Статті в журналах з теми "Stream traced inlet"
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1
DONG, HAO, CHENG-PENG WANG, and KE-MING CHENG. "EXPERIMENTAL AND NUMERICAL INVESTIGATION OF HYPERSONIC JAWS INLET." Modern Physics Letters B 24, no. 13 (May 30, 2010): 1409–12. http://dx.doi.org/10.1142/s0217984910023748.
Повний текст джерелаАнотація:
In order to obtain the flow field characteristics and the influence of boundary layer, numerical simulations and wind tunnel tests are conducted for two streamline traced Jaws inlets at Mach number 7. The inlets are designed based on a flow field with 8-7 planar shock wave (the ramp in pitch plane is inclined at 8° to the free stream and in yaw plane is inclined at 7° to the free stream, yielding planar shocks). In the study, the static pressure distributions were measured and analyzed along the plane-symmetric centerline of the inlet with and without the boundary layer correction, respectively. Results show that boundary layer correction can obviously weaken the viscous influence to the inlet, increasing the mass flow coefficient and improving total pressure recovery.
2
Wennrich, V., A. Francke, A. Dehnert, O. Juschus, T. Leipe, C. Vogt, J. Brigham-Grette, P. S. Minyuk, and M. Melles. "Modern sedimentation patterns in Lake El'gygytgyn, NE Russia, derived from surface sediment and inlet streams samples." Climate of the Past 9, no. 1 (January 22, 2013): 135–48. http://dx.doi.org/10.5194/cp-9-135-2013.
Повний текст джерелаАнотація:
Abstract. Lake El'gygytgyn/NE Russia holds a continuous 3.58 Ma sediment record, which is regarded as the most long-lasting climate archive of the terrestrial Arctic. Based on multi-proxy geochemical, mineralogical, and granulometric analyses of surface sediment, inlet stream and bedrock samples, supplemented by statistical methods, major processes influencing the modern sedimentation in the lake were investigated. Grain-size parameters and chemical elements linked to the input of feldspars from acidic bedrock indicate a wind-induced two-cell current system as major driver of sediment transport and accumulation processes in Lake El'gygytgyn. The distribution of mafic rock related elements in the sediment on the lake floor can be traced back to the input of weathering products of basaltic rocks in the catchment. Obvious similarities in the spatial variability of manganese and heavy metals indicate sorption or co-precipitation of these elements with Fe and Mn hydroxides and oxides. But the similar distribution of organic matter and clay contents might also point to a fixation to organic components and clay minerals. An enrichment of mercury in the inlet streams might be indicative of neotectonic activity around the lake. The results of this study add to the fundamental knowledge of the modern lake processes of Lake El'gygytgyn and its lake-catchment interactions, and thus, yield crucial insights for the interpretation of paleo-data from this unique archive.
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Wennrich, V., A. Francke, A. Dehnert, O. Juschus, T. Leipe, C. Vogt, J. Brigham-Grette, P. S. Minyuk, and M. Melles. "Modern sedimentation patterns in Lake El'gygytgyn, NE Russia, derived from surface sediment and inlet streams samples." Climate of the Past Discussions 8, no. 3 (June 1, 2012): 2007–39. http://dx.doi.org/10.5194/cpd-8-2007-2012.
Повний текст джерелаАнотація:
Abstract. High Arctic Lake El'gygytgyn/NE Russia holds a continuous 3.58 Ma sediment record, which is regarded as the most long-lasting climate archive of the terrestrial Arctic. Based on multi-proxy geochemical, mineralogical and granulometric analyses of surface sediment, inlet stream and bedrock samples, supplemented by statistical methods, major processes influencing the modern sedimentation in the lake were investigated. Grain-size parameters and chemical elements linked to the input of feldspars from acidic bedrock indicate a wind-induced two-cell current system as major driver of sediment transport and accumulation processes in Lake El'gygytgyn. The distribution of mafic-rock related elements in the sediment on the lake floor can be traced back to the input of weathering products of basaltic rocks in the catchment. Obvious similarities in the spatial variability of manganese and heavy metals indicate sorption or co-precipitaion of these elements with Fe and Mn hydroxides and oxides. But the akin distribution of organic matter content might also point to a fixation to organic components. An enrichment of mercury in the inlet streams might be indicative of neotectonic activity around the lake. The results of this study add to the fundamental knowledge of the in-lake processes of Lake El'gygytgyn and its lake-catchment interactions, and thus, yield crucial insights for the interpretation of paleo-data from this unique archive.
4
He, Xuzhao, Jialing Le, and Si Qin. "Design and analysis osculating general curved cone waverider." Aircraft Engineering and Aerospace Technology 89, no. 6 (October 2, 2017): 797–803. http://dx.doi.org/10.1108/aeat-12-2014-0214.
Повний текст джерелаАнотація:
Purpose Waverider has high lift to drag ratio and will be an idea aerodynamic configuration for hypersonic vehicles. But a structure permitting aerodynamic like waverider is still difficult to generate under airframe’s geometric constrains using traditional waverider design methods. And furthermore, traditional waverider’s aerodynamic compression ability cannot be easily adjusted to satisfy the inlet entrance requirements for hypersonic air-breathing vehicles. The purpose of this paper is to present a new method named osculating general curved cone (OCC) method aimed to improve the shortcomings of traditional waveriders. Design/methodology/approach A basic curved cone is, first, designed by the method of characteristics. Then the waverider’s inlet captured curve and front captured tube are defined in the waverider’s exit plane. Osculating planes are generated along the inlet captured curve and the designed curved cone is transformed to the osculating planes. Streamlines are traced in the transformed curved cone flow field. Combining all streamlines which have been obtained, OCC waverider’s compression surface is generated. Waverider’s upper surface uses the free stream surface. Findings It is found that OCC waverider has good volumetric characteristics and good flow compression abilities compared with the traditional osculating cone (OC) waverider. The volume of OCC waverider is 25 per cent larger than OC waverider at the same design condition. Furthermore, OCC waverider can compress incoming flow to required flow conditions with high total pressure recovery in the waverider’s exit plane. The flow uniformity in the waverider exit plane is quite well. Practical implications The analyzed results show that the OCC waverider can be a practical high performance airframe/forebody for hypersonic vehicles. Furthermore, this novel waverider design method can be used to design a structure permitting aerodynamic like waverider for a practical hypersonic vehicle. Originality/value The paper puts forward a novel waverider design method which can improve the waverider’s volumetric characteristics and compression abilities compared with the traditional waverider design methods. This novel design approach can extend the waverider’s applications for designing hypersonic vehicles.
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Hall Jr., Robert O., and Hilary L. Madinger. "Use of argon to measure gas exchange in turbulent mountain streams." Biogeosciences 15, no. 10 (May 18, 2018): 3085–92. http://dx.doi.org/10.5194/bg-15-3085-2018.
Повний текст джерелаАнотація:
Abstract. Gas exchange is a parameter needed in stream metabolism and trace gas emissions models. One way to estimate gas exchange is via measuring the decline of added tracer gases such as sulfur hexafluoride (SF6). Estimates of oxygen (O2) gas exchange derived from SF6 additions require scaling via Schmidt number (Sc) ratio, but this scaling is uncertain under conditions of high gas exchange via bubbles because scaling depends on gas solubility as well as Sc. Because argon (Ar) and O2 have nearly identical Schmidt numbers and solubility, Ar may be a useful tracer gas for estimating stream O2 exchange. Here we compared rates of gas exchange measured via Ar and SF6 for turbulent mountain streams in Wyoming, USA. We measured Ar as the ratio of Ar : N2 using a membrane inlet mass spectrometer (MIMS). Normalizing to N2 confers higher precision than simply measuring [Ar] alone. We consistently enriched streams with Ar from 1 to 18 % of ambient Ar concentration and could estimate gas exchange rate using an exponential decline model. The mean ratio of gas exchange of Ar relative to SF6 was 1.8 (credible interval 1.1 to 2.5) compared to the theoretical estimate 1.35, showing that using SF6 would have underestimated exchange of Ar. Steep streams (slopes 11–12 %) had high rates of gas exchange velocity normalized to Sc=600 (k600, 57–210 m d−1), and slope strongly predicted variation in k600 among all streams. We suggest that Ar is a useful tracer because it is easily measured, requires no scaling assumptions to estimate rates of O2 exchange, and is not an intense greenhouse gas as is SF6. We caution that scaling from rates of either Ar or SF6 gas exchange to CO2 is uncertain due to solubility effects in conditions of bubble-mediated gas transfer.
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Marttila, H., S. Tammela, K. R. Mustonen, P. Louhi, T. Muotka, H. Mykrä, and B. Kløve. "Contribution of flow conditions and sand addition on hyporheic zone exchange in gravel beds." Hydrology Research 50, no. 3 (February 27, 2019): 878–85. http://dx.doi.org/10.2166/nh.2019.099.
Повний текст джерелаАнотація:
Abstract We conducted a series of tracer test experiments in 12 outdoor semi-natural flumes to assess the effects of variable flow conditions and sand addition on hyporheic zone conditions in gravel beds, mimicking conditions in headwater streams under sediment pressure. Two tracer methods were applied in each experiment: 2–5 tracer-pulse tests were conducted in all flumes and pulses were monitored at three distances downstream of the flume inlet (0 m, 5 m and 10 m, at bed surface), and in pipes installed into the gravel bed at 5 m and 10 m distances. The tracer breakthrough curves (total of 120 tracer injections) were then analysed with a one-dimensional solute transport model (OTIS) and compared with data from the gravel pipes in point-dilution pulse tests. Sand addition had a strong negative effect on horizontal fluxes (qh), whereas the fraction of the median travel time due to transient storage (F200) was determined more by flow conditions. These results suggest that even small additions of sand can modify the hyporheic zone exchange in gravel beds, thus making headwater streams with low sediment transport capacity particularly vulnerable to sediments transported into the stream from catchment land use activities.
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Su, He, Pei Wu, Jing Xue, Yongan Zhang, and Haijun Zhang. "Analysis of flow field characteristics and structure optimization of the split-stream rushing muffler for diesel engine." Noise Control Engineering Journal 68, no. 1 (January 20, 2020): 101–11. http://dx.doi.org/10.3397/1/37688.
Повний текст джерелаАнотація:
In order to analyze the flow field characteristics of the split-stream rushing muffler, a theoretical model describing the velocity of the split streams is established and verified by the tracer test. For this new-principle muffler, the acoustic performance and the relationship between the velocity drop of the airflow and the pressure field are analyzed, also the structure optimization of the muffler is carried out based on the orthogonal test. Finally, a new muffler is fabricated based on the designing theory of this type of muffler for a prototype of diesel engine, and the comparative analyses are conducted compared with its original muffler. The results show that the establishment and analysis of the theoretical model for velocity during the split-streams rushing process are correct. In the frequency range of 0â–“1000 Hz, the average transmission loss of split-stream rushing muffler is better than that of the original muffler. While the speed of airflow is reduced by split-streams rushing, a certain pressure loss is caused at the same time, which is about 50% of total pressure loss of the muffler, and the average fluid resistance coefficient of the split-stream rushing process is 0.91. Compared to the original muffler of the sample engine, the average insertion loss of the optimized new muffler is increased by 61.2%. At inlet air velocity of 30 m/s, the pressure loss is reduced by 16.8%. The results provide a potential for practical engineering application of this new split-stream rushing muffler in future.
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Henríquez, Felipe, Luis Maldonado, Juan Yianatos, Paulina Vallejos, Francisco Díaz, and Luis Vinnett. "The Use of Radioactive Tracers to Detect and Correct Feed Flowrate Imbalances in Parallel Flotation Banks." J 5, no. 2 (June 12, 2022): 287–97. http://dx.doi.org/10.3390/j5020020.
Повний текст джерелаАнотація:
This work presents the application of radioactive tracers to detect and correct feed flowrate imbalances in parallel rougher flotation banks. Several surveys were conducted at Minera Los Pelambres concentrator, in banks consisting of 250 m3 mechanical flotation cells. The feed pulp distribution was estimated from the mean residence times, which were obtained from residence time distribution measurements. The tracer was injected in the feed distributor and the inlet and outlet tracer signals of cells 1 and 2 were measured by on-stream sensors. The baseline condition for the pulp distribution was defined by the valve settings in the feed distributor, which led to an unbalanced condition for two parallel rougher banks, with 34% of the pulp being fed to bank A and 66% to bank B. New valve configurations were evaluated, with a fraction of the feed being directed to the rougher bank C, which was not initially fed from the same distributor. The feed distribution was finally balanced with 49% of the pulp being fed to bank A versus 51% to bank B. Thus, the radioactive traces proved to be a powerful tool to industrially detect and improve feed distributions in parallel flotation circuits.
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Temnerud, J., A. Düker, S. Karlsson, B. Allard, K. Bishop, J. Fölster, and S. Köhler. "Spatial patterns of some trace elements in four Swedish stream networks." Biogeosciences Discussions 9, no. 5 (May 15, 2012): 5719–53. http://dx.doi.org/10.5194/bgd-9-5719-2012.
Повний текст джерелаАнотація:
Abstract. Four river basins in Southern Sweden, catchment size 0.3 to maximum 127 km2 (median 1.9), were sampled in October 2007. The 243 samples were analysed for 26 trace elements (Ag, As, Au, Ba, Be, Bi, Cd, Co, Cr, Cu, Ga, Ge, In, La, Li, Mo, Ni, Pb, Sb, Se, Sn, Tl, Ti, U, V and Zn) to identify spatial patterns within drainage networks. The sampling design made it possible to compare the difference between 40 stream reaches, 53 stream junctions with 107 tributaries vs. downstream reaches and 36 lakes with 77 inlets vs. outlets comparisons. The largest concentration differences (at reaches, junctions and lakes) were observed for lakes, with outlets usually having lower concentration compared to the inlets for As, Ba, Be, Bi, Cd, Co, Cr, Ga, Ge, Ni, Pb, Sn, Ti, Tl, U, V and Zn. Significantly lower concentrations were observed for Co and Cd when comparing headwaters with downstream sites in each catchment. We found no evidence for elevated concentration of heavy metals Cd, Cu, Zn or Pb in the two acidified areas of South-west Sweden. Common factor analysis revealed that As, Bi, Cr, Ga, Ge, Tl, V co-vary positively with Al, Fe and total organic carbon (TOC) and negatively with La, Li and pH. A better understanding of the quantitative removal of organic carbon and iron will aid in understanding metal fluxes from landscapes rich in organic matter and iron.
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Kjellstrand, R., A. Mattsson, C. Niklasson, and M. J. Taherzadeh. "Short circuiting in a denitrifying activated sludge tank." Water Science and Technology 52, no. 10-11 (November 1, 2005): 79–87. http://dx.doi.org/10.2166/wst.2005.0681.
Повний текст джерелаАнотація:
The presence of a short circuit flow in a denitrifying activated sludge tank was identified and modelled. Tracer tests with pulse addition of lithium salt were used to investigate the hydraulics of the tank. The lithium concentration in the effluent was detected and residence time distribution (RTD) curves were generated. Hydraulic models based on completely stirred tank reactors (CSTRs) in series were generated from the RTD curves and the models were compared. The short circuit problem was successfully described using the Martin model, where the inflow is divided into two strands. Each strand was modelled as a number of CSTRs in series. At a normal flow the results of the model show that the tank has 12.8% dead volume, 85.8% main volume and 1.3% short circuiting volume. The inflow was divided into 91.9% entering the main volume and 8.1% entering the short circuiting volume. The mean velocity of the short circuiting stream was estimated to 0.4m/s. At maximum flow the short circuiting stream was even larger and handled 24.3% of the flow. The short circuiting stream was identified in the upper part of the tank due to the position of the inlet and the outlet. The configuration of a tank including the use of baffles, the geometry of the inlet and mixer configuration should be considered carefully if short circuiting is to be avoided.
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Mahmoudi, Jafar. "An experimental and numerical study on the modelling of fluid flow, heat transfer and solidification in a copper continuous strip casting process." Manufacturing Review 9 (2022): 33. http://dx.doi.org/10.1051/mfreview/2022030.
Повний текст джерелаАнотація:
An experimental and “numerical study (first part of this study study) was carried out to investigate the solidification process in a copper continuous strip casting process. The model has been tuned by experimental results (i.e. cooling water flow measurements, temperature measurements and metallographic analysis). Further, the results have been used to study the possibility of improved productivity. In this report (second of the study) the flow pattern of the molten copper during a strip casting process as a manufacturing method has been studied using a full-scale water model. The dynamic similarity between model and real system has been studied. Six different types of inlet system to the mould have been studied: inlet nozzle jets with free stream, submerged nozzle jets, slot-submerged inlet system, semi slot-submerged inlet system, submerged-slot inlet nozzle jets and finally submerged-slot inlet nozzle jets with jet killer. Moreover, the effects of nozzle angle, nozzle diameter, casting speed, tundish adjustment and misalignment of the inlet nozzle jets on the flow pattern have been investigated. The vortex formation and bubble entrainment, depending upon the nozzle configuration, immersion depth and the fluid level in the mould have also been studied. It was found that the slot-submerged inlet nozzle jets with jet killer arrangement showed an obvious improvement of the fluid flow characteristics, yielding better tracer distribution in the flow pattern, lower values of back mixing flow, lower turbulence and lower vortex and recirculation flow.
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Temnerud, J., A. Düker, S. Karlsson, B. Allard, K. Bishop, J. Fölster, and S. Köhler. "Spatial patterns of some trace elements in four Swedish stream networks." Biogeosciences 10, no. 3 (March 1, 2013): 1407–23. http://dx.doi.org/10.5194/bg-10-1407-2013.
Повний текст джерелаАнотація:
Abstract. Four river basins in southern Sweden, with catchment sizes from 0.3 to 127 km2 (median 1.9), were sampled in October~2007. The 243 samples were analysed for 26 trace elements (Ag, As, Au, Ba, Be, Bi, Cd, Co, Cr, Cu, Ga, Ge, In, La, Li, Mo, Ni, Pb, Sb, Se, Sn, Tl, Ti, U, V and Zn) to identify spatial patterns within drainage networks. The range and median of each element were defined for different stream orders, and relationships to catchment characteristics, including deposition history, were explored. The sampling design made it possible to compare the differences along 40 stream reaches, above and below 53 stream junctions with 107 tributaries and between the 77 inlets and outlets of 36 lakes. The largest concentration differences (at reaches, junctions and lakes) were observed for lakes, with outlets usually having lower concentration compared to the inlets for As, Ba, Be, Bi, Cd, Co, Cr, Ga, Ge, Ni, Pb, Sn, Ti, Tl, U, V and Zn. Significantly lower concentrations were observed for Cd and Co when comparing headwaters with downstream sites in each catchment. Common factor analysis (FA) revealed that As, Bi, Cr, Ga, Ge, Tl and V co-vary positively with Al, Fe and total organic carbon (TOC) and negatively with La, Li and pH. The strong removal of a large number of trace elements when passing through lakes is evident though in the FA, where lake surface coverage plots opposite to many of those elements. Forest volume does not respond in a similar systematic fashion and, surprisingly, the amount of wetland does not relate strongly to either Fe or TOC at any of the rivers. A better understanding of the quantitative removal of organic carbon and iron will aid in understanding trace element fluxes from landscapes rich in organic matter and iron.
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Marsalek, P. M., W. E. Watt, J. Marsalek, and B. C. Anderson. "Winter operation of an on-stream stormwater management pond." Water Science and Technology 48, no. 9 (November 1, 2003): 133–43. http://dx.doi.org/10.2166/wst.2003.0510.
Повний текст джерелаАнотація:
The winter operation of an on-stream stormwater management pond in Kingston, Canada is characterised. The pond froze over in late November. Ice thickness varied from 0.2 to 0.5 m, and initially, was well described by Stefan's formula. The measured and modelled velocity field indicated a fast flow region, a small dead zone and a large recirculating zone. During a snowmelt event, near-bottom velocities reached 0.05 m·s-1, but were not sufficient to scour the bottom sediment. Pond water temperature increased with depth, from 0.5°C to 3.5°C. The dissolved oxygen (DO) levels observed in the pond (6-13 mg·L-1) indicated stable aerobic conditions at the sediment-water interface. In one brief episode, DO fell to zero after a long cold spell. Reduction in DO readings from inlet to outlet indicated an oxygen consumption of about 1.7 kg·day-1. pH ranged from 7.1 to 8.9. Conductivity readings indicated large quantities of total dissolved solids, representing mostly chloride from de-icing agents. During baseflow, conductivity increased with depth (total dissolved solids concentrations up to 1,200 mg·L-1 near the bottom), indicating density stratification. Average trace metal concentrations were mostly below detection limits.
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Vinnett, Luis, Felipe Contreras, Francisco Díaz, Catalina Pino-Muñoz, and Tania Ledezma. "Estimating Residence Time Distributions in Industrial Closed-Circuit Ball Mills." Minerals 12, no. 12 (December 8, 2022): 1574. http://dx.doi.org/10.3390/min12121574.
Повний текст джерелаАнотація:
This paper compares two deconvolution methodologies used to estimate residence time distributions (RTD) in industrial closed-circuit ball mills. Parametric and non-parametric deconvolution techniques were evaluated. Both techniques allowed for direct RTD estimates from inlet and outlet tracer measurements in the mills, with no need for mass balances nor assumptions to correct the effect of the tracer recirculation in the grinding circuits. Measurements of inlet and outlet concentrations were conducted by radioactive solid tracers and on-stream detectors. The parametric deconvolution was applied assuming the N-perfectly-mixed-reactors-in-series model, whereas the non-parametric deconvolution consisted of a constrained least squares estimation subject to non-negativity. The shapes of the estimated RTDs were consistent between these methodologies, showing mound-shaped distributions in all cases. From the parametric approach, mixing regimes described by 2–4 perfect mixers in series were observed, which indicated significant differences regarding perfect mixing. The mean (τmean) and median (τ50) residence times were more consistent with the RTD shapes when applying the parametric deconvolution. The non-parametric approach was more sensitive to noise, a disadvantage leading to mean residence times significantly higher than the median, and less consistent with the RTD locations. From the comparisons, the estimation strategies proved to be applicable in industrial closed-circuit ball mills. The parametric deconvolution led to better overall performances for τ50 = 1.7–8.3 min, given a suitable model structure for the RTDs.
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Lee, Yu-Tai, and Thomas W. Bein. "Performance Evaluation of an Air-Conditioning Compressor Part II: Volute Flow Predictions." International Journal of Rotating Machinery 5, no. 4 (1999): 241–50. http://dx.doi.org/10.1155/s1023621x99000214.
Повний текст джерелаАнотація:
A numerical method that solves the Reynolds-averaged Navier-Stokes equations is used to study an inefficient component of a shipboard air-conditioning HCFC-124 compressor system. This high-loss component of the centrifugal compressor was identified as the volute through a series of measurements given in Part I of the paper. The predictions were made using three grid topologies. The first grid closes the connection between the cutwater and the discharge diffuser. The other two grids connect the cutwater area with the discharge diffuser. Experiments were performed to simulate both the cutwater conditions used in the predictions. Surface pressures along the outer wall and near the inlet of the volute were surveyed for comparisons with the predictions. Good agreements between the predicted results and the measurements validate the calculations. Total pressure distributions and flow stream traces from the prediction results support the loss distribution through the volute. A modified volute configuration is examined numerically for further loss comparison.
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Yuan, Qiao Ling, Shi Ming Ji, Da Peng Tan, Li Zhang, and Y. C. Wang. "Analysis for Softness Abrasive Flow Field of the Greater Curvature of Small Size Tube." Advanced Materials Research 215 (March 2011): 125–30. http://dx.doi.org/10.4028/www.scientific.net/amr.215.125.
Повний текст джерелаАнотація:
As it was difficult to solve the near wall characteristics of flow field in softness abrasive flow machining (SAFM) on mould structural surface, a method for simulation the flow characteristics based on the low Re number k-ε model was proposed in this paper. The greater curvature of small size tube was used as specific simulation object. The motion law of particles and related parameters were calculated and the precision machining mechanism of SAFM was discussed. Simulation results show that the micro cutting of abrasive flow mainly appears as the transposition of cutting location influenced by the particle pressure, and as the variation of machining efficiency influenced by near-wall particle velocity. Thus via control of the inlet velocity and its corresponding machining time, it is supposed to work out the machining process according with the machining requirements. By tracking near-wall particles, it can be confirm that the movement of near-wall abrasive particles is similar to stream-wise vortices. The cutting traces on workpiece surfaces assume disorderly arrangement, so the feasibility of SAFM method can be reaffirmed.
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Yuan, Qiao Ling, Shi Ming Ji, Da Peng Tan та Li Zhang. "Analytical Method for Softness Abrasive Flow Field Based on Low Reynolds K-ε Model". Advanced Materials Research 188 (березень 2011): 230–35. http://dx.doi.org/10.4028/www.scientific.net/amr.188.230.
Повний текст джерелаАнотація:
As it was difficult to solve the near wall characteristics of flow field in softness abrasive flow machining (SAFM) on mould structural surface, a method for simulation the flow characteristics based on the low Re number k-ε model was proposed in this paper. The U-shaped tube was used as specific simulation object. The motion law of particles and related parameters were calculated and the precision machining mechanism of SAFM was discussed. Simulation results show that the micro cutting of abrasive flow mainly appears as the transposition of cutting location influenced by the particle pressure, and as the variation of machining efficiency influenced by near-wall particle velocity. Thus via control of the inlet velocity and its corresponding machining time, it is supposed to work out the machining process according with the machining requirements. By tracking near-wall particles, it can be confirm that the movement of near-wall abrasive particles is similar to stream-wise vortices. The cutting traces on workpiece surfaces assume disorderly arrangement, so the feasibility of SAFM method can be reaffirmed.
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Li, Y. S., and N. A. Cumpsty. "Mixing in Axial Flow Compressors: Part II—Measurements in a Single-Stage Compressor and a Duct." Journal of Turbomachinery 113, no. 2 (April 1, 1991): 166–72. http://dx.doi.org/10.1115/1.2929076.
Повний текст джерелаАнотація:
This paper follows directly from Part I, which contains not only the description of the facilities and the results for the C106 four-stage compressor, but also the background, list of nomenclature, acknowledgments, and references. The discussion and conclusions for Parts I and II are given here. The single-stage compressor results show the significant effects of inlet guide vane (IGV) wakes on mixing across the stage in the so-called “free-stream” region; in the casing region tip clearance flow is shown to play an important role in mixing. Explanations for these results are given. Investigations were also carried out in a two-dimensional rectangular duct flow to reveal the mixing mechanism in the corner region similar to those formed by blade surfaces and endwalls in a compressor. Turbulent diffusion has been found to be the dominant mechanism in spanwise mixing; anisotropic inhomogeneous turbulent diffusion is mainly responsible for the nonuniform mixing in the corner region. The larger spread of tracer gas in the tangential direction than in the radial direction is mainly caused by the wake dispersion and relative flow motions within the blade wakes as well as secondary flow contributions in the end-wall regions.
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Kamboj, Vipin, and Chinmoy Ranjan. "CO2 Electroreduction to Fuels Using Solid Oxide Electrodes: Beyond Ni-YSZ." ECS Meeting Abstracts MA2022-02, no. 49 (October 9, 2022): 1946. http://dx.doi.org/10.1149/ma2022-02491946mtgabs.
Повний текст джерелаАнотація:
Ni-YSZ electrodes form the benchmark in Carbon Dioxide electroreduction to CO. Ni-YSZ due its popular use in Solid Oxide Fuel Cells forms the basis of various process steps. Unfortunately, this material remains active only if a certain amount of hydrogen is supplied along side CO2 to the inlet of the reaction. Consequently, the Ni-YSZ results in CO production via reverse water gas shift (RWGS) reaction when H2 is supplied at the inlet. The currents for the electrode originate from electrolysis of H2O which is formed as a result of reverse water has shift. We have quantified the amount of CO produced from RWGS vs direct CO2 electrolysis in such a system using online mass spectrometry (MS). Electrochemical impedance spectroscopy measurements where analysed using distribution of relaxation times analysis. Under low concentration of H2 the overall impedance is dominated by H2 mass transfer. Effects of concentration of various reactants were measured using online MS. The process of pretreatment of the electrodes and catalyst surface development during reaction were tracked using in situ Raman Spectroscopy and optical spectrocopy. Electrodes were structurally characterised using SEM, TEM, XPS and ICP-OES measurememts. Various new combination of mixed metal oxide electrodes Ni(M)-YSZ were tested and compared with the performance of pure Ni-YSZ. Ni-YSZ electrode when used under pure CO2 results in catastrophic failure of the electrode performance. We have investigated this failure using in situ Raman and Mass spectrometry. The mechanism of CO2 production in pure CO2 stream was found to be drastically different from when a small amount of H2 is used. Figure 1
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Füzesi, Dániel, Milan Malý, Jan Jedelský, and Viktor Józsa. "Numerical modeling of distributed combustion without air dilution in a novel ultra-low emission turbulent swirl burner." Physics of Fluids 34, no. 4 (April 2022): 043311. http://dx.doi.org/10.1063/5.0085058.
Повний текст джерелаАнотація:
Distributed combustion, often associated with the low-oxygen condition, offers ultra-low NOx emission. However, it was recently achieved without combustion air dilution or internal flue gas recirculation, using a distinct approach called mixture temperature-controlled combustion. Here, the fuel–air stream is cooled at the inlet to delay ignition and, hence, foster homogeneous mixture formation. This numerical study aims to understand its operation better and present a robust framework for distributed combustion modeling in a parameter range where such operation was not predicted before by any existing theory. Further, liquid fuel combustion was evaluated, which brings additional complexity. Four operating conditions were presented at which distributed combustion was observed. The reacting flow was modeled by flamelet-generated manifold, based on a detailed n-dodecane mechanism. The Zimont turbulent flame speed model was used with significantly reduced coefficients to achieve distributed combustion. The droplets of airblast atomization were tracked in a Lagrangian frame. The numerical results were validated by Schlieren images and acoustic spectra. It was concluded that the reactant dilution ratio remained below 0.25 through the combustion chamber, revealing that the homogeneous fuel–air mixture is the principal reason for excellent flame stability and ultra-low NOx emission without significant internal recirculation. The potential applications of these results are boilers, furnaces, and gas turbines.
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Bruneau, Denis, and James T. Gray. "Écoulements glaciaires et déglaciation hâtive (ca 11 ka Bp ?) du nord-est de la péninsule d'Ungava, Québec, Canada." Canadian Journal of Earth Sciences 34, no. 8 (August 1, 1997): 1089–100. http://dx.doi.org/10.1139/e17-088.
Повний текст джерелаАнотація:
Studies of the lithological composition and carbonate contents in the till, the glacial striations and the glacial geomorphology allowed the identification of two distinct ice flows at the northeast end of the Ungava Peninsula and in the area of the Hudson Strait. A general northeastward ice flow, from the Ungava Plateau, has marked the overall region. It joined to an eastward ice stream occupying the Hudson Strait that left traces on Charles Island. This ice stream evacuated the Foxe Basin and the Hudson Bay and overlapped to a limited extend the head of the Ungava Peninsula at Cape Nouvelle-France. The thinness of the till associated with the Ungava flow, the presence of perched blocks among which some are pedestal, and the lack of tapered forms suggest the presence of a ice with low content of debris and cold base in some areas. Subsequently to the westward glacial recession from the Hudson Strait, a readvance of the Ungava glacier with northeast-north direction intersected the earlier eastward movement and calved in the strait at the North of Charles Island. New 14C dating by accelerator mass spectrometry on marine mollusks permitted to locate the deglaciation of the plateau margin, between Deception Bay and Cape Nouvelle-France, prior to 8.5 ka BP. Many older dates suggest the possibility of a very early opening of the Hudson Strait, as early as 10.5–11 ka BP. The early deglaciation in some areas could explain the very high levels of the marine limit of the transgression observed at Cape Nouvelle-France. Furthermore, many ages are intersecting the interval of 8.4–8.9 ka BP, making suspicious the chronology of the glacial readvance of Noble Inlet across the Hudson Strait to the east.
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Dasher, Douglas H. "Use of Regional Geochemical Survey Data and exploratory statistics to estimate natural condition concentrations for trace metals in stream sediments: a case study for the Cook Inlet watershed, Alaska." Environmental Earth Sciences 72, no. 11 (May 30, 2014): 4335–44. http://dx.doi.org/10.1007/s12665-014-3333-3.
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Bull, William B., and Philip A. Pearthree. "Frequency and size of quaternary surface ruptures of the pitaycachi fault, northeastern Sonora, Mexico." Bulletin of the Seismological Society of America 78, no. 2 (April 1, 1988): 956–78. http://dx.doi.org/10.1785/bssa0780020956.
Повний текст джерелаАнотація:
Abstract Movements along the Pitaycachi fault since the Miocene juxtaposed different alluvial units and created 2- to 45-m-high fault scarps downslope from a pedimented mountain front prior to 1887. In 1887, a major earthquake formed a 75-km-long, 12- to 4-m-high scarp along the trace of prehistoric surface ruptures. Diverse evidence from many study sites indicates that about 200,000 yr elapsed between the prior (youngest Pleistocene) event and the 1887 surface rupture. Cumulative displacements of Pliocene(?) to mid-Pleistocene alluvial fans and stream terraces decrease with decreasing age. The trace of the prior rupture was largely buried by sheets of late Pleistocene and Holocene piedmont alluvium. Late Pleistocene soils are offset about the same amount as the height of the 1887 scarp. Valleys that are as much as 40 m deep and 0.5 to 0.9 km wide have been eroded since the prior event; they contain multiple late Pleistocene and Holocene stream terraces that were not faulted until 1887. Pre-1887 alluvial fault scarps were degraded to 2° to 9° slopes before the 1887 event, even in resistant materials such as clay-rich soil horizons with unweathered rhyolite cobbles and calcrete. Scarp height-maximum slope regressions and diffusion-equation analyses for reconstructed pre-1887 scarp profiles indicate that the prior event occurred more than 100,000 yr ago. Acceleration of scarp degradation rates during the Holocene, and/or relatively resistant materials exposed in the scarps, would increase the age estimates to 200,000 yr or more. Very long recurrence intervals are the characteristic style of movement on the Pitaycachi fault. At one site, six ages of diverse valley fills were inset into pedimented granodiorite upslope from the fault between the prior and 1887 events. Only 3 m of relief remained before the 1887 rupture increased the scarp height from 3 to 6 m. Some hillslopes have triangular talus facets of carbonatecemented colluvium that resulted from infrequent fault movements and intervening periods of erosion. Smooth hillsides of resistant volcanic rocks between the facets show that virtually all of the prior surface-rupture event scarps had been removed by prolonged slope degradation.
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Moser, Peter, Sandra Schmidt, and Knut Stahl. "Investigation of trace elements in the inlet and outlet streams of a MEA-based post-combustion capture process results from the test programme at the Niederaussem pilot plant." Energy Procedia 4 (2011): 473–79. http://dx.doi.org/10.1016/j.egypro.2011.01.077.
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Kuwahara, Masayuki, Hiroshi Takahashi, Takeshi Kikko, Seiji Kurumi, and Kei’ichiro Iguchi. "Trace of outbreeding between Biwa salmon (Oncorhynchus masou subsp.) and amago (O. m. ishikawae) detected from the upper reaches of inlet streams within Lake Biwa water system, Japan." Ichthyological Research 66, no. 1 (July 3, 2018): 67–78. http://dx.doi.org/10.1007/s10228-018-0650-7.
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Soli, Alessandro, Ivan Langella, and Zhi X. Chen. "Analysis of Flame Front Breaks Appearing in LES of Inhomogeneous Jet Flames Using Flamelets." Flow, Turbulence and Combustion 108, no. 4 (November 25, 2021): 1159–90. http://dx.doi.org/10.1007/s10494-021-00306-6.
Повний текст джерелаАнотація:
AbstractThe physical mechanism leading to flame local extinction remains a key issue to be further understood. An analysis of large eddy simulation (LES) data with presumed probability density function (PDF) based closure (Chen et al., 2020, Combust. Flame, vol. 212, pp. 415) indicated the presence of localised breaks of the flame front along the stoichiometric line. These observations and their relation to local quenching of burning fluid particles, together with the possible physical mechanisms and conditions allowing their appearance in LES with a simple flamelet model, are investigated in this work using a combined Lagrangian-Eulerian analysis. The Sidney/Sandia piloted jet flames with compositionally inhomogeneous inlet and increasing bulk speeds, amounting to respectively 70 and 90% of the experimental blow-off velocity, are used for this analysis. Passive flow tracers are first seeded in the inlet streams and tracked for their lifetime. The critical scenario observed in the Lagrangian analysis, i.e., burning particles crossing extinction holes on the stoichiometric iso-surface, is then investigated using the Eulerian control-volume approach. For the 70% blow-off case the observed flame front breaks/extinction holes are due to cold and inhomogeneous reactants that are cast onto the stoichiometric iso-surface by large vortices initiated in the jet/pilot shear layer. In this case an extinction hole forms only when the strain effect is accompanied by strong subgrid mixing. This mechanism is captured by the unstrained flamelets model due to the ability of the LES to resolve large-scale strain and considers the SGS mixture fraction variance weakening effect on the reaction rate through the flamelet manifold. Only at 90% blow-off speed the expected limitation of the underlying combustion model assumption become apparent, where the amount of local extinctions predicted by the LES is underestimated compared to the experiment. In this case flame front breaks are still observed in the LES and are caused by a stronger vortex/strain interaction yet without the aid of mixture fraction variance. The reasons for these different behaviours and their implications from a physical and modelling point of view are discussed in this study.
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Behrendt, T., P. R. Veres, F. Ashuri, G. Song, M. Flanz, B. Mamtimin, M. Bruse, J. Williams, and F. X. Meixner. "Characterisation of NO production and consumption: new insights by an improved laboratory dynamic chamber technique." Biogeosciences Discussions 11, no. 1 (January 17, 2014): 1187–275. http://dx.doi.org/10.5194/bgd-11-1187-2014.
Повний текст джерелаАнотація:
Abstract. Biogenic NOx emissions from natural and anthropogenically influenced soils are currently estimated to amount to 9 Tg a−1, hence a significant fraction of global NOx emissions (45 Tg a−1). During the last three decades, a large number of field measurements have been performed to quantify biogenic NO emissions. To study biogenic NO emissions as a function of soil moisture, soil temperature, and soil nutrients, several laboratory approaches have been developed to estimate local/regional NO emissions by suitable up-scaling. This study presents an improved and automated laboratory dynamic chamber system (consisting of six individual soil chambers) for investigation and quantification of all quantities necessary to characterize biogenic NO release from soil (i.e., net NO release rate, NO production and consumption rate, and respective Q10 values). In contrast to former versions of the laboratory dynamic chamber system, the four experiments for complete characterization can now be performed on a single soil sample, whereas former studies had to be performed on four sub-samples. This study discovered that the sub-sample variability biased former measurements of net NO release rates tremendously. Furthermore, it was also shown that the previously reported variation of optimum soil moisture (i.e., where a maximum net NO release rate occurs) between individual sub-samples is most likely a methodical artefact of former versions of the laboratory dynamic chamber system. A comprehensive and detailed methodical concept description of the improved laboratory dynamic chamber system is provided. Response of all quantities (necessary to characterize net NO release) to soil temperature and NO mixing ratio of the flushing air-stream are determined by automatic monitoring of these variables during one single drying-out experiment with one single soil sample only. The method requires precise measurements of NO mixing ratio at the inlet and outlet of each soil chamber; finally, four pairs of inlet/outlet NO mixing ratios are sufficient to derive all necessary quantities. Soil samples from drylands exhibit particularly low NO production, but even lower NO consumption rates. However, with the improved laboratory dynamic chamber system those low levels can be quantified, as well as corresponding NO compensation point mixing ratios and respective Q10 values. It could be shown, that the NO compensation point mixing ratio seems to be generally independent of gravimetric soil moisture content, but, particularly for dryland soils, strongly dependent on soil temperature. New facilities have been included into the improved system (e.g. for investigation of net release rates of other trace gases, namely CO2 and VOCs). First results are shown for net release rates of acetone (C3H6O), acetaldehyde (C2H4O) and CO2. This new system is thus able to simultaneously investigate potential mechanistic links between NO, multitudinous VOC and CO2.
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Johnson, Ethan, Chase Jenquin, Jonathan McCready, Venkat Narayanaswamy, and Jack Edwards. "Experimental Investigations of the Hypersonic Stream-Traced Performance Inlet at Subdesign Mach Number." AIAA Journal, October 7, 2022, 1–14. http://dx.doi.org/10.2514/1.j062113.
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Casaday, Brian, Robin Prenter, Carlos Bonilla, Michael Lawrence, Carey Clum, Ali A. Ameri, and Jeffrey P. Bons. "Deposition With Hot Streaks in an Uncooled Turbine Vane Passage." Journal of Turbomachinery 136, no. 4 (October 24, 2013). http://dx.doi.org/10.1115/1.4025215.
Повний текст джерелаАнотація:
The effect of hot streaks on deposition in a high pressure turbine vane passage was studied both experimentally and computationally. Modifications to Ohio State's Turbine Reaction Flow Rig allowed for the creation of simulated hot streaks in a four-vane annular cascade operating at temperatures up to 1093 °C. Total temperature surveys were made at the inlet plane of the vane passage, showing the variation caused by cold dilution jets. Deposition was generated by introducing sub-bituminous ash particles with a median diameter of 11.6 μm far upstream of the vane passage. Results indicate a strong correlation between surface deposits and the hot streak trajectory. A computational model was developed in Fluent to simulate both the flow and deposition. The flow solution was first obtained without particulates, and individual ash particles were subsequently introduced and tracked using a Lagrangian tracking model. The critical viscosity model was used to determine particle sticking upon impact with vane surfaces. Computational simulations confirm the migration of the hot streak and locations susceptible to enhanced deposition. Results show that the deposition model is overly sensitive to temperature and can severely overpredict deposition. Model constants can be tuned to better match experimental results but must be calibrated for each application.
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Prenter, Robin, Ali Ameri, and Jeffrey P. Bons. "Computational Simulation of Deposition in a Cooled High-Pressure Turbine Stage With Hot Streaks." Journal of Turbomachinery 139, no. 9 (April 11, 2017). http://dx.doi.org/10.1115/1.4036008.
Повний текст джерелаАнотація:
Ash particle deposition in a high-pressure turbine stage was numerically investigated using steady Reynolds-averaged Navier-Stokes (RANS) and unsteady Reynolds-averaged Navie-Stokes (URANS) methods. An inlet temperature profile consisting of Gaussian nonuniformities (hot streaks) was imposed on the vanes, with vane cooling simulated using a constant vane wall temperature. The steady case utilized a mixing plane at the vane–rotor interface, while a sliding mesh was used for the unsteady case. Corrected speed and mass flow were matched to an experiment involving the same geometry, so that the flow solution could be validated against measurements. Particles ranging from 1 to 65 μm were introduced into the vane domain, and tracked using an Eulerian–Lagrangian tracking model. A novel particle rebound and deposition model was employed to determine particles' stick/bounce behavior upon impact with a surface. Predicted impact and capture distributions for different diameters were compared between the steady and unsteady methods, highlighting effects from the circumferential averaging of the mixing plane. The mixing plane simulation was found to generally under predict impact and capture efficiencies compared with the unsteady calculation, as well as under predict particle temperature upon impact with the blade surface. Quantitative impact and capture efficiency trends with the Stokes number are discussed for both the vane and blade, with companion qualitative distributions for the different Stokes regimes.
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Phoon, Colin K., Ruiping Ji, and Piyali Dhar Chowdhury. "Abstract 2335: Transposition Of The Great Arteries And Double Outlet Right Ventricle Have Related Early Developmental Origins: Fundamental Insights From In Vivo Imaging." Circulation 116, suppl_16 (October 16, 2007). http://dx.doi.org/10.1161/circ.116.suppl_16.ii_511.
Повний текст джерелаАнотація:
Congenital heart defects (CHD) are the most common birth defect. Proper retinoic acid (RA) signaling is required for normal development, and RA excess produces conotruncal CHD such as transposition of the great arteries (TGA) and double outlet right ventricle (DORV). We hypothesized that origins and evolution of TGA and DORV follow specific developmental patterns, definable in vivo by noninvasive ultrasound biomicroscopy (UBM)-Doppler imaging. Timed-pregnant ICR mice were injected with 70 mg/kg IP RA at 8.5 days post-conception (E8.5). Individual embryos were tracked with 40 MHz UBM-Doppler longitudinally on 5 consecutive days (E11.5–15.5: N=34 injected, N=8 uninjected controls). CHD included TGA (24%) and DORV (21%, all with right aorta, left pulmonary artery), as well as ventricular septal defect (VSD, defined at E15.5) and double-inlet left ventricle. External gross examination and histology confirmed ~90% concordance of UBM diagnosis of CHD, here (at E15.5) and in separate experiments (E11.5–15.5, N=111). All E11.5 embryos showed normal cardiac looping, with a normal unseptated heart and outflow tract (OFT) - the truncus arteriosus -arising from the right ventricle/bulbus cordis. Of embryos destined for TGA, 7/8 showed partial septation of the distal truncus into parallel OFT at E12.5; 4 showed DORV at E12.5 before evolving into TGA by E13.5. Of embryos destined for DORV, 6/7 showed partial septation of the distal truncus into parallel OFT at E12.5 as well. Thus, abnormal septation commences in the more distal truncus arteriosus as early as E12.5. In contrast, embryos destined for normal OFT development showed partial OFT septation in spiral (non-parallel) fashion, with complete/near-complete OFT septation and morphology at E13.5. All TGA/DORV embryos displayed normal cardiac function. CONCLUSIONS. TGA and DORV are developmentally related, differing only in complete (TGA) vs. incomplete (DORV) leftward truncal shift. Given normal heart, proximal OFT, and cardiac function, flow streams do not explain TGA/DORV morphogenesis. Corresponding to 4–6 weeks’ human gestation, these first in vivo data support longstanding hypotheses of TGA/DORV embryogenesis, and implicate RA signaling in the pathogenesis of abnormal truncal septation and shift.
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Nickol, Jeremy B., Randall M. Mathison, Malak F. Malak, Rajiv Rana, and Jong S. Liu. "Time-Resolved Heat Transfer and Surface Pressure Measurements for a Fully Cooled Transonic Turbine Stage." Journal of Turbomachinery 137, no. 9 (September 1, 2015). http://dx.doi.org/10.1115/1.4029950.
Повний текст джерелаАнотація:
The flow field in axial gas turbines is driven by strong unsteady interactions between stationary and moving components. While time-averaged measurements can highlight many important flow features, developing a deeper understanding of the complicated flows present in high-speed turbomachinery requires time-accurate measurements that capture this unsteady behavior. Toward this end, time-accurate measurements are presented for a fully cooled transonic high-pressure turbine stage operating at design-corrected conditions. The turbine is run in a short-duration blowdown facility with uniform, radial, and hot streak vane-inlet temperature profiles as well as various amounts of cooling flow. High-frequency response surface pressure and heat-flux instrumentation installed in the rotating blade row, stator vane row, and stationary outer shroud provide detailed measurements of the flow behavior for this stage. Previous papers have reported the time-averaged results from this experiment, but this paper focuses on the strong unsteady phenomena that are observed. Heat-flux measurements from double-sided heat-flux gauges (HFGs) cover three spanwise locations on the blade pressure and suction surfaces. In addition, there are two instrumented blades with the cooling holes blocked to isolate the effect of just blade cooling. The stage can be run with the vane and blade cooling flow either on or off. High-frequency pressure measurements provide a picture of the unsteady aerodynamics on the vane and blade airfoil surfaces, as well as inside the serpentine coolant supply passages of the blade. A time-accurate computational fluid dynamics (CFD) simulation is also run to predict the blade surface pressure and heat-flux, and comparisons between prediction and measurement are given. It is found that unsteady variations in heat-flux and pressure are stronger at low to midspan and weaker at high span, likely due to the impact of secondary flows such as the tip leakage flow. Away from the tip, it is seen that the unsteady fluctuations in pressure and heat-flux are mostly in phase with each other on the suction side, but there is some deviation on the pressure side. The flow field is ultimately shown to be highly three-dimensional, as the movement of high heat transfer regions can be traced in both the chord and spanwise directions. These measurements provide a unique picture of the unsteady flow physics of a rotating turbine, and efforts to better understand and model these time-varying flows have the potential to change the way we think about even the time-averaged flow characteristics.