Study of Wax Deposition Pattern of High Wax-Bearing Crude Oil Based on Cold Finger Experiment

In order to solve the problem of wax deposition in waxy crude oil from the Daqing oilfield, cold fingers were used in the experimentation. Compared with other methods, the cold finger method is simple, easy to operate, and takes little space. Measurements of wax deposition with temperature, temperature differences between the crude oil and the wall, deposition time, and cold finger rotation rate were made. The results showed that the deposition rate is up to 0.35 g/h at 8–24 h. The maximum deposition rate at 90 rotations/min was 0.26 g/h, which is 3% higher than the minimum deposition rate.

New single vortex generation method for flame/vortex interaction using flow behind a rotating cylinder

This paper investigates a new experimental method to generate a single two-dimensional translated vortex for flame/vortex interaction studies. A rotating cylinder is immersed in a uniform flow and, its rotating speed is impulsively reduced. This sudden action triggers the generation of a single vortex when both the initial and the final rotation speeds are in the range of a steady-state regime. Flow visualization allows confirming the applicability of this method, while a complementary two-dimensional numerical simulation is conducted to understand the vortex formation process. A vorticity layer is detached from the cylinder, initiating a feeding process and gradual growth of a single leading vortex. The feeding process is saturated at a specific distance from the cylinder and, vortex separation from the vorticity layer is observed. At the final stage of the formation process, the generated vortex is advected away and, a steady-state regime is again established behind the cylinder. The vortex characteristics appear to be related to the normalized reduction in the rotation rate ∆α, defined as the initial and final rotation rates difference normalized by the initial rotation rate. Several combinations of initial and final rotation rates corresponding to different normalized reductions are investigated experimentally and numerically. The results allow understanding the effect of this parameter; a higher normalized reduction generates a stronger, more rapidly growing vortex. However, its trajectory is related to the wake deviation corresponding to the final rotation rate.

Discovery, TESS Characterization, and Modeling of Pulsations in the Extremely Low-mass White Dwarf GD 278

We report the discovery of pulsations in the extremely low-mass (ELM), likely helium-core white dwarf GD 278 via ground- and space-based photometry. GD 278 was observed by the Transiting Exoplanet Survey Satellite (TESS) in Sector 18 at a 2 minute cadence for roughly 24 days. The TESS data reveal at least 19 significant periodicities between 2447 and 6729 s, one of which is the longest pulsation period ever detected in a white dwarf. Previous spectroscopy found that this white dwarf is in a 4.61 hr orbit with an unseen >0.4 M ⊙ companion and has T eff = 9230 ± 100 K and log g = 6.627 ± 0.056 , which corresponds to a mass of 0.191 ± 0.013 M ⊙. Patterns in the TESS pulsation frequencies from rotational splittings appear to reveal a stellar rotation period of roughly 10 hr, making GD 278 the first ELM white dwarf with a measured rotation rate. The patterns inform our mode identification for asteroseismic fits, which, unfortunately, do not reveal a global best-fit solution. Asteroseismology reveals two main solutions roughly consistent with the spectroscopic parameters of this ELM white dwarf, but with vastly different hydrogen-layer masses; future seismic fits could be further improved by using the stellar parallax. GD 278 is now the tenth known pulsating ELM white dwarf; it is only the fifth known to be in a short-period binary, but is the first with extended, space-based photometry.

3D structure of single and multiple vortices in a flow under rotation

In this paper, we analyze the 3D structure of vortices developed in a rotating cylinder nonhomogeneously heated from below, when the rotation rate is increased. The analysis has been done by using nonlinear simulations. For a fixed Rayleigh number, the rotation rate is the bifurcation parameter. At low rotation rates, one single vortex is developed. When the rotation on the system is increased, another coexistent vortex appears at mid-levels in the cell. If the rotation is high enough, multiple-vortex structures with three or four vortices are developed at different heights. For larger rotation, complex multiple vortices appear with a chaotic behavior. A force balance analysis permits to study the role of the forces being determinant.

Paleomagnetic Studies of the Late Miocene Mangapoike River Section, Northern Hawke's Bay, New Zealand

<p>The Mangapoike River section (38.9 degrees S, 177.6 degrees E), on the eastern limb of the Wairoa Syncline, northern Hawke's Bay, is a thick (> 4000 m) and well exposed sequence of Waiauan to Waipipian sediments in which foraminiferal and radiolarian biostratigraphy and silicic tuff lithostratigraphy are well known. An Early Pliocene magnetostratigraphy has been determined by Kennett and Watkins (1974). The present study extends the magnetostratigraphy to the Middle -Late Miocene, and establishes a late Miocene to Early Pliocene 3000 m magnetostratigraphic reference column for New Zealand. The only identifiable remanence carrying magnetic mineral in the Mangapoike sediments is titanomagnetite. Its chemistry does not vary with grain size. Oxidation of the titanomagnetite is deuteric, and thus pre-depositional. Fluctuations of titanomagnetite concentration between 10-3 to 10-4 wt percent are the main influence on the variation of NRM intensity. Viscous magnetisations characterised by both the alignment of NRM directions in a general present day field direction and remanence decay and aquisition over laboratory time were recognised in 85 percent of the 1204 paleomagnetic specimens. Secondary magnetisations were removed by thermal demagnetisation at temperatures varying between 200 degrees C and 320 degrees C. AF demagnetisation was not effective in removing viscous magnetisations, even at peak alternating fields of 35 mT, since the coercivities of the primary and secondary magnetisations overlap completely. The random relationship between the degree of bioturbation and in-site dispersion at individual sites indicates the magnetisation is acquired after bioturbation, and thus is a post-depositional detrital magnetisation. The time lag between deposition and acquisition of the magnetisation is approximately 1000 yrs. Six normal (MN1 - MN6) and seven reversed (MR1 - MR7) polarity magnetozones are identified within the late Miocene at Mangapoike. Only one normal magnetozone (MN6) is recognised in the stratigraphic interval equivalent to that from which Kennett and Watkins (1974) reported two normal zones (C1 and C2). MN6 is correlated to C2. C1 is inferred to be an uncleaned normal overprint. The magnetozones are correlated to Chrons 11 to 4, which implies an average sedimentation rate of 64 cm/1000 yrs. The previously known Miocene - Pliocene 3 degrees angular unconformity at Mangapoike (Hornibrook 1977) represents the period from 6.3 Ma to at least 5.41 Ma. A previously unrecognised unconformity from at least 6.86 to at least 6.42 Ma is postulated, based on the preferred magnetostratigraphic interpretation. The presence of the unconformity is supported by radiolarian and benthic foraminiferal biostratigraphy. Three distinct lithological events at Mangapoike, based both on the synchroneity with deep-sea benthic delta 18O records and unconformities of the Vail-curve, are inferred to result from glacioeustatism. At Mangapoike, the Waiauan - Tongaporutuan boundary, as defined by the incoming of Bolivinita cf pohana, has a magnetostratigraphic age of 10.3 Ma. Both the LAD of Loxostomum truncatum and the FAD of Bolivinita cf pohana are less than 42,000 yrs. younger than the late Waiauan glacioeustatic event. The Waiauan - Tongaporutuan boundary is thus postulated to result from glacioeustatism. Glacioeustatism may also explain the excellent age correlation between the base of the Tongaporutuan and the base of the Tortonian stratotype. Correlation of the late Miocene and early Pliocene magnetostratigraphies and biostratigraphies of on-shore New Zealand with either of the magnetostratigraphic interpretations of DSDP Site 594 results in an unacceptably high diachroneity of some planktic taxa of 1.8 Ma over 3.6 degrees of latitude. Of four possiblities to resolve the anomaly, incorrect magnetostratigraphic correlations at Site 594 is the most likely. The previously determined age of 6.2 Ma for the LAD of Globoquadrina dehiscens in New Zealand is erroneous. A magnetostratigraphic age for the LAD of G. dehiscens at Mangapoike is 9.2 Ma. This age is not an extinction date for the taxon throughout New Zealand, and the LAD may well be erratic and diachronous within New Zealand. The Wairoa Syncline, a forearc basin within the Hikurangi margin, has a rotation rate as determined from declination directions, of 7-8 degrees /Ma for the last 5 Ma. Of this less than 1.5 degrees /Ma is due to apparent polar wander of the Australian plate. Extrapolation of this rate towards the present is consistent with a present day rotation rate of 7 degrees /Ma derived from strain analysis of geodetic data. Prior to 10 Ma the rate of tectonic rotation is poorly constrained and may vary between 3 degrees /Ma and 0 degrees /Ma. The change in the rate of rotation of the Wairoa Syncline around 5 Ma is probably related to a marked change in regional tectonic regime involving opening and spreading to the north of New Zealand and compression and shortening to the south.</p>

Paleomagnetic Studies of the Late Miocene Mangapoike River Section, Northern Hawke's Bay, New Zealand

<p>The Mangapoike River section (38.9 degrees S, 177.6 degrees E), on the eastern limb of the Wairoa Syncline, northern Hawke's Bay, is a thick (> 4000 m) and well exposed sequence of Waiauan to Waipipian sediments in which foraminiferal and radiolarian biostratigraphy and silicic tuff lithostratigraphy are well known. An Early Pliocene magnetostratigraphy has been determined by Kennett and Watkins (1974). The present study extends the magnetostratigraphy to the Middle -Late Miocene, and establishes a late Miocene to Early Pliocene 3000 m magnetostratigraphic reference column for New Zealand. The only identifiable remanence carrying magnetic mineral in the Mangapoike sediments is titanomagnetite. Its chemistry does not vary with grain size. Oxidation of the titanomagnetite is deuteric, and thus pre-depositional. Fluctuations of titanomagnetite concentration between 10-3 to 10-4 wt percent are the main influence on the variation of NRM intensity. Viscous magnetisations characterised by both the alignment of NRM directions in a general present day field direction and remanence decay and aquisition over laboratory time were recognised in 85 percent of the 1204 paleomagnetic specimens. Secondary magnetisations were removed by thermal demagnetisation at temperatures varying between 200 degrees C and 320 degrees C. AF demagnetisation was not effective in removing viscous magnetisations, even at peak alternating fields of 35 mT, since the coercivities of the primary and secondary magnetisations overlap completely. The random relationship between the degree of bioturbation and in-site dispersion at individual sites indicates the magnetisation is acquired after bioturbation, and thus is a post-depositional detrital magnetisation. The time lag between deposition and acquisition of the magnetisation is approximately 1000 yrs. Six normal (MN1 - MN6) and seven reversed (MR1 - MR7) polarity magnetozones are identified within the late Miocene at Mangapoike. Only one normal magnetozone (MN6) is recognised in the stratigraphic interval equivalent to that from which Kennett and Watkins (1974) reported two normal zones (C1 and C2). MN6 is correlated to C2. C1 is inferred to be an uncleaned normal overprint. The magnetozones are correlated to Chrons 11 to 4, which implies an average sedimentation rate of 64 cm/1000 yrs. The previously known Miocene - Pliocene 3 degrees angular unconformity at Mangapoike (Hornibrook 1977) represents the period from 6.3 Ma to at least 5.41 Ma. A previously unrecognised unconformity from at least 6.86 to at least 6.42 Ma is postulated, based on the preferred magnetostratigraphic interpretation. The presence of the unconformity is supported by radiolarian and benthic foraminiferal biostratigraphy. Three distinct lithological events at Mangapoike, based both on the synchroneity with deep-sea benthic delta 18O records and unconformities of the Vail-curve, are inferred to result from glacioeustatism. At Mangapoike, the Waiauan - Tongaporutuan boundary, as defined by the incoming of Bolivinita cf pohana, has a magnetostratigraphic age of 10.3 Ma. Both the LAD of Loxostomum truncatum and the FAD of Bolivinita cf pohana are less than 42,000 yrs. younger than the late Waiauan glacioeustatic event. The Waiauan - Tongaporutuan boundary is thus postulated to result from glacioeustatism. Glacioeustatism may also explain the excellent age correlation between the base of the Tongaporutuan and the base of the Tortonian stratotype. Correlation of the late Miocene and early Pliocene magnetostratigraphies and biostratigraphies of on-shore New Zealand with either of the magnetostratigraphic interpretations of DSDP Site 594 results in an unacceptably high diachroneity of some planktic taxa of 1.8 Ma over 3.6 degrees of latitude. Of four possiblities to resolve the anomaly, incorrect magnetostratigraphic correlations at Site 594 is the most likely. The previously determined age of 6.2 Ma for the LAD of Globoquadrina dehiscens in New Zealand is erroneous. A magnetostratigraphic age for the LAD of G. dehiscens at Mangapoike is 9.2 Ma. This age is not an extinction date for the taxon throughout New Zealand, and the LAD may well be erratic and diachronous within New Zealand. The Wairoa Syncline, a forearc basin within the Hikurangi margin, has a rotation rate as determined from declination directions, of 7-8 degrees /Ma for the last 5 Ma. Of this less than 1.5 degrees /Ma is due to apparent polar wander of the Australian plate. Extrapolation of this rate towards the present is consistent with a present day rotation rate of 7 degrees /Ma derived from strain analysis of geodetic data. Prior to 10 Ma the rate of tectonic rotation is poorly constrained and may vary between 3 degrees /Ma and 0 degrees /Ma. The change in the rate of rotation of the Wairoa Syncline around 5 Ma is probably related to a marked change in regional tectonic regime involving opening and spreading to the north of New Zealand and compression and shortening to the south.</p>

Bearing friction effect on cup anemometer performance modelling

In the present work, the effect of the friction forces at bearings on cup anemometer performance is studied. The study is based on the classical analytical approach to cup anemometer performance (2-cup model), used in the analysis by Schrenk (1929) and Wyngaard (1981). The friction torque dependence on temperature was modelled using exponential functions fitted to the experimental results from RISØ report #1348 by Pedersen (2003). Results indicate a logical poorer performance (in terms of a lower rotation speed at the same wind velocity), with an increase of the friction. However, this decrease of the performance is affected by the aerodynamic characteristics of the cups. More precisely, results indicate that the effect of the friction is modified depending on the ratio between the maximum value of the aerodynamic drag coefficient (at 0° yaw angle) and the minimum one (at 180° yaw angle). This reveals as a possible way to increase the efficiency of the cup anemometer rotors. Besides, if the friction torque is included in the equations, a noticeable deviation of the rotation rate (0.5-1% with regard to the expected rotation rate without considering friction) is found for low temperatures.

Theoretical and Experimental Studies on Air-suction Roller-type Precision Seed-Metering Device

The seed-metering device is the key component of a precision seeder. The methods to improve the seed suction and dropping efficiency of air suction drum precision seed metering device were discussed Establishing the force and equation of motion for sucking, carrying and dropping stages, the effect of the seeding parameters on the effect of sucking and seeding is analyzed. Then, the single factor and orthogonal test are carried out on the sucking pressure, the carrying pressure, the rotation rate and the dropping pressure as the experimental factors for the optimization analysis. And the optimum experimental parameters and the predicted values of each test index are obtained. That is, when the seeding pressure of -2.87kPa, the seeding pressure of -1.91kPa, the drum rotation rate of 18.72 r min-1 and the dropping pressure of 1.74kPa, the best effect that the single rate is 93.8%.

Numerical Investigation of the Thermal Performance of an Axially Rotating Internally Finned Receiver Tube of Parabolic Trough Concentrator

Enhancement of the thermal performance of the parabolic trough receiver tube is one of the approaches to energy sustainability. In the present work, the thermal performance of an axially rotating receiver tube equipped with internal flat longitudinal fins is studied. The effects of both the fin height and the rate of axial rotation are investigated at low values of axial Reynold’s number. The numerical analysis is held at various rotation rates using ANSYS Fluent. The numerical findings showed that the effect of the axial rotation on the internally finned receiver tube is not significant yet negative where a maximum reduction of 6% in the outlet temperature is reached in the 2mm height internally finned tube at rotation rate of N=21. However, the analysis showed that as the rotation rate increases, the temperature homogeneity between the fluid layers also increases and thus the liquid stratification phenomenon between the fluid layers is eliminated. The percentage of temperature difference between the fluid layers near the pipe center and the layers near the pipe wall reaches an optimum value of 58.4% at N=21 which is confirmed by an optimum increase of 110% in Nusselt number at the same rotation rate. However, a maximum loss of 81.6% in pressure coefficient is found in the case of the 2mm internally finned tube due to the increased turbulence. Thus, the integration of pipe axial rotation and internal fins can yield an enhancement in the heat transfer to the parabolic trough concentrator receiver tube and thus its thermal performance.