A plane on which all the general properties of the compressible laminar and turbulent shear layers appear, is constructed and the generation of optimum shear layers for the critical side of the blade shape is established. The complete optimization (design) procedure is then described and discussed, while various designs realized by the present procedure are presented at the end of this paper.

APA, Harvard, Vancouver, ISO, and other styles

32

Taubenschuss, U., N. V. Erkaev, H. K. Biernat, C. J. Farrugia, C. Möstl, and U. V. Amerstorfer. "The role of magnetic handedness in magnetic cloud propagation." Annales Geophysicae 28, no. 5 (May 7, 2010): 1075–100. http://dx.doi.org/10.5194/angeo-28-1075-2010.

Full text

Abstract:

Abstract. We investigate the propagation of magnetic clouds (MCs) through the inner heliosphere using 2.5-D ideal magnetohydrodynamic (MHD) simulations. A numerical solution is obtained on a spherical grid, either in a meridional plane or in an equatorial plane, by using a Roe-type approximate Riemann solver in the frame of a finite volume approach. The structured background solar wind is simulated for a solar activity minimum phase. In the frame of MC propagation, special emphasis is placed on the role of the initial magnetic handedness of the MC's force-free magnetic field because this parameter strongly influences the efficiency of magnetic reconnection between the MC's magnetic field and the interplanetary magnetic field. Magnetic clouds with an axis oriented perpendicular to the equatorial plane develop into an elliptic shape, and the ellipse drifts into azimuthal direction. A new feature seen in our simulations is an additional tilt of the ellipse with respect to the direction of propagation as a direct consequence of magnetic reconnection. During propagation in a meridional plane, the initial circular cross section develops a concave-outward shape. Depending on the initial handedness, the cloud's magnetic field may reconnect along its backside flanks to the ambient interplanetary magnetic field (IMF), thereby losing magnetic flux to the IMF. Such a process in combination with a structured ambient solar wind has never been analyzed in detail before. Furthermore, we address the topics of force-free magnetic field conservation and the development of equatorward flows ahead of a concave-outward shaped MC. Detailed profiles are presented for the radial evolution of magnetoplasma and geometrical parameters. The principal features seen in our MHD simulations are in good agreement with in-situ measurements performed by spacecraft. The 2.5-D studies presented here may serve as a basis under more simple geometrical conditions to understand more complicated effects seen in 3-D simulations.

APA, Harvard, Vancouver, ISO, and other styles

33

Zarutskii, V. A., A. S. Pal’chevskii, and V. F. Sivak. "Influence of meridional shape on natural frequencies and the forms of oscillations of shells of rotation." International Applied Mechanics 33, no. 1 (January 1997): 53–54. http://dx.doi.org/10.1007/bf02700887.

Full text

APA, Harvard, Vancouver, ISO, and other styles

34

Adames, Ángel F., and John M. Wallace. "Three-Dimensional Structure and Evolution of the Vertical Velocity and Divergence Fields in the MJO." Journal of the Atmospheric Sciences 71, no. 12 (November 26, 2014): 4661–81. http://dx.doi.org/10.1175/jas-d-14-0091.1.

Full text

Abstract:

Abstract The features in the planetary-scale wind field that shape the MJO-related vertical velocity field are examined using the linear analysis protocol based on the daily global velocity potential field described in a companion paper, augmented by a compositing procedure that yields a more robust and concise description of the prevalent patterns over the Indo-Pacific warm pool sector (60°E–180°). The analysis elucidates the structural elements of the planetary-scale wind field that give rise to the characteristic “swallowtail” shape of the region of enhanced rainfall and the “bottom up” evolution of the vertical velocity profile from one with a shallow peak on the eastern end of the region of enhanced rainfall to one with an elevated peak on the western end. These distinctive features of the vertical velocity field in the MJO reflect the juxtaposition of deep overturning circulation cells in the equatorial plane and much shallower frictionally driven cells in the meridional plane to the east and west of the regions of enhanced rainfall. The zonal overturning circulations determine the pattern of ∂u/∂x and the meridional overturning circulations determine the pattern of ∂υ/∂y in the divergence profiles. These features are at least qualitatively well represented by the Matsuno–Gill solution for the planetary wave response to a stationary equatorial heat source–sink dipole.

APA, Harvard, Vancouver, ISO, and other styles

35

Jahn, Ingo, and Peter Jacobs. "Using Meridional Streamline and Passage Shapes to Generate Radial Turbomachinery Geometry and Meshes." Applied Mechanics and Materials 846 (July 2016): 1–6. http://dx.doi.org/10.4028/www.scientific.net/amm.846.1.

Full text

Abstract:

An important aspect for structural and aerodynamics design of radial flow turbomachinery is the definition of the geometry and the generation of meshes for computational analysis. Particularly in the area of computational design and optimization, the way the geometry is defined is important, as it can limit design space. Traditionally, radial compressors and radial turbine rotors are defined using a mechanical design approach. Effectively a hub and shroud profile, followed by a rotorblade geometry are defined and the shape is adjusted in order to meet certain aerodynamic boundary conditions. The current paper presents an alternative approach, in which the overall geometry is defined starting from an aerodynamic requirement. The corresponding rotor and blade geometry is generated automatically, based on certain constraints. The advantage of this approach is the ability to define directly the aerodynamic requirements, which may allow a simpler efficient optimization of the aerodynamics.

APA, Harvard, Vancouver, ISO, and other styles

36

Han, Ying, and Boualem Khouider. "Convectively Coupled Waves in a Sheared Environment." Journal of the Atmospheric Sciences 67, no. 9 (September 1, 2010): 2913–42. http://dx.doi.org/10.1175/2010jas3335.1.

Full text

Abstract:

Abstract A linear stability analysis, about a radiative–convective equilibrium in a sheared environment, on an equatorial beta plane, for a simple multicloud model for organized tropical convection is presented here. Both vertical/baroclinic and meridional/barotropic zonal wind shears are considered separately in a parameter regime for which the shear-free multicloud model exhibits synoptic-scale instability of Kelvin and n = 0 eastward inertio-gravity [eastward mixed Rossby–gravity (MRG)] waves only, with moderate growth rates. The maximum growth rates appear to increase significantly with the strength of the background wind shear, and new wave instabilities appear and/or disappear depending on the strength and type of the wind shear. It is found here that both high- and low-level vertical shears have a strong impact on the stability of convectively coupled waves (CCWs), consistent with the fact that the multicloud instability mechanism is controlled by both stratiform heating and low-level moisture and congestus heating. Typically, vertical shears with high-level easterly wind destabilize westward moving waves and stabilize eastward waves, whereas westerly winds aloft and on bottom tend to destabilize eastward moving and stabilize westward moving waves. In the mixed situation of high-level easterlies and low-level westerlies both eastward and westward waves are unstable, while in the case of high-level westerlies and low-level easterlies only eastward waves are unstable. In the presence of a barotropic/meridional shear, synoptic-scale convectively coupled westward MRG and Rossby waves emerge, when the shear strength is large enough, due essentially to pure shear instability of the dry dynamics. The meridional shear has also an important impact on the horizontal structure of the waves. Owing to the meridional shear, the Kelvin wave displays a nonzero meridional velocity that induces a significant contribution toward the horizontal convergence. The two-day waves adopt a crescentlike shape while the westward MRG, and somewhat the Rossby waves, become less trapped in the vicinity of the equator.

APA, Harvard, Vancouver, ISO, and other styles

37

Green, Ronald. "On: “Euler’s differential equation and the identification of the magnetic point‐pole and point‐dipole sources” by J. O. Barongo (GEOPHYSICS, 49, 1549–1553, September 1984)." GEOPHYSICS 52, no. 7 (July 1987): 1013–14. http://dx.doi.org/10.1190/1.1442353.

Full text

Abstract:

In the article by Barongo, the problem of distinguishing between the anomaly patterns arising from an isolated pole and a point dipole was examined. The method the author recommended concentrated on a detailed analysis of the shape of the principal meridional profile. I suggest that a better method is to use the isogam map, rather than the profile. From the relevant expressions for contour maps of an isolated pole and a point dipole, the salient differences between the two cases become apparent.

APA, Harvard, Vancouver, ISO, and other styles

38

Balan Sarojini, B., J. M. Gregory, R. Tailleux, G. R. Bigg, A. T. Blaker, D. R. Cameron, N. R. Edwards, A. P. Megann, L. C. Shaffrey, and B. Sinha. "High frequency variability of the Atlantic meridional overturning circulation." Ocean Science 7, no. 4 (July 18, 2011): 471–86. http://dx.doi.org/10.5194/os-7-471-2011.

Full text

Abstract:

Abstract. We compare the variability of the Atlantic meridional overturning circulation (AMOC) as simulated by the coupled climate models of the RAPID project, which cover a wide range of resolution and complexity, and observed by the RAPID/MOCHA array at about 26° N. We analyse variability on a range of timescales, from five-daily to interannual. In models of all resolutions there is substantial variability on timescales of a few days; in most AOGCMs the amplitude of the variability is of somewhat larger magnitude than that observed by the RAPID array, while the time-mean is within about 10 % of the observational estimate. The amplitude of the simulated annual cycle is similar to observations, but the shape of the annual cycle shows a spread among the models. A dynamical decomposition shows that in the models, as in observations, the AMOC is predominantly geostrophic (driven by pressure and sea-level gradients), with both geostrophic and Ekman contributions to variability, the latter being exaggerated and the former underrepresented in models. Other ageostrophic terms, neglected in the observational estimate, are small but not negligible. The time-mean of the western boundary current near the latitude of the RAPID/MOCHA array has a much wider model spread than the AMOC does, indicating large differences among models in the simulation of the wind-driven gyre circulation, and its variability is unrealistically small in the models. In many RAPID models and in models of the Coupled Model Intercomparison Project Phase 3 (CMIP3), interannual variability of the maximum of the AMOC wherever it lies, which is a commonly used model index, is similar to interannual variability in the AMOC at 26° N. Annual volume and heat transport timeseries at the same latitude are well-correlated within 15–45° N, indicating the climatic importance of the AMOC. In the RAPID and CMIP3 models, we show that the AMOC is correlated over considerable distances in latitude, but not the whole extent of the North Atlantic; consequently interannual variability of the AMOC at 50° N, where it is particularly relevant to European climate, is not well-correlated with that of the AMOC at 26° N, where it is monitored by the RAPID/MOCHA array.

APA, Harvard, Vancouver, ISO, and other styles

39

Hosotani, Takuji, Toru Shigemitsu, Yuki Kawaguchi, Takuya Inamoto, Takeru Ishiguro, and Ding Nan. "Influence of meridional plane shape on performance and internal flow of high head contra-rotating small hydroturbine." Journal of Physics: Conference Series 1909, no. 1 (May 1, 2021): 012044. http://dx.doi.org/10.1088/1742-6596/1909/1/012044.

Full text

APA, Harvard, Vancouver, ISO, and other styles

40

Tzou, H. S., W. K. Chai, and D. W. Wang. "Micro-Control Actions and Location Sensitivity of Actuator Patches Laminated on Toroidal Shells." Journal of Vibration and Acoustics 126, no. 2 (April 1, 2004): 284–97. http://dx.doi.org/10.1115/1.1687398.

Full text

Abstract:

Toroidal shell structures have been proposed for components of inflatable telescopes and space structures, etc. over the years. Thus, distributed control of toroidal shells becomes a critical issue in precision maneuver, operation, and reliability. The converse effect of piezoelectric materials has made it one of the best candidates for distributed actuators. The resultant control forces and micro-control actions induced by the distributed actuators depend on applied voltages, geometrical (e.g., spatial segmentation and shape) and material (i.e., various actuator materials) properties of the actuators. The purpose of this analysis is to study the spatial location effects of actuator placement and to evaluate the micro-control actions imposed upon toroidal shell structures. Mathematical models and governing equations of the toroidal shells laminated with distributed actuator patches are presented first, followed by formulations of distributed control forces and micro-control actions including meridional/circumferential membrane and bending control components. Spatially distributed electromechanical microscopic actuation characteristics and control effects resulting from various meridional and circumferential actions of actuator patches at various shell locations are evaluated.

APA, Harvard, Vancouver, ISO, and other styles

41

Tevelev, Al V., I. A. Prudnikov, Ark V. Tevelev, A. O. Khotylev, and E. A. Volodina. "KINEMATICAL MODEL FOR FORMING THE SIMEAN LOW OF THE URALIAN FORELAND BASIN." Moscow University Bulletin. Series 4. Geology, no. 2 (April 28, 2018): 23–32. http://dx.doi.org/10.33623/0579-9406-2018-2-23-32.

Full text

Abstract:

In this work we reported the structural features and mechanism of the formation of the Simskaya low of the Uralian foreland basin, besides the Karatau-Suleyman block as a whole. This block has the shape of a wedge, so with a general latitudinal compression, it experienced lateral extrusion to the north along the conjugated shear zones. This factor determined the local situation of meridional compression and latitudinal tension. In the central part of the block, the latitudinal stretching was compensated for by gradual deflection, which led to the formation of the Simskaya low.

APA, Harvard, Vancouver, ISO, and other styles

42

Talon, Suzanne, and Corinne Charbonnel. "Meridional Circulation, Turbulence and Lithium in Sub-Giants Originating from the Hot Side of the Dip." Symposium - International Astronomical Union 198 (2000): 516–17. http://dx.doi.org/10.1017/s0074180900167245.

Full text

Abstract:

We present the impact of meridional circulation and shear turbulence on the evolution of the lithium abundance at the surface of evolved stars originating from the hot side of the Li Dip. We show that our fully consistent treatment of the same hydrodynamical processes which can account for C and N anomalies in B type stars (Talon et al. 1997) and for the shape of the hot side of the Li dip in open clusters (Talon & Charbonnel 1998) also explains Li observations in stars with Teff higher than 7000K on the main sequence as well as in their evolved counterparts (see also Charbonnel & Talon 1999).

APA, Harvard, Vancouver, ISO, and other styles

43

Lim, Hyungsoo, Jeongmin Seo, Mooryong Park, Bumseog Choi, Junyoung Park, Jesung Bang, Donghyun Lee, et al. "A Numerical Study on Blade Design and Optimization of a Helium Expander for a Hydrogen Liquefaction Plant." Applied Sciences 12, no. 3 (January 28, 2022): 1411. http://dx.doi.org/10.3390/app12031411.

Full text

Abstract:

A design process for cryogenic expanders that supplies 0.5 TPD of liquefied hydrogen in hydrogen liquefaction plants is introduced. To improve the efficiency of the expander, the optimum design was conducted by adjusting two rotor shape parameters. The designed expander for hydrogen liquefaction has a target rotation speed of 75,000 rpm, and helium is applied as the working fluid. Since the operating temperature of the expander is as low as 49 K, a design that reflects the real gas properties must be considered. For a high-efficiency hydrogen liquefaction plant, increasing the expander efficiency is one of the most critical issues. In this study, the efficiency of the cryogenic expander was optimized using the response surface method (RSM). The hub and shroud meridional contours and blade β angle distributions were chosen as the design parameters. As a result, through the optimized design, it was possible to improve the expander efficiency by up to 1.98% compared to the original expander. Flow analysis was conducted to investigate the reason for the efficiency improvement. Through this study, the effect of the blade meridional contour and blade β angle on the cryogenic expander efficiency was verified.

APA, Harvard, Vancouver, ISO, and other styles

44

Pacileo, Giuseppe, Carlo Pisacane, Giovanna M. Russo, Roberto M. Di Donato, Carlo Vosa, and Raffaele Calabrò. "Left ventricular mechanics after early successful repair of aortic coarctation." Cardiology in the Young 5, no. 4 (October 1995): 310–18. http://dx.doi.org/10.1017/s1047951100002766.

Full text

Abstract:

SummaryA successful aortic coarctectomy performed beyond early infancy is followed, even in the long term, by persistence of left ventricular hypertrophy and by diastolic dysfunction, although systolic function is often increased. In this study we investigated whether earlier coarctectomy provides better preservation of left ventricular function. Experimental studies on the myocardial response to pressure overload show that neonates and young infants develop a functionally advantageous combination of myocytic hyperplasia (together with mild hypertrophy) and increased angiogenesis. Older patients, in contrast, generate myocytic hypertrophy in isolation, setting the scene for ventricular dysfunction. Cross-sectional echo-Doppler evaluation of left ventricular size, shape, mass and systolic and diastolic function was made in 13 patients a mean of 44±36 months (range 11 days-10 years) after successful coarctectomy in the first year of life. They were compared to 11 age, body surface area and gender-matched control subjects. In all patients, left ventricular mass normalized for body surface area was significantly greater than in the control group (66.2±12.3 vs 43±l2 p=0.0001). There was no correlation between left ventricular mass normalized for body surface area and age at operation, follow-up duration, degree of residual isthmic gradient, peak systolic wall stress, systolic blood pressure or left ventricular shape. No significant differences were noted between the two groups in regard to transverse diameter of the aortic arch, left ventricular afterload (meridional end-systolic wall stress), volume and shape (both in systole and diastole), systolic performance (fractional shortening and ejection fraction) and contractility (rate-corrected velocity of fiber shortening to meridional end-systolic wall stress relationship). Furthermore, no significant differences were found with respect to indices of mitral (including peak filling rate normalized to mitral stroke volume) and pulmonary venous flow, suggesting normal diastolic function. Repair of aortic coarctation in the first year of life promotes a more complete recovery of left ventricular function (particularly diastolic) than that reported after coarctectomy at older age, despite persistence of moderate ventricular hypertrophy.

APA, Harvard, Vancouver, ISO, and other styles

45

Lebed, Evgeny V. "Influence of the height of the ribbed-ring dome on the stress state of its frame during the overhang mounting process." Structural Mechanics of Engineering Constructions and Buildings 16, no. 6 (December 15, 2020): 452–64. http://dx.doi.org/10.22363/1815-5235-2020-16-6-452-464.

Full text

Abstract:

The aim of the research. To analyze the stress state of structures of ribbed-ring domes of different heights during overhang erection. The domes have spherical metal frames and a support contour of the same diameter. Due to different heights, the steepness of the geometric shape of the domes changes. The study is devoted to establishing the relationship between the stress state of the frame and the steepness of the dome when mounted. It was investigated how the height of the ribbed-ring dome affects the stress state of its frame during overhang mounting process. Methods. Computer models of design frames of ribbed-ring domes of different heights made of steel I-beams were developed. Based on design models, a sequence of assembly models for incomplete frames was created for different stages of installation. Both for the design and for all installation models of dome frames of different heights, computer calculations were performed for the effect of the load from its own weight. As a result of calculations for all domes and at all stages of installation, deformations and stresses in the meridional ribs were determined, which were compared with the design diagrams. Results. Comparative graphs of deformations of dome frames and diagrams of changes in the degree of use of steel strength in meridional ribs at all stages of mounted installation are obtained. Comparative graphs of installation and design stresses in the meridional ribs on different tiers for all stages of mounted installation are also shown. The assessment of the installation stress states is given, their inevitability and the degree of influence on the stress state of the dome frames are noted.

APA, Harvard, Vancouver, ISO, and other styles

46

Nguyen, Hien Nho Gia, Olivier Millet, and Gérard Gagneux. "Exact calculation of axisymmetric capillary bridge properties between two unequal-sized spherical particles." Mathematics and Mechanics of Solids 24, no. 9 (October 8, 2018): 2767–84. http://dx.doi.org/10.1177/1081286518787842.

Full text

Abstract:

A calculation method for the meridional profile of axisymmetric bridges between two spheres of different size is introduced in this manuscript. From geometrical data of the capillary bridge, such as the neck radius and boundary conditions (filling and contact angle), the shape of the capillary bridge is calculated analytically as a solution of the Young–Laplace equation. Its free surfaces, of constant mean curvature, may be classified into portions of nodoid, unduloid, and other limit cases. Moreover, other properties of the liquid bridge can be computed analytically, such as the associated capillary force exerted on the solid surfaces, liquid volume, mean curvature, and free surface area.

APA, Harvard, Vancouver, ISO, and other styles

47

Kostornoi, A. S., P. Yu Tkach, O. O. Bondariev, and N. N. Podopryhora. "Design of impeller blades in the intermediate stage of centrifugal pump to a preset shape of meridional flow pattern." Journal of Physics: Conference Series 1741 (January 2021): 012005. http://dx.doi.org/10.1088/1742-6596/1741/1/012005.

Full text

APA, Harvard, Vancouver, ISO, and other styles

48

Mojaddam, Mohammad, and Keith Pullen. "Optimization of a Centrifugal Compressor Using the Design of Experiment Technique." Applied Sciences 9, no. 2 (January 15, 2019): 291. http://dx.doi.org/10.3390/app9020291.

Full text

Abstract:

Centrifugal compressor performance is affected by many parameters, optimization of which can lead to superior designs. Recognizing the most important parameters affecting performance helps to reduce the optimization process cost. Of the compressor components, the impeller plays the most important role in compressor performance, hence the design parameters affecting this component were considered. A turbocharger centrifugal compressor with vaneless diffuser was studied and the parameters investigated included meridional geometry, rotor blade angle distribution and start location of the main blades and splitters. The diffuser shape was captured as part of the meridional geometry. Applying a novel approach to the problem, full factorial analysis was used to investigate the most effective parameters. The Response Surface Method was then implemented to construct the surrogate models and to recognize the best points over a design space created as based on the Box-Behnken methodology. The results highlighted the factors that affected impeller performance the most. Using the Design of Experiment technique, the model which optimized both efficiency and pressure ratio simultaneously delivered a design with 3% and 11% improvement in each respectively in comparison to the initial impeller at the design point. Importantly, this was not at the expense of sacrificing range, of critical concern in compressor design.

APA, Harvard, Vancouver, ISO, and other styles

49

Struthers, H., G. E. Bodeker, J. Austin, S. Bekki, I. Cionni, M. Dameris, M. A. Giorgetta, et al. "The simulation of the Antarctic ozone hole by chemistry-climate models." Atmospheric Chemistry and Physics 9, no. 17 (September 3, 2009): 6363–76. http://dx.doi.org/10.5194/acp-9-6363-2009.

Full text

Abstract:

Abstract. While chemistry-climate models are able to reproduce many characteristics of the global total column ozone field and its long-term evolution, they have fared less well in simulating the commonly used diagnostic of the area of the Antarctic ozone hole i.e. the area within the 220 Dobson Unit (DU) contour. Two possible reasons for this are: (1) the underlying Global Climate Model (GCM) does not correctly simulate the size of the polar vortex, and (2) the stratospheric chemistry scheme incorporated into the GCM, and/or the model dynamics, results in systematic biases in the total column ozone fields such that the 220 DU contour is no longer appropriate for delineating the edge of the ozone hole. Both causes are examined here with a view to developing ozone hole area diagnostics that better suit measurement-model inter-comparisons. The interplay between the shape of the meridional mixing barrier at the edge of the vortex and the meridional gradients in total column ozone across the vortex edge is investigated in measurements and in 5 chemistry-climate models (CCMs). Analysis of the simulation of the polar vortex in the CCMs shows that the first of the two possible causes does play a role in some models. This in turn affects the ability of the models to simulate the large observed meridional gradients in total column ozone. The second of the two causes also strongly affects the ability of the CCMs to track the observed size of the ozone hole. It is shown that by applying a common algorithm to the CCMs for selecting a delineating threshold unique to each model, a more appropriate diagnostic of ozone hole area can be generated that shows better agreement with that derived from observations.

APA, Harvard, Vancouver, ISO, and other styles

50

Greenspan, H. P., and M. Ungarish. "On the enhancement of centrifugal separation." Journal of Fluid Mechanics 157 (August 1985): 359–73. http://dx.doi.org/10.1017/s0022112085002415.

Full text

Abstract:

We consider the two-phase flow of a suspension in a rotating cylinder with inclined endplates for which inertial and viscous effects are small. It is shown that, when the Coriolis force is dominant, flow in the core is essentially unaffected by geometry. If a fluid particle can make a complete circuit about the rotation axis, the sedimentation velocity cannot be augmented by geometrical effects as it can in gravitational settling. However, with the insertion of a complete meridional barrier to block movement around the centre, separation becomes more sensitive to the shape of the container walls. In this case, behaviour similar to that in a gravitational field is possible once again.

APA, Harvard, Vancouver, ISO, and other styles

Journal articles on the topic 'Meridional shape'

Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles